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L_0887 | electronic signal | T_4401 | Analog signals consist of continuously changing voltage in an electric circuit. The Figure 1.1 represents analog signals. These were the first electronic signals to be invented. They were used in early computers and other early electronic devices. Analog signals are subject to distortion and noise, so they arent used as often anymore. They are used mainly in microphones and some mobile phones to encode sounds as electronic signals. | text | null |
L_0887 | electronic signal | T_4402 | Today, most electronic signals are digital signals. Digital signals consist of rapid pulses of voltage that repeatedly switch the current off and on. The Figure 1.2 represents digital signals. This type of signal encodes information as a string of 0s (current off) and 1s (current on). This is called a binary (two-digit) code. The majority of modern electronic devices, including computers and many mobile phones, encode data as digital signals. Compared with analog signals, digital signals are easier to transmit and more accurate. | text | null |
L_0887 | electronic signal | T_4402 | Today, most electronic signals are digital signals. Digital signals consist of rapid pulses of voltage that repeatedly switch the current off and on. The Figure 1.2 represents digital signals. This type of signal encodes information as a string of 0s (current off) and 1s (current on). This is called a binary (two-digit) code. The majority of modern electronic devices, including computers and many mobile phones, encode data as digital signals. Compared with analog signals, digital signals are easier to transmit and more accurate. | text | null |
L_0896 | evaporation | T_4432 | Evaporation explains why clothes dry on a clothesline. Evaporation is the process in which a liquid changes to a gas without becoming hot enough to boil. It occurs when individual liquid particles at the exposed surface of the liquid absorb just enough energy to overcome the force of attraction with other liquid particles. If the surface particles are moving in the right direction, they will pull away from the liquid and move into the air. This is illustrated in the Figure 1.1. | text | null |
L_0896 | evaporation | T_4433 | Many factors influence how quickly a liquid evaporates. They include: temperature of the liquid. A cup of hot water will evaporate more quickly than a cup of cold water. exposed surface area of the liquid. The same amount of water will evaporate more quickly in a wide shallow bowl than in a tall narrow glass. presence or absence of other substances in the liquid. Pure water will evaporate more quickly than salt water. air movement. Clothes on a clothesline will dry more quickly on a windy day than on a still day. concentration of the evaporating substance in the air. Clothes will dry more quickly when air contains little water vapor. | text | null |
L_0896 | evaporation | T_4434 | Did you ever notice that moving air cools you down when youre hot and sweaty? For example, if you sit in front of a fan, you feel cooler. Thats because moving air helps to evaporate the sweat on your skin. But why does the evaporation of sweat cool you down? When a liquid such as sweat evaporates, energetic particles on the surface of the liquid escape into the air. After these particles leave, the remaining liquid has less energy, so it is cooler. This is called evaporative cooling. Q: On a hot day, high humidity makes you feel even hotter. Can you explain why? A: Humidity is a measure of the amount of water vapor in the air. When humidity is high, sweat evaporates more slowly because there is already a lot of water vapor in the air. The slower evaporation rate reduces the potential for evaporative cooling. | text | null |
L_0903 | freezing | T_4450 | You dont have to be an ice climber to enjoy ice. Skating and fishing are two other sports that are also done on ice. What is ice? Its simply water in the solid state. The process in which water or any other liquid changes to a solid is called freezing. Freezing occurs when a liquid cools to a point at which its particles no longer have enough energy to overcome the force of attraction between them. Instead, the particles remain in fixed positions, crowded closely together, as shown in the Figure 1.1. | text | null |
L_0903 | freezing | T_4451 | The temperature at which a substance freezes is known as its freezing point. Freezing point is a physical property of matter. The freezing point of pure water is 0 C. Below this temperature, water exists as ice. Above this temperature, it exists as liquid water or water vapor. Many other substances have much lower or higher freezing points than water. You can see some examples in the Table 1.1. The freezing point of pure water is included in the table for comparison. Substance Helium Oxygen Nitrogen Pure Water Lead Iron Carbon Freezing Point ( C) -272 -222 -210 0 328 1535 3500 Q: What trend do you see in this table? A: Substances in the table with freezing points lower than water are gases. Substances in the table with freezing points higher than water are solids. Q: Sodium is a solid at room temperature. Given this information, what can you infer about its freezing point? A: You can infer that the freezing point of sodium must be higher than room temperature, which is about 20 C. The freezing point of sodium is actually 98 C. | text | null |
L_0941 | liquids | T_4584 | Water is the most common substance on Earth, and most of it exists in the liquid state. A liquid is one of four well-known states of matter, along with solid, gas, and plasma states. The particles of liquids are in close contact with each other but not as tightly packed as the particles in solids. The particles can slip past one another and take the shape of their container. However, they cannot pull apart and spread out to take the volume of their container, as particles of a gas can. If the volume of a liquid is less than the volume of its container, the top surface of the liquid will be exposed to the air, like the vinegar in the bottle pictured in the Figure 1.1. Q: Why does most water on Earths surface exist in a liquid state? In what other states does water exist on Earth? A: Almost 97 percent of water on Earths surface is found as liquid salt water in the oceans. The temperature over most of Earths surface is above the freezing point (0 C) of water, so relatively little water exists as ice. Even near the poles, most of the water in the oceans is above the freezing point. And in very few places on Earths surface do temperatures reach the boiling point (100 C) of water. Although water exists in the atmosphere in a gaseous state, water vapor makes up less than 1 percent of Earths total water. | text | null |
L_0941 | liquids | T_4585 | Two unique properties of liquids are surface tension and viscosity. Surface tension is a force that pulls particles at the exposed surface of a liquid toward other liquid particles. Surface tension explains why water forms droplets, like the water droplet that has formed on the leaky faucet pictured in the Figure 1.2. Water drips from a leaky faucet. Viscosity is a liquids resistance to flowing. You can think of it as friction between particles of liquid. Thicker liquids are more viscous than thinner liquids. For example, the honey pictured in the Figure 1.3 is more viscous than the vinegar. Q: Which liquid do you think is more viscous: honey or chocolate syrup? | text | null |
L_0941 | liquids | T_4585 | Two unique properties of liquids are surface tension and viscosity. Surface tension is a force that pulls particles at the exposed surface of a liquid toward other liquid particles. Surface tension explains why water forms droplets, like the water droplet that has formed on the leaky faucet pictured in the Figure 1.2. Water drips from a leaky faucet. Viscosity is a liquids resistance to flowing. You can think of it as friction between particles of liquid. Thicker liquids are more viscous than thinner liquids. For example, the honey pictured in the Figure 1.3 is more viscous than the vinegar. Q: Which liquid do you think is more viscous: honey or chocolate syrup? | text | null |
L_0945 | matter mass and volume | T_4593 | Matter is all the stuff that exists in the universe. Everything you can see and touch is made of matter, including you! The only things that arent matter are forms of energy, such as light and sound. In science, matter is defined as anything that has mass and volume. Mass and volume measure different aspects of matter. | text | null |
L_0945 | matter mass and volume | T_4594 | Mass is a measure of the amount of matter in a substance or an object. The basic SI unit for mass is the kilogram (kg), but smaller masses may be measured in grams (g). To measure mass, you would use a balance. In the lab, mass may be measured with a triple beam balance or an electronic balance, but the old-fashioned balance pictured below may give you a better idea of what mass is. If both sides of this balance were at the same level, it would mean that the fruit in the left pan has the same mass as the iron object in the right pan. In that case, the fruit would have a mass of 1 kg, the same as the iron. As you can see, however, the fruit is at a higher level than the iron. This means that the fruit has less mass than the iron, that is, the fruits mass is less than 1 kg. Q: If the fruit were at a lower level than the iron object, what would be the mass of the fruit? A: The mass of the fruit would be greater than 1 kg. Mass is commonly confused with weight. The two are closely related, but they measure different things. Whereas mass measures the amount of matter in an object, weight measures the force of gravity acting on an object. The force of gravity on an object depends on its mass but also on the strength of gravity. If the strength of gravity is held constant (as it is all over Earth), then an object with a greater mass also has a greater weight. Q: With Earths gravity, an object with a mass of 1 kg has a weight of 2.2 lb. How much does a 10 kg object weigh on Earth? A: A 10 kg object weighs ten times as much as a 1 kg object: 10 2.2 lb = 22 lb | text | null |
L_0945 | matter mass and volume | T_4595 | Volume is a measure of the amount of space that a substance or an object takes up. The basic SI unit for volume is the cubic meter (m3 ), but smaller volumes may be measured in cm3 , and liquids may be measured in liters (L) or milliliters (mL). How the volume of matter is measured depends on its state. The volume of a liquid is measured with a measuring container, such as a measuring cup or graduated cylinder. The volume of a gas depends on the volume of its container: gases expand to fill whatever space is available to them. The volume of a regularly shaped solid can be calculated from its dimensions. For example, the volume of a rectangular solid is the product of its length, width, and height. The volume of an irregularly shaped solid can be measured by the displacement method. You can read below how this method works. Click image to the left or use the URL below. URL: Q: How could you find the volume of air in an otherwise empty room? A: If the room has a regular shape, you could calculate its volume from its dimensions. For example, the volume of a rectangular room can be calculated with the formula: Volume = length width height If the length of the room is 5.0 meters, the width is 3.0 meters, and the height is 2.5 meters, then the volume of the room is: Volume = 5.0 m 3.0 m 2.5 m = 37.5 m3 Q: What is the volume of the dinosaur in the diagram above? A: The volume of the water alone is 4.8 mL. The volume of the water and dinosaur together is 5.6 mL. Therefore, the volume of the dinosaur alone is 5.6 mL - 4.8 mL = 0.8 mL. | text | null |
L_0948 | melting | T_4603 | The process in which rocks or other solids change to liquids is called melting. Melting occurs when particles of a solid absorb enough energy to partly overcome the force of attraction holding them together. This allows them to move out of their fixed positions and slip over one another. Melting, like other changes of state, is a physical change in matter, so it doesnt change the chemical makeup or chemical properties of matter. Q: The molten rock that erupts from a volcano comes from deep underground. How is this related to its liquid state? A: It is always very hot deep underground where molten rock originates. The high temperatures give rock enough energy to melt and remain in a molten state. Underground rock in this state is called magma. Q: What happens to magma after it erupts and starts flowing over the surface of the ground? A: After magma erupts, it is called lava. On the surface, lava eventually cools and hardens to form solid rock. Other substances that are normally solids on Earth can also be heated until they melt. You can see an example in the Figure 1.1. The photo shows molten gold being poured into a mold. When the gold cools, it will harden into a solid gold bar that has the same shape as the mold. | text | null |
L_0948 | melting | T_4604 | The temperature at which a substance melts is called its melting point. Melting point is a physical property of matter. The gold pictured in the Figure 1.1, for example, has a melting point of 1064 C. This is a high melting point, and most other metals also have high melting points. The melting point of ice, in comparison, is much lower at 0 C. Many substances have even lower melting points. For example, the melting point of oxygen is -222 C. | text | null |
L_0948 | melting | T_4605 | Because of global climate change, temperatures all over Earth are rising. However, the melting points of Earths substances, including ice, are constant. The result? Glaciers are melting at an alarming rate. Melting glaciers cause rising sea levels and the risk of dangerous river flooding on land. Click image to the left or use the URL below. URL: | text | null |
L_0955 | mixtures | T_4625 | A mixture is a combination of two or more substances in any proportion. This is different from a compound, which consists of substances in fixed proportions. The substances in a mixture also do not combine chemically to form a new substance, as they do in a compound. Instead, they just intermingle and keep their original properties. The lemonade pictured above is a mixture because it doesnt have fixed proportions of ingredients. It could have more or less lemon juice, for example, or more or less sugar, and it would still be lemonade. Q: What are some other examples of mixtures? A: Other examples of liquid mixtures include salt water and salad dressing. Air is a mixture of gases, mainly nitrogen and oxygen. The rock pictured in the Figure 1.1 is a solid mixture. This rock is a mixture of smaller rocks and minerals. | text | null |
L_0955 | mixtures | T_4626 | The lemonade in the opening picture is an example of a homogeneous mixture. A homogeneous mixture has the same composition throughout. Another example of a homogeneous mixture is salt water. If you analyzed samples of ocean water in different places, you would find that the proportion of salt in each sample is the same: 3.5 percent. The rock in Figure 1.1 is an example of a heterogeneous mixture. A heterogeneous mixture varies in its composition. The black nuggets, for example, are not distributed evenly throughout the rock. | text | null |
L_0955 | mixtures | T_4627 | Mixtures have different properties depending on the size of their particles. Three types of mixtures based on particle size are solutions, suspensions, and colloids, all of which are described in Table 1.1. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: Type of Mixture Solutions Description A solution is a homogeneous mixture with tiny parti- cles. The particles are too small to see and also too small to settle or be filtered out of the mixture. When the salt is thoroughly mixed into the water in this glass, it will form a solution. The salt will no longer be visible in the water, and it wont settle to the bottom of the glass. Colloids A colloid is a homogeneous mixture with medium- sized particles. The particles are large enough to see but not large enough to settle or be filtered out of the mixture. The gelatin in this dish is a colloid. It looks red because you can see the red gelatin particles in the mixture. However, the particles are too small to settle to the bottom of the dish. A suspension is a heterogeneous mixture with large particles. The particles are large enough to see and also to settle or be filtered out of the mixture. The salad dressing in this bottle is a suspension. It contains oil, vinegar, herbs, and spices. If the bottle sits undisturbed for very long, the mixture will separate into its component parts. Thats why you should shake it before you use it. Suspensions Q: If you buy a can of paint at a paint store, a store employee may put the can on a shaker machine to mix up the paint in the can. What type of mixture is the paint? A: The paint is a suspension. Some of the components of the paint settle out of the mixture when it sits undisturbed for a long time. This explains why you need to shake (or stir) the paint before you use it. Q: The milk you buy in the supermarket has gone through a process called homogenization. This process breaks up the cream in the milk into smaller particles. As a result, the cream doesnt separate out of the milk no matter how long it sits on the shelf. Which type of mixture is homogenized milk? A: Homogenized milk is a colloid. The particles in the milk are large enough to seethats why milk is white instead of clear like water, which is the main component of milk. However, the particles are not large enough to settle out of the mixture. | text | null |
L_0955 | mixtures | T_4628 | The components of a mixture keep their own identity when they combine, so they retain their physical properties. Examples of physical properties include boiling point, ability to dissolve, and particle size. When components of mixtures vary in physical properties such as these, processes such as boiling, dissolving, or filtering can be used to separate them. Look at the Figure 1.2 of the Great Salt Lake in Utah. The water in the lake is a solution of salt and water. Do you see the white salt deposits near the shore? How did the salt separate from the salt water? Water has a lower boiling point than salt, and it evaporates in the heat of the sun. With its higher boiling point, the salt doesnt get hot enough to evaporate, so it is left behind. Q: Suppose you have a mixture of salt and pepper. What properties of the salt and pepper might allow you to separate them? A: Salt dissolves in water but pepper does not. If you mix salt and pepper with water, only the salt will dissolve, leaving the pepper floating in the water. You can separate the pepper from the water by pouring the mixture through a filter, such as a coffee filter. Q: After you separate the pepper from the salt water, how could you separate the salt from the water? A: You could heat the water until it boils and evaporates. The salt would be left behind. | text | null |
L_0975 | ohms law | T_4688 | For electric current to flow through a wire, there must be a source of voltage. Voltage is a difference in electric potential energy. As you might have guessed, greater voltage results in more current. As electric current flows through matter, particles of matter resist the moving charges. This is called resistance, and greater resistance results in less current. These relationships between electric current, voltage, and resistance were first demonstrated in the early 1800s by a German scientist named Georg Ohm, so they are referred to as Ohms law. Ohms law can be represented by the following equation. Current(amps) = Voltage(volts) Resistance(ohms) | text | null |
L_0975 | ohms law | T_4689 | Ohms law may be easier to understand with an analogy. Current flowing through a wire is like water flowing through a hose. Increasing voltage with a higher-volt battery increases the current. This is like opening the tap wider so more water flows through the hose. Increasing resistance reduces the current. This is like stepping on the hose so less water can flow through it. | text | null |
L_0975 | ohms law | T_4690 | You can use the equation for current (above) to calculate the amount of current flowing through a circuit when the voltage and resistance are known. Consider an electric wire that is connected to a 12-volt battery. If the wire has a resistance of 2 ohms, how much current is flowing through the wire? Current = 12 volts 2 ohms = 6 amps Q: If a 120-volt voltage source is connected to a wire with 10 ohms of resistance, how much current is flowing through the wire? A: Substitute these values into the equation for current: Current = 120 volts 10 ohms = 12 amps | text | null |
L_0981 | physical change | T_4709 | A physical change is a change in one or more physical properties of matter without any change in chemical properties. In other words, matter doesnt change into a different substance in a physical change. Examples of physical change include changes in the size or shape of matter. Changes of statefor example, from solid to liquid or from liquid to gasare also physical changes. Some of the processes that cause physical changes include cutting, bending, dissolving, freezing, boiling, and melting. Four examples of physical change are pictured in the Figure Click image to the left or use the URL below. URL: Q: In the Figure 1.1, what physical changes are occurring? A: The paper is being cut into smaller pieces, which is changing its size and shape. The ice cubes are turning into a puddle of liquid water because they are melting. This is a change of state. The tablet is disappearing in the glass of water because it is dissolving into particles that are too small to see. The lighthouse is becoming coated with ice as ocean spray freezes on its surface. This is another change of state. | text | null |
L_0981 | physical change | T_4710 | When matter undergoes physical change, it doesnt become a different substance. Therefore, physical changes are often easy to reverse. For example, when liquid water freezes to form ice, it can be changed back to liquid water by heating and melting the ice. Q: Salt dissolving in water is a physical change. How could this change be reversed? A: The salt water could be boiled until the water evaporates, leaving behind the salt. Water vapor from the boiling water could be captured and cooled. The water vapor would condense and change back to liquid water. | text | null |
L_0982 | physical properties of matter | T_4711 | Physical properties of matter are properties that can be measured or observed without matter changing to an entirely different substance. Physical properties are typically things you can detect with your senses. For example, they may be things that you can see, hear, smell, or feel. Q: What differences between snow and sand can you detect with your senses? A: You can see that snow and sand have a different color. You can also feel that snow is softer than sand. Both color and hardness are physical properties of matter. | text | null |
L_0982 | physical properties of matter | T_4712 | In addition to these properties, other physical properties of matter include the state of matter. States of matter include liquid, solid, and gaseous states. For example at 20 C, coal exists as a solid and water exists as a liquid. Additional examples of physical properties include: odor boiling point ability to conduct heat ability to conduct electricity ability to dissolve in other substances Some of these properties are illustrated in the Figures 1.1, 1.2, 1.3, and 1.4. Click image to the left or use the URL below. URL: The strong smell of swimming pool water is the odor of chlorine, which is added to the water to kill germs and algae. In con- trast, bottled spring water, which contains no chlorine, does not have an odor. Coolant is added to the water in a car radiator to keep the water from boiling and evaporating. Coolant has a higher boiling point than water and adding it to the water increases the boiling point of the solution. Q: The coolant that is added to a car radiator also has a lower freezing point than water. Why is this physical property useful? A: When coolant is added to water in a car radiator, it lowers the freezing point of the water. This prevents the water in the radiator from freezing when the temperature drops below 0 C, which is the freezing point of pure water. Q: Besides being able to conduct electricity, what other physical property of copper makes it well suited for electric wires? A: Copper, like other metals, is ductile. This means that it can be rolled and stretched into long thin shapes such as wires. This teakettle is made of aluminum except for its handle, which is made of plastic. Aluminum is a good conductor of heat. It conducts heat from the flames on the range to the water inside the kettle, so the water heats quickly. Plastic, on the other hand, is not a good conductor of heat. It stays cool enough to touch even when the rest of the teakettle becomes very hot. | text | null |
L_0982 | physical properties of matter | T_4712 | In addition to these properties, other physical properties of matter include the state of matter. States of matter include liquid, solid, and gaseous states. For example at 20 C, coal exists as a solid and water exists as a liquid. Additional examples of physical properties include: odor boiling point ability to conduct heat ability to conduct electricity ability to dissolve in other substances Some of these properties are illustrated in the Figures 1.1, 1.2, 1.3, and 1.4. Click image to the left or use the URL below. URL: The strong smell of swimming pool water is the odor of chlorine, which is added to the water to kill germs and algae. In con- trast, bottled spring water, which contains no chlorine, does not have an odor. Coolant is added to the water in a car radiator to keep the water from boiling and evaporating. Coolant has a higher boiling point than water and adding it to the water increases the boiling point of the solution. Q: The coolant that is added to a car radiator also has a lower freezing point than water. Why is this physical property useful? A: When coolant is added to water in a car radiator, it lowers the freezing point of the water. This prevents the water in the radiator from freezing when the temperature drops below 0 C, which is the freezing point of pure water. Q: Besides being able to conduct electricity, what other physical property of copper makes it well suited for electric wires? A: Copper, like other metals, is ductile. This means that it can be rolled and stretched into long thin shapes such as wires. This teakettle is made of aluminum except for its handle, which is made of plastic. Aluminum is a good conductor of heat. It conducts heat from the flames on the range to the water inside the kettle, so the water heats quickly. Plastic, on the other hand, is not a good conductor of heat. It stays cool enough to touch even when the rest of the teakettle becomes very hot. | text | null |
L_0982 | physical properties of matter | T_4712 | In addition to these properties, other physical properties of matter include the state of matter. States of matter include liquid, solid, and gaseous states. For example at 20 C, coal exists as a solid and water exists as a liquid. Additional examples of physical properties include: odor boiling point ability to conduct heat ability to conduct electricity ability to dissolve in other substances Some of these properties are illustrated in the Figures 1.1, 1.2, 1.3, and 1.4. Click image to the left or use the URL below. URL: The strong smell of swimming pool water is the odor of chlorine, which is added to the water to kill germs and algae. In con- trast, bottled spring water, which contains no chlorine, does not have an odor. Coolant is added to the water in a car radiator to keep the water from boiling and evaporating. Coolant has a higher boiling point than water and adding it to the water increases the boiling point of the solution. Q: The coolant that is added to a car radiator also has a lower freezing point than water. Why is this physical property useful? A: When coolant is added to water in a car radiator, it lowers the freezing point of the water. This prevents the water in the radiator from freezing when the temperature drops below 0 C, which is the freezing point of pure water. Q: Besides being able to conduct electricity, what other physical property of copper makes it well suited for electric wires? A: Copper, like other metals, is ductile. This means that it can be rolled and stretched into long thin shapes such as wires. This teakettle is made of aluminum except for its handle, which is made of plastic. Aluminum is a good conductor of heat. It conducts heat from the flames on the range to the water inside the kettle, so the water heats quickly. Plastic, on the other hand, is not a good conductor of heat. It stays cool enough to touch even when the rest of the teakettle becomes very hot. | text | null |
L_0984 | plasma | T_4715 | Compare and contrast the basic properties of matter, such as mass and volume. | text | null |
L_0984 | plasma | T_4716 | Here is a riddle for you to ponder: What do you and a tiny speck of dust in outer space have in common? Think you know the answer? Both you and the speck of dust consist of matter. So does the ground beneath your feet. In fact, everything you can see and touch is made of matter. The only things that are not matter are forms of energy. This would include things such as light and sound. Although forms of energy are not matter, the air and other substances they travel through are. So what is matter? Matter is defined as anything that has mass and volume. You may recall that atoms are the building blocks of matter. Even things as small as atoms have mass and volume. The more atoms, or matter, the more mass and volume are present. Different types of atoms have different amounts of mass and volume. So, its not enough to know the count of atoms to determine the mass. You must also know the type of atoms an item is made of. Mass and volume are just two ways to describe the physical property of a substance. Physical properties are all determined by the amounts and type of atoms that compose items. | text | null |
L_0984 | plasma | T_4717 | Mass refers to the amount of matter. Mass is usually measured with a balance. A balance allows an object to be matched with other objects of known mass. The SI unit for mass is the kilogram. For smaller masses, grams are often used instead. You may have a balance in your classroom. The balance may be either a triple-beam balance or an electronic balance. The figure below of the old-fashioned balance may give you a better idea of what mass is. What does it mean when both sides of the balance are at the same level? Thats correct, it would mean the masses of each object are equal. In that case, the fruit would have a mass of 1 kg. It would have the same mass as the iron. As you can see, the fruit is at a higher level than the iron. This means the fruit has less mass than the 1 kg iron object. Q: What If the fruit were at a lower level than the iron object? A: The mass of the fruit would be greater than 1 kg. | text | null |
L_0984 | plasma | T_4718 | Mass is often confused with weight. The two are closely related, but they are not the same. Mass is the amount of matter. Weight is a measure of the force of gravity acting on the mass. On Earth, the force of gravity is constant. If we are comparing objects on Earth, objects with a greater mass also have a greater weight. Weight is measured with a device called a scale. Remember, mass is measured with a balance. You might find an example of a scale in your kitchen or bathroom. Scales detect how forcefully objects are being pulled downward by gravity. The SI unit for weight is the newton (N). A mass of 10 kg has a weight of 100 newtons (N). | text | null |
L_0984 | plasma | T_4719 | At Earths gravity, what is the weight in newtons of an object with a mass of 10 kg? At Earths gravity, 1 kg has a weight of 10 N. Therefore, 10 kg has a weight of (10 kg x 10 m/s2 ) = 100 N. | text | null |
L_0984 | plasma | T_4720 | If you have a mass of 50 kg on Earth, what is your weight in newtons? An object with more mass is pulled by gravity with greater force. Mass and weight are closely related. However, the weight of an object can change if the force of gravity changes. On Earth, the force of gravity is the same everywhere. So how does the force of gravity change? It doesnt if you stay on Earth. What if we travel to another planet or moon in our solar system? Look at the photo of astronaut Edwin E. Aldrin Jr. taken by fellow astronaut Neil Armstrong in the Figure ??. They were the first humans to walk on the moon. An astronaut weighs less on the moon than he would on Earth. This is because the moons gravity is weaker than Earths. The astronauts mass, on the other hand, did not change. He still contained the same amount of matter on the moon as he did on Earth. If the astronaut weighed 175 pounds on Earth, he would have weighed only 29 pounds on the moon. If his mass on Earth was 80 kg, what would his mass have been on the moon? [Figure 3] | text | null |
L_0984 | plasma | T_4721 | The amount of space matter takes up is its volume. How the volume of matter is measured depends on its state. The volume of liquids is measured with measuring containers. In the kitchen, liquid volume is usually measured with measuring cups or spoons. In the lab, liquid volume is measured with containers such as graduated cylinders. Units in the metric system for liquid volume include liters (L) and milliliters (mL). The volume of gases depends on the volume of their container. Thats because gases expand to fill whatever space is available to them. For example, as you drink water from a bottle, air rushes in to take the place of the water. An "empty" liter bottle actually holds a liter of air. How could you find the volume of air in an "empty" room? The volume of regularly shaped solids can be calculated from their dimensions. For example, the volume of a rectangular solid is the product of its length, width, and height (l x w x h). For solids that have irregular shapes, the displacement method is used. You can see how it works in the video below. The SI unit for solid volumes is cubic meters (m3 ). However, cubic centimeters (cm3 ) are often used for smaller volume measurements. The displacement method is used to find the volume of irregularly shaped objects. It measures the amount of water that the object displaces, or moves out of the way. What is the volume of the toy dinosaur in mL? [See Figure ??] Click image to the left or use the URL below. URL: Q: How could you find the volume of air in an otherwise empty room? A: If the room has a regular shape, you could calculate its volume from its dimensions. For example, the volume of a rectangular room can be calculated with this formula: Volume = length width height If the length of the room is 5.0 meters, the width is 3.0 meters, and the height is 2.5 meters, then the volume of the room is: Volume = 5.0 m 3.0 m 2.5 m = 37.5 m3 Q: What is the volume of the dinosaur in the diagram above? A: The volume of the water alone is 4.8 mL. The volume of the water and dinosaur together is 5.6 mL. Therefore, the volume of the dinosaur alone is 5.6 mL - 4.8 mL = 0.8 mL. | text | null |
L_0984 | plasma | T_4722 | Density is also an important physical property of matter. The concept of density combines what we know about an objects mass and volume. Density reflects how closely packed the particles of matter are. When particles are packed together more tightly, matter is more dense. Differences in density of matter explain many phenomena. It explains why helium balloons rise. It explains why currents such as the Gulf Stream flow through the oceans. It explains why some things float in or sink. You can see this in action by pouring vegetable oil into water. You can see a colorful demonstration in this video. Click image to the left or use the URL below. URL: To better understand density, think about a bowling ball and volleyball, pictured in the Figure 1.1. Imagine lifting each ball. The two balls have about the same volume. The bowling ball feels much heavier than the volleyball, but why? It is because the bowling ball is made of solid plastic. Plastic contains a lot of tightly packed particles of matter. In contrast, the volleyball is full of a gas (air). The air atoms are further apart than in the solid bowling ball. Therefore, the matter inside the bowling ball is more dense than the matter inside the volleyball. Q: If you ever went bowling, you may have noticed that all the bowling balls are the same size. This means they have the same volume. Even though they are the same size, some bowling balls feel heavier than others. How can this be? A: Bowling balls that feel lighter are made of matter that is less dense. | text | null |
L_0984 | plasma | T_4723 | The density of matter is actually the amount of matter in a given space. The amount of matter is measured by its mass. The space matter takes up is measured by its volume. Therefore, the density of matter can be calculated with this formula: Density = mass volume Assume, for example, that a book has a mass of 500 g and a volume of 1000 cm3 . Then the density of the book is: Density = 500 g = 0.5 g/cm3 1000 cm3 Q: What is the density of a liquid that has a volume of 30 mL and a mass of 300 g? A: The density of the liquid is: Density = 300 g = 10 g/mL 30 mL | text | null |
L_0984 | plasma | T_4724 | By clicking a link below, you will leave the CK-12 site and open an external site in a new tab. This page will remain open in the original tab. | text | null |
L_0993 | properties of solutions | T_4756 | Salt water in the ocean is a solution. In a solution, one substance, called the solute, dissolves in another substance, called the solvent. In ocean water, salt is the solute and water is the solvent. When a solute dissolves in a solvent, it changes the physical properties of the solvent. In particular, the solute generally lowers the freezing point of the solvent, which is called freezing point depression, and raises the boiling point of the solvent, which is called boiling point elevation. For example, adding either salt to water lowers the freezing point and raises the boiling point of the water. | text | null |
L_0993 | properties of solutions | T_4757 | Pure water freezes at 0 C, but the salt water in the ocean freezes at -2.2 C because of freezing point depression. We take advantage of the freezing point depression of salt in water by putting salt on ice to melt it. Thats why the truck in the Figure 1.1 is spreading salt on an icy road. Did you ever see anyone add a fluid to their car radiator? The fluid might be antifreeze, like in the Figure 1.2. Antifreeze lowers the temperature of the water in the car radiator so it wont freeze, even when the temperature falls far below 0 C. For example, a 50 percent antifreeze solution wont freeze unless the temperature goes below -37 C. | text | null |
L_0993 | properties of solutions | T_4757 | Pure water freezes at 0 C, but the salt water in the ocean freezes at -2.2 C because of freezing point depression. We take advantage of the freezing point depression of salt in water by putting salt on ice to melt it. Thats why the truck in the Figure 1.1 is spreading salt on an icy road. Did you ever see anyone add a fluid to their car radiator? The fluid might be antifreeze, like in the Figure 1.2. Antifreeze lowers the temperature of the water in the car radiator so it wont freeze, even when the temperature falls far below 0 C. For example, a 50 percent antifreeze solution wont freeze unless the temperature goes below -37 C. | text | null |
L_0993 | properties of solutions | T_4758 | Antifreeze could also be called antiboil because it also raises the boiling point of the water in a car radiator. Hot weather combined with a hot engine can easily raise the temperature of the water in the radiator above 100 C, which is the boiling point of pure water. If the water boils, it could cause the engine to overheat and become seriously damaged. However, if antifreeze has been added to the water, the boiling point is much higher. For example a 50 percent antifreeze solution has a boiling point of 129 C. Unless the water gets hotter than this, it wont boil and ruin the engine. | text | null |
L_1001 | rate of dissolving | T_4782 | Did you ever get impatient and start drinking a sweetened drink before all the sugar has dissolved? As you drink the last few drops, you notice that some of the sugar is sitting on the bottom of the container. Q: What could you do to dissolve the sugar faster? A: The rate of dissolving is influenced by several factors, including stirring, temperature of solvent, and size of solute particles. | text | null |
L_1001 | rate of dissolving | T_4783 | Stirring a solute into a solvent speeds up the rate of dissolving because it helps distribute the solute particles throughout the solvent. For example, when you add sugar to iced tea and then stir the tea, the sugar will dissolve faster. If you dont stir the iced tea, the sugar may eventually dissolve, but it will take much longer. | text | null |
L_1001 | rate of dissolving | T_4784 | The temperature of the solvent is another factor that affects how fast a solute dissolves. Generally, a solute dissolves faster in a warmer solvent than it does in a cooler solvent because particles have more energy of movement. For example, if you add the same amount of sugar to a cup of hot tea and a cup of iced tea, the sugar will dissolve faster in the hot tea. | text | null |
L_1001 | rate of dissolving | T_4785 | A third factor that affects the rate of dissolving is the size of solute particles. For a given amount of solute, smaller particles have greater surface area. With greater surface area, there can be more contact between particles of solute and solvent. For example, if you put granulated sugar in a glass of iced tea, it will dissolve more quickly than the same amount of sugar in a cube (see Figure 1.1). Thats because all those tiny particles of granulated sugar have greater total surface area than a single sugar cube. | text | null |
L_1004 | refraction | T_4791 | Physical properties of matter can be measured and observed. Physical properties can be detected with your senses . For example, they may be things that you can see, hear, smell, feel, or even taste. Q: What are some differences between snow and sand? Which senses could you use to find out the differences? A: You can see that snow and sand have a different color . You can also feel that snow is softer than sand. Both color and hardness are physical properties of matter . You can notice that ice will melt at room temperature. Sand will remain a solid at room temperature. | text | null |
L_1004 | refraction | T_4792 | Physical properties include the state of matter. We know these states as solid, liquid, or gas. Properties can also include color and odor. For example, oxygen is a gas. It is a major part of the air we breathe. It is colorless and odorless. Chlorine is also a gas. In contrast to oxygen, chlorine is greenish in color. It has a strong, sharp odor. Have you ever smelled cleaning products used around your home? If so, you have probably smelled chlorine. Another place you might smell chlorine is at a public swimming pool. The chlorine is used to kill bacteria that may grow in the water. Other physical properties include hardness, freezing, and boiling points. Some substances have the ability to dissolve in other substances. Some substances cannot be dissolved. For example, salt easily dissolves in water. Oil does not dissolve in water. Some substances may have the ability to conduct heat or electricity. Some substances resist the flow of electricity and heat. These properties are demonstrated in Figure 1.1. Can you think of other physical properties? The video below compares physical properties. | text | null |
L_1004 | refraction | T_4793 | By clicking a link below, you will leave the CK-12 site and open an external site in a new tab. This page will remain open in the original tab. | text | null |
L_1010 | saturation | T_4809 | The maximum amount of sugar that will dissolve in a liter of 20 C water is 2000 grams. A sugar-water solution that contains 1 liter of water and 2000 grams of sugar is said to be saturated. A saturated solution is a solution that contains as much solute as can dissolve in a given solvent at a given temperature. If you add more than 2000 grams of sugar to a liter of 20 C water, the extra sugar wont dissolve. On the other hand, a solution containing less than 2000 g of sugar in 1 liter of 20 C water can hold more sugar. A solution that contains less solute than can dissolve at a given temperature is called an unsaturated solution. You can learn more about saturated and unsaturated solutions by watching the video at this URL: . | text | null |
L_1010 | saturation | T_4810 | The Figure 1.1 shows the amounts of several different solutes that will dissolve in a liter of water at 20 C. As you can see from the graph, solutes vary greatly in how soluble they are in water. For example, you can dissolve almost 20 times as much sugar as baking soda in the same amount of water at this temperature. Q: Assume that a solution contains 150 grams of Epsom salt in 1 liter of water at 20 C. Is the solution saturated or unsaturated? A: A saturated solution of Epsom salt in 1 liter of 20 C water would contain 250 grams of Epsom salt. Therefore, this solution is unsaturated. It can hold another 100 grams of Epsom salt. Q: What do you think would happen if you added more than 250 grams of Epsom salt to a liter of 20 C water? A: Any Epsom salt over 250 grams would not dissolve in the solution. | text | null |
L_1015 | scientific measuring devices | T_4825 | Youve probably been using a ruler to measure length since you were in elementary school. But you may have made most of the measurements in English units of length, such as inches and feet. In science, length is most often measured in SI units, such as millimeters and centimeters. Many rulers have both types of units, one on each edge. The ruler pictured below has only SI units. It is shown here bigger than it really is so its easier to see the small lines, which measure millimeters. The large lines and numbers stand for centimeters. Count the number of small lines from the left end of the ruler (0.0). You should count 10 lines because there are 10 millimeters in a centimeter. Q: What is the length in millimeters of the red line above the metric ruler? A: The length of the red line is 32 mm. Q: What is the length of the red line in centimeters? A: The length of the red line is 3.2 cm. | text | null |
L_1015 | scientific measuring devices | T_4826 | Mass is the amount of matter in an object. Scientists often measure mass with a balance. A type of balance called a triple beam balance is pictured in Figure 1.1. To use this type of balance, follow these steps: 1. Place the object to be measured on the pan at the left side of the balance. 2. Slide the movable masses to the right until the right end of the arm is level with the balance mark. Start by moving the larger masses and then fine tune the measurement by moving the smaller masses as needed. 3. Read the three scales to determine the values of the masses that were moved to the right. Their combined mass is equal to the mass of the object. The Figure 1.2 is an enlarged version of the scales of the triple beam balance in Figure 1.1. It allows you to read the scales. The middle scale, which measures the largest movable mass, reads 300 grams. This is followed by the top scale, which reads 30 grams. The bottom scale reads 5.1 grams. Therefore, the mass of the object in the pan is 335.1 grams (300 grams + 30 grams + 5.1 grams). Q: What is the maximum mass this triple beam balance can measure? A: The maximum mass it can measure is 610 grams (500 grams + 100 grams + 10 grams). Q: What is the smallest mass this triple beam balance can measure? A: The smallest mass it can measure is one-tenth (0.1) of a gram. To measure very small masses, scientists use electronic balances, like the one in the Figure 1.3. This type of balance also makes it easier to make accurate measurements because mass is shown as a digital readout. In the picture, the balance is being used to measure the mass of a white powder on a plastic weighing tray. The mass of the tray alone would have to be measured first and then subtracted from the mass of the tray and powder together. The difference between the two masses is the mass of the powder alone. | text | null |
L_1015 | scientific measuring devices | T_4826 | Mass is the amount of matter in an object. Scientists often measure mass with a balance. A type of balance called a triple beam balance is pictured in Figure 1.1. To use this type of balance, follow these steps: 1. Place the object to be measured on the pan at the left side of the balance. 2. Slide the movable masses to the right until the right end of the arm is level with the balance mark. Start by moving the larger masses and then fine tune the measurement by moving the smaller masses as needed. 3. Read the three scales to determine the values of the masses that were moved to the right. Their combined mass is equal to the mass of the object. The Figure 1.2 is an enlarged version of the scales of the triple beam balance in Figure 1.1. It allows you to read the scales. The middle scale, which measures the largest movable mass, reads 300 grams. This is followed by the top scale, which reads 30 grams. The bottom scale reads 5.1 grams. Therefore, the mass of the object in the pan is 335.1 grams (300 grams + 30 grams + 5.1 grams). Q: What is the maximum mass this triple beam balance can measure? A: The maximum mass it can measure is 610 grams (500 grams + 100 grams + 10 grams). Q: What is the smallest mass this triple beam balance can measure? A: The smallest mass it can measure is one-tenth (0.1) of a gram. To measure very small masses, scientists use electronic balances, like the one in the Figure 1.3. This type of balance also makes it easier to make accurate measurements because mass is shown as a digital readout. In the picture, the balance is being used to measure the mass of a white powder on a plastic weighing tray. The mass of the tray alone would have to be measured first and then subtracted from the mass of the tray and powder together. The difference between the two masses is the mass of the powder alone. | text | null |
L_1015 | scientific measuring devices | T_4826 | Mass is the amount of matter in an object. Scientists often measure mass with a balance. A type of balance called a triple beam balance is pictured in Figure 1.1. To use this type of balance, follow these steps: 1. Place the object to be measured on the pan at the left side of the balance. 2. Slide the movable masses to the right until the right end of the arm is level with the balance mark. Start by moving the larger masses and then fine tune the measurement by moving the smaller masses as needed. 3. Read the three scales to determine the values of the masses that were moved to the right. Their combined mass is equal to the mass of the object. The Figure 1.2 is an enlarged version of the scales of the triple beam balance in Figure 1.1. It allows you to read the scales. The middle scale, which measures the largest movable mass, reads 300 grams. This is followed by the top scale, which reads 30 grams. The bottom scale reads 5.1 grams. Therefore, the mass of the object in the pan is 335.1 grams (300 grams + 30 grams + 5.1 grams). Q: What is the maximum mass this triple beam balance can measure? A: The maximum mass it can measure is 610 grams (500 grams + 100 grams + 10 grams). Q: What is the smallest mass this triple beam balance can measure? A: The smallest mass it can measure is one-tenth (0.1) of a gram. To measure very small masses, scientists use electronic balances, like the one in the Figure 1.3. This type of balance also makes it easier to make accurate measurements because mass is shown as a digital readout. In the picture, the balance is being used to measure the mass of a white powder on a plastic weighing tray. The mass of the tray alone would have to be measured first and then subtracted from the mass of the tray and powder together. The difference between the two masses is the mass of the powder alone. | text | null |
L_1015 | scientific measuring devices | T_4827 | At home, you might measure the volume of a liquid with a measuring cup. In science, the volume of a liquid might be measured with a graduated cylinder, like the one sketched below. The cylinder in the picture has a scale in milliliters (mL), with a maximum volume of 100 mL. Follow these steps when using a graduated cylinder to measure the volume of a liquid: 1. Place the cylinder on a level surface before adding the liquid. 2. After adding the liquid, move so your eyes are at the same level as the top of the liquid in the cylinder. 3. Read the mark on the glass that is at the lowest point of the curved surface of the liquid. This is called the meniscus. Q: What is the volume of the liquid in the graduated cylinder pictured above? A: The volume of the liquid is 67 mL. Q: What would the measurement be if you read the highest point of the curved surface of the liquid by mistake? A: The measurement would be 68 mL. | text | null |
L_1023 | series and parallel circuits | T_4844 | An electric circuit consists of at least one closed loop through which electric current can flow. Every circuit has a voltage source such as a battery and a conductor such as metal wire. A circuit may have other parts as well, such as lights and switches. In addition, a circuit may consist of one loop or two loops. | text | null |
L_1023 | series and parallel circuits | T_4845 | A circuit that consists of one loop is called a series circuit. You can see a simple series circuit below. If a series circuit is interrupted at any point in its single loop, no current can flow through the circuit and no devices in the circuit will work. In the series circuit below, if one light bulb burns out, the other light bulb wont work because it wont receive any current. Series circuits are commonly used in flashlights. Q: If one light bulb burns out in this series circuit, how can you tell which bulb it is? A: It may not be obvious, because neither bulb will light if one is burned out. You can tell which one it is only by replacing first one bulb and then the other to see which replacement results in both bulbs lighting up. | text | null |
L_1023 | series and parallel circuits | T_4846 | A circuit that has two loops is called a parallel circuit. A simple parallel circuit is sketched below. If one loop of a parallel circuit is interrupted, current can still flow through the other loop. In the parallel circuit below, if one light bulb burns out, the other light bulb will still work because current can bypass the burned-out bulb. The wiring in a house consists of parallel circuits. | text | null |
L_1026 | solenoid | T_4857 | A solenoid is a coil of wire with electric current flowing through it. You can see a solenoid in the Figure 1.1. Current flowing through the coil produces a magnetic field that has north and south poles. Click image to the left or use the URL below. URL: Q: How is a solenoid like a bar magnet? A: Like a bar magnet, a solenoid has north and south magnetic poles and is surrounded by a magnetic field. | text | null |
L_1026 | solenoid | T_4858 | Any wire with current flowing through it has a magnetic field. However, the magnetic field around a coiled wire is stronger than the magnetic field around a straight wire. Thats because each turn of the wire in the coil has its own magnetic field. Adding more turns to the coil of wire increases the strength of the field. Increasing the amount of current flowing through the coil also increases the strength of the magnetic field. | text | null |
L_1026 | solenoid | T_4859 | A solenoid is generally used to convert electromagnetic energy into motion. Solenoids are often used in devices that need a sudden burst of power to move a specific part. In addition to paintball markers, you can find solenoids in machines ranging from motor vehicles to electric dishwashers. Another device that uses solenoids is pictured in the Figure 1.2. | text | null |
L_1027 | solids | T_4860 | A snowflake is made of ice, or water in the solid state. A solid is one of four well-known states of matter. The other three states are liquid, gas, and plasma. Compared with these other states of matter, solids have particles that are much more tightly packed together. The particles are held rigidly in place by all the other particles around them so they cant slip past one another or move apart. This gives solids a fixed shape and a fixed volume. | text | null |
L_1027 | solids | T_4861 | Not all solids are alike. Some are crystalline solids; others are amorphous solids. Snowflakes are crystalline solids. Particles of crystalline solids are arranged in a regular repeating pattern, as you can see in the sketch in Figure chloride). Crystals of table salt are pictured in the Figure 1.1. Amorphous means shapeless. Particles of amorphous solids are arranged more-or-less at random and do not form crystals, as you can see in the Figure 1.2. An example of an amorphous solid is cotton candy, also shown in the Figure 1.2. Q: Look at the quartz rock and plastic bag pictured in the Figure 1.3. Which type of solid do you think each of them is? A: The quartz is a crystalline solid. Rocks are made of minerals and minerals form crystals. You can see their geometric shapes. The bag is an amorphous solid. It is made of the plastic and most plastics do not form crystals. | text | null |
L_1027 | solids | T_4861 | Not all solids are alike. Some are crystalline solids; others are amorphous solids. Snowflakes are crystalline solids. Particles of crystalline solids are arranged in a regular repeating pattern, as you can see in the sketch in Figure chloride). Crystals of table salt are pictured in the Figure 1.1. Amorphous means shapeless. Particles of amorphous solids are arranged more-or-less at random and do not form crystals, as you can see in the Figure 1.2. An example of an amorphous solid is cotton candy, also shown in the Figure 1.2. Q: Look at the quartz rock and plastic bag pictured in the Figure 1.3. Which type of solid do you think each of them is? A: The quartz is a crystalline solid. Rocks are made of minerals and minerals form crystals. You can see their geometric shapes. The bag is an amorphous solid. It is made of the plastic and most plastics do not form crystals. | text | null |
L_1027 | solids | T_4861 | Not all solids are alike. Some are crystalline solids; others are amorphous solids. Snowflakes are crystalline solids. Particles of crystalline solids are arranged in a regular repeating pattern, as you can see in the sketch in Figure chloride). Crystals of table salt are pictured in the Figure 1.1. Amorphous means shapeless. Particles of amorphous solids are arranged more-or-less at random and do not form crystals, as you can see in the Figure 1.2. An example of an amorphous solid is cotton candy, also shown in the Figure 1.2. Q: Look at the quartz rock and plastic bag pictured in the Figure 1.3. Which type of solid do you think each of them is? A: The quartz is a crystalline solid. Rocks are made of minerals and minerals form crystals. You can see their geometric shapes. The bag is an amorphous solid. It is made of the plastic and most plastics do not form crystals. | text | null |
L_1028 | solubility | T_4862 | Solubility is the amount of solute that can dissolve in a given amount of solvent at a given temperature. In a solution, the solute is the substance that dissolves, and the solvent is the substance that does the dissolving. For a given solvent, some solutes have greater solubility than others. For example, sugar is much more soluble in water than is salt. But even sugar has an upper limit on how much can dissolve. In a half liter of 20 C water, the maximum amount is 1000 grams. If you add more sugar than this, the extra sugar wont dissolve. You can compare the solubility of sugar, salt, and some other solutes in the Table 1.1. Solute Baking Soda Epsom salt Table salt Table sugar Grams of Solute that Will Dissolve in 0.5 L of Water (20 C) 48 125 180 1000 Q: How much salt do you think Rhonda added to the half-liter of water in her experiment? A: The solubility of salt is 180 grams per half liter of water at 20 C. If Rhonda had added less than 180 grams of salt to the half-liter of water, then all of it would have dissolved. Because some of the salt did not dissolve, she must have added more than 180 grams of salt to the water. | text | null |
L_1028 | solubility | T_4863 | Certain factors can change the solubility of a solute. Temperature is one such factor. How temperature affects solubility depends on the state of the solute, as you can see in the Figure 1.1. If a solute is a solid or liquid, increasing the temperature increases its solubility. For example, more sugar can dissolve in hot water than in cold water. If a solute is a gas, increasing the temperature decreases its solubility. For example, less carbon dioxide can dissolve in warm water than in cold water. The solubility of gases is also affected by pressure. Pressure is the force pushing against a given area. Increasing the pressure on a gas increases its solubility. Did you ever open a can of soda and notice how it fizzes out of the can? Soda contains dissolved carbon dioxide. Opening the can reduces the pressure on the gas in solution, so it is less soluble. As a result, some of the carbon dioxide comes out of solution and rushes into the air. Q: Which do you think will fizz more when you open it, a can of warm soda or a can of cold soda? A: A can of warm soda will fizz more because increasing the temperature decreases the solubility of a gas. Therefore, less carbon dioxide can remain dissolved in warm soda than in cold soda. | text | null |
L_1029 | solute and solvent | T_4864 | A solution forms when one substance is dissolved by another. The substance that dissolves is called the solute. The substance that dissolves it is called the solvent. The solute is present in a lesser amount that the solvent. When the solute dissolves, it separates into individual particles, which spread throughout the solvent. Q: In bronze, what are the solute and solvent? A: Because bronze consists mainly of copper, copper is the solvent and tin is the solute. The two metals are combined in a hot, molten state, but they form a solid solution at room temperature. | text | null |
L_1029 | solute and solvent | T_4865 | In the example of bronze, a solid (tin) is dissolved in another solid (copper). However, matter in any state can be the solute or solvent in a solution. For example, in a saltwater solution, a solid (salt) is dissolved in a liquid (water). The Table 1.1 describes examples of solutions consisting of solutes and solvents in various states of matter. Type of Solution: Example Gas dissolved in gas: dry air Gas dissolved in liquid: carbonated water Liquid dissolved in gas: moist air Liquid dissolved in liquid: vinegar Solid dissolved in liquid: sweet tea Solute oxygen carbon dioxide Solvent nitrogen water water acetic acid sugar air water tea | text | null |
L_1029 | solute and solvent | T_4866 | Salt isnt the only solute that dissolves in water. In fact, so many things dissolve in water that water is sometimes called the universal solvent. Water is such a good solvent because it is a very polar compound. A polar compound has positively and negatively charged ends. Solutes that are also charged are attracted to the oppositely charged ends of water molecules. This allows the water molecules to pull the solute particles apart. On the other hand, there are some substances that dont dissolve in water. Did you ever try to clean a paintbrush with water after painting with an oil-based paint? It doesnt work. Oil-based paint is nonpolar, so its particles arent charged. As a result, oil-based paint doesnt dissolve in water. (You can see how to dissolve oil-based paint in the Figure 1.1.) | text | null |
L_1029 | solute and solvent | T_4867 | These examples illustrate a general rule about solutes and solvents: like dissolves like. In other words, polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes. You can see below a students video demonstrating solutes that do and solutes that dont dissolve in water. Click image to the left or use the URL below. URL: | text | null |
L_1029 | solute and solvent | T_4868 | All solutes separate into individual particles when they dissolve, but the particles are different for ionic and covalent compounds. Ionic solutes separate into individual ions. Covalent solutes separate into individual molecules. Salt, or sodium chloride (NaCl), is an ionic compound. When it dissolves in water, it separates into positive sodium ions (Na+ ) and negative chloride ions (Cl ). You can see how this happens in the Figure 1.2. The negative oxygen ends of water molecules attract the positive sodium ions, and the positive hydrogen ends of water molecules attract the negative chloride ions. These forces of attraction pull the ions apart. The sugar glucose is a covalent compound. When sugar dissolves in water, it forms individual glucose molecules (C6 H12 O6 ). You can see how this happens in the Figure 1.3. Sugar is polar like water, so sugar molecules also have positive and negative ends. Forces of attraction between oppositely charged ends of water and sugar molecules pull individual sugar molecules away from the sugar crystal. Little by little, the sugar molecules are separated from the crystal and surrounded by water. Click image to the left or use the URL below. URL: | text | null |
L_1030 | solution concentration | T_4869 | A solution is a mixture of two or more substances in which dissolved particles are distributed evenly throughout the solution. The substance that dissolves in a solution is called the solute, and the substance that does the dissolving is called the solvent. The concentration of a solution is the amount of solute in a given amount of solution. A solution with a lot of dissolved solute has a high concentration and is called a concentrated solution. A solution with little dissolved solute has a low concentration and is called a dilute solution. | text | null |
L_1030 | solution concentration | T_4870 | The concentration of a solution represents the percentage of the solution that is the solute. You can calculate the concentration of a solution using this formula: Concentration = Mass (or volume) of Solute Mass (or volume) of Solution 100% For example, if a 100-gram solution of salt water contains 3 grams of salt, then its concentration is: Concentration = 3g 100g 100% = 3% Q: A 1000 mL container of brand A juice drink contains 250 mL of juice and 750 mL of water. A 600 mL container of brand B juice drink contains 200 mL of juice and 400 mL of water. Which brand of juice drink is more concentrated, brand A or brand B? 250 mL 1000 mL 100% = 25% 200 mL 600 mL 100% = 33% A: Concentration(A) = Concentration(B) = You can conclude that brand B is more concentrated. | text | null |
L_1031 | solutions | T_4871 | A solution is a mixture of two or more substances, but its not just any mixture. A solution is a homogeneous mixture. In a homogeneous mixture, the dissolved particles are spread evenly through the mixture. The particles of the solution are also too small to be seen or to settle out of the mixture. Click image to the left or use the URL below. URL: | text | null |
L_1031 | solutions | T_4872 | All solutions have two parts: the solute and the solvent. The solute is the substance that dissolves, and the solvent is the substance that dissolves the solute. Particles of solvent pull apart particles of solute, and the solute particles spread throughout the solvent. Salt water, such as the ocean water in the Figure 1.1, is an example of a solution. In a saltwater solution, salt is the solute and water is the solvent. Q: A scientist obtained a sample of water from the Atlantic Ocean and determined that the sample was about 3.5 percent dissolved salt. Predict the percent of dissolved salt in a sample of water from the Pacific Ocean. A: As a solution, ocean water is a homogeneous mixture. Therefore, no matter where the water sample is obtained, its composition will be about 3.5 percent dissolved salt. | text | null |
L_1031 | solutions | T_4873 | Not only salt, but many other solutes can dissolve in water. In fact, so many solutes can dissolve in water that water has been called the universal solvent. Even rocks can dissolve in water, which explains the cave that opened this article. A solute that can dissolve in a given solvent, such as water, is said to be soluble in that solvent. Conversely, a solute that cannot dissolve in a given solvent is said to be insoluble in that solvent. Although most solutes can dissolve in water, some solutes are insoluble in water. Oil is an example. Did you ever try to mix oil with water? No matter how well you mix the oil into the water, after the mixture stands for a while, the oil separates from the water and rises to the top. You can see how oil floats on ocean water in the Figure 1.2. | text | null |
L_1031 | solutions | T_4874 | Like salt water in the ocean, many solutions are normally in the liquid state. However, matter in any state can form a solution. An alloy, which is a mixture of a metal with one or more other substances, is a solid solution at room temperature. For example, the alloy bronze is a solution of copper and tin. Matter in the gaseous state can also form solutions. Q: What is an example of a gaseous solution? A: Air in the atmosphere is a gaseous solution. It is a mixture that contains mainly nitrogen and oxygen gases, with very small amounts of several other gases. The circle graph in the Figure 1.3 shows the composition of air. Oil from an oil spill floats on ocean water. Because air is a solution, it is homogeneous. In other words, no matter where you go, the air always contains the same proportion of gases that are shown in the graph. | text | null |
L_1031 | solutions | T_4874 | Like salt water in the ocean, many solutions are normally in the liquid state. However, matter in any state can form a solution. An alloy, which is a mixture of a metal with one or more other substances, is a solid solution at room temperature. For example, the alloy bronze is a solution of copper and tin. Matter in the gaseous state can also form solutions. Q: What is an example of a gaseous solution? A: Air in the atmosphere is a gaseous solution. It is a mixture that contains mainly nitrogen and oxygen gases, with very small amounts of several other gases. The circle graph in the Figure 1.3 shows the composition of air. Oil from an oil spill floats on ocean water. Because air is a solution, it is homogeneous. In other words, no matter where you go, the air always contains the same proportion of gases that are shown in the graph. | text | null |
L_1034 | specific heat | T_4883 | Specific heat is a measure of how much energy it takes to raise the temperature of a substance. It is the amount of energy (in joules) needed to raise the temperature of 1 gram of the substance by 1 C. Specific heat is a property that is specific to a given type of matter. Thats why its called specific. | text | null |
L_1034 | specific heat | T_4884 | The Table 1.1 compares the specific heat of four different substances. Metals such as iron have low specific heat. It doesnt take much energy to raise their temperature. Thats why a metal spoon heats up quickly when placed in a cup of hot coffee. Sand also has a relatively low specific heat. Water, on the other hand, has a very high specific heat. It takes a lot more energy to increase the temperature of water than sand. This explains why the sand on a beach gets hot while the water stays cool. Differences in the specific heat of water and land even affect climate. Substance iron sand wood Specific Heat (joules) 0.45 0.67 1.76 Q: Metal cooking pots and pans often have wooden handles. Can you explain why? A: Wood has a higher specific heat than metal, so it takes more energy to heat a wooden handle than a metal handle. As a result, a wooden handle would heat up more slowly and be less likely to burn your hand when you touch it. | text | null |
L_1037 | states of matter | T_4892 | The photo above represents water in three common states of matter. States of matter are different phases in which any given type of matter can exist. There are actually four well-known states of matter: solid, liquid, gas, and plasma. Plasma isnt represented in the iceberg photo, but the other three states of matter are. The iceberg itself consists of water in the solid state, and the lake consists of water in the liquid state. Q: Where is water in the gaseous state in the above photo? A: You cant see the gaseous water, but its there. It exists as water vapor in the air. Q: Water is one of the few substances that commonly exist on Earth in more than one state. Many other substances typically exist only in the solid, liquid, or gaseous state. Can you think of examples of matter that usually exists in just one of these three states? A: Just look around you and you will see many examples of matter that usually exists in the solid state. They include soil, rock, wood, metal, glass, and plastic. Examples of matter that usually exist in the liquid state include cooking oil, gasoline, and mercury, which is the only metal that commonly exists as a liquid. Examples of matter that usually exists in the gaseous state include oxygen and nitrogen, which are the chief gases in Earths atmosphere. | text | null |
L_1037 | states of matter | T_4893 | A given kind of matter has the same chemical makeup and the same chemical properties regardless of its state. Thats because state of matter is a physical property. As a result, when matter changes state, it doesnt become a different kind of substance. For example, water is still water whether it exists as ice, liquid water, or water vapor. | text | null |
L_1037 | states of matter | T_4894 | The most common states of matter on Earth are solids, liquids, and gases. How do these states of matter differ? Their properties are contrasted in the Figure 1.1. Click image to the left or use the URL below. URL: Properties of matter in different states. Q: The Figure 1.2 shows that a liquid takes the shape of its container. How could you demonstrate this? A: You could put the same volume of liquid in containers with different shapes. This is illustrated below with a beaker (left) and a graduated cylinder (right). The shape of the liquid in the beaker is short and wide like the beaker, while the shape of the liquid in the graduated cylinder is tall and narrow like that container, but each container holds the same volume of liquid. Q: How could you show that a gas spreads out to take the volume as well as the shape of its container? A: You could pump air into a bicycle tire. The tire would become firm all over as air molecules spread out to take the shape of the tire and also to occupy the entire volume of the tire. | text | null |
L_1037 | states of matter | T_4894 | The most common states of matter on Earth are solids, liquids, and gases. How do these states of matter differ? Their properties are contrasted in the Figure 1.1. Click image to the left or use the URL below. URL: Properties of matter in different states. Q: The Figure 1.2 shows that a liquid takes the shape of its container. How could you demonstrate this? A: You could put the same volume of liquid in containers with different shapes. This is illustrated below with a beaker (left) and a graduated cylinder (right). The shape of the liquid in the beaker is short and wide like the beaker, while the shape of the liquid in the graduated cylinder is tall and narrow like that container, but each container holds the same volume of liquid. Q: How could you show that a gas spreads out to take the volume as well as the shape of its container? A: You could pump air into a bicycle tire. The tire would become firm all over as air molecules spread out to take the shape of the tire and also to occupy the entire volume of the tire. | text | null |
L_1039 | sublimation | T_4898 | Solid carbon dioxide is also called dry ice. Thats because when it gets warmer and changes state, it doesnt change to a liquid by melting. Instead, it changes directly to a gas without going through the liquid state. The process in which a solid changes directly to a gas is called sublimation. It occurs when energy is added to a solid such as dry ice. Click image to the left or use the URL below. URL: Q: Alyssas mom put some mothballs in her closet in the spring to keep moths away from her wool clothes. By autumn, the mothballs were much smaller. What happened to them? A: Mothballs are made of naphthalene, a substance that undergoes sublimation at room temperature. The solid mothballs slowly changed to a gas during the summer months, explaining why they were much smaller by autumn. | text | null |
L_1039 | sublimation | T_4899 | Snow and ice may also undergo sublimation under certain conditions. This is most likely to happen where there is intense sunlight, very cold temperatures, and dry winds. These conditions are often found on mountain peaks. As snow sublimates, it gradually shrinks without any runoff of liquid water. Click image to the left or use the URL below. URL: | text | null |
L_1047 | temperature | T_4917 | No doubt you already have a good idea of what temperature is. You might say that its how warm or cool something feels. In physics, temperature is defined as the average kinetic energy of the particles of matter. When particles of matter move more quickly, they have more kinetic energy, so their temperature is higher. With a higher temperature, matter feels warmer. When particles move more slowly, they have less kinetic energy on average, so their temperature is lower. With a lower temperature, matter feels cooler. | text | null |
L_1047 | temperature | T_4918 | Many thermometers measure temperature with a liquid that expands when it gets warmer and contracts when it gets cooler. Look at the common household thermometer pictured in the Figure 1.1. The red liquid rises or falls in the glass tube as the temperature changes. Temperature is read off the scale at the height of the liquid in the tube. Q: Why does the liquid in the thermometer expand and contract when temperature changes? A: When the temperature is higher, particles of the liquid have greater kinetic energy, so they move about more and spread apart. This causes the liquid to expand. The opposite happens when the temperature is lower and particles of liquid have less kinetic energy. The particles move less and crowd closer together, causing the liquid to contract. | text | null |
L_1047 | temperature | T_4919 | The thermometer pictured in the Figure 1.1 measures temperature on two different scales: Celsius (C) and Fahrenheit (F). Although some scientists use the Celsius scale, the SI scale for measuring temperature is the Kelvin scale. If you live in the U.S., you are probably most familiar with the Fahrenheit scale. The Table 1.1 compares all three temperature scales. Each scale uses as reference points the freezing and boiling points of water. Notice that temperatures on the Kelvin scale are not given in degrees ( ). Scale Kelvin Celsius Fahrenheit Freezing Point of Water 273 K 0 C 32 F Boiling Point of Water 373 K 100 C 212 F Because all three temperature scales are frequently used, its useful to know how to convert temperatures from one scale to another. Its easy to convert temperatures between the Kelvin and Celsius scales. Each 1-degree change on the Kelvin scale is equal to a 1-degree change on the Celsius scale. Therefore, to convert a temperature from Celsius to Kelvin, just add 273 to the Celsius temperature. For example, 10 C equals 283 Kelvin. Q: How would you convert a temperature from Kelvin to Celsius? A: You would subtract 273 from the Kelvin temperature. For example, a temperature of 300 Kevin equals 27 C. Converting between Celsius and Fahrenheit is more complicated. The following conversion factors can be used: Celsius Fahrenheit: ( C 1.8) + 32 = F Fahrenheit Celsius: ( F - 32) 1.8 = C 3. Assume that the temperature outside is 293 Kelvin but youre familiar only with the Fahrenheit scale. Do you need to wear a hat and gloves when you go outside? To find out, convert the Kelvin temperature to Fahrenheit. (Hint: Convert the Kelvin temperature to Celsius first.) | text | null |
L_0001 | the nature of science | T_0001 | The scientific method is a set of steps that help us to answer questions. When we use logical steps and control the number of things that can be changed, we get better answers. As we test our ideas, we may come up with more questions. The basic sequence of steps followed in the scientific method is illustrated in Figure 1.1. | text | null |
L_0001 | the nature of science | T_0002 | Asking a question is one really good way to begin to learn about the natural world. You might have seen something that makes you curious. You might want to know what to change to produce a better result. Lets say a farmer is having an erosion problem. She wants to keep more soil on her farm. The farmer learns that a farming method called no-till farming allows farmers to plant seeds without plowing the land. She wonders if planting seeds without plowing will reduce the erosion problem and help keep more soil on her farmland. Her question is this: Will using the no-till method of farming help me to lose less soil on my farm? (Figure 1.2). | text | null |
L_0001 | the nature of science | T_0002 | Asking a question is one really good way to begin to learn about the natural world. You might have seen something that makes you curious. You might want to know what to change to produce a better result. Lets say a farmer is having an erosion problem. She wants to keep more soil on her farm. The farmer learns that a farming method called no-till farming allows farmers to plant seeds without plowing the land. She wonders if planting seeds without plowing will reduce the erosion problem and help keep more soil on her farmland. Her question is this: Will using the no-till method of farming help me to lose less soil on my farm? (Figure 1.2). | text | null |
L_0001 | the nature of science | T_0003 | Before she begins, the farmer needs to learn more about this farming method. She can look up information in books and magazines in the library. She may also search the Internet. A good way for her to learn is to talk to people who have tried this way of farming. She can use all of this information to figure out how she is going to test her question about no-till farming. Farming machines are shown in the Figure 1.3. | text | null |
L_0001 | the nature of science | T_0004 | After doing the research, the farmer will try to answer the question. She might think, If I dont plow my fields, I will lose less soil than if I do plow the fields. Plowing disrupts the soil and breaks up roots that help hold soil in place. This answer to her question is a hypothesis. A hypothesis is a reasonable explanation. A hypothesis can be tested. It may be the right answer, it may be a wrong answer, but it must be testable. Once she has a hypothesis, the next step is to do experiments to test the hypothesis. A hypothesis can be proved or disproved by testing. If a hypothesis is repeatedly tested and shown to be true, then scientists call it a theory. | text | null |
L_0001 | the nature of science | T_0005 | When we design experiments, we choose just one thing to change. The thing we change is called the independent variable. In the example, the farmer chooses two fields and then changes only one thing between them. She changes how she plows her fields. One field will be tilled and one will not. Everything else will be the same on both fields: the type of crop she grows, the amount of water and fertilizer that she uses, and the slope of the fields she plants on. The fields should be facing the same direction to get about the same amount of sunlight. These are the experimental controls. If the farmer only changes how she plows her fields, she can see the impact of the one change. After the experiment is complete, scientists then measure the result. The farmer measures how much soil is lost from each field. This is the dependent variable. How much soil is lost from each field depends on the plowing method. | text | null |
L_0001 | the nature of science | T_0006 | During an experiment, a scientist collects data. The data might be measurements, like the farmer is taking in Figure labeled. Labeling helps the scientist to know what each number represents. A scientist may also write descriptions of what happened during the experiment. At the end of the experiment the scientist studies the data. The scientist may create a graph or drawing to show the data. If the scientist can picture the data the results may be easier to understand. Then it is easier to draw logical conclusions. Even if the scientist is really careful it is possible to make a mistake. One kind of mistake is with the equipment. For example, an electronic balance may always measure one gram high. To fix this, the balance should be adjusted. If it cant be adjusted, each measurement should be corrected. A mistake can come if a measurement is hard to make. For example, the scientist may stop a stopwatch too soon or too late. To fix this, the scientist should run the experiment many times and make many measurements. The average of the measurements will be the accurate answer. Sometimes the result from one experiment is very different from the other results. If one data point is really different, it may be thrown out. It is likely a mistake was made in that experiment. | text | null |
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