Q: What is the transfer of heat by a current?   Read this paragraph and choose the correct option from the provided answers:  Convection is the transfer of heat by a current. Convection happens in a liquid or a gas. Air near the ground is warmed by heat radiating from Earth's surface. The warm air is less dense, so it rises. As it rises, it cools. The cool air is dense, so it sinks to the surface. This creates a convection current, like the one in Figure below . Convection is the most important way that heat travels in the atmosphere.   Choices:  - radiation  - combustion  - diffusion  - convection   A:
convection

Q: What layer of earth contains abundant oxygen, which can combine with other elements to create oxide minerals?   Read this paragraph and choose the correct option from the provided answers:  Earth’s crust contains a lot of oxygen. The oxygen can combine with other elements to create oxide minerals. Oxides contain one or two metal elements combined with oxygen. Oxides are different from silicates, because they do not contain silicon. Many important metals are found as oxides. For example, hematite and magnetite are both oxides that contain iron. Hematite (Fe 2 O 3 ) has a ratio of two iron atoms to three oxygen atoms. Magnetite (Fe 3 O 4 ) has a ratio of three iron atoms to four oxygen atoms. Notice that the word “magnetite” contains the word “magnet. " Magnetite ( Figure below ) is a magnetic mineral.   Choices:  - the core  - the surface  - the tectonic plates  - the crust   A:
the crust

Q: What do you call the electrons in the outermost energy level of an atom?   Read this paragraph and choose the correct option from the provided answers:  Electrons in the outermost energy level of an atom are called valence electrons. They determine many of the properties of an atom, including how reactive it is.   Choices:  - Inner electrons  - shell electrons  - Proper electrons  - valence electrons   A:
valence electrons

Q: Snippet 2: one of the reasons the periodic table is so useful is because its structure allows us to qualitatively determine how some properties of the elements vary versus their position on the periodic table. the variation of properties versus position on the periodic table is called what?   Read this paragraph and choose the correct option from the provided answers:  One of the reasons the periodic table is so useful is because its structure allows us to qualitatively determine how some properties of the elements vary versus their position on the periodic table. The variation of properties versus position on the periodic table is called periodic trends. There is no other tool in science that allows us to judge relative properties of a class of objects like this, which makes the periodic table a very useful tool. Many periodic trends are general. There may be a few points where an opposite trend is seen, but there is an overall trend when considered across a whole row or down a whole column of the periodic table. The first periodic trend we will consider atomic radius. The atomic radius is an indication of the size of an atom. Although the concept of a definite radius of an atom is a bit fuzzy, atoms behave as if they have a certain radius. Such radii can be estimated from various experimental techniques, such as the x-ray crystallography of crystals. As you go down a column of the periodic table, the atomic radii increase. This is because the valence electron shell is getting a larger and there is a larger principal quantum number, so the valence shell lies physically farther away from the nucleus. This trend can be summarized as follows:.   Choices:  - chemical trends  - gravity trends  - acoustic trends  - periodic trends   A:
