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. 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 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.) 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: 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:
when covalent compounds dissolve, they separate into individual