Answer the following question given this paragraph: Crystallization separates mixtures based on differences in solubility, a measure of how much solid substance remains dissolved in a given amount of a specified liquid. Most substances are more soluble at higher temperatures, so a mixture of two or more substances can be dissolved at an elevated temperature and then allowed to cool slowly. Alternatively, the liquid, called the solvent, may be allowed to evaporate. In either case, the least soluble of the dissolved substances, the one that is least likely to remain in solution, usually forms crystals first, and these crystals can be removed from the remaining solution by filtration. Figure 1.9 "The Crystallization of Sodium Acetate from a Concentrated Solution of Sodium Acetate in Water" dramatically illustrates the process of crystallization. Most mixtures can be separated into pure substances, which may be either elements or compounds. An element, such as gray, metallic sodium, is a substance that cannot be broken down into simpler ones by chemical changes; a compound, such as white, crystalline sodium chloride, contains two or more elements and has chemical and physical properties that are usually different from those of the elements of which it is composed. With only a few exceptions, a particular compound has the same elemental composition (the same elements in the same proportions) regardless of its source or history. The chemical composition of a substance is altered in a process called achemical change. The conversion of two or more elements, such as sodium and chlorine, to a chemical compound, sodium chloride, is an example of a chemical change, often called a chemical reaction. Currently, about 115 elements are known, but millions of chemical compounds have been prepared from these 115 elements. The known elements are listed in the periodic table (see Chapter 32 "Appendix H: Periodic Table of Elements"). In general, a reverse chemical process breaks down compounds into their elements. For example, water (a compound) can be decomposed into hydrogen and... Q: Crystallization separates mixtures based on differences in what, which usually increases with temperature? Choices: - density - viscosity - humidity - solubility A:
solubility

Answer the following question given this paragraph: Mass can be destroyed to release energy. We do not ordinarily notice the increase or decrease in mass of an object because the change in mass is so small for a large increase in energy. The relativistic work-energy theorem is W net = E E 0 = mc 2 mc 2 = 1mc 2 . Relativistically,. Q: Mass can be destroyed to release what? Choices: - acceleration - mass - velocity - energy A:
energy

Answer the following question given this paragraph: You can see several examples of people or things in motion in Figure below . You can probably think of many other examples. You know from experience what motion is, so it may seem like a straightforward concept. Motion can also be defined simply, as a change in position. But if you think about examples of motion in more depth, you'll find that the idea of motion is not quite as simple and straightforward as it seems. Q: What can be defined simply, as a change in position? Choices: - velocity - gravity - speed - motion A:
motion

Answer the following question given this paragraph: Some solutes, such as sodium acetate, do not recrystallize easily. Suppose an exactly saturated solution of sodium acetate is prepared at 50C. As it cools back to room temperature, no crystals appear in the solution, even though the solubility of sodium acetate is lower at room temperature. A supersaturated solution is a solution that contains more than the maximum amount of solute that is capable of being dissolved at a given temperature. The recrystallization of the excess dissolved solute in a supersaturated solution can be initiated by the addition of a tiny crystal of solute, called a seed crystal. The seed crystal provides a nucleation site on which the excess dissolved crystals can begin to grow. Recrystallization from a supersaturated solution is typically very fast. Q: What is used to recrystallize excess dissolved solute in a supersaturated solution? Choices: - starter crystal - energy crystal - fertilizer crystal - seed crystal A:
seed crystal