Unit+2+-+Classification+of+Matter

1) Which of the following can be best classified as a homogeneous mixture. a. Veggie soup b. copper wire c. pizza d. hot tea

2) Which of the following statements about compounds is true? a. A compound contains only one element. b. A compound can be classified as either heterogeneous or homogeneous. c. A compound has a defined ratio by mass of the elements that it contains. d. A compound varies in chemical composition depending on the sample size.

3) Which of the follow is an element? a. BaCl2 b. CO c. He d. NaOH

4) Which of the following is an endothermic physical change? a. An explosion b. Melting of butter c. Condensation of a gas d. Formation of a solid when two liquids are mixed

5) Every chemical change involves a. The formation of a different substance b. The vaporization of a liquid c. Separation of states of matter d. The release of energy.

6) What law is described by the fact that carbon dioxide (CO2) consists of 27.3% C and 72.7% O by mass? a. Law of Conservation of Mass b. Law of Definite Proportions c. Law of Multiple Proportions d. None of the laws we learned

7) What law supports the idea that carbon dioxide (CO2) and carbon monoxide (CO) can both be formed under given laboratory settings? a. Law of Conservation of Mass b. Law of Definite Proportions c. Law of Multiple Proportions d. None of the laws we learned

8) If 5.235 g of S and 5.314 g of O2 react to form sulfur dioxide (SO2), how much sulfur dioxide (SO2) will be formed? a. 5.235 g SO2 b. 5.314 g SO2 c. 0.079 g SO2 d. 10.549 g SO2

Answers to the questions: 1) d. Hot Tea it is uniform throughout 2) d. varies in chemical composition depending on size the others are false 3) c. He it is the only element 4) d. formation of a solid when two liquids are mixed energy is going into it 5) a. the formation of a different substance chemical reactions make a new substance 6) b. law of definite proportion a pure compound will always have the same elements, and in the same proportion and mass 7) D. The Law of Multiple Proportions When two elements combine to form more than one compound, the mass of element A which combines in the first compound with a given amount of element B has a simple whole number ratio with the mass of element A which combines in the second compound with the same given mass of element B. This sounds confusing, but an example clarifies this statement. Consider the carbon oxides, and let carbon be element B and oxygen be element A. Take a fixed given mass of carbon (element B), say 1 gram. The mass of oxygen which combines with 1 gram of carbon to form the first oxide is 1.33 grams. The mass of oxygen which combines with 1 gram of carbon to form the second oxide is 2.66. These masses are in ratio 2.66:1.33=2:1, a simple whole number ratio. In explaining our observations of the Law of Multiple Proportions for the carbon oxides and the nitrogen oxides, we have concluded that the simple mass ratio arises from the simple ratio of atoms contained in the individual molecules

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