Question

1. ____ cacl₂ is an example of

a. a phase
b. an element
c. a metal
d. a compound

1. ____ which statement is not a description of a chemical reaction?

a. a solid is dropped into a beaker of liquid and a gas is released.
b. two liquids are mixed in a beaker and the color of the liquids changes and a solid forms at the bottom of the beaker.
c. a solid is dropped into a beaker of liquid and an explosion occurs.
d. a liquid is heated on a bunsen burner and its temperature rises.

1. ____ suppose you pour nitric acid on some copper powder in a test tube. a brown gas is produced and a light blue liquid is all that remains in the test tube. what happened to the copper atoms?

a. they escaped as part of a brown gas.
b. they were destroyed by the acid.
c. they are now in the light blue liquid as copper compounds that contain copper atoms.
d. they became a different element entirely.

1. ____ the copper cycle, shown below, is a demonstration of what principle of chemistry?

a. elements exist as gases, liquids, or solids.
b. mass is conserved in chemical reactions.
c. metals are excellent conductors.
d. most elements are metallic solids.
znso₄(aq) → cu(s) hno₃(aq)
zn(s) → no₂(g)
cuso₄(aq) cu(no₃)₂(aq)
h₂so₄(aq) → cuo(s) naoh(aq)
cu(oh)₂(s)
heat and filter

Explanation:

1. A compound is a substance made up of two or more different elements chemically combined. CaCl₂ is composed of calcium (Ca) and chlorine (Cl) elements, so it is a compound.
2. A chemical reaction involves a change in the chemical composition of substances. Heating a liquid to raise its temperature is a physical change (change in state or temperature without changing the chemical identity), not a chemical reaction.
3. When copper powder reacts with nitric acid, a chemical reaction occurs. Copper atoms are incorporated into new copper - containing compounds in the light - blue liquid. Atoms are conserved in chemical reactions and do not escape as part of the gas, are not destroyed, and do not change into a different element.
4. The copper cycle shows a series of chemical reactions where copper undergoes various transformations but the amount of copper remains the same throughout. This demonstrates the law of conservation of mass in chemical reactions.

Answer:

1. D. a compound
2. D. A liquid is heated on a Bunsen burner and its temperature rises.
3. C. They are now in the light blue liquid as copper compounds that contain copper atoms.
4. B. Mass is conserved in chemical reactions.