Question

Tijuan mixed a solid and a liquid together in a beaker. He determined that a chemical change occurred.

If his conclusion is correct, which substances could he have been observing and why?

ice mixed into warm oil, because the change of state that occurred when the ice melted cannot be reversed
baking soda mixed into vinegar, because the production of bubbles indicates that a new substance formed
sugar mixed into hot water, because the disappearance of solid indicates that the chemical identity of the sugar changed
sand mixed into water, because when sand was added the mass of the beaker increased



Calcium carbonate (CaCO3) is a white solid with no odor. When CaCO3 is heated, the resulting substances are calcium oxide (CaO) and carbon dioxide (CO2). CaO is a white to gray solid with no odor, and CO2 is a gas with no odor and color.

Which statement describes CaCO3?

It is a diatomic molecule that can’t be broken down by physical means.
It is a diatomic molecule that can’t be broken down by chemical means.
It is a compound that can be broken down by physical means.
It is a compound that can be broken down by chemical means.



Which state of matter consists of ionized particles?

solid
liquid
gas
plasma


The diagram shows changes of state between solid, liquid, and gas. The atoms of a substance gain energy during a change of state. Before the change, the atoms are close together and cannot slide past one another. After the change, the substance can fill its container.

A diagram has a triangle at center with gas on top, liquid on bottom right, solid on bottom left. An arrow from gas to liquid is labeled O, and an arrow from liquid to gas is labeled N. An arrow from solid to liquid is labeled P, and an arrow from liquid to solid is labeled Q. An arrow from solid to gas is labeled L, and an arrow from gas to solid is labeled M.
Which arrow represents the change of state described above?

L
M
N
O

Answer 1

1) baking soda mixed into vinegar — The bubbling is CO2 gas from a chemical reaction (NaHCO3 + acetic acid), so a new substance formed.

2) It is a compound that can be broken down by chemical means — CaCO3 decomposes on heating to CaO and CO2 (a chemical change).

3) plasma — Plasma consists of ionized particles.

4) L — Arrow L is solid → gas (sublimation); the substance gains energy and goes from tightly packed solid to a gas that fills its container.