Chemical reactions test review

Chemical Reactions
Test Review

Every substance has characteristic properties that can be used to identify that substance.

When some substances are combined, they undergo a chemical reaction, or chemical change, that forms a new substance.

The appearance of a new substance with new properties provides evidence of a chemical reaction.

Evidence of Chemical Reactions

Multiple Choice

Which of the following shows signs of a chemical reaction?

• 1. a colorless liquid and a gray solid are mixed to produce a gas and a green liquid.

• 1. large brown rocks are ground into smaller pieces to produce a brown powder.

Multiple Choice

A student pours two different liquids into a glass beaker.Which of the following would indicate that a chemical reaction occurred between the two liquids?

• 1. an increase in total mass of the liquids.

• 1. a decrease in total volume of the liquids.

• 1. the formation of a solid in the beaker.

• 1. the complete mixing of the two liquids.

Multiple Choice

Which of the following is an example of a chemical process?

• 1. cutting a piece of wood into small wood chips

• 1. burning a marshmallow

• 1. dissolving table salt in a glass of water

• 1. boiling water turning into steam

Some of the signs that provide evidence that new substances have formed due to a chemical reaction are:

• bubbling or fizzing,

• formation of a precipitate, and

• color change.

• absorption or release of energy (ex: temperature change).

Evidence of Chemical Reactions

Multiple Choice

5. Which of the following statements is correct?

• In a chemical reaction, the total mass of the products is more than the total mass of the reactants.

• In a chemical reaction, the total mass of the products is less than the total mass of the reactants.

• In a chemical reaction, the total mass of the products is equal to the total mass of the reactants.

• 2. In a chemical reaction, the total mass of the products is unrelated to the total mass of the reactants.

Multiple Choice

5. Which of the following is an example of using a chemical process to release energy?

• 1. cutting wood into small wood chips

• 1. dissolving copper chloride powder in a beaker of water

• 1. using a battery to power a flashlight

• 1. heating an ice cube to melt it

Multiple Choice

9. When an endothermic chemical reaction absorbs thermal energy from the environment,

• 1. there is no change in temperature, but there is a change in state.

• 1. the temperature of the products is higher than the temperature of the reactants.

• 1. the temperature of the products is lower than the temperature of the reactants.

• 1. the temperature of the products is the same as the temperature of the reactants.

Chemical changes are differentiated from physical changes by the fact that physical changes do not produce new substances. Physical changes include changes in state, such as the change from solid to liquid or liquid to gas, and the process of dissolving.

Chemical Change vs. Physical Change

Multiple Choice

Cracker and digestive substances: solid changed to a gas and water, and released energy.

• Chemical change

• Physical Change

Multiple Choice

Powdered drink mix added to water: The sugar and food coloring are just mixing into the water.

• Chemical change

• Physical Change

Multiple Choice

Epoxy hardens: Two liquids combine to form a solid, and heat is released.

• Chemical change

• Physical Change

Multiple Choice

Car burns gasoline: The starting liquid and gas are very different from the final substances. For example, octane burns but water does not.

• Chemical change

• Physical Change

Multiple Choice

5. Which of the following is an example of using a chemical process to ABSORB energy?

• 1. when the substances get warmer after a reaction occurs

• 1. when the substances get colder after a reaction occurs

Multiple Choice

Ozone forms: he starting gas is clear, odorless, and breathable. The final gas is blue and toxic.

• Chemical change

• Physical Change

Multiple Choice

Puddle evaporates: The soil is still soil, wet or dry, and water and water vapor are both H2O

• Chemical change

• Physical Change

During a chemical reaction, atoms regroup into different molecules.These changes in structure cause changes in properties that you can observe or measure.

Rearrangement of Atoms in Chemical Reactions

Multiple Choice

Which one IS NOT an example of conservation of mass?

Multiple Choice

Which of the following demonstrates conservation of atoms?

Multiple Choice

Which of the following demonstrates conservation of atoms?

In contrast, physical changes affect the distances and interactions between atoms and molecules, or how they mix with other atoms and molecules, but they do not change how the atoms are grouped into molecules.

Rearrangement of Atoms

Multiple Choice

5. A reaction occurs between two liquids. Before the reaction, liquid A is clear and colorless. Liquid B clear and light blue in color.When the two liquids are combined in a closed system, a cloudy, pale green solution is formed.Which of the following describes what has occurred?

• 1. a chemical reaction where mass was conserved

• 1. a physical reaction where mass was conserved

• 1. a chemical reaction where mass was not conserved

• 1. a physical reaction where mass was not conserved

Multiple Choice

• Solid

• Liquid

• Gas

Multiple Choice

• Solid

• Liquid

• Gas

Multiple Choice

• Solid

• Liquid

• Gas

Atoms are conserved in a chemical reaction. Although atoms rearrange into new molecules, the total number and kinds of atoms in the products are the same as the number and kinds of atoms in the reactants.

Conservation of Atoms and Mass

​Since each kind of atom has a characteristic mass, the total mass before and after the reaction remains constant. This is called the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction.

Multiple Choice

What substance(s) are the reactants in the chemical equation below:

2H2(g) + O2(g) → 2H2O(l )

• H2O

• H2

• O2

• H2 and O2

Multiple Choice

What substance(s) are the products in the chemical equation below:

2H2(g) + O2(g) → 2H2O(l )

• H2O

• H2

• O2

• H2 and O2

Multiple Choice

9. A student measures out 5mL of calcium chloride solution in a small container and 5mL of sodium carbonate solution in another small container.The total mass of both chemicals and the containers they are in is 15.23g.When the student combined the two clear liquid chemicals, a gooey, cloudy precipitate formed.What would the total mass of the products and the two containers be after this reaction took place?

• 0. 15.20g

• 0. 15.23g

• 0. 15.25g

• 0. 30.46g

Multiple Choice

5. A closed system is one in which:

• 1. reactants can enter or leave, but products cannot.

• 1. reactants cannot enter or leave, but products can.

• 1. reactants and products can both enter or leave.

• 1. reactants and products cannot enter or leave.