8. A reaction that produces heat is an endothermic reaction.

Question

A) True
B) False

9. The chemical equation for the reaction between magnesium (Mg) and hydrochloric acid (HCl) is shown.
Mg + 2HCl → MgCl2 + H2
Fiona weighs the magnesium and hydrochloric acid before the reaction and finds a total mass of 55 grams. After the reaction, she measures the mass of the products, magnesium chloride (MgCl2) and hydrogen (H2), and finds a total mass of 55 grams again. Does Fiona's data support the law of conservation of matter, and why?

a
Yes, because the mass of the reactants is the same as the mass of the products in her data.
b
No, because the mass of the reactants is lower than the mass of the products in her data.
c
No, because the mass of the reactants is the same as the mass of the products in her data.
d
Yes, because the mass of the reactants is lower than the mass of the products in her data.

10. What would happen if a scuba tank (a rigid, sealed gas cylinder) heats up?
a
The pressure exerted by the gas in the tank would increase.
b
The size of the gas particles in the tank would increase.
c
The density of the gas in the tank would increase.
d
The number of particles in the tank would increase.

11. Classify each change listed below as either a chemical or physical change in matter.

Column A
1. Liquid water boiling and becoming steam
2. Silver metal tarnishing and becoming silver sulfide.
3. Paper burning
4. Bending copper wire
5. Dissolving salt in water
6. Iron rusting to become iron oxide.
Column B
a. Chemical Change
b. Physical Change

12. Determine whether the statement is true or false.
Is this chemical reaction balanced:
1N2 + 3H2 - 2NH3

Answer 1

Here are the answers to your questions:

8. A reaction that produces heat is an endothermic reaction.

• B) False (A reaction that produces heat is an exothermic reaction. An endothermic reaction absorbs heat.)

9. Does Fiona's data support the law of conservation of matter, and why?

• a Yes, because the mass of the reactants is the same as the mass of the products in her data. (The law of conservation of matter states that mass is neither created nor destroyed in a chemical reaction.)

10. What would happen if a scuba tank (a rigid, sealed gas cylinder) heats up?

• a The pressure exerted by the gas in the tank would increase. (According to the gas laws, increasing the temperature of a gas in a rigid container increases its pressure because the gas particles move more quickly and collide with the walls of the container more forcefully.)

11. Classify each change listed below as either a chemical or physical change in matter.

| Change | Classification | |------------------------------------------------|------------------------| | 1. Liquid water boiling and becoming steam | b. Physical Change | | 2. Silver metal tarnishing and becoming silver sulfide | a. Chemical Change | | 3. Paper burning | a. Chemical Change | | 4. Bending copper wire | b. Physical Change | | 5. Dissolving salt in water | b. Physical Change | | 6. Iron rusting to become iron oxide | a. Chemical Change |

12. Is this chemical reaction balanced: 1N2 + 3H2 → 2NH3?

• True (The equation is balanced because there are 2 nitrogen atoms and 6 hydrogen atoms on both sides of the equation.)