chapter 13 - chemical energetics

Question 1

What are endothermic changes?

Answer 1

Absorb thermal energy from the surroundings and cause a decrease in temperature of the surroundings

Endothermic changes include processes that require energy input, often resulting in cooling of the environment.

Question 2

Give an example of a chemical reaction that is endothermic.

Answer 2

Thermal decomposition (e.g. heating of calcium carbonate forms carbon dioxide and calcium oxide)

This reaction absorbs heat and is a classic example of an endothermic process.

Question 3

What is photosynthesis classified as?

Answer 3

An endothermic reaction

Photosynthesis absorbs sunlight to convert carbon dioxide and water into glucose and oxygen.

Question 4

List three physical processes that are endothermic.

Answer 4

• Boiling
• Melting
• Sublimation

These processes require heat absorption to occur.

Question 5

What happens during the dissolution of some ionic compounds in water?

Answer 5

It can be an endothermic process

Examples include sodium chloride, ammonium chloride, and barium nitrate which absorb heat when dissolved.

Question 6

What are exothermic changes?

Answer 6

Release thermal energy into the surroundings and cause an increase in temperature of the surroundings

Exothermic changes are characterized by the release of heat.

Question 7

Give an example of a chemical reaction that is exothermic.

Answer 7

Combustion

Combustion reactions release heat and light, exemplifying exothermic processes.

Question 8

What is neutralisation in chemistry?

Answer 8

An exothermic reaction (e.g. reaction between hydrochloric acid and sodium hydroxide)

This reaction releases energy as heat.

Question 9

List three physical processes that are exothermic.

Answer 9

• Freezing
• Condensation
• Dissolution of acids and alkalis

These processes release heat to the surroundings.

Question 10

What is the effect of exothermic changes on the temperature of surroundings?

Answer 10

Temperature of surroundings increases

Exothermic reactions are generally characterized by the release of heat.

Question 11

What is the effect of endothermic changes on the temperature of surroundings?

Answer 11

Temperature of surroundings decreases

The absorption of heat during endothermic processes results in a cooling effect.