Energy Changes

Question 1

define an exothermic reaction

Answer 1

• one in which heat energy is given off to the surroundings

- heat energy is given off to the surroundings thus, the container feels hot as the temperature increases

Question 2

what are some examples involving physical changes of an exothermic reaction?

Answer 2

• freezing
• condensation
• dissolving sodium hydroxide in water

Question 3

what are some examples of chemical changes involving an exothermic reaction?

Answer 3

• combustion
• neutralisation
• respiration

Question 4

what is combustion?

Answer 4

fuel reacts with oxygen

Question 5

what is neutralisation?

Answer 5

acid reacts with alkali

Question 6

what is respiration?

Answer 6

‘slow combustion in our bodies’

Question 7

what is the chemical equation of respiration?

Answer 7

C6H12O6 + 6CO2 -> 6CO2 + 6H2O

Question 8

define an endothermic reaction

Answer 8

• one in which heat energy is taken in from the surroundings
• heat energy is absorbed from the surroundings, thus the container feels cold as the temperature decreases

Question 9

what are some examples of physical changes involving endothermic reactions?

Answer 9

• melting
• boiling
• sublimation
• dissolving ammonium nitrate, ammonium chloride in water

Question 10

what are some examples of chemical changes involving endothermic reactions?

Answer 10

• thermal decomposition

- photosynthesis

Question 11

what is the chemical equation for thermal decomposition?

Answer 11

CaCO3 -> CaO + CO2

Question 12

what is the chemical equation for photosynthesis?

Answer 12

6CO2 + 6H2O -> C6H12O6 + 6O2