Topic 5-Energy Changes

Question 1

What is an exothermic reaction?

Answer 1

A reaction which transfers heat to the surroundings, usually be heating

Question 2

How is an exothermic reaction represented?

Answer 2

A rise in temperature

Question 3

Name 3 examples of exothermic reactions?

Answer 3

-Combustion (burning fuels)
- Neutralisation reactions
- Oxidation reactions

Question 4

Give an example of an oxidation reaction?

Answer 4

Adding sodium to water, the reaction energy and the sodium moves about on the water as it is oxidised

Question 5

Explain 2 everyday uses of Endothermic reactions?

Answer 5

-Some Hand warmers- use the exothermic oxidation of iron in air (with a salt solution catalyst) to release energy
Self heating cans- of hot chocolate and coffee also rely on exothermic reactions between chemicals in their bases

Question 6

Explain how energy is moved around in reactions?

Answer 6

• Different chemicals store different amounts of energy
• Products and reactants may have different amounts of energy either because some as transferred to or from the surroundings
  energy cannot be created or destroyed, it only moves around

Question 7

What is an endothermic reaction?

Answer 7

a reaction that takes in energy from the surroundings

Question 8

What is an endothermic reaction represented by?

Answer 8

A fall in temperature

Question 9

Give 2 examples of endothermic reactions

Answer 9

-The reaction of citric acid and sodium hydrogencarbonate
- Thermal decomposition

Question 10

Give an example of a thermal decomposition reaction

Answer 10

Heating calcium carbonate causes it to decompose into quicklime (calcium oxide) and carbon dioxide

Question 11

What is an everyday use of endothermic reactions?

Answer 11

Sports injury packs- the chemical reaction allows the pack to become instantly cooler without having to put it in the freezer