C2.4 Rates and energy

Question 1

How do you calculate reacting masses?

Answer 1

1) Find relative atomic mass (top number on periodic table)
2) Multiply relative atomic mass by the big number at the front (if one) or small number e.g. 2Ca
3) Add two new relative atomic masses together
4) Which ever substance you are working out do that number divided by the other substance then multiply number of grams given

Question 2

Define exothermic

Answer 2

Transfer energy from the reactants to the surroundings, bonds forming, energy released gets hot (gives out energy)

Question 3

Define endothermic

Answer 3

Transfer energy from surroundings to the reactants, breaks the bonds, gets cold (takes in heat)

Question 4

What is the equation for a exothermic reaction?

Answer 4

Calcium oxide + water –> calcium hydroxide

Question 5

Say whether this is endothermic or exothermic

• Fuels burning
• thermal decomposition
• Neutralisation
• Respiration

Answer 5

• Fuels burning - exothermic
• Thermal decomposition - endothermic
• Neutralisation - exothermic
• Respiration - exothermic