Chaper 5

Question 1

Exothermic reactions

Answer 1

Transfer thermal energy to the surroundings leading to an increase in temperature of the surroundings

Question 2

Endothermic reactions

Answer 2

Takes in thermal energy from surroundings leading to a decrease in temperature of the surroundings

Question 3

Bond breaking

Answer 3

Endothermic process -> energy must be supplied to break existing bonds
- Overall enthapy change: positive -> energy used to break bonds is greater than energy released by forming them

Question 4

Bond formation

Answer 4

Exothermic process -> energy is released when new bonds are formed
- Overall enthapy change: is negative -> energy released by forming bonds is greater than energy used to break them

Question 5

Enthaply change

Answer 5

Overall amount of energy given out or taken in during a reaction

Question 6

Exothermic examples

Answer 6

Combustion
- Reacting with oxygen
Hand warmers
Self-heating cans
Neutralisation
- When acid reacts with alkali

Question 7

Endothermic examples

Answer 7

Sports injury packs
Thermal decomposition reactions
- Adding heat to make a chemical compound
Photosynthesis

Question 8

Activation energy

Answer 8

The energy required for a reaction to occur
- For a reaction to occur, particles need to collide with sufficient amount of energy. The minimum energy required to particles to react upon collision is the activation energy

Question 9

Exothermic reactions

Answer 9

• Exothermic reactions TRANSFER ENERGY to the surroundings -> so the product molecules have less energy than the reactions
• The minimum energy needed for the reaction to start
  “ Activation energy “

Question 10

Endothermic reactions

Answer 10

• Endothermic reactions take in energy from the surroundings -> so the product molecules have more energy than the reactants
• The minimum energy for the reaction to start is called the “ activation energy “