C5 Energy changes

State the law of conservation of energy.

• Energy cannot be created or destroyed, it can only transferred from one place to another.

• Energy can be created or destroyed, it can only transferred from one place to another.

• Energy cannot be light or sound it can only be kinetic energy moving from one place to another.

• Energy can destroyed, and then can reform to be transferred from one place to another.

How does the law of conservation of energy apply to chemistry?

• In all physical reactions, energy is either transferred to the surroundings or from the surroundings.

• In all chemical reactions, energy is either transferred to the surroundings only.

• In all chemical reactions, energy is either transferred to the surroundings or from the surroundings.

• In all physical reactions, energy is absorbed by the surroundings.

What is an exothermic reaction?

• A reaction where energy is transferred from the surroundings.

• A reaction where energy is transferred to the surroundings.

• A reaction where energy is absorbed into surroundings.

• A reaction where energy is absorbed from the surroundings.

Give two examples of exothermic reactions.

• Combustion, photosynthesis

• Decomposition, respiration

• Neutralisation, photosynthesis

• Combustion, respiration

What happens to the temperature of the surroundings during an exothermic reaction?

• They increase.

• They decrease.

• They stay the same.

What is an endothermic reaction?

• A reaction where energy is transferred from the surroundings.

• A reaction where energy is transferred to the surroundings.

• A reaction where energy is absorbed into surroundings.

• A reaction where energy is absorbed from the surroundings.

Give two examples of endothermic reactions.

• Combustion, photosynthesis

• Decomposition, respiration

• Neutralisation, photosynthesis

• Thermal decomposition reactions, citric acid and sodium hydrogencarbonate.

What happens to the temperature of the surroundings during an endothermic reaction?

• They increase.

• They decrease.

• They stay the same.

State two uses of exothermic reactions

• Self-heating cans, hand warmers

• Making fertilisers and explosives

• Fireworks, fire extinguishers

• Radiators, Air-conditioning

State uses of endothermic reactions

• Self-heating cans, hand warmers

• Some cooling sports injury packs

• Fireworks, fire extinguishers

• Radiators, Air-conditioning