Topic 5; Energy Changes

Question 1

What is the conservation of energy principle?

Answer 1

Energy is conserved in chemical reactions.

Amount of energy at end of reaction is same as before reaction

Question 2

What is an exothermic reaction (and examples)

Answer 2

Reaction where energy is transferred to surroundings so the surroundings temp increases
Combustion, oxidation reactions, neutralisation
Negative energy charge

Question 3

What is an endothermic reaction? (Give examples)

Answer 3

Energy taken from surroundings so surroundings temp decreases
Thermal decomposition
Positive sign of energy change

Question 4

What is activation energy?

Answer 4

Minimum amount of energy that particles need to react

Question 5

What is a reaction profile?

Answer 5

Graph shows relative energies of reactant and products

Question 6

What occurs in chemical reactions of terms of bond energies?

Answer 6

Energy supplied to break bonds and released to make bonds
Exothermic- energy released from forming bonds is greater than that needed to break bonds
Endothermic- energy needed to bream bonds greater than that released when making them

Question 7

What is the equation to find energy change in terms of bond energies?

Answer 7

Energy of reaction= sum of broken bonds- sum of bonds made

Question 8

What is a cell?

Answer 8

Two electrodes dipped in an electrolyte solution. Produces electricity from a chemical reaction

Question 9

What is a battery?

Answer 9

Two or more cells connected in series