Topic 5 – Energy Changes

Question 1

Activation energy

Answer 1

The minimum amount of energy for particles to collide with in order for a successful reaction to occur.

Question 2

Alkaline batteries

Answer 2

Alkaline batteries are non-rechargeable. In non-rechargeable cells and
batteries the chemical reactions stop when one of the reactants has been used up.

Question 3

Battery

Answer 3

Batteries consist of two or more cells connected together in series to provide a
greater voltage.

Question 4

Chemical cells

Answer 4

Cells contain chemicals which react to produce electricity

Question 5

Endothermic reaction

Answer 5

An endothermic reaction is one that takes in energy from the
surroundings so the temperature of the surroundings decreases.

In an endothermic
reaction, the energy needed to break existing bonds is greater than the energy
released from forming new bonds.

Question 6

Exothermic reaction

Answer 6

An exothermic reaction is one that transfers energy to the
surroundings so the temperature of the surroundings increases.

In an exothermic reaction,
the energy released from forming new bonds is greater than the energy needed to
break existing bonds.

Question 7

Fuel cells

Answer 7

Fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen
or air. The fuel is oxidised electrochemically within the fuel cell to produce a potential
difference

Question 8

Overall energy change of the reaction

Answer 8

The difference between the sum of the energy
needed to break bonds in the reactants and the sum of the energy released when
bonds in the products are formed.

Question 9

Reaction profile

Answer 9

Reaction profiles can be used to show the relative energies of reactants
and products, the activation energy and the overall energy change of a reaction.

Question 10

Rechargeable cells

Answer 10

Rechargeable cells and batteries can be recharged because the
chemical reactions are reversed when an external electrical current is supplied.