C5 ENERGY CHANGES

Question 1

conservation of energy principle?

Answer 1

we can’t ‘lose’ or ‘gain’ energy: Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 2

exothermic reaction?

Answer 2

energy is transferred to the surroundings (temp increases)

Question 3

endothermic reaction?

Answer 3

energy is taken in from the surroundings (temp decreases)

Question 4

activation energy?

Answer 4

minimum amount of energy that particle needs to react

Question 5

reaction profile?

Answer 5

graph shows the relative energies of reactants and product as well as activation energy of the reaction.

Question 6

cell?

Answer 6

composed of two electrodes dipped in electrolyte solution, it produces electricity from a chemical reaction

Question 7

battery?

Answer 7

two or more cells connected in series.

Question 8

what determines the voltage obtained from a cell?

Answer 8

identities of metals used as electrodes and the identity and concentration of an electrolyte

Question 9

what determines the voltage obtained from a cell?

Answer 9

identities of metals used as electrodes and the identity and concentration of an electrolyte

Question 10

advantages / disadvantages of using cells and batteries?

Answer 10

(+) more cheap , less cheap , some are rechargeable , a convenient source of electrical energy.
(-) harmful chemicals

Question 11

describe rechargeable and non-rechargeable cells?

Answer 11

rechargeable - chemical reactions are reversed when an external current is supplied

non-rechargeable - reactants are used up cannot be recharged.