Calculating and Explaining Energy Change

Question 1

How can relative amounts of energy released be measured and what is the equation?

Answer 1

when substances are burnt, the energy released can be measured using a calorimetry

Q = mc ΔT

q = heat energy transfered (J)

m = mass of liquid being heated (g)

c= specific heat capacity of liquid (J/g°C)

ΔT = change in temperature (°C)

Question 2

How can energy released or absorbed in a chemical reaction in solution be calculated?

Answer 2

from the measured temperature change of the solution when the substances are mixed in an insulated container.

This method can be used for reactions of solids with water or for neutralisation reactions.

Question 3

In a reaction, energy is…

Answer 3

supplied to break bonds

released when bonds are formed

Question 4

What happens in an exothermic reaction?

Answer 4

energy released to form new bonds is greater than the energy needed to break existing bonds

Question 5

What happens in an endothermic reaction?

Answer 5

the energy need to break existing bonds is greater than the energy released from forming new bonds

Question 6

What do catalysts do?

Answer 6

provide a different pathway for a chemical reaction that has a lower activation energy

Question 7

What are the uses of hydrogen?

Answer 7

burned as fuel in combustion engines
hydrogen + oxygen -> water

it can be used in fuel cells that produce electricity to power vehicles