C3.3 Energy Change

Question 1

Give two of the social, economical and environmental aspects of using fuels? (6 marks)

Answer 1

(a) Provides employment BUT causes noise/visual pollution
(b) Can improve the economy BUT energy needed can cost a lot
(c) Habitats destroyed AND less trees to absorb CO2

Question 2

How can you measure the relative amounts of energy released when substances burn? Give a short example of what you could do.

Answer 2

Through simple calorimetry e.g. through heating water in a glass or metal container

Question 3

What equation is used in calorimetry?

Answer 3

Q=MCΔT

q = m cat

Question 4

How can you calculate the amount of energy released (or absorbed) by a chemical reaction in solution?

Answer 4

To calculate, look at the measured temperature change of the solution when the reagents are mixed in an insulated container

Question 5

What do energy level diagrams show? (4 marks)

Answer 5

• Activation energy
• The overall energy change
• The relative energy of:
  
  • the reactants
  • the products

Question 6

In an endothermic reaction, is more energy released forming new bonds or breaking existing bonds?

Answer 6

Breaking existing bonds (bENDOmEX)

Question 7

What effect does a catalyst have on the activation energy?

Answer 7

Catalysts provide a different pathway that has a lower activation energy.

Question 8

What is an advantage of using a catalyst?

Answer 8

• Reactions happen more quickly

- More economical (less energy required for industrial-scale reactions)

Question 9

Give an advantage and a disadvantage of using hydrogen as a fuel

Answer 9

+Only product is water, no carbon dioxide

- Making hydrogen pollutes (electricity is passed through water, electricity is made from fossil fuels)