Heat energy changes in chemical reactions

Question 1

What do the terms exothermic and

endothermic mean?

Answer 1

Endothermic - a reaction that takes in
heat energy from the surroundings.

Exothermic - a reaction that gives out
energy to the surroundings.

Question 2

Are neutralisation reactions endothermic or

exothermic?

Answer 2

Exothermic

Question 3

Are displacement reactions endothermic or

exothermic?

Answer 3

Either exothermic or endothermic.

Question 4

Is a salt dissolving in water endothermic or

exothermic?

Answer 4

Either exothermic or endothermic.

Question 5

Are precipitation reactions endothermic or

exothermic?

Answer 5

Exothermic

Question 6

How could you measure the temperature change of

a neutralisation reaction?

Answer 6

1. Measure initial temperature of the solutions.
2. Mix both reactants in a polystyrene cup.
3. Record the highest temperature reached.
4. Calculate the temperature change.

Question 7

When measuring the temperature change of a
reaction, heat loss means that measurements may
be inaccurate. How could heat loss be minimised
during an experiment?

Answer 7

• Use polystyrene cup.
• Place reaction cup in a beaker full with cotton
  wool for extra insulation.
• Lid on the reaction cup.

Question 8

In terms of bond energies, what happens during a
chemical reaction? Describe exothermic and
endothermic reactions in terms of bonds
breaking/forming.

Answer 8

Energy is needed to break bonds and is released when bonds are made.

Exothermic: Energy released from breaking bonds is greater than the energy
used to make bonds.

Endothermic: Energy released in forming new bond is greater than the energy
used to break old bonds.

Question 9

What two types of reaction are exothermic?

Answer 9

Combustion

Neutralisation

Question 10

Give an example of an endothermic reaction

Answer 10

Thermal decomposition

Photosynthesis

Question 11

How can the energy change of a reaction be

calculated from bond energies?

Answer 11

Energy change (kJ mol-1) =

Total energy of bonds broken - total energy of bonds made.

Question 12

If the energy change of a reaction is negative, is the

reaction exothermic or endothermic?

Answer 12

Exothermic, energy has been lost to the

surroundings.

Question 13

What is a reaction profile?

Answer 13

Agraph showing the relative energies of reactants and products, as well as the activation energy of a reaction.

Question 14

Draw a reaction profile for an

endothermic reaction

Answer 14

https://pmt.physicsandmathstutor.com/download/Chemistry/GCSE/Notes/Edexcel/7-Rates-of-Reaction-and-Energy-Changes/Flashcards%20-%20Topic%207%20Rates%20of%20Reaction%20and%20Energy%20Changes%20-%20Edexcel%20Chemistry%20GCSE.pdf

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Question 15

Draw a reaction profile for an exothermic

reaction

Answer 15

https://pmt.physicsandmathstutor.com/download/Chemistry/GCSE/Notes/Edexcel/7-Rates-of-Reaction-and-Energy-Changes/Flashcards%20-%20Topic%207%20Rates%20of%20Reaction%20and%20Energy%20Changes%20-%20Edexcel%20Chemistry%20GCSE.pdf

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