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Year 10
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Higher

Reaction profiles

I can draw, label and interpret reaction profiles for exothermic and endothermic reactions, and understand the changes these cause in the surroundings.

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New
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Year 10
OCR
Higher

Reaction profiles

I can draw, label and interpret reaction profiles for exothermic and endothermic reactions, and understand the changes these cause in the surroundings.

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Lesson details

Key learning points

  1. A reaction profile compares the amount of energy the products of a reaction have compared to the reactants.
  2. Exothermic chemical reactions transfer energy from reactants to the surroundings causing an increase in temperature.
  3. Endothermic chemical reactions transfer energy from the surroundings to the products causing a decrease in temperature.
  4. Activation energy is the minimum amount of energy transferred to reactants that allows a chemical reaction to start.

Keywords

  • Exothermic - An exothermic chemical reaction is a type of reaction in which energy is transferred from the reactants to the surroundings, e.g. combustion.

  • Endothermic - An endothermic chemical reaction is a type of reaction in which energy is transferred from the surroundings to the products, e.g. photosynthesis.

  • Activation energy - The minimum energy that the particles must have in order to react is known as the activation energy.

  • Reaction profile - A reaction profile is a diagram showing the energy changes during exothermic and endothermic reactions.

Common misconception

Pupils often confuse energy with temperature and therefore expect the products to be higher than the reactants for exothermic reactions i.e. due to temperature increase, and lower for endothermic.

It is useful to discuss the energy transfers occurring during the reaction e.g. exothermic reactions involve the reactant's chemical energy store converting to a smaller chemical energy store in the products and a thermal energy store.

Get the pupils to draw an energy transfer diagram for both exo and endothermic reactions before introducing reaction profiles i.e. exo = chemical energy store -> chemical and thermal energy stores, endo = chemical and thermal energy stores -> chemical energy store.
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This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
What is the role of a catalyst in a chemical reaction?
It has no effect on the activation energy.
It increases the activation energy required for the reaction to start.
Correct answer: It lowers the activation energy required for the reaction to start.
Q2.
What happens during an exothermic reaction?
Correct answer: Energy is transferred from the reactants to the surroundings.
Energy is transferred from the surroundings to the reactants.
No energy transfer occurs.
Q3.
What happens during an endothermic reaction?
Energy is transferred from the reactants to the surroundings.
Correct answer: Energy is transferred from the surroundings to the reactants.
No energy transfer occurs.
Q4.
is needed for a chemical reaction to start.
Correct Answer: activation energy, energy
Q5.
What is energy transfer in a chemical reaction?
the creation of energy in a reaction
the disappearance of energy during a reaction
Correct answer: the movement of energy from one store to another
Q6.
What is the role of activation energy in a chemical reaction?
the energy absorbed during the reaction
the energy released during the reaction
Correct answer: the minimum energy needed for the reaction to start

Exit quiz

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6 Questions

Q1.
What does a reaction profile show?
Correct answer: energy changes during a chemical reaction
pressure changes during a reaction
temperature changes during a reaction
Q2.
Which of the following reaction profiles shows an endothermic reaction?
energy profile A
energy profile B
Correct answer: energy profile C
Q3.
Which of the following reaction profiles correctly represents the activation energy of the reaction with a red arrow, and where R is the reactant and P is the product?
energy profile A
energy profile B
energy profile C
Correct answer: energy profile D
Q4.
How can you identify an exothermic reaction from its reaction profile?
The energy of the products is higher than the reactants.
Correct answer: The energy of the products is lower than the reactants.
There is no change in energy.
Q5.
How does the activation energy of a reaction influence its rate?
Activation energy does not affect the reaction rate.
Higher activation energy means a faster reaction rate.
Correct answer: Higher activation energy means a slower reaction rate.
Q6.
Why might a reaction with a low activation energy be preferred in industrial processes?
Correct answer: It can occur at lower temperatures, saving energy costs.
It produces more products.
It requires more reactants.