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Year 10
OCR
Higher

Surface area and rate: analysis

I can represent graphically and describe how the rate of reaction depends on the surface area of a solid reactant.

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New
New
Year 10
OCR
Higher

Surface area and rate: analysis

I can represent graphically and describe how the rate of reaction depends on the surface area of a solid reactant.

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Share activities with pupils
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Lesson details

Key learning points

  1. The changing rate of a chemical reaction can be represented by a graph of mass of gas produced against time.
  2. When reacting excess marble chips with acid, the same mass of gas is produced for all surface areas of chips.
  3. The mean rate of reaction = total mass of gas produced ÷ total time of reaction
  4. The instantaneous rate of reaction is equal to the gradient of the graph.
  5. The gradient of a rate of reaction graph can be calculated from a tangent drawn at a point on the curve.

Keywords

  • Gradient - The gradient on a graph represents the rate at which one quantity changes relative to another.

  • Mean rate of reaction - The mean rate of reaction is the average rate at which reactants are converted into products in a given time.

  • Instantaneous rate of reaction - The instantaneous rate of reaction is the rate at which reactants are converted into products at a specific moment in time.

  • Tangent - A tangent is a straight line that touches a curve at exactly one point without crossing it.

Common misconception

Pupils often confuse the mean rate of reaction with the instantaneous rate of reaction, thinking they are the same or not understanding the distinction between the two.

The tasks give pupils s the opportunity to distinguish between mean and instantaneous rate of reaction by calculating both from the same set of data.

Provide additional guidance to pupils who need extra support on how to draw a tangent.
Teacher tip

Equipment

Graph paper for drawing graphs. Ruler or straight edge to draw tangents. Calculator to calculate rate of reaction.

Licence

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.
If you want to make a solid react faster with a liquid, what should you do to the solid?
dilute the liquid
Correct answer: break the solid into smaller pieces
compress the solid
cool the solid
Q2.
Why do smaller particles of a solid react faster than larger particles of the same solid?
they have a lower mass
they have a smaller volume
Correct answer: they have a larger surface area
they have a higher density
Q3.
Which has a greater surface area to volume ratio: 5g of large calcium carbonate chips, 5g of small calcium carbonate chips or 5g of powdered calcium carbonate?
5g of large calcium carbonate chips
5g of small calcium carbonate chips
Correct answer: 5g of powdered calcium carbonate
they all have the same surface area
Q4.
Why is it important to control variables in a rate of reaction experiment?
to change the outcome of the experiment
Correct answer: to ensure the experimental results are reliable
to increase the reaction rate
to decrease the reaction rate
Q5.
Which of the following should be kept constant in an experiment investigating the effect of surface area on reaction rate?
the surface area of a solid reactant
Correct answer: the concentration of a reacting solution
the volume of gas produced
the time taken for the reaction to reach completion
Q6.
What will we have calculated if we divide the amount of product made by the time taken?
concentration of a reacting solid
temperature of the reaction mixture
mass of catalyst added
mass of reacting solid needed for the reaction to reach completion
Correct answer: rate of reaction

Exit quiz

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6 Questions

Q1.
What will we calculate if we determine the gradient at a specific point on a graph of mass of product versus time.
mean rate of reaction
Correct answer: instantaneous rate of reaction
tangent
concentration of reacting solution
Q2.
On a graph of mass of gas produced against time, what does a steeper gradient indicate?
Correct answer: a higher rate of reaction
a lower rate of reaction
no reaction occurring
constant rate of reaction
Q3.
Why does the surface area of marble chips affect the rate of reaction but not the total mass of gas produced?
surface area changes the concentration of acid
Correct answer: surface area affects the frequency of collisions
surface area changes the mass of acid used
surface area has no effect on reaction rate
the marble chips are the limiting reactant
Q4.
How is the mean rate of reaction calculated?
total mass of gas produced × total time of reaction
total time of reaction ÷ total mass of gas produced
Correct answer: total mass of gas produced ÷ total time of reaction
total mass of reactants × total time of reaction
Q5.
If 30 grams of gas are produced in 10 minutes, what is the mean rate of reaction?
Correct answer: 3 grams per minute
30 grams per minute
0.3 grams per minute
10 grams per minute
Q6.
When reacting excess marble chips with acid, how does the surface area of the chips affect the total mass of gas produced?
more gas is produced with larger chips
less gas is produced with smaller chips
Correct answer: the same mass of gas is produced for all surface areas
no gas is produced with smaller chips