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      Concentration and rate: practical using gas collection method

      Lesson details

      Learning outcome

      I can carry out a fair test to investigate how the rate of reaction depends on the concentration of a reacting solution.

      Key learning points

      1. The changing rate of a reaction can be found by measuring the amount of gas produced as the reaction progresses.
      2. Increasing concentration of a reacting solution introduces more reactant particles, so they collide more frequently.
      3. When reacting excess acid with equal amounts of magnesium, the same volume is produced for all concentrations of acid.

      Keywords

      • Rate of reaction - Rate of reaction is the speed with which a chemical reaction takes place.

      • Independent variable - The independent variable is the single variable that is changed in an investigation.

      • Dependent variable - The dependent variable is the single variable that is measured or observed in an investigation.

      • Control variables - The control variables are variables that are kept constant in an investigation.

      Common misconception

      Thinking that as the concentration of a solution in excess changes, so does the volume of gas produced.

      The slide deck uses graphical data to show that the same volume of gas is produced when different concentrations are used, so long as the reacting solution is in excess.

      Teacher tip

      To highlight to pupils that when we use magnesium strips of the same length we are assuming we have the same mass.

      Equipment

      Conical flask, bung and delivery tube, water trough, measuring cylinder, timer, magnesium strips, different concentrations of hydrochloric acid and eye protection.

      Content guidance

      Risk assessment required - equipment

      Supervision

      Adult supervision required

      Licence

      This content is © Oak National Academy Limited (2026), 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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      Prior knowledge starter quiz

      6 Questions

      Q1.
      How can we increase the rate of a reaction?

      Correct answer: increase the surface area of a solid reactant
      increase the volume of a reacting solution in excess
      decrease the volume of a reacting solution in excess
      Correct answer: increase the concentration of a reacting solution
      decrease the concentration of a reacting solution

      Q2.
      According to the collision theory, what must happen for a reaction to occur?

      Correct answer: particles must collide with sufficient energy
      particles must collide with energy lower than the activation energy
      particles must collide without any energy
      particles must move in opposite directions
      particles must move in opposite directions with the activation energy

      Q3.
      Which equipment can be used to measure the volume of gas in a rate of reaction investigation?

      Correct answer: a gas syringe
      a stopwatch
      a thermometer
      a pipette
      Correct answer: an upturned measuring cylinder

      Q4.
      The rate of reaction can be defined as:

      the total energy produced in a reaction
      Correct answer: the amount of reactant used per unit time
      Correct answer: the amount of product made per unit time
      the time it takes for the reaction to start
      the maximum temperature reached during the reaction

      Q5.
      If 10 grams of a reactant are used up in 5 seconds, what is the rate of reaction?

      0.2 g/s
      0.2 cm³/s
      0.2 cm³/s²
      Correct answer: 2 g/s
      2 cm³/s

      Q6.
      What is activation energy?

      the energy needed to form new chemical bonds
      the energy released during the reaction
      Correct answer: the minimum energy required for particles to react upon collision
      the maximum energy that particles can have when colliding

      6 Questions

      Q1.
      What does a graph of volume of gas produced against time show?

      the total amount of reactants
      Correct answer: the changing rate of the reaction
      the pH change over time
      the temperature change over time

      Q2.
      What is a common error when using a measuring cylinder to measure the amount of gas produced during a reaction?

      incorrect pH readings
      Correct answer: parallax error in reading volumes
      using too much reactant
      incorrect temperature measurement

      Q3.
      Why does increasing the concentration of a reacting solution increase the rate of reaction?

      it decreases the activation energy
      it increases the energy of the particles
      Correct answer: it increases the frequency of collisions
      it changes the state of the reactants

      Q4.
      Why does increasing the concentration of a solution increase the frequency of particle collisions?

      more energy is added to the system
      Correct answer: more particles are present in the same volume
      the temperature increases
      the pressure decreases

      Q5.
      When reacting excess acid with equal amounts of magnesium, how does the concentration of acid affect the volume of gas produced?

      higher concentration produces more gas
      lower concentration produces more gas
      Correct answer: the same volume of gas is produced for all concentrations
      no gas is produced

      Q6.
      To ensure a fair test when investigating how concentration affects rate of reaction, which of the following must be kept constant?

      concentration of the reactant solution
      Correct answer: surface area of the solid reactant
      volume of gas produced
      time taken for a certain volume of gas to be produced

      To help you plan your 10 chemistry lesson on: Concentration and rate: practical using gas collection method, download all teaching resources for free and adapt to suit your pupils' needs...