Required Practical: Temperature Changes
Chemistry: AQA GCSE Higher, topic 5.1.4
Investigating Temperature Changes in Chemical Reactions
The aim of this experiment is to explore how different variables influence the change in temperature when substances react in solution.
Apparatus
- Polystyrene cup (for insulation)
- 250 cm3 beaker (to support the cup)
- Thermometer
- Measuring cylinder
- Top-pan balance
- Stopwatch (if required for timing reactions)
Planning
- You can examine different temperature changes by choosing suitable reaction types, such as:
- acid + metals
- acid + carbonates
- acid + alkali (neutralisation)
- displacement of metals
Variables
- Independent variable:
- Concentration of acid, or type of metal, or surface area of solid
- Dependent variable:
- The temperature change (increase or decrease)
- Control variables:
- Volume of reactants, initial temperature, and duration of measurement
Method: Solution + Solution
- Place a polystyrene cup inside a beaker to prevent it from tipping.
- Measure a fixed volume of the first solution and pour it into the cup.
- Record its starting temperature.
- Measure an equal volume of the second solution and add it quickly to the cup.
- Stir and note the maximum or minimum temperature reached.
- Repeat the procedure for different values of your independent variable (e.g. acid concentration or type of acid).
Method: Solid + Solution
- Place a polystyrene cup inside a beaker for safety.
- Measure and pour a fixed volume of acid into the cup.
- Record the starting temperature of the solution.
- Measure the mass of the metal.
- Add the solid to the acid and gently swirl the mixture.
- Record the highest or lowest temperature reached.
- Repeat using different variables such as the type of metal, surface area, or acid concentration.
Analysis
- A larger temperature change indicates that more energy has been transferred.
- Exothermic reactions release heat into the surroundings, causing a temperature rise.
- Endothermic reactions absorb energy, resulting in a temperature drop.
- Plot the data on a graph of temperature change (°C) against the chosen independent variable to observe trends.
Hazards and precautions
- Dilute acids or alkalis:
- These may irritate the skin or eyes
- Wear goggles and handle with care
- Metal salt solutions:
- Some may be harmful to the environment
- Dispose of waste properly; do not pour it into sinks
- Exothermic reactions:
- Heat can be released suddenly
- Avoid holding the reaction vessel; use a beaker for support
Test yourself on Required Practical: Temperature Changes
What would happen to the temperature reading if a polystyrene cup was not used in this experiment?
Why should you avoid holding the reaction vessel during this experiment?
In this experiment, a reaction between an acid and a carbonate causes the temperature reading to rise. What type of reaction is taking place?
In this experiment, which measurement is taken during the solid + solution method but not during the solution + solution method?
What is one step that both the solution + solution method and the solid + solution method have in common?