How To Demonstrate an Exothermic Change with Sodium Hydroxide (NaOH)

In this short video, Denise Ralph RSciTech will show how to demonstrate a neutralisation reaction using sodium hydroxide, which is a required GCSE Chemistry practical covering temperature changes in reacting solutions.

The aim of the experiment is to monitor and measure the temperature change as the reaction occurs.

The demonstration uses a beaker but an insulated cup like a Styrofoam cup could be used to reduce heat loss and for an additional layer of safety. Styrofoam has low thermal conductivity, meaning it does not allow heat to easily pass through it. This property helps in containing the heat generated during the exothermic reaction within the cup, allowing for better temperature measurement and observation.

You will need:

• • • 50ml beaker
    • 100ml beaker
    • 30ml water
    • 3g sodium hydroxide (NaOH) solution or pellets
    • Thermometer or temperature sensor
    • Stirring rod or spoon (or use the thermometer!)
    • Eye protection
    • Graph paper

Method:

1. Put on safety goggles to protect your eyes during the experiment.
2. Take the 100ml beaker and add a small amount of water to it, around 30 ml.
3. Measure the initial temperature of the water in the beaker using a thermometer and record it.
4. Slowly add sodium hydroxide pellets or solution to the water in the cup while stirring gently. Continue adding until you observe a noticeable reaction.
5. Observe the changes occurring in the cup, such as temperature increase, gas formation, or bubbling.
6. Stir the mixture gently to ensure thorough mixing.
7. Continuously monitor and record the temperature of the reaction mixture using the thermometer. Note any changes that occur.
8. Observe and discuss the exothermic nature of the reaction, as evidenced by the temperature increase.

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