Dissolving and temperature
In grade 10 you listed the signs that a reaction has happened. One of them is a change in temperature. Activity 8.1 looks at it more closely.
Activity 8.1
You will need: two small beakers of about 100 cm3, a thermometer, a glass rod, solid sodium hydroxide (NaOH), solid ammonium chloride (NH4Cl)
- Half fill a beaker with water and record its temperature. Add a little solid sodium hydroxide, stir with the glass rod, and record the temperature again.
- Do the same in the other beaker with a little solid ammonium chloride.
Sodium hydroxide
The temperature rises.
Heat is given out as it dissolves.
Ammonium chloride
The temperature falls.
Heat is taken in as it dissolves.
Both temperature changes come from the heat change that goes with the process. A change in temperature can be taken as a measure of the heat released or absorbed.