Cambridge Secondary (7-9). Stage 8. MCE Science. Workbook - Unit 7: Exothermic and Endothermic Changes - Question 13

In this investigation, 2 g each of calcium chloride (A), sodium carbonate (B), magnesium chloride (C) and potassium chloride (D) are placed in separate polystyrene cups. Add 10 cm³ water to each salt, stir gently and record initial and final temperatures. Keep a fifth cup with water only. Rinse the thermometer before each test. Work in groups. Put on your safety goggles and gloves. Use a spoon or spatula to avoid direct contact with chemicals. Add 50 cm³ of water to the unlabelled cup. Measure and record its initial temperature. Add 10 cm³ of this water to cup A, stir gently and place the thermometer in the solution. When the temperature stops changing, record the final temperature. Repeat for B and C. For D, add 10 cm³ water, stir and wait two minutes for the temperature to stop changing; record the final temperature. Measure and record the final temperature of the water in the unlabelled cup. Complete the table.

| Type of salt | Initial temperature (°C) | Final temperature (°C) | Temperature change (°C) |
|---|---|---|---|
| – (water only) | | | |
| Calcium chloride | | | |
| Sodium carbonate | | | |
| Magnesium chloride | | | |
| Potassium chloride | | | |