Testing Water Purity Using Melting Point
Chemistry: Cambridge International GCSE Supplement, topic 10.1.2
Testing Water Purity Using Melting Point
Water purity is tested by its melting (0°C) and boiling (100°C) points. Impurities lower the melting point and raise the boiling point.
Introduction to water purity testing
- The purity of water is important to ensure safety and quality.
- Pure water has fixed melting and boiling points.
- Impurities change these points.
- Testing melting point helps identify purity.
- Boiling point tests also check water quality.
Melting point and water purity
- Pure water melts at 0°C exactly.
- Impurities lower the melting point.
- This is called freezing point depression.
- Measure the melting point using a thermometer in melted ice.
- Use the melting point value to assess water purity.
Boiling point and water purity
- Pure water boils at 100°C at sea level.
- Impurities raise the boiling point.
- This is known as boiling point elevation.
- Boil the water and measure temperature with a thermometer.
- Compare with 100°C to check purity.
How to test water
- Take a sample of the water.
- Cool it to find melting point using a thermometer.
- Heat it to find boiling point using a thermometer.
- Record temperatures.
- Compare results to 0°C and 100°C to determine purity.
Test yourself on Testing Water Purity Using Melting Point
What effect do impurities have on the melting point of water?
The phenomenon where impurities cause the melting point of water to decrease is known as what?