Ice cube melt

Watch the video, then follow the instructions.

1. Add food colouring to water in a jug before pouring into an ice cube tray and put the tray in a freezer overnight.

2. Place 2 containers of water (about 2/3rds full) and a plate on a surface indoors.

3. Dissolve salt in one water container (about 5 teaspoons per litre). Then wait for about an hour for it all to reach room temperature.

4. Take 3 equal sized ice cubes, place one in each container and one on the plate. (Optional: measure water temperature.) Start the timer.

5. Record the time each ice cube takes to melt.

6. See what happens to the melted ice by watching the food dye. If you have a thermometer, measure water temperature once cube has melted.

7. Enter results below.

SI measurement units

• second (s) for time (and minute = 60 seconds)
• kelvin (K) for temperature (optional)

Challenge Topics: climate measurement, measurement science, maths

• Do differences in food colouring flow give a clue about what happens in the two water samples?
• NPL is helping check average ocean level changes with mm precision
• Fresh water from melted glacial ice may affect the world’s thermohaline circulation of the global ocean conveyer belt