5. Up, Down & Around (Temperature)

Vibrating (jiggling) molecules can move up, down and around

The purpose of this simple experiment is for students to determine the relationship between temperature and speed of molecules in a liquid.

QUESTION

• How could we design an experiment to find an answer to the above problem?

EXPERIMENT

• If nobody can come up with a better solution, here is one experiment to try…

PROBLEM QUESTIONS:

1. what is a molecule?
2. how do molecules move?
3. does heat affect the way molecules move?
4. how could we find out if heat affects the way things move?
5. do you think that heat changes the temperature of the molecules themselves?

Students will use water & food dye to discover more about 'jiggling' and heat: Source

Think about what you are going to do, then write down a prediction about how you think the temperature of water might make a difference when food dye is dropped into the water

Materials you’ll need:

• 3 clear jars
• water: cold, room-temperature, hot water - 1 jar full of each
• concentrated food colouring
• masking tape
• markers
• thermometer (digital thermometer is best, but even no thermometer is OK)

Method to conduct the experiment:

• Label the outside of each jar with the water temperatures you are going to use.
• Fill three bottles. One bottle for room temperature water (about 25C), one with hot water (about 60C), and one with cold water with ice cubes added (about 10C).
• Add a drop (same amount) of food colouring to each of the jars
• Observe what happens over time and write down your results

Perform your experiment, then write down your results in a table similar to this:

Discuss the results that you wrote into your table.

Using your results, discuss the result that you observed and what they might show about heat.

Can you use your own/other evidence to help convince the class that molecules move slower/same/faster when they are warmer, slower/same/faster when they are colder, or move the same amount when warmer as they do when cooler.

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• How could this experiment be improved if someone wanted to run a similar test?