It’s one thing to explain that molecules move faster when hot and slower when cold, but it’s another to visually see it happen.
Thankfully, this simple experiment is a great way to show how the temperature of something (in this case water) changes the way the molecules behave.
Water Temperature Science Experiment Video
- 3 Glass Jars
- Cold Water
- Room Temperature Water
- Hot Water
- Food Coloring
Step 1 – Begin by preparing three jars of water. Fill one with cold water, one with room temperature water, and one with hot water.
Helpful Tip: For cold water, fill the jar and put it in the fridge for an hour or two. For the room temperature water, fill the jar and leave it on the counter for an hour or two. For the hot water, boil the water on the stove or put it in the microwave for a minute or two.
Step 2 – Place 2-3 drops of food coloring in each jar.
Step 3 – Observe what happens to the food coloring. Does it behave differently in each jar?
How Does the Experiment Work?
When observing the food coloring in the water, you will immediately notice that it behaves differently based on the temperature of the water.
Even though the glasses of water look the same, the difference in the water temperature causes the molecules that make up the water to behave differently. Molecules that make up matter move faster when they are warmer because they have more thermal energy and slower when they are colder because they have less thermal energy. In this experiment, the molecules in the hot water are moving around much faster than the molecules in the cold water.
Thermal Energy is the total energy of the particles in an object.
When placed into water, food coloring will begin to mix with the water. The food coloring will mix the fastest in the hot water because the molecules are moving fast due to their increased thermal energy. These fast-moving molecules are pushing the molecules of food coloring around as they move, causing the food coloring to spread faster. The food coloring in the room temperature water will take longer to mix with the water because the molecules are moving more slowly due to their decreased thermal energy. And the food coloring in the cold water will take a long time to mix with the water because the molecules are moving even slower due to a further decrease in thermal energy.
More Science Fun
Eventually, the food coloring will mix throughout all of the jars. Expand on the experiment, by estimating how long it will take to mix with the water in each jar. Then set a timer and find out how close your estimate was.
In addition, you can also try these other fun experiments using water and food coloring:
I hope you enjoyed the experiment. Here are some printable instructions: