Visualize variations in water density due to temperature.
Use colored warm and cold water and see what happens when they are combined.
Time: 30 minutes
Level: Intermediate
This experiment was adapted from the temperature experiment shown in this video "Warm and Cold Water Mixing Experiment"
Science Notes:
After doing the experiment, use these resources to help understand the temperature of a material affects its density.
2 containers for mixing water with food coloring
cold and warm tap water
food coloring
4 identical clear containers, either glass jars (such as mason jars or food jars) OR small clear plastic film canisters
2 thin pieces of smooth waterproof sheet to fit over the tops of the jars (such as laminated paper, waxy milk carton, or a thin plastic material)
stirring sticks or spoons
tape and markers
temperature sensor (optional)
a tray or container to work in in case the water spills
Specifics and purchasing links are on this spreadsheet Materials list for CCSAE experiments
Step 1
Fill 1 container with water cool enough to drink: 50 to 60 °F (10 to 15 °C).
Fill another container with water warm enough for hand-washing: 80 to 100 °F (27 to 38 °C). Check the temperature with temperature sensors if sensors are available.
Note that even a 20 °F (~10 °C) difference in temperature will work well in this experiment.
Choose 2 colors of food coloring. Avoid using both red and green as they might be very difficult for color-blind to distinguish between them. Typically, blue represents cool water and red represents warm water. Add a few drops of each to the water and mix it in.
Mark the containers as cold and warm.
Step 2
Fill 2 of the clear containers (jars or canisters) with the cold water, up to the very top. Do the same with the warm water.
Mark the containers, or otherwise note which color is cold and which is warm. In the example shown, red is warm and blue is cold.
Cover one jar of each color with a piece of thin waterproof material.
Step 3
Carefully hold the plastic cover on the warm container and place it over the cold container.
Do the same with the plastic cover on the cold container, placing it on the hot one.
clear film canisters
glass jars
Step 4
Be ready to record images or videos of this step!
Quickly, but carefully, pull out each sheet while keeping the top jar aligned on top of the bottom one.
Observe what happens to the fluids.
Touch the containers and see if you notice differences in the temperatures.
Images of water mixing:
Upper images: Cold water over Warm water in film canisters
Lower images: Cold water over Warm water in glass jars
Step 5
For the set of jars that doesn’t mix, try some things:
shake it up/down
turn it sideways and create layers
tip it back to original orientation to get layers of each color plus a mix in the middle
If you are using a temperature sensor, predict the temperature of the mixed water and measure it.
Suggestions:
Cold water is more dense and sinks
Cold water is heavier than warm water
Cold water is more dense, and sinks when it comes into warm water.
Pathway for Changes to Atlantic Ocean Circulation.pdfWe’d love to hear how you used this tool in your community, how the students responded, and your suggestions to improve the experiments and other resources. Contact us at ccsae@mit.edu.