Observe water expanding and contracting when heated and cooled.
Use a plastic water bottle with a straw in the cap, or a film canister with clear plastic tubing.
Time: 40 min
Level: Intermediate
Adapted from this experiment: https://www.jpl.nasa.gov/edu/teach/activity/thermal-expansion-model/
Science Notes:
After doing the experiment, use these resources to help understand the thermal expansion property of matter.
Option 1: film canister with clear plastic tubing
This model is easier and cheaper, but only qualitative. Students can make demos on their own or in small groups. The observations will be qualitative.
Option 2: water bottle with straw and temperature probe
This model is good for a class demo or a science lab setting. It can also be a quantitative experiment where students measure volume and calculate the coefficient of thermal expansion for water.
clear film canisters with lids
Clear PVC tubing, 3/16" OD, 1/8" ID
room temperature water
food coloring
Container that is large than the film canisters (glass bowl or measuring cup)
hot water (from electric kettle or other source)
ice cubes (optional)
Specifics and purchasing links are on this spreadsheet Materials list for CCSAE experiments
plastic water bottle (sturdy, not easy crushed)
Clear drinking straw
ruler
marker
sealing putty such as clay or blu-tack
thermometer with long waterproof probe
room temperature water
food coloring
Container that is large than the water bottle (glass beaker, large measuring cup)
hot water (from electric kettle or other source)
ice cubes (optional)
Specifics and purchasing links are on this spreadsheet Materials list for CCSAE experiments
Step 1
Make a 3/16" diameter hole in the cap of the film canister.
The hole can be centered or off-center.
Step 2
For each film canister, cut a piece of PVC tubing about 5" long. Cut one end at an angle (so it will be easy to insert in the film canister cap).
Step 3
Mix food coloring with room temperature water. Pour it into the film canisters to the very top.
Carefully snap the lids onto the canisters - water may shoot out through the hole when they snap shut.
Step 4
Insert the plastic tubing into the covers. It should extend into the canisters about half way. Some water will come up the tube since the tubing in the canister is taking up space.
You can check that the tube has made an air-tight seal by blowing into it. You should not be able to get any air in it or hear air escape the canister.
Mark the level of the water in the tube.
Step 5
Place the canisters in a glass bowl and pour boiling or hot water around them.
At first, the water in the tube will drop. This is due to the thermal expansion of the canister itself. The canister expanded slightly when it heated up and had more room for water.
As the water in the canister heats up, it will expand and climb up the tube. It should only take a few minutes for it to get to the top of the tube.
Step 6
Prepare a bowl of ice water and place the film canisters in it. Once again, the first thing that happens is a reaction to the thermal effect of the cold water on the canister. The canister contracts in the cold water and pushes the water further up the tube, or even out of the tube.
As the water in the canister cools, it will contract and go back down the tube and into the canister. It takes about 10 minutes for the water to cool and return to its original level.
For the water level to drop further, add more ice to the water and leave the canisters longer.
Step 1
Make 2 holes in a bottle cap, spaced as far apart as possible. One will be the diameter of the drinking straw, the other the diameter of the temperature probe.
Mark the straw with lines 1 cm apart.
Step 2
Insert the temperature probe and straw through the two holes in the bottle cap. Seal the hole with the putty. Keep the temperature probe in the center of the plastic bottle, not touching the sides.
Step 3
Mix food coloring in water and pour it into the bottle up to the top.
Screw on the cap with the straw and temperature probe.
Test the seals on the bottle cap by gently squeezing the bottle to make water climb the straw. Make sure there are no leaks! Squeeze the putty around the holes to fix any leaks. If necessary, take the cap apart, dry it thoroughly and start again.
It is okay if the water level in the straw is a little below the cap or the first mark.
Step 4
Place the plastic bottle in the large container and fill the container with boiling water (around the plastic bottle). The colored water will increase in volume and rise up through the straw.
Once liquid starts climbing the straw, take temperature and liquid height readings. It can help to record a video of the experiment.
When the liquid is close to the top, remove the bottle from the container. Pour out the hot water.
Watch our example of this experiment:
Step 5
Place the plastic bottle in the large container. If there is no colored water showing in the straw. add some through the straw as needed (this is not easy, a dropper can help). Prepare ice water.
Fill the container with ice water (around the plastic bottle).The colored water will cool down, decrease in volume, and sink back down the straw and into the bottle.
Once liquid starts dropping in the straw, take temperature and liquid height readings. It can help to record a video of the experiment.
Step 6 (optional)
Look up the coefficient of thermal expansion of water (at room temperature, 20°C) and compare it to other substances in the table below.
Step 7 (optional)
Calculate the coefficient of thermal expansion from your data
To calculate the coefficient of thermal expansion of water on your own, follow these steps:
Measure the diameter of the straw in cm. Divide by 2 for radius R (ours was .3 cm)
Measure the volume of water in the plastic bottle VB (ml).
Plot your height and temperature data and choose 2 points on the line.
For those points calculate the change in height ΔH (cm), and the change in temperature ΔT (°C) (If you measured Δ°F, just multiply by 5/9 for Δ°C).
Calculate the change in volume ΔV = ΔH * π R2 . Note that 1 cubic cm = 1 ml, so ΔV is in both cm3 and ml
Now the final calculation: Coefficient of Thermal expansion =
change in water volume (ml) * 1
starting water volume (ml) change in temperature (°C)
= ΔV * 1___
VB ΔT (°C)
Reference for calculations and table of coefficients of linear and volumetric expansion: https://pressbooks.bccampus.ca/collegephysics/chapter/thermal-expansion-of-solids-and-liquids/
Additional references:
https://www.basic-mathematics.com/thermal-expansion-of-water.html - why ice floats and fish do not freeze to death
For isotropic materials the coefficients linear thermal expansion α and volumetric thermal expansion αV are related by αV = 3α. For liquids usually the coefficient of volumetric expansion is listed and linear expansion is calculated here for comparison. https://en.wikipedia.org/wiki/Thermal_expansion
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
https://www.engineeringtoolbox.com/cubical-expansion-coefficients-d_1262.html
https://byjus.com/physics/coefficient-of-linear-expansion/
Suggestions:
When the canisters were in hot water the colored water came out through the tube.
When water in the canisters got warmer, it expanded and came out the tube.
When the water in the canisters was cooled the colored water went back down the tubes.
The mechanism is thermal expansion of water
When water gets warmer, the molecules have more energy and move faster.
The water gets less dense and its volume increases.
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.
