Grade 3 Hot or cold experiment | BCHydro Power Smart for Schools

Hot or cold experiment

Discover how insulation keeps things warm through a hot water experiment.

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30 mins
Hands on


Lead an experiment to see how insulation plays a part in keeping things hot or cold. Your students will test the temperature of water in two different mugs to learn which one keeps the water warmer and why.


What you'll need

For each group of 2 to 4 students:

  • Hot water (safe to touch)
  • Insulated travel mug
  • Regular coffee cup or mug
  • Thermometer 
  • "Hot or cold" recording sheet
  • Pencils

  1. Ask students what helps us stay warm when we go outside in cold weather. 
    • Examples might include coats, hats, gloves, boots, and socks.
  2. Discuss what animals use to keep warm. 
    • Many animals have fur, feathers and thick body fat to help keep their bodies warm. Explain we call this insulation and that insulation keeps the heat in and the cold out.
  3. Explain to the students that they are now scientists and will do an experiment to see how insulation works.
  4. Divide the class into groups of about two to four students, and get ready to do the experiment.
  5. Provide each group with the following supplies: 
    • Hot water (safe to touch)
    • Insulated travel mug
    • Regular coffee cup or mug
    • Thermometer
    • "Hot or cold" recording sheet
    • Pencils
  6. Ask students to fill their travel mug and regular mug with hot water.
  7. Have students take turns measuring the temperature of each mug and have them write it on their recording sheet. 
    • Both the mugs should be the same temperature.
  8. Set a timer and wait 5 minutes. While waiting, discuss with the students what they think will happen to the temperature in each vessel after 5 minutes. 
    • Ask the students to think about how the water was heated, for example using natural gas or electricity. 
  9. After 5 minutes, ask students to take turns measuring the temperature of each mug a second time, and have them record it on their sheet. 
    • The temperature in the regular mug will be lower, while the temperature in the travel mug will be closer to the first reading.
  10. Ask students to share what happened. 
    • Why is the water in the travel mug staying warmer for longer?
    • Can they guess that the travel mug is insulated?
  11. Ask the students to consider what would happen if the water was cold. 
    • Would the travel mug help keep the water colder?
  12. Share that to keep our schools and homes warm, there's insulation in the walls that help keep the heat in and the cold out. However, heating uses a lot of energy. We can save energy by turning down the heat and dressing warmly indoors. 
    • Putting on a sweater or a blanket helps insulate our bodies.

Modify or extend this activity

  • Have the students test the water in the travel mug and the regular mug after 1 hour to see if the water in the thermos is still warm.

Curriculum Fit

Grade 3 Applied Design, Skills and Technologies

Big idea

  • Designs grow out of curiosity

Curricular competencies

Applied skills
  • Use materials, tools, and technologies in a safe manner in both physical and digital environments

Grade 3 Science

Big idea

  • Thermal energy can be produced and transferred


  • Sources of thermal energy

Curricular competencies

Questioning and predicting
  • Make predictions based on prior knowledge
Planning and conducting
  • Safely use appropriate tools to make observations and measurements, using formal measurements and digital technology as appropriate and collect simple data
Processing and analyzing data and information
  • Compare results with predictions, suggesting possible reasons for findings
  • Identify some simple environmental implications of their and others’ actions

Teaching Notes

Insulation to keep warm

Insulation is defined as a material that limits the travel of heat, sound or electricity from one place to another. 

Insulation comes in many forms like fur, feathers, and fat which help keep animals warm in the winter. We dress warmly when we go outside in the winter. When indoors, we can choose to wear a sweater or use a blanket instead of turning up the heat to save energy. Many travel mugs or flasks are insulated using an air gap, similar to double-glazing for windows.

Buildings are constructed using insulation in the walls and roof. More insulation means that less heat is lost from the building, resulting in energy savings. 


  • Assess students’ understanding of insulation and how it can keep their bodies and homes warm.
  • Assess students’ ability to follow direction, read and record results. 
  • Assess students’ communication and cooperation in groups.

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