The science of hot and cold

Ithink I am finally getting settled back into a steady routine as school is well underway! It has been great to see so many teachers reach out and inquire about how we can support them this year in their STEM education!

Nothing makes me more excited than to share my love of science with everyone. Quite a few requests have been coming in with the topic of weather for the classroom. This week, I thought I would share a visually exciting experiment that replicates how hot and cold masses react when they meet in the atmosphere. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

• Hot water

• Hold water

• Masking tape

• Marker

• Red food colouring

• Blue food colouring

• Two glass bottles (or two clear plastic ones)

• Index card

Procedure

1. Label one bottle HOT water.

2. On the second bottle label it COLD water.

3. Fill the HOT bottle with very HOT tap water and the COLD bottle with very cold water.

4. Add a couple of drops of BLUE food colouring to the COLD bottle and RED in the HOT bottle.

5. Set the COLD bottle on a sturdy table.

6. Take the index card and place it over the mouth of the HOT water bottle.

7. Holding the index card in place, invert the HOT bottle onto the top of the COLD water bottle.

8. Gently pull out the card.

9. Observe what happens.

10. Repeat BUT do the opposite with the bottles. COLD on top and HOT on the bottom.

11. Overserve.

What is going on?

The hot water is less dense than the cold water. When you place the bottle of hot water on the cold water the denser cold water, stays at the bottom and the hot or less dense water stays where it is. When you switch things up and have the cold water on the top, there is a movement in the water. It is amazing to watch it happen. The two colours will begin to swirl and mix. This is very similar to hot and cold air (we just cannot see it that well). This movement is called a CONVECTION CURRENT.

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact with Praxis at praxis@praxismh.ca, www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: