Thermal chameleon

Study how calcium chloride interacts with water and ice.

Difficulty:
Danger:
Duration:
20 minutes
Thermal chameleon

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

How should I crush the ice?

This experiment requires finely-crushed ice. Remove the ice from the freezer and wrap it in a towel or some thick fabric. Put it on any hard surface, and carefully tap the bundle with a hammer. Next, transfer the ice into a plastic cup.

The cup didn’t freeze to the cork stand. Why not?

This can happen if you leave the ice in rather large chunks, which draws out the freezing process. Press the plastic cup firmly to the stand and stir for another few minutes. If this doesn’t help, try repeating the experiment.

What kind of weight can I put on the lightweight cork stand?

Anything that fits onto the stand and doesn’t roll off will work — little stones, keys, or even reagent bottles. Try experimenting more with different items!

Most of the water has run off the cork stand. What should I do?

Turn the stand over and pour some water onto its dry side. Try your best to pour the water into the center.

Step-by-step instructions

Prepare some ice in advance.

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Will a cup of ice freeze to a cork stand?

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It looks like ice by itself cannot freeze the water on the stand.

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What if we add some calcium chloride CaCl2?

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As it turns out, the mixture of ice and calcium chloride can freeze water. You can even try placing some weight on the stand.

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Will water freeze if we add calcium chloride?

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Wash the vial to repeat the experiment.

Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Most chemical changes, like dissolving, involve a change in temperature. For example, when you added dry CaCl2 to water H2O, some heat was released as the CaCl2 dissolved. You probably noticed the significant rise in temperature.

Large_CaCl2-Dissolution

But why did the temperature go down when you mixed the same CaCl2 with ice? Ice is also H2O, after all! It’s actually pretty interesting! CaCl2 dissolves in some of the melted ice, making a CaCl2 solution. This process, as you already know, makes some heat. At the same time, the ice dissolves in the CaCl2 solution—and this process absorbs a lot of heat. This makes the mixture colder!

Large_IceDissolution

Pure water freezes at 0°C (32°F). A solution of CaCl2, however, does not! So ice will continue to dissolve in it, and the temperature will just keep going down. The temperature of the CaCl2 solution could go as low as about -50°C (-58°F)! In fact, anything that is dissolved in water lowers its freezing point, which will allow ice to dissolve and cool the solution below 0°C. Pour some cold soda (a water-based solution) into a paper cup full of crushed ice, and maybe you’ll spot some frost forming on the outside!

Large_SodaIce