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Chemical Energy

Rockets Rusty Heat Elephant Toothpaste Easy Endothermic Reaction Dry Ice Activities
Classic Mentos Geyser Hot Ice Homemade Soap Balloon Inflator Endothermic Polymer

Rusty Heat

Materials:
glass beaker or jar
a small bowl
steel wool
white vinegar
thermometer

Place the steel wool in the bowl and soak it in white vinegar for a couple of minutes. Squeeze out excess vinegar and wrap the steel wool around the thermometer such that you are still able to read the temperature. Put the steel wool in the jar or beaker, then place a cover or lid on the top (a small book or paper will do). Record the temperature immediately, then again in a minute or so, and again every minute for about five minutes.

Explanation: When you soak the steel wool in vinegar you remove the protective oil and the steel begins to oxidize (rust). The chemical reaction is exothermic, meaning that it generates energy in the form of heat. This principle is used in the manufacturing of disposable hand warmers.

Easy Endothermic Reaction

Materials:
citric acid (available as a fruit preservative and also at craft stores for making bath bombs)
water
baking soda (sodium bicarbonate)
glass jar or beaker (or plastic)
thermometer

Dissolve 1/2 teaspoon citric acid in 2 tablespoons of water. Slowly stir in a teaspoon of baking soda. Place the thermometer in the container and record the temperature immediately, then again every minute for about five minutes. What do you notice?
Try adjusting the proportions of baking soda, water and citric acid to optimize the temperature change.

Now try this: wash the thermometer and let dry. Leave the mixture to sit for an hour or more. Record the temperature on the thermometer, then stir the mixture and inert the thermometer. Take a temperature reading after 30 seconds, then again every 30 seconds for a couple of minutes. Now remove the thermometer and wait 30 seconds and record the temperature with it away from the mixture. What do you notice?
Thanks to my eldest son for thinking to try this second part and showing me this interesting phemomenon I would have otherwise missed!

Classic Mentos Geyser

Make a geyser up to 30 feet high!

Materials:
a tube of Mentos candy
a bottle of diet cola
a sheet of notebook paper
an outdoor area that is ok to spray diet cola around

  1. Cut your paper into a semi-circle shape and form into a cone.
  2. Cut a small hole in the bottom of the cone mall enough to fit in the neck of the bottle, but big enough that the mentos can pass through it. This will act as a funnel for the candy.
  3. Loosen the wrapping on the candy but keep it lined up in a row in the wrapper.
  4. Carefully open the bottle.
  5. Use your paper as a funnel to drop the candy into the bottle (do this as quickly as possible), then stand back and watch it go!

Variation: Glowing geyser
Instead of using diet cola, use tonic water and do this at night. If you shine a black light on it, the whole thing will glow an eerie blue colour.

Hot Ice

When this "ice" crystalizes, it gives off heat!

Materials:
1 litre (4 cups) white vinegar
4 tablespoons baking soda
saucepan and stove
a pie plate or other shallow dish
a beaker or pyrex measuring cup

  1. First you will make sodium acetate. Pour the vinegar into the saucepan, then gradually stir in the baking soda (work slowly so it doesn't overflow the pan).
  2. Stir and boil the mixture until a film starts to form on the top.
  3. Remove from heat immediately, then pour it into a beaker/cup and refrigerate. The refrigerated liquid is being supercooled, which means that it is cooled below the point at which it would normally solidify.
  4. Once it has cooled, pour it into a shallow pan. If it does not immediately crystallize, then you can touch it or drop a crystal left over from the saucepan into the liquid. You can also try starting the crystallization (through touching it or dropping in a crystal) as you pour so you can make small mounds and other formations as you pour.
  5. Be sure to feel the temperature as you do this--from cooled to very warm (but it shouldn't become hot enough to burn).

Variation: try adding a drop or two of food colouring to the vinegar to make coloured ice.




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