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Chemistry with kids in the kitchen

5 December, 2011

Science is seen by many as an intimidating subject, full of long Latin words and abstract concepts, however, science at its most basic is studying something to gain knowledge about it. Chemistry is the study of substances and the ways they react together.

Chemistry is involved each and every time we prepare food in our kitchen. Heat transforms fluid, transparent egg white into a more solid, opaque fried egg. Ground coffee when mixed with hot water (and even cold water) dissolves. Pancakes can be made fluffier by the addition of baking powder or beaten egg white. Cooking involves chemical change produced by heat.

Chemistry experiments can be quite tasty. Learn about how acids and bases (or alkalis – the “opposite” of an acid) react together by using foods you can find in your pantry or in the food aisles of the supermarket. Mix 1/2 tsp bi carb (baking soda) and 1 tsp citric acid (found alongside cream of tartar and baking powder in the baking aisle of the supermarket). The resulting powder doesn’t do anything. However, place a small amount on your tongue and you will feel the “fizz” of the chemical reaction. When the powdered acid (citric acid) and powdered base (bi carb) mix with water it produces small bubbles of carbon gas, creating the tingling sensation on your tongue.

A tastier way to see how acids and bases work is to make sherbet. Put ½ tsp citric acid, ½ tsp tartaric acid (alongside the citric acid in the supermarket), ½ tsp bi carb, ½ cup icing sugar (not icing mixture) and 1 tbsp of jelly crystals or powdered cordial into a bowl and mix well to make delicious sherbet.

For an experiment with a little more “bang” try making an erupting volcano. Get a small plastic drink bottle or jar, preferably with a narrow mouth. Put about a cup of white vinegar into the bottle. Use a funnel to quickly add 1 tsp of bi carb and quickly remove the funnel to see the eruption. For even more mess, I mean, fun try this in a squeezy bottle from sauce, replacing the lid quickly after putting the bi carb into the bottle.

Another great kitchen chemistry experiment is to grow your own crystals. Start by bringing 1 cup of water to a rolling boil and add 1/4 cup of normal table salt. Add some food colouring if you’d like coloured crystals. Stir to dissolve and continue adding more salt until no more salt will dissolve in the water. Take a clean glass jar and a larger plastic lid from your recycling bin, and place the jar (right side up) on the plastic lid (which will act as a tray). Pour the salt solution into the glass jar. Get 5-6 pieces of yarn (about 15cm long) and knot them together at one end with one big knot. Place the knotted end in the bottom of the jar and drape the ends of the yarn over the lip of the jar. Leave somewhere where it will not be disturbed.

After a few days you will notice that the yarn has grown fat with salt crystals. If you repeat the first part of the experiment and create more hot salty water and gently add it to the jar (taking care to not pour it on the yarn that is hanging out of the jar) your salt crystals will continue to grow. You could even try adding a different colour to the second (and subsequent) batches of salt solution.

The crystals grow because more salt can be dissolved into water at a high temperature than it can in water at room temperature. As the water cools, and later evaporates, it releases the salt, which forms crystals as the water evaporates. The faster the water cools and evaporates, the smaller the individual crystals will be.

For younger children, you could try some basic experiments in solubility. Solubility is just the fancy name for whether a solid will dissolve into a liquid. Gather together some jars or something similar to hold water, about half a cup in each one. Try adding different kitchen items to the water. Does sugar dissolve? What about cinnamon? Salt? Ground coffee? Oil? Desiccated coconut? Milk? Try a few different foods and then ask your children to predict whether a food will dissolve in the water before you try it. Perhaps another day, try the experiment again with cold, warm or hot water, noticing if there is any difference in the way the foods do (or don’t) dissolve.

Chemistry, presented in a familiar environment with familiar ingredients is fun and shouldn’t feel as intimidating as the chemistry involving specialised equipment, lab coats and scientists. If these experiments only whet your appetite for more, then try the Science of Cooking website at http://www.exploratorium.edu/cooking/index.html

This article originally appeared in Mixtapezine.

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