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Science is Fun: Kid's Experiments

This section which will be of some interest to "home schoolers"

MEASURING AND ESTIMATING

1. Measuring themselves
   Children can develop measuring skills by answering questions about the size of their own bodies and then measuring with a piece of string or a long stick to check the answers. One interesting question is "Which is longer; your foot or the distance between your wrist and elbow?" Children have to do measurements to prove they are both about the same length. Other questions might be "Are you as tall as your arms can stretch? Are most children as tall as their arms can extend?"
2. Estimating size
   Interesting activities to help children estimate equal amounts, compensating for differences in volume, can be developed from carrot slicing activities. Two pieces of carrot or parsnips sliced as in Figure (a) are not equal, even though they are all about the same length. Two pieces of carrot from Figure (b) are equal even though they are different lengths. Without necessarily introducing mass (weight) formally, a simple stick, thread and styrofoam cup balance shows up inequalities in the carrot or parsnip pieces.

   
   

   

3. Can you be sure of your measurement?
   You can help students understand the need for external measuring instruments in science by having them estimate whether water is hot or cold using their fingers instead of a thermometer. Use three bowls, one containing hot water, one containing cold water and one containing luke warm water in the middle. Students should place one hand in the cold water and the other in the hot water and wait for about a minute. Then both hands are put together into the luke warm water. It will feel hot to one hand and cold to the other. Each hand feels the water as being opposite to the temperature it was used to.

COMPETITION AND CONTROL

1. Racing objects
   The formal introduction of the controlled experiment is inappropriate for very young children. However, they will soon grasp the idea that conditions should be the same for a fair comparison to be made if you involve them in some unfair races! Rolling balls from different points on a slope or down different angles of incline will quickly generate protests with respect to the unfairness of the race. Children quickly recognize when one has an advantage over the other.
2. Predicting outcomes
   The above activity can be developed further by encouraging children to predict outcomes. If an empty soup can races a full soup can down the slope which one will win? Children will quickly find that the full one wins. The heavier can travels fastest.

   Simple races can be used to help students understand that changing the conditions changes the outcome and it is often possible to change the conditions in order to determine the outcome. Have two children each drop a sheet of flat paper from the same height. The papers float slowly through the air. Now challenge them to change things to make the paper fall faster. If one sheet is rolled into a ball the air doesnt slow it down and it falls faster.

3. Surprising Outcomes
   It is always good to have some activities where the outcome is a complete surprise. For example a coffee can becomes a trick can when a heavy nut is tied to a long rubber band hidden inside the can. Roll the can away from you on level ground. The surprising outcome is that when the can stops it starts rolling back towards you! As the can rolls away the nut causes the rubber band to twist and store energy. When the can stops and the band untwists, the energy released causes the can to roll back towards you. For an even more surprising outcome make this trick can to roll up the inclined plane used in Predicting outcomes above.

   Grape juice and red cabbage as an acid/base indicator.

   Diluted red grape juice stays red when an acid like vinegar is added but goes green when a substance which neutralizes acids (a base isadded). There are many such substances on the grocery store shelves. Household ammonia is a good choice. Children can use grape juice as an indicator to find out what else is " basic" or alkaline around the house.

   Red cabbage chopped and stirred with some methyl hydrate (methanol) makes an excellent indicator. Allow the red cabbage to sit in the methanol for about one hour in order to extract a reasonable concentration of natural indicator. You can do a good 'traffic signals' demonstration in dishes on an overhead projector. The solution goes bright red with acid and bright green with alkali (e.g. Drano).

   The lemon battery

   If two different metals are pushed into a lemon and the lemon squeezed slightly, a measurable voltage can be obtained. For example, a piece of copper wire and an iron or zinc galvanised nail will give enough current to really make the end of the tongue tingle.