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101 SCIENCE EXPERIMENTSBASIC PRINCIPLES MADE CLEAR BY SIMPLE DEMONSTRATIONS

I PODENDORF

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101

SCIENCE EXPERIMENTS

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SCIENCE

By Ilia Podendorf

Illustrations by Robert Borja

EXPERIMENTS

ODHAMS PRESS LTD LONDON

Ilia Podendorf is a science teacher w h o encourages children to work on their own and to investigate and solve problems as scientists do. Doing experiments, like t h e ones outlined in this book, not only helps children develop better concepts but, incidentally, improves reading skill and t h e capacity to follow directions intelligently. T h u s children become equipped to explore t h e everexpanding world of knowledge to which science leads. By doing t h e experiments in this book, children see or hear or otherwise observe w h a t happens in certain situations. W h e n they learn w h a t happens in a very small part of t h e universe they acquire knowledge t h a t helps to explain events in a larger universe. Doing these experiments is fun. This is a good reason to do them for children can learn while having fun. But there is a more basic reason. Through experiments children get first-hand knowledge that certain things do indeed take place. T h e knowledge gained t h r o u g h experimenting, supplemented by other types of learning, enables children to build concepts with which to interpret t h e world around them.

Copyright, 1960, Childrens Press First published in Britain 1961 Reprinted 1962 All rights reserved under international and Pan-American Copyright Conventions. Published pursuant to agreement with Cresset & Dunlap Inc., N e w York, N . Y U . S. A.

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EXPERIMENTING

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10 . . 15 . . . 59 73 . . . 87 94 . ... . 128 107 115 29 . 43

EXPERIMENTS WITH AIR

EXPERIMENTS WITH MAGNETS

EXPERIMENTS WITH ELECTRICITY EXPERIMENTS WITH WATER EXPERIMENTS WITH HEAT EXPERIMENTS WITH SOUND EXPERIMENTS WITH LIGHT . . . . . .

EXPERIMENTS WITH MACHINES EXPERIMENTS WITH CHEMISTRY EXPERIMENTS WITH PLANTS MORE EXPERIMENTS . . . 147 . .

INDEX OF EXPERIMENTS

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E P RM N X E I E T

Most people like to experimentto try something which they have never tried b e f o r e a n d see w h a t happens. Scientists do a great deal of experimenting. T h e y experiment to find the right answers to questions a n d to find ways of m a k i n g n e w things. W h e n scientists do a n experiment, they look, listen, read a n d m a k e records. T h e y are almost sure to p l a n a n experiment if an experiment is t h e best w a y to find a n a n s w e r to a question or to s o m e t h i n g which they wish to know. Experiments are i m p o r t a n t b u t scientists also use other ways of getting a c c u r a t e information. T h e y m a y w a t c h growing plants or animals for a period of time a n d m a k e careful records of w h a t happens. T h e y m a y collect a n d look at things. T h e y m a y listen to different sounds. T h e y read w h a t other people have written about t h e subject t h a t interests them. Scientists m a y use several ways to find answers to their m a n y questions. W h e n a scientist does a n experiment, there are certain things w h i c h he is almost sure to do. H e first decides w h a t his question i s w h a t it is t h a t he w a n t s to find out. T h e n he decides u p o n a p l a n for doing the experiment a n d gathers the materials which he will need. As he thinks a b o u t the e x p e r i m e n t , he will most likely form a n opinion a b o u t w h a t will h a p p e n . T h e n he will do the experim e n t . H e will w a t c h e v e r y t h i n g t h a t h a p p e n s a n d , if it is necessary, he will m a k e a record of it. H e will note whether his opinion was correct or not. H e m a y need to repeat the experiment several times before he c a n be sure of the answer to his question.11

It is easy to see that a scientist plans a n d carries on the experiment in a very careful way. Some experiments need to be planned with a control. This means planning the experiment in two parts. The parts will be just alike, as n e a r l y as possible, with t h e exception of one thing. T h e way in which they are different has to do with the question w h i c h he is t r y i n g to answer. T h e e i g h t h e x p e r i m e n t with h e a t is a n example of a controlled experiment. In this book there are one h u n d r e d a n d one questions which we are almost sure to ask ourselves. For e a c h question t h e r e is a suggestion for a w a y to find a n a n s w e r to it. Most of these suggestions are experiments.. T h e y are experiments which scientists have d o n e a n d ones which you m i g h t like to do. W h e n you do t h e e x p e r i m e n t s , y o u will w a n t to w o r k as scientists work. You must have the question clearly in m i n d . You must gather the materials together. You might then form a n opinion a b o u t w h a t you think will h a p p e n or w h a t the answer to the question will be. You must think over the plan for doing the experiment, a n d t h e n follow t h e p l a n carefully. As you are doing the e x p e r i m e n t watch, listen a n d think carefully to find out w h a t happens in order to decide u p o n the answer to the question. T h e answers to these questions m a y c a u s e y o u to t h i n k of other questions. You may then plan other experiments for yourself. T h e answers to these questions a n d others which you m a y plan for yourself help you to understand the environment in which you live. 12

Flasks, test tubes, rubber corks, etc., mentioned in these experim e n t s are found in most Chemistry Sets. F u r t h e r suggestions for w h e r e to find satisfactory a n d s i m p l e m a t e r i a l s for e x p e r i m e n t s are given in the back of the book.13

AE XV

1. Is this empty bottle really empty? Tou are sure to think it is. Try this experiment and find out.

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Turn the bottle upside down a n d lower it into the p a n of water. N o w tip the bottle a little to one side. Notice the bubbles that come from the bottle and rise to the top of the water. Try the experiment again and see whether the same thing happens. T h e same thing does h a p p e n . T h e bubbles are bubbles of something. They are bubbles of air. T h e bottle h a d air in it a n d the air h a d to be removed before the water could go into it. Try other shaped bottles a n d see w h e t h e r they c a n be m a d e to b u b b l e too.

2. Can this ship be sunk below the water without getting it wet?

M a k e a ship by putting a sail on a cork as you see in the picture. Float the ship on the water in a j a r or a deep pan. Be sure to keep it dry as you float it. Turn a glass upside down over the ship a n d push it down. Raise the glass and examine the sail of the ship to see w h e t h e r it is now wet. Try the e x p e r i m e n t again to see whether the same thing happens. T h e sail stayed dry because there was air in the glass. T h e air kept the water away from the ship's sail. This experiment and the first experiment show that air takes u p space. Air is somethingit is a material. If you r e m e m b e r this you will be able to u n d e r s t a n d the next experiment and explain the reason for what happens.

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3.

Into which of these flasks can water be poured easily?

Pour water into the one with the two-holed r u b b e r stopper. W a t e r r u n s into it evenly a n d w i t h o u t interference. Pour water into the other one. T h e water runs slowly a n d with interference. C a n you explain why this is so? You are right if you say t h e one with t h e second hole in the r u b b e r stopper makes it possible for the air to escape as the water runs into it. T h e other one makes it difficult for t h e air to escape. T h i s c a n be explained because air takes u p space. Could you think of something to do to the one with hiccups to make the water r u n into it evenly? You may sayloosen the cork. Try it and see if it works. It should.

4. Can this flask be made to blow bubbles?

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Put the stopper which has a tube through it into the flask. Any bottle may be used. But the best results are obtained with lightweight glass. Now put the end of the tube in water. Hold the ball of the flask in both hands for a few minutes. See what happens. See how many bubbles you are able to get. C a n you explain why the bubbles come out of the tube? You are right if you say it is because the air in the flask gets w a r m a n d needs m o r e room. We say t h a t air expands when it is heated. Now you have learned another important fact about air.

5. What happens when the air in this flask is heated?

Hold both your h a n d s on the flask above the water line. Try. to decide what you think will happenin other words m a k e a prediction. After several minutes decide whether your prediction was correct. W h a t did happen? Did the water in the flask rise in the tube? W h y do you t h i n k the w a t e r c a m e u p in t h e t u b e ? You are right if you say it is because the air in the flask e x p a n d e d a n d pushed the water u p in the tube. If you t a k e y o u r h a n d s off a n d t h e air cools, the water in the tube will go down again. It goes down because the air in the flask contracts a n d takes u p less room.

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6. What happens when the air in this flask is heated? Make a prediction about what you think will happen.

Put a balloon on an empty flask.

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M a k e your prediction before you read any further. Now hold the flask over a spirit lamp and see what h a p p e n s . T h e balloon is sure to blow up. It blows u p because the air in the flask e