h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

One of the things that got me into science was the experiments we did at junior school. I can only think of a few at the moment(i did stick up about 5 in a thread a few months ago) but hopefully others can add to them:

Experiment 1: Mainly to show that air contains oxygen and fire requires oxygen to burn.

Tools: One hard-boiled egg (de-shelled)
One old style pasteurised milk bottle
Piece of newspaper twisted up tightly into a twizzler sort of shape
Matches

What you do is light the newspaper drop it in the bottle place the egg pointy end upwards on top of it.

The burning paper uses up the oxygen in the bottle producing a vacuum which sucks the egg into the bottle. I think the fire usually goes out before the egg gets totally sucked in proving that the fire needs oxygen and it has been used up.

you can also prove that animals need oxygen to breathe by putting your kids hamster into an air tight box with a hole just big enough for a vacuum cleaner hose and the turn it on. If the hamster doesn;t get sucked up the tube before it dies from lack of oxygen you have taught your child another important lesson...do not let your parent use your pets in experiments.

Experiment 2: Looking at the capillary action of plants to draw up water.

Tools: Stick of celery
Glass
Water with red food dye in it

Put a stick of celery into a glass of coloured water. The celery will draw the red water into its system and turn red.

Experiment 3: I have only read about this one and it does require quite a few kids.

Tools: Quite a few kids
A wall

One child stands at arms length from the wall with arms horizontal and touching the wall. The others then line up in a similar fashion behind the first brat they put their arms striaght out and against the shoulders of the little darling in front of them.

Now, they all push forwards with their arms at the same time. The 'logical' thing that should happen is the kid at the front gets squashed up against the wall. But this is not the case. What happens is that each child whose shoulders are being pushed forwards takes the force of the person behind them into their own arms and couteracts this force so that the only force the person in front of them feels is the force of one person pushing against them. In theory. Someone with access to a lot of kids could try this...hint hint

Experiment 4: More of an A-level project - proving that the acceleration due to gravity is 9.81m/s/s.

Tools: A camera with a bulb setting(i.e. you can hold the shutter open)
A room that can be made totally dark
A silver ball of tennis bal size(wrapped in sliver foil or similar)
A light that can be strobed at set time periods
A graduated back ground that can be measured from.

Method: You drop the ball in the darkened room against the graduated backdrop. With the camera on bulb setting and the strobe light flashing towards the ball but not at the camera the flash lights up the ball as it drops down every fraction of a second. when the ball hits the ground switch the camera off bulb.

Then once the film is developed (or the digital image processed) measure how far the ball has dropped during each strobed flash and apply the relevant equation to work out 'a'.

This can be done as I did it back in 1987 when we didn't have fangled pc's and digital cameras.

Experiment 5: To show that wood is full of voidage and capillaries similar to the celery.

Tools: woodshavings(not dust but good curly quality ones)
A couple of pint glasses or measuring jugs
water

Method: Pack a glass with the woodshaving.
Start pouring in the water.
Now, one would think that with all the wood in the glass how could you possibly get any water in the same jug? You can because the wood soaks the water up like a sponge due to all the small open areas in its structure.
I have no idea how much it does hold I was only 11y.o.s when I saw it done and that was 25years ago...

Being a little pedantic, Experiment 2 doesn't necessarily show capillary action, since there *could* be other processes at work in a plant, but I guess it's OK for young kids (though you may need to be ready with a truthful answer to "Is that how it works in *really* *big* trees, then?", for which the answer is more complicated, with capillary action only being the lesser of 3 main mechanisms.

Experiment 4 could be done with a digital camera with a movie mode of sufficient resolution, possibly down the side of a building, especially if some building features enable measurements to be taken. Possibly some regularly-knotted string or similar could be lowered down the building as a backdrop for measurement.
There's a possible historical linkage with Galileo dropping balls off the Leaning Tower of Pisa, and also a possible foray into air resistance.

Thanks for the pedantic reassurance...I told you it was 26yearsago

I had wondered about air resistance as well - feather and ball for example.

However, you would then need to do it in a vacuum to prove it. There must be a video on the web if the hammer/feather experimant being done on the moon.

I've lost count of the amount of times we at school did the age-old baking-soda-and-vinegar volcano. Fill a volcano-like mold with baking soda, pour in some vinegar, and the thing fizzes a bit. Mildly amusing, I must admit.

How sound travels differently through air and water
clicking rocks or similar together above and below the surface at a pool, river etc (requires/could improve confidence re going under water)
Ooh, String can telephones too!
_________

Showing how the speed of light is faster than the speed of sound
can be done very easily in a variety of ways
e.g. observe someone chopping wood, slamming a door etc from a distance
_________

How liquids have differing freezing points
put glasses/jars of tap water, heavily-salted water, vodka, olive oil etc in a domestic ( ususally approx -4°C) freezer for a few hours/overnight
_________

How thermal conductivity varies
(works best in a cool/cold house)
leave a few thermometers (the cheap outdoor/garden types are safe-ish in kids hands) overnight on e.g a carpeted floor, a very wet towel left on a bathroom floor, a lino/vinyl floor etc etc and get the kids to observe that they are all (roughly) the same temp and then get them to stand, bare-footed, on each surface

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I do this through solids too.
Get the kids to stand about 1m apart and get one of them to hold up a ticking watch. The other can't hear it. Then ask the one with the watch to hold it against a piece of wood (a metre rule stick usually) and the other to put their ear against the other end. They can then hear it.

Alex.

Hey, don't you think we should put a book together here?

Or at least a guide entry?

How about if I take all your ideas, write a book and make millions?
I could do with a bit of cash.



Alex.

to show how the tubes and lungs work you can make model lungs out of a plastic bottle, balloons and straws and a lump of plastacine.

"How about if I take all your ideas, write a book and make millions?"

Not before me, chuck. It is a future project of mine - to write a book of Science experiments suitable for Primary school. Given the variable standards of Science teaching at KS2 it must be worthwhile.

B

I recall an experiment to demonstrate air pressure from my science class days that really, really impressed me at the time. But may require a bit of supervision of youngsters.
It involved an old oilcan of the metal type that was prevelant at the time with about an inch of water in it. You might have difficulty finding one of those these days though.
It was put over a Bunsen burner with the cap off until the water had boiled for a couple of minutes, by which time the steam had removed the greater part of the air inside.
The cap was replaced and sealed down and the can removed from the heat. As the internal steam condensed the pressure dropped and external air pressure collapsed the can. It was really quite impressive watching the can fold and buckle as it cooled.
DK

Ah, yes. I do that on a regular basis.

B

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Maybe I'll beat you to it.

Alex.

Any more nifty experiments we can do at home?

Alex.

Bicarb and lemon juice is fun.

B

Well, I seem to recall another experiment showing that metals expand when heated

A short bar of metal, about a foot long, fixed/clamped at one end and aligned horizontally. A light source on one side casting a shadow against a plain wall. There should be a differential between the light/metal and metal/wall distances so that the shadow is enlarged.
Mark off the edge of the shadow on the wall then apply heat to the metal, (out with the old Bunsen burner again) and watch the shadow expand along the wall.
There was also a way of calculating the coefficient of expansion of the metal but my maths on that are a bit lacking now.

There was another to show the expansion of gasses under heating. That involved a thin necked jar sealed at the end with a take off pipe leading to a balloon. Heating the jar caused the gas (air) to expand and (semi) inflate the balloon.

Another one to show that liquids rise when heated was to half fill a beaker with water and using a pipe gently lay in a layer of coloured/inky water underneath so that it forms two seperate layers. Apply the heat to the base of the beaker and watch the coloured water rise up the side.
All the best
DK

I like the shadow thingy. I haven't got a bunsen burner at home but I guess I could use a camping stove.

The lemon juice and Bicarb does sound fun. Definitely going to try that one.



Alex.

Alternatively, you could ask Odo for her honeycomb recipe. That comes out of the oven rapidly expanding and looking like the Blob From Outer Space.

b

I will ask her. It sounds fab.
If only I had an oven that works! (I use the grill and hob, which do work).

I'll have to do it at Hoo's

Alex.

What's her ID?

Some experiments have been cheerfully used for years to demonstrate a scientific principle, but the actual explanation for how they work is something different. Alex's burning newspaper in a bottle sucking an egg into the bottle is said to demonstrate that the burning uses up the oxygen, but is more likely due to the fact that the air inside the bottle heats up and expands. It contracts as it cools, sucking in the egg.

This was demonstrated by the classic candle in a bell jar experiment, where water was sucked up into the bell jar as the candle "burns away the oxygen". If you use more candles, more water is sucked into the bell jar, showing that this is to do with heat and not chemistry. Of course a very carefully regulated experiment, in which the candles are lit after the bell jar has been put in place and in which no air bubbles out of the bell jar during the experiment would demonstrate the burning of oxygen. But it is not as simple as we make out to the kiddies.

Odo? U192764, if my memory serves correctly...

B