Another one for you to vote for:
Vote for you favourite experiment here
Saturday, February 24, 2007
National Science and Engineering Week 9-18th March
The last one for this week - remember to check for me next week!
Vote for you favourite experiment here
Vote for you favourite experiment here
National Science and Engineering Week 9-18th March
Have you been watching these experiments? Which one is your favourite so far? You can vote for them online (see link under the video). Here is the 3rd of 8 (see Feb archives for previous experiments).
Vote for you favourite experiment here
Vote for you favourite experiment here
Tuesday, February 20, 2007
A-maze-ing onions
You will need:
An onion (ideally already sprouting)
A shoe box
Another spare cardboard box
Strong scissors
Sticky tape
What to do:
First build a maze for your onion!
Use your spare cardboard box to cut rectangles about the same size as the smaller side of the shoe box. These will be the dividers inside your maze. You need at least two but you could make more if you like.
For each divider, cut a ‘window’ in the cardboard about 3 cm square. It will make the maze more interesting if they are in different positions on each divider.
Cut an ‘exit’ door for the onion shoot at one end of the shoe box.
Put the onion at the other end of the shoe box..
Fit the dividers into the box, spacing them out between the onion and the exit. Try to put them in so the onion will have to change direction to get through each hole.
Try to find a sunny place to leave it (so the sun can shine on the exit) but where it won’t be disturbed.
Leave for about 3 weeks and then check to see how it’s getting on.
What’s going on?
The sprouts on your onion should have started to find their way out of the maze. They are growing towards the light coming through the exit. Biologists call this phototropism. You might have noticed this already with indoor plants. They grow towards the light, and can get very lopsided unless you turn their pots round occasionally.
So how does the onion ‘know’ where the light is, and how does it grow towards it? The tips of plant shoots contain a growth hormone called an auxin, which makes the shoot grow faster. But light destroys the auxin, so it only works on the side that doesn’t have any light. The side without any light grows longer and the shoot ends up bending towards the light.
You might have also noticed that plants without much light grow long and spindly. This is because there is lots of auxin in the plant and it grows fast – but the plant won’t be very healthy because it needs light to make food for itself by photosynthesis.
More ideas
Try seeing if a sprouting potato can find its way through the maze. Have a race between the potato and the onion to see which shoots grow quicker.
You could grow plants from identical seeds, one in the dark and one in the light to compare them. Look especially at the colour of the leaves. Think of ways to test whether the auxin is only in the tips of the shoots or all along the shoots.
Friday, February 16, 2007
Secret writing
There are many ways of writing secretly. A good spy should know at least three but we'll give you FOUR!
You will need:
Candle or white wax crayon
Paper
Water-based paint
Cotton buds
Lemon juice
Bicarbonate of soda
Red cabbage water (see instructions)
Pencil
Paintbrush
What to do:
Method 1: Candle or white wax crayon
Write your message on a piece of paper using the candle or crayon.
Now paint over the message with water based paint. See the message now? Aha!
Method 2: Lemon juice
Write your message on a piece of paper using a cotton bud dipped in lemon juice. Now either iron over the message (ask an adult to do this) or place it near a light bulb (ask an adult to do this). We don't want anyone getting burnt! See the message now? Oooh yes! And it's gone brown!
Method 3: Pencil and wet paper
Wet some paper, just a bit, and place another sheet of paper on top. Use the pencil to write your message quite gently. Take the topmost paper off. Wait for the wet paper to dry.
Now wet the paper again. Well would you believe it? There's the message.
Method 4: Bicarbonate of soda and red cabbage water
Dissolve two teaspoons of bicarbonate of soda in four tablespoons of warm water.
Write your message on the paper using a cotton bud dipped in the solution.
Let it dry.
Pour hot water over some shredded red cabbage leaves. Leave for 15 mins and then strain. You should have a dark purple solution.
Paint the red cabbage water over your message. Well I never!
Try it again but this time use lemon juice instead of bicarbonate of soda.
What's going on?
Method 1: Candle or wax crayon
Wax is oil based and oil and water do not mix. The paint will not stick to the wax message so the paint soaks into the paper and leaves the waxy areas paint-free. Your message will show up white against a coloured background.
Method 2: Lemon juice
The lemon juice is very nearly clear so does not show up on the paper when it is dry. When you heat the paper, the lemon juice starts to burn. Like all organic material (i.e. anything that was once living), the lemon juice contains carbon. When it burns, some of the carbon is released in the same way a candle releases soot. The brown writing is just the carbon that has come out of the charred lemon juice.
Method 3: Pencil and wet paper
The pressure from your pencil will mash up the fibres on the lower, damp sheet of paper. Mashed up fibres reflect the light differently to normal, unmashed fibres.
But when the paper dries, the fibres look the same, so your message disappears - until you wet the paper again.
Method 4: Bicarbonate of soda and red cabbage water
Red cabbage water is a dark purple colour. It is a natural indicator which means it changes colour in the presence of acids or alkalis. With acids it turns red or pink and with alkalis it turns blue or green. Bicarbonate of soda is alkaline and when the red cabbage water is painted on it turns blue and shows up against the purple background. If you use lemon juice instead the message will appear red against a purple background.
You will need:
Candle or white wax crayon
Paper
Water-based paint
Cotton buds
Lemon juice
Bicarbonate of soda
Red cabbage water (see instructions)
Pencil
Paintbrush
What to do:
Method 1: Candle or white wax crayon
Write your message on a piece of paper using the candle or crayon.
Now paint over the message with water based paint. See the message now? Aha!
Method 2: Lemon juice
Write your message on a piece of paper using a cotton bud dipped in lemon juice. Now either iron over the message (ask an adult to do this) or place it near a light bulb (ask an adult to do this). We don't want anyone getting burnt! See the message now? Oooh yes! And it's gone brown!
Method 3: Pencil and wet paper
Wet some paper, just a bit, and place another sheet of paper on top. Use the pencil to write your message quite gently. Take the topmost paper off. Wait for the wet paper to dry.
Now wet the paper again. Well would you believe it? There's the message.
Method 4: Bicarbonate of soda and red cabbage water
Dissolve two teaspoons of bicarbonate of soda in four tablespoons of warm water.
Write your message on the paper using a cotton bud dipped in the solution.
Let it dry.
Pour hot water over some shredded red cabbage leaves. Leave for 15 mins and then strain. You should have a dark purple solution.
Paint the red cabbage water over your message. Well I never!
Try it again but this time use lemon juice instead of bicarbonate of soda.
What's going on?
Method 1: Candle or wax crayon
Wax is oil based and oil and water do not mix. The paint will not stick to the wax message so the paint soaks into the paper and leaves the waxy areas paint-free. Your message will show up white against a coloured background.
Method 2: Lemon juice
The lemon juice is very nearly clear so does not show up on the paper when it is dry. When you heat the paper, the lemon juice starts to burn. Like all organic material (i.e. anything that was once living), the lemon juice contains carbon. When it burns, some of the carbon is released in the same way a candle releases soot. The brown writing is just the carbon that has come out of the charred lemon juice.
Method 3: Pencil and wet paper
The pressure from your pencil will mash up the fibres on the lower, damp sheet of paper. Mashed up fibres reflect the light differently to normal, unmashed fibres.
But when the paper dries, the fibres look the same, so your message disappears - until you wet the paper again.
Method 4: Bicarbonate of soda and red cabbage water
Red cabbage water is a dark purple colour. It is a natural indicator which means it changes colour in the presence of acids or alkalis. With acids it turns red or pink and with alkalis it turns blue or green. Bicarbonate of soda is alkaline and when the red cabbage water is painted on it turns blue and shows up against the purple background. If you use lemon juice instead the message will appear red against a purple background.
Saturday, February 10, 2007
Thursday, February 8, 2007
Saturday, February 3, 2007
Animation vs Animator
Ok so it's not related to Science, but I enjoyed this so much I thought I'd share it with you. Enjoy!
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