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Wednesday, December 16, 2009

Floating Sinking Diver and Fish

Wednesday, December 16th, 2009
Teacher had a fish that floats in water. He floated in a 2litre bottle. He had his own air tank (a biro cap, with no hole in the top, held on to the fish with a paper clip and elastic band). We had to figure out a way to get the fish to sink and then float again. We tried turning the bottle upside down (couldn't do this in the sea though), shaking the bottle and holding it sideways. The way to get the fish to sink was to squeeze the bottle. When you do this, the fish sinks to the bottom, and when you stop squeezing, the fish floats again. This happens because the air in the pen top helps the fish float.

When you squeeze the bottle, the air in the cap gets squashed a little (it compresses). This means that the bottle fills a little with water instead. Now the fish hasn't enough air to keep him floating, and the fish sinks.

When you stop squeezing, the air in the pen cap expands again, and now there is enough air in the cap again so the fish can float. We also tried this with a diver and it works in just the same way.

Detergent Power

Wednesday, December 16th, 2009
We got a cardboard boat to float on the water. The top of the water has surface tension on it. It is like a skin made by water molecules holding tightly on to one another. The boat floated, but didn't move. When we put just one drop of washing up liquid at the back of the boat, the surface tension is broken and the boat shoots forward. This was really impressive, but we could only do it once. (Actually, we did manage to try again, but only after the basin had been washed and dried to get rid of all traces of wash up liquid). We can't wait to try this in the bath!

Water Falling Sideways

Wednesday, December 16th, 2009
Normally when you spill water out of a jug, it will fall straight down. It is gravity that pulls it down. We could get water to spill sideways. First of all we tried lots of things - pouring it out of the side or the back of the jug, using our fingers or hands to get the water to spill sideways. We managed best of all when we used a piece of string, and got the water to run sideways along the string.
Water sticks to string with surface tension. Surface tension is like a skin of water caused by water molecules holding tightly on to one another. They were holding so tightly to each other around the string, that even when the string is held sideways, the water will hold on to it and drip sideways, instead of straight down.

Bath Tricks

Wednesday, December 16th, 2009
We did some interesting science that we can easily practise in the bath at home.
We got a bottle and filled it with water, put a hand on top, turned the bottle over and took the hand away. We had to guess what would happen. It was as we thought - the water that was in the bottle rushed out once the hand was taken away. The second time we tried this, we only took our hand away when the bottle was under water. This time the water stayed in the bottle. This is because the water in the bottle wanted to get out, while the water in the basin wanted to get in, so the water ended up going nowhere and stayed in the bottle.

Next we got a yoghurt pot and a square of cardboard. We filled the pot with water, put the card on top, turned the pot and card upside down and took our hand away. Surprise, surprise, the card stayed on the bottom of the pot without falling off. This is because the air on the bottom of the card is pushing the card up into the pot, and the water is trying to get out, so both end up going nowhere at all.

Friday, December 4, 2009

Volcanic Activity in Room 5

Friday, December 4th, 2009
We made a volcano today.
We got an acitmel bottle and put newspaper round it so that it looked like a volcano, and a tray underneath in case we made a mess. To make an ordinary volcano you need bread soda and vinegar, but we wanted a delux model so we used red food dye and wash up liquid as well. Bread soda and vinegar mixed together make a fizzy gas called Carbon Dioxide. This gas comes rushing out of the bottle. To make the foam red we used red food colouring, and for lovely bubbles we used a little wash up liquid as well.
The second time we tried this, we used only the bread soda and vinegar, but we used a bottle with a small opening so the fizz squirted a little. For best results we would have liked to have used an even smaller bottle. The third and final time we put the bread soda into a balloon and the vinegar in the bottle. When we stood the balloon up, the bread soda dropped into the bottle with the vinegar in it. The gas that was made blew the balloon up. It was exciting!

Fire Extinguisher

Friday, December 4th, 2009
We made a great fire extinguisher today. Teacher lit a candle and carefully put it into a big glass. This is our fire. Next she put in a few spoonfuls of baking powder. She was very careful not to put the powder on top of the candle. One of the boys held the funnel while teacher put a little vinegar on top of the powder.
The powder and vinegar mixture began to fizz. We heard that when you mix vinegar and baking powder together, a gas called CO2 or Carbon Dioxide (bad air) is made. This gas is heavier than air, so it sits at the bottom of the glass. When enough CO2 is made, it pushes the Oxygen (O2 good air) up higher in the glass. Now that the candle can't reach the O2, the flame goes out.We also learned that we breathe in Oxygen and breathe out Carbon Dioxide. Plants and trees do the opposite - they breathe in CO2 and breathe out O2. That is why it is so important to have lots of trees planted around us, and lots of trees in the world.
There is Carbon Dioxide in fizzy drinks too. When we drink it the gas goes into our tummies. If we can't get it out of our tummies, it gives us a tummy ache. When it does escape from our tummies it can go up (burp) or down (fart). Both of these seem very rude, but they are natural. We just have to try and not upset the people around us by being too noisy or smelly, and always say "excuse me" if one slips out. We have often seen mammies put their babies on their shoulder and pat their backs to help them burp. They must have gas in their tummies too!