ELEMENTS of SCIENCE
(Revúca - Slovensko)

Valladolid

Investigate evaporation

Equipment

  • Two jars, the same shape and size
  • Tin foil
  • A marker pen

Instructions
1.- Fill the two jars about half full of water. Check the water level is the same in both. JPEG

2.- Make a foil cover for one of the jars.
3.- Leave both jars in a warm place for a few days.
4.- Check the water levels again. Which jar has less water in it? JPEG

How it works
The heat makes the water evaporate in both jars. But the foil cover stops the water vapour escaping into the air, so the level of water remains higher in this jar.

Magic toothpicks

Equipment

  • Some toothpicks
  • A plate with water
  • Soap
  • A sugar lump

Instructions
1.- Carefully lay the matches on the surface of the water.
2.- Place the sugar lump in the middle of the plate and wait a few seconds. (The toothpicks should move towards the sugar)
3.- Now place the soap in the middle of the bowl. (The toothpicks should move away from the soap) JPEG JPEG JPEG

How it works
When you put the sugar lump in the middle of the plate, it absorbs some of the water. A small current of water flows towards the sugar and pulls the toothpicks with it. But when you hold the soap in the middle of the plate the stronger surface tension around the edge of the bowl pulls the toothpicks outwards.

Lift an ice cube with a toothpick

Equipment

  • A bowl of water
  • An ice cube
  • A toothpick
  • Some salt

Instructions
1.- Float the ice cube in the bowl of water. JPEG

2.- Lay the toothpick carefully on the top of the ice cube. JPEG

3.- Sprinkle a little salt around the toothpick. JPEG

4.- Wait a few seconds and try to use the matchstick to lift the ice cube. JPEG

How it works
When you sprinkle salt onto the ice cube, it makes the ice around the matchstick melt. This is because salty water freezes at a lower temperature than fresh water. But no salt falls under the toothpick and it becomes frozen again into ice. This allows you to lift the ice cube with the toothpick.

Underwater volcano

Equipment

  • A small bottle
  • A large glass jar full of water
  • A piece of string
  • Food colouring or ink
  • Hot water

Instructions
1.- Tie the string around the neck of the bottle.
2.- Fill the bottle with hot water and add some drops of food colouring or ink.
3.- Carefully lower the small bottle into the large glass jar. Watch as the coloured water rises upwards, like a volcano. JPEG

How it works
The hot water is lighter than the cold water so it rises and floats to the top of the jar.
Later, as the hot water cools, it will mix evenly with the cold water and all the water will become the same colour. JPEG


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