PROJECTS

 

 

 

Testing for Hardness of Rocks

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Materials:

  • Several rock samples;
  • Bowl of water;
  • Nail brush;
  • Coin;
  • Glass jar;
  • Steel file;
  • Sandpaper.

 

1) Clean some rock samples with water using a nail brush. On Moh's scale, a mineral is harder than any minerals that it scratches.

2) A fingernail has a hardness of just over 2. Scratch each rock with a fingernail &endash; if it scratches the rock, the minerals of which the rock is made have a hardness of 2 or less.

3) Put aside those rocks scratched by a fingernail. Use a coin to scratch the remaining rocks. A coin has a hardness of about 3, so any rocks it scratches contain minerals with a hardness of 3 or less.

4) Now try scratching the remaining rocks on a glass jar. If any scratch it they must be harder than glass, which has a hardness of between 5 and 6.

5) Put aside any rocks that will not scratch the glass. Try scratching the remainder with a steel file (hardness 7) and finally with a sheet of sandpaper (hardness 8).

 

v The hardest natural material is diamond, with a hardness of 10. It will scratch all other minerals.

 

Making Igneous Rocks

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  • Materials:
  • Sugar;
  • Water;
  • Saucepan;
  • Safety glasses;
  • Wooden spoon;
  • Milk.

 

1) Ask an adult to heat 500g of sugar with a little water in a pan. Heat until the mixture turns brown, but not black, then add a dash of milk.

2) Leave the mixture in the pan to cool at room temperature.

3) After an hour, you should see tiny crystal grains in the fudge mixture.

4) Once it is completely cool, feel its texture in your hands.

 

Making Sedimentary (Conglomerate) Rocks

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Materials:

  • Rubber gloves;
  • Old plastic tub;
  • Plaster of Paris;
  • Water;
  • Fork or spoon;
  • Pebbles;
  • Sand;
  • Earth;
  • Spare paper.

 

1) Put on a pair of rubber gloves. In an old plastic tub, make up some plaster of Paris with water, following the instructions on the packet.

2) Mix in small pebbles, sand and earth into the plaster of Paris. Mix them in well, to make sure they are evenly distributed.

3) Leave the mixture for ten minutes, until it starts to harden, then mould a small lump of it into a ball shape in your hand.

4) Make some more conglomerate rocks in different amounts of pebbles in. Place the rocks on a spare piece of paper to harden and dry out completely.

Identifying Minerals (The Streak Test)

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Materials:

  • A white tile;
  • Several samples of different rocks or minerals;
  • Field guide.

1) Place a tile face down, so that the rough side is facing upwards. Choose one of your samples and rub it against the tile. You should see a streak of colour appear on the tile.

2) Make streaks using other samples and compare the colours. Rocks made of several minerals may leave several coloured streaks.

 

What is Soil Made Of?

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Materials:

  • Scissors;
  • Large clear plastic bottle;
  • Small stones or gravel;
  • Earth;
  • Sand;
  • Wooden spoon;
  • Water.

1) Using scissors, cut off the top of a large, clear plastic bottle. Throw away the top part.

2) Put small stones or gravel, earth and san in the bottom of the bottle. Add water nearly to the top.

3) Mix the stones, gravel, earth, sand and water vigorously together. In a river, rock particles are mixed together and carried along by the moving water.

4) Leave the mixture to settle. You should find that the particles settle in different layers, with the heaviest particles at the bottom and the lightest on top.

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