Thames & Kosmos Kids First: Crystals, Rocks & Minerals handleiding

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Thames & Kosmos

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Handleiding

WHAT’S HAPPENING

When a solid substance — such as the alum in this case —

dissolves, water pushes between its smallest component parts

(molecules) and releases them from their compounds. These

building blocks are then floating around individually in the

water. Since they are very tiny, you can’t see them. With many

substances, their ability to dissolve increases with temperature

(a well-known exception is table salt). A solution that can’t

dissolve anything further at a certain temperature

is called saturated. When the solution cools off it

becomes supersaturated, and the excess alum

separates out in the form of crystals. This cooling

method provides crystals very rapidly.

Overnig ht

TIP !

If the resulting crystals are not big enough, you can put them

back into the solution, warm it up again, and then wrap the

cooling jar with a thick towel so that it cools more slowly.

Larger crystals will form when the solution cools more slowly.

Cooling method

YOU WILL NEED

› Large measuring cup

› Double-ended measuring spoon

›  g Potassium aluminum sulfate

(alum powder)

› Wooden spatula

› Display box

› Distilled water

› Pot of hot water (40-50 °C, 100-120 °F)

› Paper towels

› 2 Empty glass jelly jars with lids

› Sheet of paper

› Pencil

HERE’S HOW

1. Use the measuring cup to measure 200 ml

of distilled water and pour it into the empty

jelly jar.

2. Add the alum powder and stir. Even after

you have stirred for a long time, a large

part of the alum will remain undissolved at

the bottom.

3. Set the jar into the pot of hot water and

resume stirring. Now everything dissolves.

4. Screw the lid onto the jar, and place it in a

quiet place for a few hours. A lot of crystals

will form.

5. Pour the solution into the second jar. Label

the jar and save it for the next experiment.

6. Shake the small crystals onto a paper

towel with the help of the wooden spatula.

Let them dry and select a few large and

pretty crystals.

7. Put them in the display box and close it

well (see page 9). You will need them later

when you make your geode.

6 7

Be careful when

handling hot water!

Wear protective

goggles!

200 ml

Important:

For all of the

experiments, wear

your safety goggles!



EXPERIMENT 1

Homemade Crystals

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