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

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Handleiding

WHAT’S HAPPENING

With this procedure for determining density, you don’t even have

to know the weight of the individual matchsticks — they all just

have to weigh the same. It turns out that the density is around 3

for minerals such as calcite and fluorite, and the ores have much

higher densities of around 5. But what is density in the first

place? See page 27.

More or less dense

YOU WILL NEED

› Large measuring cup

› Weighing scale from the die-cut sheet

› Wooden stick

› Minerals

› 2 or 3 Boxes of matches

› Paper and pencil

› Adhesive tape, all-purpose adhesive

› Yarn or string, scissors

HERE’S HOW

First, assemble the scale.

1. Remove the parts from the die-cut sheet.

2. Tape the scale pans together into cones.

3. Thread a 10-cm-long (4 in) piece of yarn

through the prepunched center hole of scale

A, and secure it with tape. Thread a 15-cm-

long (6 in) piece of yarn through each of the

scale pan holes. Secure the ends of each of

the four sections of yarn to the end of the

stick above it.

4. Tie another piece of yarn to the exact center

of the stick, securing it with a drop of all-

purpose glue, and use it to hang the scale

from a desk lamp or another similar

support. It should hang freely, with the

scale pans about 15-20 cm (6 to 8 in) above

the table surface. Adjust the scale pans

until they are perfectly balanced, and then

secure them with tape.

Now for the actual measurement:

5. Secure one mineral sample to one of the

scale pan’s yarn (A) with some glue. In the

other pan (B), place as many matchsticks as

is necessary to balance the scale.

Fill half the measuring cup with water, and

submerge the mineral sample in it. Be sure

there are no air bubbles sticking to it! The

scale is now unbalanced, so place as many

matchsticks into scale pan (A) as is

necessary to balance the scale when the

mineral sample is fully submerged in water.

7. Count each of the groups of matchsticks, and divide the number from

B by the number from A. The result is the density of the mineral

sample. Example: 112 matchsticks on B, 27 matchsticks on A. 112

divided by 27 gives you 4.1 — so the density is 4.1.

8. Using this method, measure all the minerals contained in the kit.

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EXPERIMENT 12

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