Thames & Kosmos Chemistry C500 (Version 2.0) handleiding

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Thames & Kosmos

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Handleiding

Color change

YOU WILL NEED

→ 2 test tubes, with stopper

→ pipette

→ measuring spoon

→ litmus solution

→ sodium carbonate

→ cup of sparkling mineral

water

→ cup of stale, flat mineral

water (let it sit out for a day)

→ cup of plain bottled water

→ 2 cups of tap water

HERE’S HOW

1. Dissolve 4 large spoonfuls sodium

carbonate in a test tube ﬁlled halfway with

tap water. Insert the stopper and shake

vigorously to dissolve all the sodium

carbonate. This is your “standard solution.”

2. Pour 3 cm of mineral water into the second

test tube and ad 5 drops of litmus solution.

Does the color of the solution change?

3. Now drip some of the standard solution

into the test tube from the pipette. Keep

track of the number of drops! Lightly swirl

the test tube.

Do you see the “blue clouds” that appear

and disappear again as you swirl the

liquid?

4. Keep adding drops of the standard solution

until a distinct blue color is still

recognizable after 10 seconds. Take note of

the number of drops you used! Repeat the

experiment with stale mineral water and

plain bottled water.

Safety Note:

For sodium carbonate, note the

“Information about hazardous substances” on page 7!

There is carbonic acid in mineral water,

which turns the litmus solution red.

The standard solution is a base, and

gradually cancels out the effect of the

acid. The more acid there is in the

mineral water, the more standard

solution you have to add for the color

to change.

LITMUS

SOLUTION

3 CM

STANDARD

SOLUTION

STANDARD

SOLUTION

SODIUM

CARBONATE

1/2

WATER

→

WHAT’S HAPPENING?

Still Water and Sparkling Water | 25

EXPERIMENT 12

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