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• Food colouring
• Pasteur pipette
• Scissors
• Plastic spatula
• Tweezers
3. Add a drop of food colouring to each cup. Do not stir the
mixture.
What do you observe?
WARNING. When you have finished, throw away any food
used during the experiment.
Explanation:
The food colouring moves faster in the cup only containing water
than in the cup containing both water and salt. However, the liquids
in both cups after a while become completely coloured.
Even though they are not visible, the water molecules are always
in motion. When food colouring is added to the water, the water
molecules intermix with the food colouring molecules and both types
of molecules move together. Eventually, the food colouring will mix
completely with the liquid and it becomes impossible to see where the
liquid ends and water begins. The water takes on the colour of the dye.
The faster the molecules move, the faster the food colouring
molecules move. Both water and food colouring molecules move
moreslowlyinthe water containing salt.Thesaltaddsmoremolecules
to the solution, which take up space. This solution contains more
molecules and less space in which the molecules can move, making
the movement slower.
SUPER SCIENTIST: Try the same experiment by mixing
water with other substances, like sugar or sodium bicar-
bonate.
The phenomenon taking place in this experiment
is called diffusion. The rate of the food colouring’s
diusion is less in the water containing salt than it is
in the water that lacks salt.
Experiment 11
Coloured bottle
What you will need:
• Small plastic bottle
•Small measuring cup (25 ml)
•Large measuring cup (100 ml)
•Pasteur pipette
•Wooden spatula
•Water
•96% ethanol or commercial ethanol
•Honey
•Cooking oil
•Food colouring
• Pen
Steps:
1. Using the small measuring cup, add 25 ml of water to plastic bottle.
2. Using the pen, identify and mark the water level.
3. Pour the water from the bottle into the large
measuring cup.
4. Add honey to the bottle until reaching the level
previously identied.
Experiment 12
Let go of the drop!
What you will need:
• Two Petri dishes
• Two tablespoons of virgin olive oil
• Two tablespoons of water
• Filter paper
• Paper napkins
• Small measuring cup (25 ml)
5. Using the Pasteur pipette, pour two drops of colouring into the cup
of water. Stir the mixture using the wooden spatula.
6. Pour the water containing the colouring into the bottle. The water
should oat atop the honey.
7. Using the small measuring cup, add 25 milliliters of oil to the bottle.
8. Now, using the small measuring cup, measure out 25 ml of ethanol
and add to it two drops of food colouring of another colour. Then,
carefully and slowly add it to the bottle.
What do you observe?
WARNING. When you have finished, throw away any food
used during the experiment.
Explanation:
The substances you’ve used in this experiment have dierent
densities. The four oat separately on top of each other without
mixing. At the bottom is honey, then comes water, followed by oil,
and ethanol sits on top.
Each substance has a dierent density. Denser substances have more
particles per unit of volume than less dense ones. This is why less
dense substances oat on top of denser ones.
In the case of this experiment, honey is the densest substance,
followed by water and oil. Ethanol oats on top because it is the least
dense.
SUPER SCIENTIST: Repeat this experiment, but try to
pour oil into the bottle before you pour water. What do
you think will happen?
Steps:
1. Pour two tablespoons of olive oil in one Petri dish and two tables-
poons of water in another Petri dish.
2. Cut two strips of lter paper and dip one in the olive oil and the
other in the water.
