66953_Prof CHEM INS_Cover(6L) - Imaginarium

SURFACE TENSION
What is surface tension? The surface of a liquid is like elastic skin that always stretches
toward the centre: it's what we call the surface tension of a liquid. To experiment and
observe this type of tension, you will need:
• A bowl
• A piece of soap
• Toothpicks
• Water
• A sugar cube
First, fill a clean bowl with water and place the toothpicks on the water at equal distance all
around the rim of the bowl. Then, drop a sugar cube in the centre of the bowl and see how
the toothpicks move toward one another. The sugar cube absorbs the water, increasing the
surface tension.
To get the opposite effect, drop a piece of soap in the centre of the bowl. The toothpicks
will move away from each other. A thin layer of soap has spread through the water,
reducing the surface tension.
BREAK THE TENSION
If you want to break the tension, you will need the following material:
• A bowl
• Water
• Talcum powder
• A piece of soap
First, fill the bowl with water and wait for the surface to settle. Then, sprinkle
some talcum powder over the surface.
Afterward, wet a finger and dab it on a piece of soap, then put it in the water
close to the rim of the bowl. What happens? The talcum powder will move
toward that side of the bowl. How has the soap affected the surface tension of
the water?
GIGANT BUBBLES
Making gummy sweets is really easy! All you need is:
• A packet of flavoured jelly (50g)
• Water
• A plate
• A dropper
• Tweezers
Put the flavoured jelly powder on a small plate (a layer about 2cm thick). Using the
dropper, put a drop of water in the centre of the jelly powder layer. Then add another and
wait for the jelly to absorb the water. Repeat the process until you have added 6 drops of
water to the jelly powder.
The jelly powder absorbs the water and grows, forming a similar substance to gummy
sweets. Peel the layer of jelly from the sides of the plate using tweezers. The flavoured
gummy sweets are ready!
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