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Soda volcano
If you drop mints into
a bottle of fizzy drink,
the drink turns to foam
and explodes out in an
instant. This is a physical
change rather than a
chemical reaction. The
rough surface of the mints
helps gas, dissolved in the
drink, to turn into bubbles
much more quickly than it
normally would.
Reactions and
changes
Tarnishing. It happens when silver atoms react with oxygen atoms in air.
Speeding up reactions
Cooking makes carrots softer
because the heat causes a
chemical reaction. Chopping
carrots into small bits speeds up
the reaction because it increases
the area of contact between
the carrots and the hot water.
Glow in the dark
Light sticks glow in
the dark thanks to
a chemical reaction
that releases energy
as light. You can slow
down this reaction by
putting a light stick in
a fridge, which makes
it last longer.
Sliced carrots
cook faster than
whole carrots.
Ask an adult to
boil some red
cabbage and save the
coloured water. Let the water
cool. Then add acid (vinegar) or
alkali (bicarbonate of soda) and
watch for a spectacular
change of colour!
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