How do chemical reactions happen?
• When particles collide / bump together, they
can react and become chemically joined. This
is how chemical reactions happen.
Chemical reactions can occur at
Reaction SLOW MEDIUM FAST
Frying an egg
• Aim: To see what effect the particle size has
on the speed of a chemical reaction.
Weigh marble chips/powder
• Put a piece of filter paper on the top of your
balance and turn on
• Measure out approximately 2g of marble
chips – put to side for your experiment
• Using a new piece of filter paper on the scales:
• Measure out the same weight of the
powdered calcium carbonate (chalk powder)
using the spatula onto the filter paper
Method: Collect 2 small beakers and fill
each with 25cm3 of hydrochloric acid.
Add the calcium carbonate to each beaker as
shown above. Observe and record what
The calcium carbonate powder
reacted faster than the lumps.
• A quick explanation:
Imagine you had a square which
would be like a large particle. The
other particle would only be able to
hit off 4 sides - there is a small surface
• Watch the animation which follows…
• If we break the large square up
into many smaller squares (smaller
particle size) then there are many
more surfaces for the other
particle to hit, increasing the
chance of a chemical reaction…
• Watch the following animation…
• The smaller the particle size, the faster the
speed of the reaction
• When the particles are smaller, there is a
greater surface area of the solid exposed to
the acid. More of the particles are able to
collide and so the reaction happens faster.