Experiences

Experiments about the air

Aleksandar Angelov (center for creative education)

Bulgaria

Primary school

Maths, Science

Teaching in class

Direct

Key competences
communication in the mother toungue, mathematical competence
learning to learn.

School subjects/ areas
interdisciplinar activity: maths, science, motherlanguage.

Place
the classroom

Duration
1 hour lesson

Materials
exercise book, a trasparent basin, a quite large container made of glass, a
candle, matches, water coloured with mint syrop

Activity description
The activity starts with a brainstorming, to understand what students
know on the topic.
Double aim:
to make the students aware that air is in every space we think to be
empty;
to make evidence that almost the fifth part of air consisted of oxygen.
Fix the candle in the middle of a plate with some drops of melted wax and
cover it with a jar of glass.
See what happens and ask pupils for explaining what they observed.
Ask pupils to make some hypotesis on what would happen if there is some
water on the plate.
Light the candle, fix it on the plate, pour some coloured water (use mint syrop) and cover it
with a jar of glass.
See what happens and ask pupils for explaining what they observed.
Teacher suggestions: Before performing the experiments, ask students to give their hypotheses
about what is necessary to make the candle burning.
Drive them to discover that the fire needs air to keep on burning.
EXPERIMENT N.1:
Fix a candle in the
middle of a plate
helping yourself with
some drops of
melted wax and then
cover the candle with a jar of glass. Observe
while the candle burned out.
Ask pupils to represent on their exercise books what theyobserved,
following the steps of the scientific method: observation – hypothesis –
verification - conclusion.

Later, to emphasize in a practical manner that 21% of air is oxygen (that
means 1/5), repeat the same experiment, setting the candle on a plate
containing a little quantity of water.

EXPERIMENT n.2:
Light the candle and fix it in the middle of the plate. Put in the plate some
water with mint syrup, to make the liquid visible. Cover the candle with
the jar of glass and, let students observe that, as soon as the candle
burned out, the water rised up the jar, filling almost 1/5 of the space.
Drive students to understand that the candle needs oxygen to burn, and
this is the reason why, when the oxygen under the jar finish, it lets a
depression that is compensated by sucking the water in the plate.

N.B.: it would be good to explain students that the explanation about
water rising up 20% of the jar is not just referable to the fact that oxygen
consumes. Infact the oxygen does not disappear from the jar, but
combines and transforms in carbon dioxide (CO2)...