Read the article and
complete the gaps with the names of tests.
Paper is
composed of fibres and they of cellulose molecules having a polymer structure.
Paper is
going to undergo a series of tests. Each test includes three steps:
1. Predict:
what will happen in the test?
2. Observe:
what happens in the test?
3. Explain:
how can the observation be explained with models?
пустоDropping test
Predict: There
will rip so that it will form a long hole. The paper consists of cluster
fibres. The fibres consist of cellulose molecules that have lot of interactions
between them making the fibre hard. Between the cluster fibres there are less
interactions and so the paper will rip between fibres.
Observe: The
paper broke and a linear hole was formed.
Explain: The
interactions between fibres are weak. That is why the paper more easily rips in
the direction of the fibres.
пустоConductivity test
Predict: There
are no free electrons in paper to conduct electricity.
Observe:
When a piece of paper was connected to the circuit, the lamp didn’t glow.
Explain:
Paper does not conduct electricity because there are no free electrons to do
so.
пустоRipping test
Predict: The
fibres in paper are mostly aligned in one direction. Paper will rip linearly
and more easily in the direction of the fibres because there is only weak
interaction between the fibres.
Observe: Paper
rips more easily and straight in the other directions. When ripped in the other
direction, the rip tends to turn.
Explain: The
interaction between fibres is weak and thus the paper rips in their direction.
Paper rips unevenly when it is ripped perpendicular to the direction of the
fibers because the fibers are strong and don’t break.
пустоHeat conductivity test
Predict: Paper
lacks the free electrons which have a central role in thermal conductivity.
Paper will conduct heat slowly and it will take a long time for the butter to
melt.
Observe: The
butter on the cardboard melts slower than on metal.
Explain: The
cardboard conducted heat very slowly because it hasn’t got free electrons and
it’s very porous which also slows down the conductivity.
пустоBending test
Predict: When
paper is rolled up it will bend really well but when the weak interactions
between the fibers fail, paper will stay curvy.
Observe: Paper
is bended easily but doesn’t return from the bended position very well.
Explain: The
net-like fibre structure of paper stands some bending but when the bending is
too strong, the weak interactions between fibres fail and the paper stays
bended.