|
|
 |
|
|
TGV3:
Questions
|
|
 |
LINKS |
 |
|
|
|
|
Notes
on the ‘Think for Yourself’ questions
What is the flame?
The flame is a chemical reaction
between methane and oxygen.
Why doesn’t the whole bag of methane set alight at once?
There is no oxygen inside. There
needs to be a mixture of methane and oxygen so that the particles
of the two
substances can collide with each other.
When the jar is placed over the top, why does the flame go
out with plenty of methane still left?
The reaction needs a mixture of methane
and oxygen, and putting a jar over the top cut the supply
of oxygen.
The oxygen that started inside the jar is used up.
Why does the condensation form on the sides of the jar but
not at the top?
The sides of the jar are much cooler.
Suggest what substance the condensation might be, and explain
your reasoning.
Water. Hydrogen atoms from the methane
can combine with oxygen atoms from oxygen to make water molecules.
Some people might say that the condensation could be from
water that was already in the air. What is the
argument against this?
The glass was not cold enough for
condensation to form at the start. Even the sides got warmer
during the experiment. There must be a high concentration
of water particles for condensation to form at warmer temperatures:
extra water must be coming from the flame.
There must be at least one other substance formed: why?
There are carbon atoms in the methane
to account for.
In fact, there is just one new substance. Why can’t
we see it and what might it be?
It must stay in the gas state, even
on cooling to room temperature: it could be carbon dioxide.
Carbon atoms from methane could combine with oxygen atoms
from oxygen.
How could we test for this other new substance?
Use the limewater test. (This
is shown in the next video) condensation forms on the inside
of the bell jar.
|
|
|
|
|
| a
Science Enhancement Programme CD-ROM 2005 |
|
user
guide |
| |
|
|
|
|
