UNESCO resource kit - science and technology educa...

UNESCOModule 12: Wood as a structural material
Wood as a structural material
The lines that you can see running
along a piece of wood are called
the grain.
If you cut the piece of wood like
this, you have cut it along the
grain.
O Spring
growth
The piece of wood came from a tree trunk. When you
look at the cut end of a tree trunk you can see growth
rings. These show each year's growth.
1 Why does wood have a grain?
•
Summer
growth
2 What happens to the fibres inwood
(a) when you cut the wood along the grain?
(b) when you cut the wood across the grain?
If you cut the piece of wood like
this, you have cut it across the
grain
Springgrowth
Summergrowth
Springgrowth
If you look at wood through a magnifying
glass or binocular microscope, you can see
that it is made of lots of long, hollow fibres.
Each fibre is made from lots of cells joined
end-to-end.
__ ...• 1
oneceD
3 Some of the hollow fibres in a piece of wood have a larger diameter than
others. Explain why.
4 How old is the tree trunk shown in the diagram? Explain your answer.
5
The wood from trees that grow in tropical rain forests do not have growth
_________________________________________________________________________ rings. Suggest why.
Pagel