.
.
13. Water content of living beings
Barley
of our bread, the boiled egg for breakfast and the potatos for lunch are more
than food. They can be the origin of new living beings: a barley
plant , eine a potato plant , a chicken. Living
beings consist of different quantities of water: Up to 99% of jelleyfish is
water.
Now you will weigh samples of white and yellow of a boiled egg and a cylinder
cut from a potato. Keep them at a warm and dry place and weigh them again until
there is no more loss of mass.
Material
Tray, kitchen scales, Two pan scale with weights (1-Euro
coins are exactly 7,5 g) or digital pocket scale,
corer for an apple, hard boiled egg, cylinder cut from a potato
by a corer.
Experiment
1. Half a hard boiled
egg, separate its white and it yellow from it, weigh both of them (Photo 2).
2. Weigh a cylinder cut
from a potato
(right photo, left side).
3. Keep these pieces at
a dry warm place until there is no more loss of weight.
Observations
a) The white of the egg
shrinks extremely, a hard, brittle yellow transparent residue is kept. The
yellow of the egg does not change much (Photo
3) .
b) 40 g "white"
(40 - 6) g ........., (please calculate: 1
g loses ..........g, 100 g lose ........g, water content ...... of 100 (%).
9
19 g "yellow" (19 - 16) g ........, (please
calculate: 1 g loses ..........g, 100 g lose ........g,
water content ...... of 100 (%).
c) The
potato cylinder also shrinks very much.
A grey, very hard and sulcate residue is left.
a) The
weight of the fresh potato ......... (6,8) g. After
total drying: ............ (1,4) g. (please
calculate: 1 g loses ..........g, 100 g lose ........g,
water content ...... of 100 (%).
Explanation
The white
of the egg egg consists of 85 % water. During
the development of the chick is has a task similar to the amniotic liquor: It
protects the baby against knocks. The yellow
of the egg contains only 32 % of water.
The rest are food and building materials. 79% of the potato are water. The rest
are nutrients (starch and proteins) and fibres.
back....... go on............first publication: 26.10.2001..........last modification: 16.12.2008