Chemistry of water
H2O
H2O + NaCl
DENSITY OF WATER
Do a research with an egg in different kinds of water (fresh and salty).
Take a graduated cylinder and make saturated salt water solution in it (as salty liquid as possible:
100 ml of water and a few table spoonfuls of salt). Put some caramel colour in to solution to help
your observation.
Then put a whole egg (not broken) in to graduated cylinder. What can you say about densities of
egg and salt water? Add some fresh water to the same glass. Use beaker and pour the water gently
so that layers of water don't mix up.
What happened and why? Arrange egg, fresh water and salty water in order from most dense to
less dense.
Watch a small video clip ("vettä verkossa" : http://virtuaaliyliopisto.jyu.fi/oppi/ako/). What
happened and why? Why this phenomenon is important? Write down some examples from
nature.
Chemistry of water
DETERMINATION OF pH
Equipment: micro dwells, pipets, red cabbage indicator, pH-paper, orange, lemon, Coca-Cola,
coffee, detergent, washing powder & baking soda
First make a hypothesis of pH of substances. Then add approximately 10 drops of red cabbage
indicator to six micro dwells. Add substances to the micro dwells containing the indicator and to
six empty micro dwells. Observe the change in colour in the dwells containing red cabbage
indicator and substances. Then determine pH with pH-paper from the dwells containing only
added substances (NOT from those containing indicator).
Substance Hypothesis
colour with red
cabbage indicator
pH with pH-paper
Lemon
Coca-Cola
Coffee
Detergent
Washing powder
Baking soda
What causes differences in pH? Why some solutions are acidic and some alcalic?
Chemistry of water
SURFACE TENSION
1. Take approximately 150 ml of water into a 250 ml beaker and put a piece of pencil graphite
gently into the surface of water so that it floats.
What do you see at the ends of the piece of graphite?
Mix some detergent with a small amount of water in a beaker and pour this solution into the
beaker with graphite. What happens and why?
2. Put some cinnamon evenly with sieve in water so that it makes a sort of thin "film" into the
surface. Put a drop of water (with a pipet) gently into the film of cinnamon. Then put a drop of
detergent in the same way. What do you see on the surface? Can you explain this?
(OBS! Don't wash the sieve so that other groups can also use it.)
Chemistry of water
FORMS OF WATER (solid, liquid, gas)
Make a drama of forms of water.
Each member of the group is one water molecule.
What happens to a group of water molecules when ice is melting or liquid is evaporating and how
are they organized in different states? Demonstrate by means of drama.
2. Why do lakes freeze only on the water surface? Why is this important?
deposition
freezing condensation
evaporationmelting
sublimation
SOLID LIQUID GAS