Summary 1.
Water is the most abundant substance on the surface of the earth.
About 71% of the earth's surface is covered by water.
2. Hydrogen is prepared in the laboratory by the action of zinc on
dilute hydrochloric acid or dilute sulphuric (VI) acid.
3. Hydrogen burns in oxygen to produce water. Water is an oxide
of hydrogen.
4. Active metals react with cold water to produce hydrogen gas
and the hydroxide of the metal in solution. Less active metals
react with steam to produce hydrogen and the oxide of the metal.
Copper and lead do not react with water.
5. Hydrogen is a reducing agent. It removes combined oxygen
from metal oxides of the less reactive metals.
6.
Reduction is the loss of oxygen from a compound. Oxidation is
the gain of oxygen by a substance.
7.
A reducing agent is a substance which removes oxygen from
another substance. An oxidising agent is a substance which gives
out oxygen to another substance.
when
water changes the
colour of coppe - 11
Revision Exercise sulphatorom blueto
1. (a) State the chemical tests for presence of water.
water change the color
(b) State the test, which is used to show that water is pure. Chistide paper from b
of copper anhydrous cobele
2.
Describe an experiment to show that water is an oxide of hydrogen. t non
3. State the precautions that must be taken when carrying out experiments with hydrogen.
Why is it not advisable to use iron in making steam boilers?
Write a word equation for a reaction in which hydrogen acts as a reducing agent.
Name the products formed when kerosene is burned in air.
State what is observed when a small piece of potassium is placed in water. Write a
word equation for the reaction.
Draw a labelled diagram to show how a reaction between steam and magnesium should
be carried out.
Describe how dry hydrogen is prepared in the laboratory.
Property of the Government of Kenya
Potassium
sodium
Calcim
Magne
Alun
Corbi
Zin​