WATER
Water is formed when Hydrogen chemically combines with Oxgen {H2(g) + O2(g) -> H2O(l)}
Physical properties of Water
Colorless
Ordourless
Tasteless
At a temperature of 0°C, Water freezes and at 100°C, Water melts
It has a density of 1g/cc at 4°C
On freezing, Water expands and the more it expands , the less its density .Thats why ice floats.
Chemical properties of Water
Water reacts with non-metals(Acidic Oxides) to form acids
Water reacts with metals to form a metal Hydroxide and a Hydrogen gas
Water reacts with ionic metal oxides to form a Hydroxide and resultant basic solutions.
WATER IN THE ATMOSPHERE
1.Hygroscopy
Hygroscopy is the absorption of water from the atmosphere
Examples of Hygroscopic substances include:
Copper (ii) oxide
Ethanol
Methanol
Glycerine
Honey
*
Hygroscopic substances are used as drying agents
2.Deliquescene
Deliquescene is the absorption of water from the atmosphere by a solid and then dissolved in the water
Examples of Deliquscent substances include:
Calicium chloride
Sodium hydroxide
Potassium hydroxide
Iron(iii) oxide
Sodium nitrate
*
Deliquscent substances are hygroscopic but Hygroscopic substances are not Deliquescent
3.Efflorescence
Efflorescence is the giving up of the water of crystallization from the atmosphere by a crystal.
Examples of Efflorescent substance include:
Sodium sulphate - 10 Water (Na
2
SO
4
.10H
2
O)
Sodium carbonate - 10 Water (Na
2
CO
3
.10H
2
O
Hydrated Copper(ii) sulphate crystal (CuSO
4
.5H
2
O)
Test for water
It turns anhydrous Copper(ii) sulphate to white
It turns anhydrous Cobalt(ii) chloride to pink