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A candle is a hydrocarbon
Other hydrocarbons include Petrol diesel Kerosene and Laboratory gas Hydrocarbons burn in air to form water and carbon IV oxide gas
Hydrocarbons Oxygen Water Oxygen
Water pollution
Water pollution takes place when undesirable substances are added into the water Sources of water pollution include
iIndustrial chemicals being disposed into water bodies like rivers lakes and oceans
iiDischarging untreated raw sewage into water bodies
iiiLeaching of insecticidesherbicides form agricultural activities into water bodies
ivDischarging nonbiodegradable detergents after domestic and industrial use into water bodies
vPetroleum oil spilling by ships and oil refineries
viToxicpoisonous gases from industries dissolving in rain
vii Acidic gases from industries dissolving in rain to form acid rain
viiiDischarging hot water into water bodies This reduces the quantity of dissolved Oxygen in the water killing the aquatic fauna and flora
Water pollution can be reduced by
i Reducing the use of agricultural fertilizers and chemicals in agricultural activities
ii Use of biological control method instead of insecticides and herbicides
iii Using biodegradable detergents
REACTION OF WATER WITH METALS
Some metals react with water while others do not The reaction of metals with water depends on the reactivity series The higher the metal in the reactivity series the more reactive the metal with water The following experiments shows the reaction of metals with cold water and water vapoursteam
aReaction of sodium potassium with cold water
Procedure
Put about 500cm3 of water in a beaker Add three drops of phenolphthalein indicatorlitmus solutionuniversal indicator solutionmethyl orange indicator into the water
Cut a very small piece of sodium Using a pair of forceps put the metal into the water
Observation
Sodium melts to a silvery ball that floats and darts on the surface decreasing in size Effervescencefizzing bubbles of colourless gas produced
Colour of phenolphthalein turns pink
Colour of litmus solution turns blue
Colour of methyl orange solution turns Orange
Colour of universal indicator solution turns blue
Explanation
Sodium is less dense than water Sodium floats on water and vigorously reacts to form an alkaline solution of sodium hydroxide and producing hydrogen gas Sodium is thus stored in paraffin to prevent contact with water
Chemical equation
Sodium Water Sodium hydroxide Hydrogen gas
2Nas 2H2O l 2NaOH aq H2g
To collect hydrogen gas Sodium metal is forced to sink to the bottom of the troughbeaker by wrapping it in wire gauzemesh
Potassium is more reactive than Sodium On contact with water it explodesburst into flames An alkaline solution of potassium hydroxide is formed and hydrogen gas
Chemical equation
Potassium Water Potassium hydroxide Hydrogen gas
2Ks 2H2O l 2KOH aq H2g
Caution Reaction of Potassium with water is very risky to try in a school laboratory
bReaction of Lithium Calcium with cold water
Procedure
Put about 200cm3 of water in a beaker Add three drops of phenolphthalein indicatorlitmus solutionuniversal indicator solutionmethyl orange indicator into the water
Cut a small piece of Lithium Using a pair of forceps put the metal into the water
Repeat with a piece Calcium metal
Observation
Lithium sinks to the bottom of the water Rapid effervescencefizzing bubbles of colourless gas produced
Colour of phenolphthalein turns pink
Colour of litmus solution turns blue
Colour of methyl orange solution turns Orange
Colour of universal indicator solution turns blue
Explanation
Lithium and calcium are denser than water Both sink in water and vigorously react to form an alkaline solution of Lithium hydroxide calcium hydroxide and producing hydrogen gas Lithium is more reactive than calcium It is also stored in paraffin like Sodium to prevent contact with water
Chemical equation
Lithium Water Lithium hydroxide Hydrogen gas
2Lis 2H2O l 2LiOH aq H2 g
Calcium Water Calcium hydroxide Hydrogen gas
Cas 2H2O l Ca OH 2aq H2 g
c Reaction of MagnesiumZinc Iron with Steamwater vapour
Procedure method1
Place some wet sand or cottonglass wool soaked in water at the bottom of an ignitionhard glass boiling tube
Polish magnesium ribbon using sand paper
Coil it at the centre of the ignitionhard glass boiling tube
Set up the apparatus as below
Heat the wet sand or cottonglass wool soaked in water gently to
i Drive away air in the ignitionhard glass boiling tube
ii Generate steam
Heat the coiled ribbon strongly using another burner Repeat the experiment using Zinc powder and fresh Iron filings
Set up of apparatus
Observations
iWith Magnesium ribbon
The Magnesium glows with a bright flame and continues to burn even if heating is stopped
White solid ash formed
White solid ash formed dissolve in water to form a colourless solution
Colourless gas producedcollected that extinguish burning splint with pop sound
ii With Zinc powder
The Zinc powder turns red hot on strong heating
Yellow solid formed that turn white on cooling
White solid formed on cooling does not dissolve in water
iiiWith Iron fillings
The Iron fillings turn red hot on strong heating
Dark blue solid formed
Dark blue solid formed does not dissolve in water
Procedure method 2
Put some water in a round bottomed flask
Polish magnesium ribbon using sand paper
Coil it at the centre of a hard glass tube
Set up the apparatus as below
Heat water strongly to boil so as to
i drive away air in the glass tube
ii generate steam
Heat the coiled ribbon strongly using another burner Repeat the experiment using Zinc powder and fresh Iron filings
Observations
iWith Magnesium ribbon
The Magnesium glows with a bright flame and continues to burn even if heating is stopped
White solid ash formed
White solid ash formed dissolve in water to form a colourless solution
Colourless gas producedcollected that extinguish burning splint with pop sound
ii With Zinc powder
The Zinc powder turns red hot on strong heating