Form 1:
Air and Combustion

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III. Burning Calcium

Procedure

(a)Using a pair of tongs hold the piece of calcium on a bunsen flame.

Observe.

Place the products in a beaker containing about 2cm3 of water.

Test the solution/mixture using litmus papers

(b)Using a pair of tongs hold another piece of calcium on a Bunsen flame.

Quickly lower it into a gas jar containing Oxygen gas .

Observe.

Place about 2cm3 of water. Swirl.

Test the solution/mixture using litmus papers

Observations

(a)In air

Calcium burns with difficulty producing a faint red flame in air forming a white solid.

Blue litmus paper remains blue.

Red litmus paper turns blue

b) In pure Oxygen

Calcium burns with difficulty producing a less faint red flame Oxygen forming a white solid.

Blue litmus paper remains blue.

Red litmus paper turns blue

Explanation

(a)Calcium burns in air forming white calcium Oxide. Calcium Oxide coat/cover the calcium preventing further burning.

Chemical equations

Calcium + Oxygen/air -> calcium Oxide
2Ca(s) + O2(g) -> 2CaO(s)

Small amount of Calcium Oxide dissolves in water to form a basic/alkaline solution of Calcium hydroxide.

The common name of Calcium hydroxide is lime water.

Chemical equations

Calcium Oxide + Water -> Calcium hydroxide
CaO(s) + H2O (l) -> Ca (OH) 2 (aq)

IV. Burning Iron

Procedure

(a)Using a pair of tongs hold the piece of Iron wool/steel wire on a Bunsen flame.

Observe.

Place the products in a beaker containing about 2cm3 of water.

Test the solution/mixture using litmus papers

(b)Using a pair of tongs hold another piece of Iron wool/steel wire on a Bunsen flame.

Quickly lower it into a gas jar containing Oxygen gas .Observe.

Place about 2cm3 of water.

Swirl.

Test the solution/mixture using litmus papers Observations

(a)In air

Iron wool/steel wire burns producing an Orange flame in air forming a brown solid.

Blue litmus paper remains blue.

Red litmus paper turns faint blue

(b) In pure Oxygen

Iron wool/steel wire burns producing a golden Orange flame in Oxygen forming a Brown solid.

Blue litmus paper remains blue.

Red litmus paper turns faint blue

Explanation

(a)Iron burns in air forming brown Iron (III) Oxide Chemical equations

Iron + Oxygen/air -> Iron (III) Oxide
4Fe(s) + 3O2 (g) -> 2Fe2O3(s)

Very small amount of Iron (III) Oxide dissolves in water to form a weakly basic/alkaline brown solution of Iron (III) hydroxide.

Chemical equations

Calcium Oxide + Water -> Iron (III) hydroxide
Fe2O3(s) + 3H2O (l) -> 2Fe (OH) 3 (s)

V. Burning Copper

Procedure

(a)Using a pair of tongs hold the piece of copper turnings/shavings on a Bunsen flame.

Observe.

Place the products in a beaker containing about 2cm3 of water.

Test the solution/mixture using litmus papers

(b)Using a pair of tongs hold another piece of Copper turnings/shavings on a Bunsen flame.

Quickly lower it into a gas jar containing Oxygen gas .

Observe.

Place about 2cm3 of water.

Swirl.

Test the solution/mixture using litmus papers

Observations

(a)In air

Copper turnings/shavings burns with difficulty producing a green flame in air forming a black solid.

Blue litmus paper remains blue.

Red litmus paper turns faint blue

(b) In pure Oxygen

Copper turnings/shavings burns less difficulty producing a green flame in Oxygen forming a Brown solid.

Blue litmus paper remains blue.

Red litmus paper turns faint blue

Explanation

(a)Copper burns in air forming black Copper (II) Oxide

Chemical equations

Copper + Oxygen/air -> Copper (II) Oxide
2 Cu(s) + O2 (g) -> 2CuO(s)

Very small amount of Copper (II) Oxide dissolves in water to form a weakly basic/alkaline blue solution of Copper (II) hydroxide.

Chemical equations

Copper (II) Oxide + Water -> Copper (II) hydroxide
CuO(s) + H2O (l) -> Cu (OH) 2 (s)

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