Page 61 - Chemistry_Form_2

Chemistry
for Secondary Schools

Properties of covalent compounds
The properties of covalent compounds include the following:

(a) Their melting and boiling points are usually low.

(b) They are usually liquids or gases at room temperatures.
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(c) They do not conduct electricity.

(d) They are generally soluble in non-polar solvents such as oil, carbon
tetrachloride and hexane.
(e) They are generally insoluble in polar solvents like water.

(f) They can easily vaporise at room temperature.

(g) They have distinct molecular structures.

(h) They are generally non-metallic compounds.

Task 3.2

Use chemical drawing software such as ChemDraw or ChemSketch to draw
the chemical structures for sodium chloride and carbon dioxide based on their
molecular formulas. Then, identify the type of bond present in each compound.

Activity 3.2

Aim: To demonstrate the formation of covalent bonds in molecules

Requirements: Ball-and-stick molecular model kit (or coloured playdough and
toothpicks), manila paper, pens, coloured markers and a pair of
compasses
Procedure
1. Use different coloured balls or playdough to make spheres representing
atoms of hydrogen, oxygen, nitrogen and carbon.

2. Use two hydrogen atoms and one oxygen atom to model a water molecule
(H O). Connect the hydrogen atoms to the oxygen atom using sticks or
2
toothpicks.

3. For oxygen gas (O ), connect two oxygen atoms.
2
4. Use similar steps to create models of methane (CH ), carbon dioxide (CO ),
4
2
and NH .
3
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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 54