C2a Topic 3 -m

Question 1

covalent bonding

Answer 1

- sharing electrons so they can both acquire a full outer shell
examples
hydrogen H - H
hydrogen chloride H - Cl
oxygen O = O
carbon dioxide O = C = O

Question 2

covalent substances

Answer 2

simple molecular
- atoms in these substances make very strong covalent bonds
- forces between these molecules are very weak
- melting and boiling points are low as molecules are easily separated
- most molecular substances are gases or liquids at room temp
- molecular substances don’t conduct electricity - no ions
egs hydrogen and oxygen
Giant molecular
- similar to ionic lattices except no charge ions
- all atoms are bonded to each other by strong covalent bonds
- very high melting and boiling points
- other than graphite, they don’t conduct electricity
- usually insoluble in water
egs diamond and graphite
- diamond - each carbon atom forms four covalent bonds in a rigid covalent structure - makes hard - good as cutting tools
- graphite - each carbon atom forms three covalent bonds which are free to slide over each other - useful lubricant

Question 3

separation

Answer 3

Separating funnel - immiscible liquids - separate out into layers denser liquid sinks to bottom, less dense forms top layer. separated using a funnel with tap. e.g oil and water
Fractional distillation - miscible liquids - different boiling points

Question 4

chromatography

Answer 4

can use paper chromatography to identify different substances in a mixture. different substances wash through wet filter paper at different rates