C2.3- Covalent Compounds And Separation Techniques

Question 1

Can covalent bonds for, between two of the same element?

Answer 1

Yes, this is called a molecule, for example hydrogen or oxygen

Question 2

What is a double bond?

Answer 2

When atoms share two pairs of electrons.

Question 3

What are the properties of simple molecular covalent substances?

Answer 3

• low melting and boiling points because the bonds within molecules are strong but intermolecular bonds are weak.
• don’t conduct electricity because they have no charge.

Question 4

What are the properties of giant molecular covalent structures?

Answer 4

• high melting and booing points because the strong bonds require a lot of energy to break apart.
• normally very hard.

Question 5

What are the properties of graphite?

Answer 5

• the layers have very strong bonds within themselves, however the bonds between the layers are weak, so easily slide over each other, making graphite a good lubricant.
• there is a free moving electron from each carbon, meaning that graphite can conduct electricity, so are used as electrodes.

Question 6

What are the properties of diamond?

Answer 6

• it is very strong because all the atoms are joined with strong covalent bonds. They a re used to make cutting tools.
• it doesn’t conduct electricity, no charge or free moving electrons.

Question 7

What is an immiscible liquid?

Answer 7

Liquids which do not mix with each other, for example oil and water.

Question 8

How do you separate immiscible liquids?

Answer 8

A separating funnel can be used to separate immiscible liquids. The tap is opened and the lower liquid is collected in the beaker. Once all of that liquid has been collected use another beaker to collect the second.

Question 9

What are miscible liquids?

Answer 9

If two liquids dissolve into each other, they make a solution and are miscible.

Question 10

How do you separate miscible liquids?

Answer 10

Miscible liquids can be separated using fractional distillation. The mixture is first heated so that evaporates, and these vapours condense in the fractionating column. The feat ions with the highest boiling point condenses near the bottom and the one with the lowest rescues the top.

Question 11

How do you separate air?

Answer 11

First of all the air is condensed into a mixture of liquids. This is done by cooling the air, so the water can be freezes and removed from the solution. The remains air is dolled to -200degreesC so that it becomes liquified. The air is then warmed to the boiling point of nitrogen, -196, causing it to evaporate and condense at the column. The liquid oxygen is then pumped out.

Question 12

What is chromatography?

Answer 12

Chromatography is used to separate coloured compounds from a solvent. Compounds in a solvent have different solubilises, which means that coloured compounds can be analyse.

Question 13

How do you workout the Rf value?

Answer 13

Rf=distance moved by compound/ distance moved by solvent.

Question 14

What are the uses of chromatography?

Answer 14

• it is used to analyse food colourings used in food to keep our food safe.
• police use it to analyse DNA
• it is also used to analyse paints and dyes, helping museums make exact copies of ancient paints to restore old paintings or identify forgeries.

Question 15

What is a covalent bond?

Answer 15

A bind formed between two atoms sharing a pair of electrons.