Chapter 6 - Chemical analysis

Question 1

What is a pure substance ?

Answer 1

A pure substance is a single element or compound not mixed with any other substances

Question 2

Give some examples of pure substances

Answer 2

Diamond, water, tables salt.

Question 3

What does the term melting point mean ?

Answer 3

Melting point is the temperature at which a solid changes into a liquid

Question 4

What does the term boiling point mean ?

Answer 4

Boiling point is the temperature at which a liquid changes into a gas

Question 5

What is unique about pure substances melting and boiling points ?

Answer 5

Pure substances have a sharp, specific melting and boiling point

Question 6

What is unique about mixtures melting and boiling points ?

Answer 6

melt or boil over a range of temperatures

also has a lower melting point and a higher boiling point

Question 7

What is a formulation ?

Answer 7

A formulation is a mixture that has been designed as a useful product.

Question 8

How is a formulation formed ?

Answer 8

It is formed by mixing together several different substances in carefully measured quantities

Question 9

What is a mixture ?

Answer 9

A mixture is defined as two or more substances mixed together

Question 10

What is a solute ?

Answer 10

A solute is the substance that dissolves in a solvent

Question 11

What is a solvent ?

Answer 11

A solvent is the liquid in which a solute dissolves

Question 12

What is a solution ?

Answer 12

A solution is a solute dissolved in a solvent

Question 13

What is a soluble substance ?

Answer 13

A soluble substance is one which will dissolve in a solvent

Question 14

What is a insoluble substance ?

Answer 14

An insoluble substance is one which will not dissolve in a solvent

Question 15

What is filtration used to separate ?

Answer 15

An insoluble solid from a liquid

Question 16

What is filtrate ?

Answer 16

The liquid that passes through the filter paper during filtration is called the filtrate.

Question 17

What is residue ?

Answer 17

The solid that remains on the filter paper after filtration is called residue

Question 18

What is evaporation used to separate ?

Answer 18

A dissolved solid from a solvent.

Question 19

What is evaporation ?

Answer 19

Evaporation is the change of state from a liquid to a gas when heated.

Question 20

What is another way of separating an dissolved solid in a solute ?

Answer 20

crystallisation

Question 21

What is a saturated solution ?

Answer 21

A saturated solution is one in which no more solid can dissolve at that temperature

Question 22

What does simple distillation separate ?

Answer 22

It separates a solvent from a solution.

Question 23

What is condensation ?

Answer 23

condensation is the change of state from a gas to liquid when cooled

Question 24

What are anti-bumping granules ?

Answer 24

anti-bumping granules are added to the mixture in the flask to promote smooth boiling

Question 25

What is distillate ?

Answer 25

The distillate is the liquid that is cooled from vapour and collected during distillation

Question 26

What is the basic process of simple distillation ?

Answer 26

Evaporation followed by condensation

Question 27

What is fractional distillation used to separate ?

Answer 27

Fractional distillation is used to separate miscible liquids which have different boiling points

Question 28

What is a miscible liquid ?

Answer 28

miscible liquids are liquids that mix together

Question 29

What are immiscible liquids ?

Answer 29

immiscible liquids are liquids which do not mix together but form two distinct layers

Question 30

How does fractional distillation work ?

Answer 30

• the mixture of liquids is heated up
• each boil and turn into a gas at different temps
• each vapor rises up is condensed and collected
• each separate distillate is called a fraction

Question 31

What is chromatography used to separate ?

Answer 31

mixture of soluble substances in a solution

Question 32

What is the solvent font ?

Answer 32

The solvent font is the furthest travelled by the solvent

Question 33

How many spots does a pure substance produce in chromatography

Answer 33

1

Question 34

What are the stationary and mobile phases of chromatography ?

Answer 34

stationary phase : paper

Mobile : solvent

Question 35

What factor affects the speed that a solvent travels up the paper ?

Answer 35

substances that have a higher attraction to the paper move slowly and only travel a short distance.

substances that have a high attraction to the solvent are more soluble in it and will travel up the paper quicker

Question 36

What is the equation to find Rf values ?

Answer 36

distance moved by substance
Rf = ——————————————–
distance moved by solvent

Question 37

What is potable water ?

Answer 37

Potable water is water that is safe to drink

Question 38

What three processes water must go through to become potable ?

Answer 38

• filtration
• sedimentation
• chlorination

Question 39

Explain how (potable water) filtration is carried out

Answer 39

water is sprayed onto specially designed layers of sand/gravel called filter beds. insoluble solids are removed as the water trickles through them.

Question 40

Explain how sedimentation is carried out

Answer 40

aluminium sulfate is added to clump tiny particles together to make larger particles, then it is passed through a fine filter such as carbon granules yo remove very small particles

Question 41

Explain how chlorination is carried out

Answer 41

Chlorine gas is bubbled into the water to kill microbes and sterilise the water

Question 42

What is desalination ?

Answer 42

Desalination is the process of removing dissolved substances from sea water

Question 43

How is desalination usually carried out ?

Answer 43

Usually carried out by distillation

Question 44

What is the process of desalination ?

Answer 44

It requires large amounts of energy to boil the water, which makes it very expensive.