3.1 INTRODUCTION + SEPARATING TECHNIQUES

Question 1

3 signs of a PHYSICAL change

Answer 1

• Creates no new substances
• Are usually easy to reverse
• Absorb or release small ammounts of energy

Question 2

3 signs of a CHEMICAL change

Answer 2

• Creates new substances
• Usually difficult to reverse
• Absorb or release large amounts of energy

Question 3

Chemical test for water

Answer 3

Anhydrous Copper(II) Sulfate turns from white to blue

Question 4

Physical test for water

Answer 4

Pure water will boil at 100c

Question 5

Define an element

Answer 5

A substance containing one type of atom only

Question 6

Typical properties of metals

Answer 6

• High MP/BP
• Electrical conductors
• Malleable
• Shiny

Question 7

Typical properties of non-metals

Answer 7

• Low MP/BP
• Electrical insulators
• Brittle
• Dull

Question 8

Diatomic Molecules

Answer 8

Nitrogen, Oxygen, Hydrogen + Halogens

Question 9

Define a compound

Answer 9

A substance containing more than one type of atom, chemically bonded together

Question 10

Define a mixture

Answer 10

A substance containing more than one type of atom not chemically bonded together

Question 11

How does the ammonium chloride tube illustrate diffusion

Answer 11

• Ammonium chloride forms as a white smoke towards the hydrogen chloride end
• The hydrogen chloride molecules are heavier so diffuse slower compared to ammonia
• Heating the tube will speed up the reaction but not change the results

Question 12

Define solute

Answer 12

The substance which is going to be dissolved

Question 13

Define solvent

Answer 13

The liquid which is going to do the dissolving

Question 14

Define solution

Answer 14

The resulting mixture of a solute dissolved in a solvent

Question 15

Define saturated

Answer 15

A solution in which no more solute can be dissolved

Question 16

Define suspension

Answer 16

A solid floating in a liquid because it cannot dissolve

Question 17

Define soluble

Answer 17

A substance which can be dissolved

Question 18

Define insoluble

Answer 18

A substance which cannot be dissolved

Question 19

How is solubility measured

Answer 19

• g / 100g solvent
• You can use it as a ratio and scale it up and down

Question 20

How do solubility curves work

Answer 20

• Measures solubility compared to temperature
• Below the line = soluble
• On the line = saturated
• Above line = insoluble

Question 21

How do you carry out a chormatography experiment

Answer 21

• Draw a line near the bottom of the paper in pencil - as it won’t dissolve in the solvent
• Add spots of different dyes at regular intervals
• Place paper in beaker of solvent - with solvent below pencil line, so inks don’t dissolve into solvent
• Place lid on beaker - to stop solvent evaporating
• Allow solvent to move up paper until it is just below the top
• Take paper out and mark solvent front
• Allow paper to dry

Question 22

How do you carry out paper chromatography

Answer 22

• Draw a base line in pencil at the bottom of the chromatography paper - so it doesn’t dissolve in solvent
• Add spots of dye on line in different inks
• Place paper in beaker of solvent - ensure below solvent line so it doesn’t dissolve into solvent
• Place lid on beaker - to prevent solvent evaporating
• Allow solvent to move up paper, until it is near the top
• Take the paper out and mark solvent front
• Allow paper to dry

Question 23

What happens to soluble dyes in chromatography

Answer 23

They will move further up the paper

Question 24

What happens to soluble dyes in chromatography

Answer 24

They will move further up the paper

Question 25

What happens if a dye is insoluble in chromatography

Answer 25

It will not move from the baseline

Question 26

In terms of physical properties, what is the differance between a pure substance and a mixture

Answer 26

A Pure substance has a fixed boiling point, but a mixture may melt/boil over a range of temperatures

Question 27

What is filtration used for

Answer 27

To seperate a solid from a liquid

Question 28

Describe how to carry out filtration

Answer 28

* Place filter paper in funner and pour in solution * Residue is substance left in filter paper * Filtrate is liquid that comes through filter paper

Question 29

What is crystalisation used for

Answer 29

To seperate a solute from a solution

Question 30

Describe how to carry out crystalisation

Answer 30

* Solution is heated in evaporating basin to boil off water, until an almost saturated solution is formed * Bunsen is turned off and crystals allowed to form as more water evaporates and solution forms * Crystals removed by filtration

Question 31

Describe how to carry out crystalisation

Answer 31

* Solution is heated in evaporating basin to boil off water, until an almost saturated solution is formed * Bunsen is turned off and crystals allowed to form as more water evaporates and solution forms * Crystals removed by filtration

Question 32

What is simple distillation used for

Answer 32

To seperate pure water from a solution

Question 33

Describe how to carry out simple distillation

Answer 33

* Water from solution boils and is condensed back into liquid by condenser

Question 34

What is fractional distillation used for

Answer 34

Seperate ethanol from a mixture of ethanol and water

Question 35

How to carry out fractional distillation

Answer 35

* Control heating temperature to ensure water condenses in column and trickles back into flask * Only ethanol with lower boiling point (than water) remains as vapour at top of fractionating column, and into condensor

Question 36

Where to measure ink from a chromatgram

Answer 36

Centre of the spot

Question 37

How to calculate Rf

Answer 37

Distance oved by spot (from pencil line) / Distance moved by solvent (from pencil line)

Question 38

Purpose of chromatography

Answer 38

To seperate inks from dyes