C2

Question 1

What are the two phases in chromatography?

Answer 1

`A stationary phase that does not move. A mobile phase that does move

Question 2

What is the stationary phase in paper chromatography?

Answer 2

The absorbent paper

Question 3

What is the stationary phase of gas chromatography?

Answer 3

Silica or alumina powder packed into a metal column

Question 4

Why can carbon form many different compounds?

Answer 4

It has 4 valence electrons and can form 4 covalent bonds. It can join with other carbon atoms to form chains and rings or form covalent bonds with other elements

Question 5

Why are diamond and graphite different?

Answer 5

Because they have different structure and bonding

Question 6

What is a nanotube?

Answer 6

A sheet of graphene rolled into a tube. Strong. Used to reinforce some sports equipment.

Question 7

Why are metals malleable?

Answer 7

Metal ions are held in a lattice by forces that attract them to a sea of delocalised electrons. When a large enough force is applied layers of metal ions slide over one another but delocalised electrons are free to move so overall no bonds are broken.

Question 8

What is a material made from nanoparticles called?

Answer 8

Nanoparticulate

Question 9

Risks of nanoparticles

Answer 9

• May be breathed in, absorbed by skin or pass into cells
• May take a long time to break down once released into environment and toxic substances may stick to their surfaces
• Harmful to health and environment in ways difficult to predict, with risks difficult to determine

Question 10

What is bonding in a simple molecule like?

Answer 10

• Covalent bonds involve electrostatic forces of attraction but the forces are between the nucleus of each bonded atom and the shared electrons
• Covalent bonds are strong. Intermolecular forces are weak.

Question 11

What is a phase?

Answer 11

A substance in the solid, liquid or gas state.

Question 12

What is the mobile phase in paper chromatography?

Answer 12

A solvent in the liquid state

Question 13

What is thin layer chromatography?

Answer 13

Same way as paper chromatography, but stationary phase is a thin layer of silica or alumina powder spread over a plate of glass or plastic

Question 14

What are Rf values?

Answer 14

Compare the different spots on a chromatogram

Question 15

What is the mobile phase in gas chromatography?

Answer 15

Inert carrier gas such as nitrogen

Question 16

What does gas chromatography do?

Answer 16

Separates components and measures their amounts

Question 17

What happens in gas chromatography?

Answer 17

• Sample is turned into gas state and injected into column
• Different components take different times to travel through the column, depending on how strongly they bind to the stationary phase
• A detector sends a signal to a computer as each component leaves the column
• The computer produces a chromatogram in which each component is a peak plotted against the travel time

Question 18

How to calculate Rf values?

Answer 18

Distance travelled by substance/distance travelled by solvent

Question 19

What are the advantages of thin-layer chromatography?

Answer 19

Quicker, more sensitive, there are more choices of stationary phases and solvents to use

Question 20

How to choose separation method?

Answer 20

• Insoluble and soluble substance -filtration
• A solute dissolves in solvent - crystallisation or simple distillation
• Two or more liquids-fractional distillation
• Coloured soluble substances- paper or thin-layer chromatography

Question 21

What is a diamond like?

Answer 21

• Transparent and very hard
• Exists as a giant covalent structure where each carbon atom is covalently bonded to 4 other carbon atoms
• Has very high melting point
• No delocalised electrons as all valence electrons are shared so it doesn’t conduct electricity.

Question 22

What is an allotrope?

Answer 22

Different forms of an element in the same state but with different atomic arrangements

Question 23

What is graphite like?

Answer 23

• Grey-black and soft
• Giant covalent structure where each carbon atom is covalently bonded to three other, so one electron is not shared so it becomes delocalised and is free to move through the structure.
• It conducts electricity even though it is a non-metal. Has a layered structure
• Atoms in each layer form interlocking hexagons
• Very high melting point
• Forces between layers are weak so layers can slide over easily
• Graphite is hence slippery, used in pencil.

Question 24

Difference between diamond and graphite

Answer 24

Diamond bonded to 4 graphite 3. Diamond is transparent and very hard , graphite is very-black and soft

Question 25

Examples of allotropes of carbon

Answer 25

Diamond, graphite, graphene, fullerenes

Question 26

What is graphene like?

Answer 26

A single layer of graphite. Almost transparent. Extremely strong and conducts electricity.

Question 27

What is a fullerene like?

Answer 27

Comes from large family of carbon allotropes and the molecules are shaped like tubes or balls.

Question 28

What is a buckyball?

Answer 28

- Resembles sheet of graphene closed to make a hollow ball - But carbon atoms may be in pentagons as well as hexagons. - Have potential uses as lubricants with molecules acting like tiny ball bearings - Small size allows buckyballs to pass through cell membranes and might deliver medical drugs directly to cells one day.

Question 29

What happens when a substance melts?

Answer 29

Some bonds break going from the solid to the liquid state

Question 30

What happens when a substance boils?

Answer 30

All remaining bonds bream going from the liquid to the gas state

Question 31

When do substances have high melting points?

Answer 31

If they have many strong bonds in the solid state

Question 32

When do substances have high melting points?

Answer 32

If they have many strong bonds in the liquid state

Question 33

What happens when a substance condenses?

Answer 33

Some bonds form going from the gas to the liquid state

Question 34

What happens when a substance freezes?

Answer 34

Many bonds form going from the liquid to the solid state

Question 35

How is stored chemical energy transferred to the surroundings?

Answer 35

Usually by heating , when chemical bonds form

Question 36

Relative strength of a metallic bond

Answer 36

Strong

Question 37

Relative strength of an ionic bond

Answer 37

Strong

Question 38

Relative strength of a covalent bond

Answer 38

Strong

Question 39

Relative strength of intermolecular forces

Answer 39

Weak

Question 40

Which substance are usually in the solid state at room temp?

Answer 40

Metals, ionic compounds, giant covalent substances

Question 41

What state are simple molecular substances in at room temp?

Answer 41

Liquid or gas or solid that is easily melted

Question 42

What does the difference between malleable and brittle depend on?

Answer 42

How easily particles in the substance can change their positions in the lattice structure.

Question 43

Why are other substances brittle?

Answer 43

- Giant covalent structures contain very many atoms held together by strong covalent bonds - If large enough force applied many covalent bonds break at once so the substance breaks - Similar situation for ionic compounds.

Question 44

Simple molecules and polymer molecules are attracted to each other by what? Are they brittle or malleable?

Answer 44

- Weak intermolecular forces which are easily broken | - In solid state and arranged in lattice they may be brittle. If molecules

Question 45

Why do some substances conduct electricity?

Answer 45

If it has charged particles that can move. Metals conduct in liquid and solid state. Simple molecules, most polymers and most substances with a giant covalent structure do not conduct electricity as no delocalised electrons.

Question 46

Do ionic compounds conduct electricity?

Answer 46

Contain oppositely charged ions. Free to move in liquid state (molten) or when dissolved in solution but not in solid state. So conducts when molten or in solutions but not when solid

Question 47

How big are nanoparticles?

Answer 47

1nm-100nm consists of just a few hundred atoms

Question 48

What do nanoparticulate materials have?

Answer 48

Different properties to the same substance in bulk

Question 49

What is the small size of nanoparticles useful for?

Answer 49

New paints, cosmetics, medicine

Question 50

What are many nanoparticle properties due to?

Answer 50

Their very large surface area compared to with the same substance in bulk

Question 51

What developments can nanoparticularw properties lead to?

Answer 51

New catalysts to speed up industrial chemical reactions. Self-cleaning windows, oven and clothes

Question 52

What are ionic bonds?

Answer 52

Strong electrostatic forces of attraction between oppositely charged ions

Question 53

What is a molecule?

Answer 53

Particle in which non metal atoms are joined together by covalent bonds

Question 54

What is a simple molecule?

Answer 54

Contains few atoms that are covalently bonded but has weak intermolecular forces that are easily overcome

Question 55

What do giant covalent structures consist of?

Answer 55

Many non-metal atoms joined by covalent bonds and arranged in a repeating regular pattern called a giant lattice.

Question 56

Structure of metals

Answer 56

Giant metallic lattice

Question 57

How are metallic bonds formed?

Answer 57

vElectrons leave outer shells forming a sea of electrons around positively charged metal ions. They are delocalised electrons.

Question 58

What are metallic bonds?

Answer 58

The strong electrostatic forces of attraction between the delocalised electrons and the closely packed, positively charged metal ions.