Unit 3 - Chemistry In Society

Question 1

Metallic bond definition

Answer 1

A metallic bond is the electrostatic force of attraction between positively charged ions and delocalised electrons.

Question 2

Matallic bond properties

Answer 2

Metallic elements can conduct electricity in any state.

This is because they have delocslised electrons (free to move).

Question 3

Thermosoftening plastic

Answer 3

Thermosoftening plastics will melt when heated, so they can be reshaped, reused and recycled.

Question 4

Thermosetting plastics

Answer 4

Thermosetting plastics can be reshaped as they are made and then permanently set. They cannot be reshaped, reused or recycled.

(E.g. kettles, plugs)

Question 5

What do all monomers units contain?

Answer 5

A carbon to carbon double bond.

Monomers are alkene based and are unsaturated molecules.

Question 6

What are polymers?

Answer 6

Polymers are long chained molecules which are made by joining monomers together.

Polymers are examples of plastics.

Question 7

How are polymers made?

Answer 7

Polymers are made when lots of single unit monomers join together.

The reaction is called addition polymerisation.

A lot of energy is needed. It is often carried out at high pressure with a catalyst.

Question 8

Addition polymerisation definition

Answer 8

Addition polymerisation is a chemical reaction that involves making a polymer through an addition reaction.

The polymer is made from unsaturated monomers joining together in long chains.

(Polymers are made when lots of single unit monomers join together).

Question 9

Monomer definition

Answer 9

A monomer is a small molecule that can be joined together to form a polymer.

Question 10

Repeating unit

Answer 10

The repeating unit is the shortest repeating section of the polymer.

Question 11

Radioactive decay

Answer 11

Radioactive decay is when unstable nuclei become stable by giving out alpha, beta or gamma radiation.

Heavier isotopes are more unstable and so are more likely to be radioactive.

Question 12

What are unstable nuclei called?

Answer 12

Radioisotopes

To become stable radioisotope undergo radioactive decay.

Question 13

Alpha radiation/ particles properties

Answer 13

It is a positively charged particle so is attracted to negative plate.

Can only travel a few cm and are easily stopped by a piece of paper.

Question 14

Beta particles/ radiation properties

Answer 14

(Caused when a neutron breaks down.)

Beta particles are electrons given out by the nucleus of an atom - has a negative charge and is attracted to a positive plate.

Can travel about 1m in air but can be stopped by 5mm of aluminium.

Question 15

Gamma rays/ radiation properties

Answer 15

They are electromagnetic waves so are not affected by any charged plates.

They can travel long distances and can be stopped by 25mm of lead.

Question 16

What are alpha particles

Answer 16

Alpha particles consist of 2 protons and 2 neutrons and have a positive charge. (Charge = 2+)

It is the nucleus of a helium atom.

Question 17

What are beta particles?

Answer 17

Beta particles are electrons ejected from the nucleus of an atom.

Question 18

What are gamma rays

Answer 18

Gamma rays are electromagnetic waves emitted from within the nucleus of an atom.

Question 19

Half-life definition

Answer 19

Half-life is the time taken for the radioactivity of a substance to fall to half of it’s original value.

Question 20

Uses of radioisotopes

Answer 20

Medicine - sterilising equipment, cancer treatment, used as a tracer in diagnostics.

Industry - used in smoke alarms, to ensure the thickness of paper, detect leaks.

Used to date materials.

Isotopes used in medicine are usually beta or gamma as they have short half-lives so they don’t stay in the patient too long.

In Industry, they tend to have much longer half-lives.

Question 21

What is the half-life of an isotope effected by?

Answer 21

The half-life of an isotope is constant. It is unaffected by chemical or physical conditions.

Question 22

Importance of fertilisers

Answer 22

Fertilisers are used to provide plants with the essential elements for growth. They restore essential nutrients in the soil.

Question 23

Elements found in fertilisers

Answer 23

Nitrogen (N)

Phosphorus (P)

Potassium (K)

Question 24

Ammonia properties

Answer 24

Clear, colourless gas

Pungent smelling

Very soluble - makes an alkaline solution.

Ammonia solution + acid —> ammonium salt + water

Question 25

What is ammonia?

Answer 25

Ammonia is nitrogen hydride (NH3) which is used to make fertilisers.

Question 26

Ammomia reaction

Answer 26

Ammonia solution + acid –> ammonium salt + water

Question 27

What is produced in the haber process?

Answer 27

Ammonia (NH3)

Question 28

Haber process balanced equation

Answer 28

H2(g) + 3N2(g) 2NH3(g)

Question 29

Conditions used in the haber process

Answer 29

The haber process uses moderate temperatures.
- (too low then the reaction is too slow, too high then too fast and so a reverse reaction takes place)

High pressure

An iron catalyst is used

Question 30

Ostwald process

Answer 30

Product - nitric acid

Reactant - ammonia, oxygen and water

Catalyst - platinum

Question 31

Equations for the reactions of metals

Answer 31

Metal + oxygen –> metal oxide

Metal + water –> metal hydroxide + hydrogen

Metal + dilute acid –> salt + hydrogen

Question 32

What happens when metals combine

Answer 32

They form alloys.

Question 33

Redox reaction definition

Answer 33

A redox reaction is when an oxidation and reduction reaction take place at the same time.

Question 34

Oxidation definition

Answer 34

Oxidation - loss of electrons by a reactant

O - oxidation 
I - is
L - loss
R - reduction 
I - is
G - gain

Question 35

Reduction definition

Answer 35

Reduction - gain of electrons by a reactant.

O - oxidation 
I - is
L - loss
R - reduction 
I - is
G - gain

Question 36

Extraction of metal

Answer 36

The higher up a metal is on the electrochemical series, the harder it is to extract the metal from its ore.

During extraction the metal ions are REDUCED to metal atoms.

Question 37

Extracting metals - heat alone

Answer 37

Some metals can be extracted from their ore (metal oxide) bu heat alone. This is only the case for the least reactive metals.

• Silver (Ag)
• Gold (Au)
• Mercury (Hg)

Question 38

Extracting metals - heat and carbon

Answer 38

The heat and carbon caused the metal to be displaced and the carbon to join up with the oxygen.

The carbon is called a reducing agent.

• copper (Cu)
• lead (Pb)
• iron (Fe)
• tin (Sn)
• zinc (Zn)

Question 39

Extracting metals - electrolysis

Answer 39

Any metal above aluminium (Al) on the electrochemical series is attracted by electrolysis.

The positive metal ion is attracted to the negative electrode where it gains electrons to turn back into a metal atom.

Question 40

Electrolysis

Answer 40

Electrolysis is the process of separating a compound into its elements using electric current.

A D.C. Power supply is used so that the products can be identified and collected.

The negative ions go to the positive electrode.
The positive metal ions go to the negative electrode where they gain electrons and turn back into a metal atom.

Any metal from Al upwards in the E.C.S is extracted by electrolysis.

Question 41

Electrolyte definition

Answer 41

Electrolyte is a solution (ionic compound) that contains ions which can conduct electricity.

Question 42

What is needed to make a basic electrochemical cell

Answer 42

2 different metals and an electrolyte.

Question 43

What is the use of an ion bridge?

Answer 43

The salt/ion bridge is used to complete the circuit by linking the 2 half cells.

Question 44

Voltage - electrochemical series

Answer 44

The further apart the metals an the ECS, the greater the voltage that would be produced l.