Chemistry unit 2 wjec

What is atomic structure?
The number of protons in an atom, how the protons electrons and neutrons are arranged in the energy shells

What two particles are equal
Protons and electrons

Give the charge on all of the particles
Electrons-negative protons -positive neutron -negative

What is the format of the energy shells
Nucleus containing protons and neutrons and then electrons around in the energy levels

What is the maximum number of electrons in the first shell and second shell ?
2 and 8

The number of electrons is equal to which other particle?
Protons meaning they have no overall charge

What is the number of protons called in an atom?
Atomic number- arranged in the periodic in increasing atomic number

If carbons atomic number is 6 what is the arrangement of electrons
2, 4

What is ionic bonding?
When atoms with no full outer shell want to gain or loose electrons so they become a noble property and so they become stable, they do this by exchanging electrons with other elements, such as sodium, it has a structure of 2,8,1 so it wants to loose the last electron so it has a full outer shell

How do you present ionic bonding ?
You put the structure in brackets and give them a charge, if the charge is negative it means they have gained an electron and if it is positive it means they have lost an electron.

Do metals form positive or negative ions?
Positive

What are the ionic bonds also know as?
Strong electrostatic forces of attraction between oppositely charged ions.

What can you say about ionic compounds melting and boiling points?
They are very high

What would happen to the structure of chlorine (2,8,7) in ionic bonding?
It would gain an electron and become Cl- (2,8,8)-

What is covalent bonding?
Where two non metals share electrons to act as a full outer shell making them become noble and have a stable structure.

What are some properties of covalent compounds?
They are small molecules with low melting and boiling points and they are usually gases

What do covalent bonds also form ?
Giant structures such as diamond and graphite

Describe the bonding in metals:
Arranged in regular layers, positively charged ions form the core and their outer negative electrons form the sea of electrons also know as delocalised electrons which help the metal conduct electricity as they carry the current as the drift around, there is a neutral electrostatic attraction between the positive and negative ions

Give two properties of giant metallic structures?
Malleable and ductile

What are simple molecules?
They are molecules with no overall charge, they contain strong covalent bonds but weak intermolecular forces, they have low melting and boiling points.

What are ionic compounds?
They have an electrostatic attraction and they are held together in a lattice, between a metal and non metal, conduct electricity an they have a high melting and boiling point.

What are macro molecules also known as?
Giant covalent substances

What are some examples?
Graphite, diamond and silica

Why can graphite conduct electricity?
Because it contains delocalised electrons and it's arranged in layers which slide over each other.

What are fullerenes and give an example?
They are carbon giant structures and they where only recently discovered e.g bucket ball

What is the size of nano science ?
1x10-9m

What are uses of nano science?
Self cleaning titanium oxide glass, nano silver particles in socks to stop odour

What are possible dangers of nano science?
We don't know long term effects, they are so small they can absorb into the body

When fullerenes are joined together what do they form?
Nanotubes which conduct electricity

Give an example of a redox reaction.
Copper oxide + carbon --> carbon dioxide + copper
The copper oxide to copper is reduction
The carbon to carbon dioxide is oxidation

What is oxidation?
Gaining oxygen or loosing electrons

What is reduction?
Loosing oxygen or gaining electros

What is electrolysis?
The process in which ionic substances are broken down into simpler substances using electricity.

What does the substance have to be in to ensure the ions can move freely?
Molten form or in solution

What is the electrolyte?
The liquid that contains the free ions which conduct electricity

What is the negative electrode called?
Anode

What is the positive electrode called?
Cathode

What reaction happens to the positively charged ions?
They move to the anode, they receive electrons and are reduced

What happens to the negatively charged ions?
The move to the cathode, they loose electrons and are oxidised.

What is the balanced equation that takes place at the anode?
2O2- - 4e- --> O2

What is the balanced equation that takes place at the cathode?
Al3+ + 3e- --> Al

What are some uses of aluminium ?
Packaging due to low density, air craft body's as light but strong, headlamp reflectors as it reflects light

What are some properties of titanium?
High melting point strong and resistant to corrosion

What are the four types of steel.
-carbon steels
-low alloy steels
-high alloy steels
-stainless steels

What is relative atomic mass? Ar
All atoms compared to carbon12 just the atomic number

What is relative molecular mass? Mr
Relative formula mass, you add all individual atomic masses together

What is the empirical formula?
The simplest RATIO, find the masses, find the atomic mass, divide masses by atomic mass, simplify.

What is percentage yeild?
How much product is made compared to the 100%

What's the formula for percentage yeild?
(Ar x number of atoms) / mr x 100

Why don't you get 100% yeild?
the reaction may be reversible
May not be pure, may be left on apparatus.

What does the symbol of an equilibrium arrow indicate?
A reversible reaction

What happens when you reach equilibrium ?
The forward and the backward reaction are at the same rate, they level out.

What is the process that makes ammonia?
The harder process

What two things make ammonia and where are the from?
Nitrogen from the air and hydrogen from methane.

What is the equation for ammonia ?
N2 + 3H2 <---> 2NH3

How do you stop backward reaction in this process?
Temp is at 450 degrees, pressure is at 200 atm and hydrogen and nitrogen is passed over an iron catalyst.

What do these conditions provide?
An optimum condition

What are some advantages of fertilisers?
The provide a better yeild, More profitable farming and it improves soil condition

"" disadvantages?
Eutrophication, can make streams and rivers acidic,

What is a test for ammonia?
Damp red litmus will turn the blue as ammonia is the only alkaline gas

What are nearly all the compounds in crude oil ?
Hydrocarbons containing hydrogen and carbon

What iOS the general formula for Alan's?
Cn + H2n + 2

What are alkanes?
Saturated hydrocarbons containing single bonds

What are the first four alkanes and what are their formula?
Methane- ch4
Ethane- c2h6
Propane-c3h8
Butane - c4h10

What is catalytic cracking and what does is produce?
How alkanes are broke down, large hydrocarbon molecules broken down into smaller molecules using a catalyst whi h produces a mixture of smaller alkanes & alkenes

What are alkenes?
They are formed by cracking, the they can be made into polymers and then are unsaturated hydrocarbons that contain double bonds

What is the general formula for alkenes?
Cn+ H2n

What are the first three alkenes and what is their formula?
Ethene-C2h4
Propene -C3h6
Butene -C4h8

What is a test to distinguish betweens saturated and unsaturated compounds?
Red bromine water- in the presence of unsaturated compounds the bromine water decolourises

Whar are polymers?
Large molecules that are made when monomers are joined together to form long chains, held together by covalent bonds

What are many polymers made from?
Alkenes

What is polymerisation?
Turning monomers into polymers

Example?
Ethene --> polythene

What must you do to the double bond?
Break it, and put the repeating unit in brackets with an n next to it.

What are some properties of plastics?
They don't conduct electricity, poor conductors of heat, very unreactive, persist I the environment for a long time .

What do the properties of plastics depend on?
How the chains are made

What are branching chains?
Chains that give the properties: light soft and easy to melt such as plastic bags

What are lined up chains?
Chains that give the properties: dense, rigid and hard to melt e.g bins- hard plastics

What factors effect properties of plastics?
Reaction conditions, monomersm additives

What are thermosoftening plastics?
Plastics that are solid when cols, they can be moulded into shapes, they have weak intermolecular forces for example carrier bags and natural rubber

What are thermosetting plastics?
Cannot be stretched, high melting points, they are strong rigid and brittle, they have strong intermolecular forces, for example; hard plastic chair

What are the three ways to dispose waste plastics?
Landfill incineration and recycling.

What's and advantage of landfill ?
Convinient, it's possible to extract and cell methane from

Disadvantage?
Bin lorries create noise and traffic pollution, potential for environmental damage, expensive

Advantage for incineration?
Burns all the rubbish away

Disadvantage?
Creates toxins

Advantage for recycling?
Uses less water and energy, fewer green house gases

Disadvantage?
Storing, sorting and cleaning is expensive, risk on contamination

What are the three main plastics that can be recycled?
PET- oven metal trays
HDPE- milk bottles
PVC- shampoo bottles

Why use biodegradable plastics?
Better for the environment as plastics can be broken down and converted in to CO2 water and minerals by micro organisms

What are smart materials?
Materials that have properties that can react to change with their environment e.g pressure temperature and light.

What are shape memory alloys ?
Alloys that can change shape easily when heated, used in spectacle frames

What are thermochemistry materials?
They change colour with the temperature used in food packaging

What are photochromic materials?
Change colour according to light intensity, e.g security markers

What are polymer gels?
Have the ability to absorb or expel water used in nappies

What does the term solvent mean?
The liquid the solute dissolves in

What does solute mean?
The substance that dissolves in a liquid to form a solution

What does solution mean?
The mixture formed when a solute has dissolved in a solvent

Soluble?
A substance that will dissolve

Insoluble?
A substance that won't dissolve.

Saturated?
No more solute can dissolve

How can solubility be increased?
By increasing temperature, adding more solvent and stirring.

What's a solubility curve?
Helps predict the mass of solute that will dissolve in a particular mass of a solvent at a certain temperature

What's hard water?
Water that contains minerals and salts that have been dissolved in the water

Whats an advantage if hard water?
People prefer the taste, it's good for children, helps redue heart illness

"" disadvantage?
Scale forms inside kettles, can clog pipes

What is an experiment to distinguish between hard and soft water?
How much soap is needed to form a lather when the water is shaken

What is water treatment also know as?
Water purification

What are the stages?
Filtration
Sedimentation
Chlorination