AQA GCSE Chemistry - Paper 1

What is the charge of a proton?

What is the charge of a proton?

+1

What is the charge of a neutron?

0

What is the charge of an electron?

-1

What is the relative mass of a proton?

1

What is the relative mass of a neutron?

1

What is the relative mass of an electron?

Very small

How many types of atoms do elements contain?

Only one type

What are compounds?

Substances containing two or more different elements that are chemically bonded together

What are mixtures?

Substances containing two or more different elements that are not chemically bonded together

What pattern is formed from carrying out paper chromatography?

Chromatogram

Which method of separation is useful to separate an insoluble solid from a liquid?

Filtration

Which method of separation is useful to separate a soluble solid from a liquid?

Evaporation or Crystillisation

Which method of distillation separates liquids with similar boiling points?

Fractional distillation

Who discovered that the plum pudding model was wrong?

Ernest Rutherford

Who devised an experiment that proved the existence of the neutron?

Niels Bohr

Why did Mendeleev leave gaps in his Table of Elements?

To ensure that elements with similar properties stayed in the same groups. The gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be

How are the group number and the number of electrons in the outer shell of an element related?

The group number tells you how many electrons are in the outer shell of an element. E.g. sodium is in Group 1 therefore it has 1 electron on its outer shell

What kind of ions do metals form?

Positive

Where are the non-metals on the periodic table?

On the right hand side

Give three properties which are specific to transition metals

1) They can form more than one ion e.g cobalt form Co2+
2) They are often coloured, therefore compounds which contain them are colourful e.g. potassium chromate is yellow
3) They often make good catalysts e.g. nickel based catalysts are used in the hydrogenation of alkenes

State three trends as you go down Group 1

1) Increased reactivity - the outer electron is more easily lost as the attraction between the nucleus and the electron decreases because the electron is further away from the nucleus
2) Lower melting and boiling points
3) Higher relative atomic mass

What are the products of the reaction of a Group 1 metal and water

Hydrogen gas and a metal hydroxide
E.g. sodium + water --> sodium hydroxide + hydrogen

What's the difference between the hardness of Group 1 and transition metals?

Transition metals are harder, denser and stronger than Group 1 metals

What's the difference between the reactivity of Group 1 and transition metals?

Group 1 metals are much more reactive than transition metals

What's the difference between the melting points of Group 1 and transition metals?

Transition metals have higher melting points than Group 1 metals

What trends occur as you go down Group 7?

1) They become less reactive - it's harder to gain an extra electron because the outer shell's further from the nucleus
2) They have higher melting and boiling points
3) They have higher relative atomic masses

What is the charge of the ions that halogens form when they react with metals?

They form negative ions

What is the trend in boiling point as you go down Group 0?

The boiling points increase

What subatomic particles does the nucleus contain?

Protons and neutrons

What is relative atomic mass?

The mass number which refers to the element as a whole

How are positive ions formed?

A metal atom loses electrons

How are negative ions formed?

A non-metal gains electrons

What is air a mixture of?

Gases, mainly nitrogen, oxygen, carbon dioxide and argon

What is crude oil a mixture of?

Different length hydrocarbon molecules

How can you separate substances in a mixture?

Chromatography

What is simple distillation used for?

Separating out a liquid from a solution
E.g. separating pure water from seawater

How were elements arranged in the early 1800s?

By their physical and chemical properties and their relative atomic mass

How are columns arranged?

Elements with similar properties

What are the three similar basic properties of metals?

1) They're strong but are malleable
2) They're great at conducting heat and electricity
3) They have high boiling and melting points

What is the product of the reaction of a Group 1 metal with chlorine?

A metal chloride salt
E.g. sodium + chlorine --> sodium chloride

What is the product of the reaction of a Group 1 metal with oxygen?

A metal oxide, depending on the Group 1 metal
-Lithium + oxygen --> lithium oxide
-Sodium + oxygen --> sodium oxide + sodium peroxide
-Potassium + oxygen --> potassium peroxide + potassium superoxide

What are halogens?

Non-metals in Group 7 with coloured vapours

What colour is fluorine?

A very reactive, poisonous yellow gas

What colour is chlorine?

A fairly reactive, poisonous dense green gas

What colour is bromine?

A dense, poisonous red-brown volatile liquid

What colour is iodine?

A dark grey crystalline solid or a purple vapour

What do halogens exist as?

Molecules - pairs of atoms

What do halogens form?

1) Molecular compounds - halogens share electrons via covalent bonding with other non-metals too achieves a full outer shell
2) Ionic compounds with metals - they form 1- ions called halides

What do noble gases exist as?

Monatomic gases - single atoms not bonded to each other

What are the noble gases at room temperature?

Colourless gases

Are the noble gases flammable?

No - they're non-flammable

Why does the boiling point of noble gases increase as you move down the group?

There's an increase in the number of electrons in each atom leading to greater intermolecular forces between them which to be overcome

Paper Chromatography - Method

1) Draw a pencil line near the bottom of a sheet of filter paper
2) Add a spot of ink to the line & place the sheet in a beaker of solvent e.g. water - the solvent used depends on what's being tested - some compounds dissolve well in water, but sometimes other solvents e.g. ethanol are needed
3) Ensure the ink isn't touching the solvent - you don't want it to dissolve
4) Place a lid on top of the container to stop the solvent evaporating
5) The solvent seeps up the paper, carrying the ink with it
6) Each different dye in the ink will move up the paper at a different rate so that the dyes will separate out - each dye will form a spot in a different place, 1 spot per dye in the ink
7) If any of the dyes in the ink are insoluble in the solvent used, they'll stay on the baseline
8) When the solvent has nearly reached the top of the paper, take the paper out of the beaker & leave it to dry

Simple Distillation - Method

1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first
2) The vapour is then cooled, condensed & is collected
3) The rest of the solution is left behind in the flask

What is the problem with simple distillation?

You can only use it to separate things with very different boiling points - if the temperature goes higher than the boiling point of the substance with the highest boiling point, they will mix again

Fractional Distillation - Method

1) Put your mixture in a flask & stick a fractionating column on top. Then you heat it
2) The different liquids will all have different boiling points - they'll evaporate at different temperatures
3) The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column
4) Liquids with higher boiling points might also start to evaporate, but the column is cooler towards the top, therefore they will only get part of the way up before condensing & running back down towards the flask
5) When the first liquid has been collected, you raise the temperature until the next one reaches the top

Radius of an atom

0.1 nanometers

Radius of a nucleus

1/10,000 of the radius of an atom

What type of ion do elements from Group 1 form?

Positive ions

What type of ion do elements from Group 7 form?

Negative ions

Describe how an ionic bond forms

When a metal and a non-metal react together, the metal loses its one electron on its outer shell to form a positively charged ion. This one electron is gained by the non-metal to complete its outer shell, forming a negative ion.

Describe the structure of a crystal of sodium chloride

It's a giant ionic lattice. The positive sodium and negative chlorine ions form a closely packed regular arrangement and there are very strong electrostatic forces of attraction between the oppositely charged ions.

List the main properties of ionic compounds

1) High melting and boiling points - many strong bonds between the ions
2) They can't conduct electricity when they're solid - the ions are held in a fixed arrangement therefore they can't pass on the electrical current.
3) They can conduct electricity when they're liquids because the ions are free to move therefore they can pass on the electrical current.
4) They dissolve easily in water - they are free to move in the solution and can carry electrical current.

Describe how covalent bonds form

When two non-metals bond together, they share electrons to make covalent bonds. The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces - this makes covalent bonds very strong.

Explain why simple molecular compounds typically have low melting and boiling points

The intermolecular forces between the atoms are very weak, therefore it takes only a small amount of energy to break them apart.

Describe the structure of a polymer

Polymers are long chains of repeating units joined together to make a long molecule. Between the atoms are strong covalent bonds.

Give three examples of giant covalent substances

-Diamond
-Graphite
-Silicon Dioxide

Explain why graphite can conduct electricity

It contains delocalised electrons which can carry electrical charge

What is metallic bonding?

The electrons in the outer shell of a metal atom are delocalised. There are strong forces of electrostatic attraction between the positive metal ions and the negative electrons. These forces of attraction hold the atoms together in a regular structure.

List three properties of metals and explain how metallic structure causes each property

1)Solid at room temperature - they have very high melting and boiling points because a lot of energy is needed to break the strong electrostatic forces of attraction between the metal atoms and delocalised electrons.
2)Good conductors of heat and electricity - the delocalised electrons can carry electrical current and thermal energy through the structure.
3)Malleable - the layers of metal atoms can slide over each other

Explain why alloys are harder than pure metals

When two metals are mixed together, both of their atoms are different sizes which causes a disruption in the neat layers of metal atoms. This makes it more difficult for the layers to slide over each other.

Name three states of matter

Solid, liquid and gas

State Symbols

solid - s
liquid - l
gas - g
aqueous - aq

What is the name of the temperature at which a liquid becomes a gas?

Boiling

Describe giant covalent structures

-All the atoms are bonded to each other by strong covalent bonds
-They have very high melting and boiling points, therefore, lots of energy is required to break the covalent bonds
-Most of them don't conduct electricity because they don't contain delocalised electrons or ions

Describe the structure of diamond

Each carbon atom forms four strong covalent bonds in a very rigid giant covalent structure.

Describe the structure of graphite

Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron.

What is silicon dioxide?

Sand. Each grain of sand is one giant structure of silicon and oxygen.

Describe the properties of diamond

-Very hard because of its structure
-Very high melting point because it takes a lot of energy to break the bonds
-No delocalised electrons, therefore it cannot conduct electricity

What is graphene?

A sheet of carbon atoms joined together in hexagons - it's one atom thick, therefore it's a 2-dimensional compound
The network of covalent bonds makes it very strong
Very light - added to composite materials to improve their strength but not to add weight
Contains delocalised electrons - conducts electricity through the whole structure
Can be used in electronics

What are fullerenes?

Molecules of carbon, shaped like closed tubes or hollow balls - the carbon atoms are arranged in hexagons but also pentagons & heptagons

Uses of Fullerenes

1) To 'cage' other molecules - the fullerene structure forms around another atom/molecule, which is then trapped inside - used to deliver drugs into the body
2) Make good industrial catalysts due to their large surface area
3) Make good lubricants

Nanotubes

Tiny carbon cylinders formed from fullerenes
Ratio between length & diameter is very high
Conduct electricity & thermal energy
High tensile strength - don't break when stretched
Used for nanotechnology - used in electronics or to strengthen materials without adding much weight e.g. tennis racket frames

Melting

When a solid is heated, the particles gain more energy which causes them to vibrate - weakens the forces that hold the solid together
At the melting point, the particles will have enough energy to break free from their positions - the solid turns into a liquid

Boiling

When a liquid is heated, the particles will gain even more energy, making them move faster - weakens and breaks the bonds holding them together
At the boiling point, the particles have enough energy to break their bonds - the liquid becomes a gas

Condensing

As a gas cools, the particles no longer have enough energy to overcome the force of attraction between them, causing bonds to form between the particles
At the boiling point, so many bonds have formed between the gas particles that the gas becomes a liquid

Freezing

When a liquid cools, the particles have less energy, so move around less
There's not enough energy to overcome the attraction between the particles, so more bonds form between them
At the melting point, so many bonds have formed between the particles that they're held in place - the liquid becomes a solid

What are coarse particles?

Particles that have a diameter between 2,500 nm and 10,000 nm - also known as dust

What are fine particles?

Particles that have diameter between 100 nm and 2,500 nm

What are nanoparticles?

Particles that have a diameter between 1 nm and 100 nm - these are the smallest particles that contain only a few hundred atoms

Equation for surface area to volume ratio

Surface area to volume ratio = surface area / volume

Do nanoparticles have a high or low surface area to volume ratio?

Very high surface area to volume ratio - the surface area is very large compared to the volume, therefore, they make good catalysts

What is nanoscience?

The science that investigates the uses & properties of nanoparticles

Uses for nanoparticles

1) Catalysts
2) Nanomedicine - they could deliver drugs right into the cells when they're needed as they're more easily absorbed by the body
3) Tiny electric circuits for computer chips - some conduct electricity
4) Silver nanoparticles have antibacterial properties - added to polymer fibres that are used to make surgical masks & wound dressings and they're added to deodorants
5) Used in cosmetics e.g. to improve moisturisers without making them really oily

Effects of Nanoparticles on Health

1) The way they affect the body isn't fully understood
2) Some people are worried that products containing them have been made available before the effects on human health have been investigated properly
3) We don't know what the long-term impacts on health will be
4) Many people believe that products containing nanoparticles should be clearly labelled

Benefits of Nanoparticles

1) Used in sun creams - shown to be better than the materials in traditional sun creams at protecting skin from harmful UV rays
2) Give better skin coverage than traditional sun creams

Problems with Nanoparticles

1) Not yet clear whether the nanoparticles can get into your body, and if they do, whether they damage cells or not
2) Possible that when they are washed away, they might damage the environment

Simple Molecular Structures

Very strong covalent bonds
Very weak intermolecular forces
Most are liquids & gases at room temperature
The bigger the molecule, the stronger the intermolecular forces
Don't conduct electricity - no delocalised electrons or ions as they're not charged

Why is Buckminsterfullerene a good lubricant?

It's shaped like a hollow ball, thus it can roll

What is the relative formula mass?

The relative atomic masses of all the atoms in the molecular formula added together