AQA GCSE Triple Science - Chemistry

What is in the nucleus?

Protons and neutrons

What is the charge of the nucleus and why?

Positive as there are no electrons

Give the relative mass and relative charge of protons, neutrons and electrons

RM:
P = 1
N = 1
E = 0
RC:
P = 1
N = 0
E = -1

Give four features of electrons

They move around the nucleus in electron shells
They are negatively charged
They cover a lot of space
They have virtually no mass

What is the overall charge of an atom and why?

Neutral. This is because they have the same number of protons and electrons, so the charges cancel each other out

How do you find the number of neutrons an element has?

Subtract the atomic number from the mass number

What is an element?

A substance made up of atoms that all have the same number of protons in their nucleus

Roughly, how many different elements are there?

100

What are isotopes?

Different forms of the same element, which have the same number of protons, but a different number of neutrons

What is relative atomic mass?

Relative atomic mass is an average mass taking into account the different masses and abundances of all the isotopes that make up the element

How do you calculate the relative atomic mass?

Sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes

What are compounds?

Substances formed from two or more elements, the atoms of each are in fixed proportions throughout the compound, and they're held together by chemical bonds

What is ionic bonding?

A compound formed through bonding between a metal and non-metal (consists of ions). The metals become positive as they lose electrons, and the non-metals become negative as they lose electrons. E.g. the metal gives an electron to a chlorine atom. The oppositely charged ions are attracted to each other by electrostatic forces

What are five properties of ionic compounds?

High melting points
High boiling points (due to the strong bonds between the ions)
Cannot conduct electricity in solid form
Conduct electricity in molten form as the ions are free to move
Dissolve easily in water

What is covalent bonding?

A compound formed from non-metals consists of molecules. Each atom shares an electron with another atom.

Give an example of an ionic compound

NaCl (Sodium chloride)

Give an example of a compound that is covalently bonded

HCl (Hydrogen chloride)

What are 5 features of simple molecular structures?

Weak intermolecular forces
Low melting points
Low boiling points
Melting and boiling points increase as the molecules get bigger
Don't conduct electricity

What is the formula for carbon dioxide?

CO2

What is the formula for ammonia?

NH3

What is the formula for water?

H2O

What is the formula for sodium chloride?

NaCl

What is the formula for carbon monoxide?

CO

What is the formula for hydrochloric acid?

HCl

What is the formula for calcium chloride?

CaCl2

What is the formula for sodium carbonate?

Na2CO3

What is the formula for sulfuric acid?

H2SO4

What are mixtures?

Two or more elements not chemically bonded together

Give five methods of separating mixtures

Filtration
Crystallisation
Simple distillation
Fractional distillation
Chromatography

How do you do paper chromatography?

Draw a line near the bottom of a sheet of filter paper
Add a spot of ink to the line
The solvent seeps up the line

How do you separate a soluble salt from a solution using evaporation?

Pour the solution into an evaporating dish
Heat the solution
The solution will get more concentrated as the solvent evaporates and crystals will form
Heat until the only thing left is dry crystals

How do you separate a soluble salt from a solution using crystallisation?

Pour the solution into an evaporating dish
Heat the solution
Once some of the solution has evaporated, or when you see crystals start to form, remove from heat and allow solution to cool
The salt should for crystals as it becomes insoluble in the cold, highly concentrated solution
Filter the crystals out of the solution

How do you use filtration and crystallisation to separate rock salt?

Grind the mixture so the salt crystals dissolve easier
Dissolve the salt in water
Filter the mixture
Evaporate the water from the salt so it forms dry crystals

How do you use simple distillation to separate solutions?

The solution is heated and the part of the solution that has the lowest boiling point evaporates
The vapour is then cooled, condensed, and collected

What is an issue with simple distillation?

It can only be used to separate mixtures with very different boiling points

What method is used to separate mixtures with similar boiling points?

Fractional distillation

How do you do fractional distillation?

Put the mixture in a flask with a fractionating column on top
Heat the mixture to a certain temperature
When the temperature on the thermometer matches the boiling point of the liquid with the lowest boiling point, the first one will evaporate.
When the first fraction boils, it evaporates. It is collected through a condenser
This process is repeated at higher temperatures

How was the 'plum pudding model' of the atom formed?

At the start of the 19th century, Dalton thought atoms were solid spheres. In 1897, JJ Thomson concluded they weren't solid spheres. He believed they contains a smaller, negatively charged particle - electrons. The plum pudding model shows the atom as a ball of positive charge with electrons stuck in it

What is the alpha scattering experiment?

Rutherford set up an experiment where he fired a beam of alpha particles towards some thin gold foil. He found most of the particles went straight through the foil. This suggested that there was lots of empty space, however he noticed that some alpha particles were deflected, with a few by more than 90 degrees. This suggested that there was a concentrated positive nucleus in the centre of the atom since two positive forces repel. This led to the current model being developed as the plum pudding model thought electrons were suspended in a positive cloud.

Who suggested that all electrons were contained in shells?

Niels Bohr

What is the maximum number of electrons in each of the first three shells?

2, 8, 8

How has the periodic table developed?

Dalton suggested the periodic table was arranged by mass, measured by chemical reactions. Newlands built on this theory with the 'law of octaves'. He noticed he properties of every 8th element were similar. Dmitri Mendeleev arranged them by atomic mass, and left space for elements that were undiscovered at the time.

How many outer electrons do elements in group 1 have?

1

Give some features of group 1 metals

They react with water more vigorously as you go down the periodic table as the electrons are further away from the pull of the positive nucleus. They have low melting and boiling points compared to the other metals, and they are softer. As you go down the group, the melting point decreases, the density increases, and they become more reactive

Give some features of group 7 halogens

They become less reactive as you go down the group as the positive nucleus is needed to pull the electrons in, and this force is weaker as the shells get further away.
The halogens are: fluorine, chlorine, bromine, iodine, and astatine
They are diatomic

Roughly how much of the periodic table is metals?

75%

What are the features of most metals?

They're strong, but can be bent or hammered into different shapes
They're great at conducting heat and electricity
They have high melting and boiling points

What are five features of non-metals?

Dull looking
Brittle
Not always solids at room temperature
Don't usually conduct electricity
Usually have a lower density

What are three features of transition metals?

They can have more than one ion
They are often coloured, so compounds that contain them are colourful
They often make good catalysts

What happens when you react alkali metals with water?

They produce hydrogen gas and metal hydroxides

What types of compounds do ionic compounds form?

White solids that dissolve in water to form colourless solutions

Give an example of a reaction of an alkali metal with water

Sodium + water --> sodium hydroxide + hydrogen
2Na(s) + 2H20(l) --> 2NaOH(aq) + H2(g)

What happens when you react an alkali metal with chlorine gas?

They form white metal chloride salts

Give an example of a reaction of an alkali metal with chlorine gas

Sodium + chlorine --> sodium chloride
2Na(s) + Cl2(g) --> 2NaCl(s)

When lithium reacts with oxygen, what does it form?

Lithium oxide (Li2O)

When sodium reacts with oxygen, what does it form?

A mixture of sodium oxide (Na2O) and sodium peroxide (Na2O2)

When potassium reacts with oxygen, what does it form?

A mixture of potassium peroxide (K2O2) and potassium superoxide (KO2)

What is fluorine?

A very reactive, poisonous yellow gas

What is chlorine?

A fairly reactive, poisonous, dense green gas

What is bromine?

A dense, poisonous, red-brown volatile liquid

What is iodine?

A dark grey crystalline solid or a purple vapour

What will more reactive halogens do to less reactive ones?

Displace them

Give an example of a displacement reaction involving halogens?

Cl2(g) Pale green + 2KI(aq) --> I2(aq) Brown + 2KCI(aq)

How do the boiling point of the noble gases change as you go down the group?

Boiling points increase (greater intermolecular forces between atoms)

What are ions?

Charged particles

Why do atoms gain or lose electrons?

To gain a full outer shell

What type of ions do metals form?

Positive

What type of ions do non-metals form?

Negative

What are cations?

Positive ions

What are anions?

Negative ions

What are polymers?

Long chains of repeating units joined together by covalent bonds

What are giant covalent structures?

Macro-molecules. They have strong covalent bonds.

What are three properties of most giant covalent structures?

High melting point
High boiling point
Don't conduct electricity as they don't contain charged particles

What is the structure of diamond?

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

What is the structure of graphite?

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

Give three properties of diamond

Really hard
Very high melting point
Doesn't conduct electricity

Give three properties of graphite

Soft and slippery due to the layers, which makes it good as a lubricating material
High melting point
Conducts electricity and thermal energy

Give three properties of graphene

Strong due to the covalent bonds
Very light so it can be added to composite materials to improve their strength without adding weight
Can conduct electricity, meaning it is used in electronics

What do fullerenes form?

Spheres and tubes

What can fullerenes be used to do?

Deliver drugs into the body as they 'cage' other molecules
Catalysts as they have a huge surface area
Lubricants

Give three features of nanotubes

Conduct electricity
Conduct heat
High tensile strength

What can nanotubes be used in?

Electronics, or to strengthen materials without adding much weight (e.g. tennis racket frames)

What does metallic bonding involve?

Delocalised electrons

Why are alloys harder than pure metals?

Different elements have different sized atoms. When elements are combined to form alloys, the different sizes make it harder for the layers to slide over each other

What three things does the strength of the force between the particles in a material depend on?

The material
The temperature
The pressure

What features do all solids have?

The particles don't move around like in a liquid or gas
They keep a definite shape and volume
The particles vibrate as they become hotter

What features do all liquids have?

They have a definite volume
They move to fit the shape of the container
They expand slightly when heated

What features do all gases have?

They don't have a definite shape
They don't have a definite volume
The particles move randomly, and get faster as it gets hotter

How do solids change to liquids?

When a solid is heated, the particles gain energy. This makes the particles vibrate more, which weakens the forces that hold the solid together. At the melting point, the particles have enough energy to break free from their positions

How do liquids change to gases?

When a liquid is heated, the particles gain more energy. This means they move faster, and can eventually break all bonds, so the liquid becomes a gas.

What are the four state symbols?

solid (s), liquid (l), gas (g), and aqueous (aq)

What are coarse particles?

Paricles with a diameter between 2500nm and 10000nm. They are also known as dust

What are fine particles?

Particles with a diameter between 100nm and 2500nm

What are nano particles?

Particles that have a diameter between 1nm and 100nm. They only contain a few hundred atoms.

What happens to the surface area to volume ratio as particles decrease in size?

The ratio increases

How do you calculate the surface area to volume ratio?

surface area / volume

Give some uses for nanoparticles

Nanomedicine
Since some nano particles conduct electricity, they can be used in electric circuits for computer chips
Silver nano particles have antibacterial properties. They can be added to polymer fibres used to make wound dressings and surgical masks
Improve moisturisers without making them very oily

How do you calculate the percentage mass of an element in a compound?

((Relative atomic mass x number of atoms of that element) / formula mass of the compound) x 100

What is one mole of a substance?

The amount of that substance that contains an Avogadro number of particles (6.02 x 10^23)

What does one mole of carbon weigh?

12g