GCSE Chemistry- All Y9

Methyl Orange colour in acids

Red

Methyl Orange colour in Neutral

Orange

Methyl Orange Colour in Alkalis

Yellow

Phenolphthalein colour in Acidic

colourless

Phenolphthalein colour in neutral

colourless

Phenolphthalein colour in Alkalis

Pink

Acid

A substance with pH lower than 7 and produces H+ ions when dissolved in water.

Base

A substance with pH greater than 7

Alkali

A soluble base that releases OH- ions in solution

Indicator

Any substance that changed colour when it is added to acidic or alkaline solutions

Neutral

A solution with a pH of 7

How can pH be measured?

Using an indicator, pH meter or pH probe

What is the ionic equation of neutralisation?

H + OH = H20

Acid + Alkali =

Salt + Water

Acid + Metal =

Salt + Hydrogen

Acid + Metal Oxide =

Salt + Water

Acid + Metal Carbonate =

Salt + Water + Carbon Dioxide

Formula for Hydrochloric Acid

HCl

Formula for Sulfuric Acid

H₂SO₄

Formula for Nitric Acid

HNO₃

Formula for Carbonic Acid

H2CO3

Formula for Phosphoric Acid

H3PO4

Salt derived from hydrochloric acid

Chloride

Salt derived from Sulfuric Acid

Sulfate

Salt derived from Nitric Acid

Nitrates

Salt derived from carbonic acid

carbonate

Salt derived from phosphoric acid

phosphate

Forming soluble salts from an insoluble base

1. gently warm dilute acid using a bunsen burner

2. add the insoluble base in excess to the acid until no more reacts

3. filter out the excess solid that hasn’t reacted

4. gently evaporate the solution using a water bath or bunsen burner to get pure crystals

Crystallisation

Heating a salt solution to evaporate, water, leaving behind pure salt crystals

What state symbol do acids always have?

Aqueous

Strong Acids

Completely ionised in solution, meaning that all the acid particles dissociate to release H+ ions into solution.

Weak Acids

Do not fully ionise in solution, meaning only a small proportion dissociate to release H+ ions

What does an acid’s STRENGTH tell you?

What proportion of the acid molecules ionise in water

What does an acid’s CONCENTRATION tell you?

How much acid there is in a certain volume of water

What would happen to the pH of an acid if it was mixed with water?

increase

What would happen to the pH of an acidic solution when more acid is added?

decrease

What does aqueous mean?

Dissolved in water

How many electrons do group 1 elements have in their outer shell?

1

What are group 1 metals also known as?

Alkali Metals

Relative Mass of Proton

1

Relative Mass of Neutron

1

Relative mass of election

very small

Relative charge of proton

+1

Relative charge of neutron

0

Relative charge of Electron

-1

How many electrons can the innermost shell of an atom hold?

2

How many electrons can the second and third shells of the electron hold?

8 per shell (16 in total)

On which side of the periodic table are metals found?

Left

On which side of the periodic table are non-metals found?

right

How were elements arranged in the periodic table in the 1800s?

By mass number.

Why did elements used to be ordered by mass number?

• scientist had no idea of atomic structure

• the term ‘atomic number’ didn’t even exist

What changes did Dmitri Mendeleev make to the periodic table?

• He sorted elements into groups based on their properties

• He realised that if he put elements in order of atomic mass, elements with similar chemical properties fell into columns

• A few elements, however, ended up in the wrong columns

What did Mendeleev do when elements didn’t fit the pattern?

• switched the order of the elements so they did

• left gaps for undiscovered elements

How were elements arranged once protons and electrons were discovered?

In order of atomic number

State one difference between Mendeleev’s periodic table and the modern periodic table.

Noble gases were not present in Mendeleev’s periodic table, and several other gaps were left for undiscovered elements.

Johann Dobereiner put the elements lithium, sodium and potassium in a Triad because they have similar chemical properties. Use ideas about electron arrangement to explain this.

Lithium, sodium and potassium all have the same number of electrons in their outer shell.

Many chemists suggested different patterns for the elements while using the same data. Suggest why these chemists could not agree.

• the same data can be interpreted in different ways

• they were reluctant to say their ideas were wrong

Mendeleev placed copper in group 1 of his periodic table. It is now a transition metal. Explain why copper should not be in group 1.

• copper doesn’t have similar properties to other group 1 metals

• copper is unreactive unlike group 1 metals.

What does atomic number tell us about an element?

The number of protons/electrons in an atom

What does the mass number tell us about an element?

The number of protons and neutrons in an atom.

Why are group 1 metals considered to be highly reactive?

• there is only one electron in the outer shell

• readily loses this electron to obtain a full outer shell

Suggest reasons why Newland’s periodic table was not accepted by most chemists in 1866

• some boxes contain two elements

• groups contain elements with different properties

• Newlands was not a well-known scientist

What type of ions do group 1 metals form?

1+

Properties of group 1 metals

• low density (floats on water)

• soft (can be cut with a knife)

• low MP and BP (< 200)

• reactivity increases as you descend the group

Why does reactivity increase as you descend group 1?

• Atoms get larger and have more shells

• therefore less energy is required to remove the outer electron

What type of substance is a metal hydroxide?

Alkaline

What happens to reactions with water as you descend group 1?

They become more violent and vigorous

Why are group 1 metals referred to as alkali metals?

They form metal hydroxides when they react with water

What group are halogens?

group 7

What type of molecule are all halogens?

diatomic molecules

What colour and state is fluorine?

A (highly reactive) yellow gas

What colour and state is chlorine?

(poisonous) green gas

What colour and state is bromine?

(poisonous) red-brown liquid (which gives off an orange vapour)

What colour and state is iodine?

A grey solid (which gives off a purple vapour)

What increases as you descend group 7?

Melting and Boiling points

What ions do group 7 elements form?

1-

What can more reactive halogens do to less reactive ones?

More reactive halogens can displace less reactive halogens from their compounds

What group are noble gases?

Group 0

Which is the only group 0 element that does not have 8 electrons in its outer shell?

Helium

Reactivity of noble gases

They are highly unreactive as they have a full outer shell.

Properties of noble gases

• colourless gases at room temperature

• monoatomic (gases are made up of single atoms)

• inert

• last gases to be discovered

Use of Argon and why

• Used in filament lamps

  • because it is non-flammable and stops the filament from burning away

Use of helium and why

• airships and party balloons

  • low density, non-flammable, unreactive

How can argon and helium protect metals that are being welded?

Their inertness stops the hot metal reacting with oxygen

What increases as you descend group 0?

Boiling point, melting point and density

Why does BP, MP and density increase as you descend group 0?

The number of electrons increases, which leads to greater intermolecular forces that need to be overcome.

Properties of non-metals

• brittle, dull, soft

• low melting point, good insulator

Properties of metals

• hard, shiny, malleable

• high melting point, good conductor

Why is gold used in jewellery?

It is shiny and malleable

Why is gold used in electrical components?

It is a good electrical conductor and corrosion resistant

Why is copper used for water pipes?

Because it is malleable and corrosion resistant.

Why is copper used for electrical wiring?

Because it is a good conductor

Similarities between transition metals and group 1 metals

• conductors in solid and liquid states

• shiny when freshly cut

Differences between transition metals and group 1 metals

• transition metals have higher melting points

• transition metals have higher densities

• transition metals have greater strength

• transition metals have greater hardness

What temperature does mercury melt at, and therefore what state is it at room temperature?

- 39C, therefore it is a liquid at room temperature

How are metals above carbon extracted from their ore?

via electrolysis

How are metals below carbon extracted from their ore?

via carbon reduction in a blast furnace

Why is carbon included in the reactivity series?

To show how a metal is extracted from its ore

Why is Hydrogen included in the reactivity series?

To show the reactivity of metals with dilute acid

Equation for oxidation

Metal + Oxygen → Metal Oxide