Chemistry GCSE (4ths)

What does a chromatogram show us?

Number of spots (components) show how many substances are present

What is the Rf value calculation

Distance moved by substance / Distance moved by solvent

Are metals a base or acid and what do they react with

They’re a base and react with acids

Does a metal or non-metal conduct electricity?

Metals

why do metals conduct electricity?

They have a delocalised electron

why do elements in the same group have similar chemical properties?

they are the same number of electrons in the outer shell?

what happens when a group of metal react with water?

Metal hydroxide + hydrogen gas

What happens if you go down group one during a reaction?

Reaction is more vigourous

What can you predict about Caesium a group one?

Reacts violently with water, soft low melting point more reactive than potassium

Litmus (Acid - Alkali)

Red - Blue

Phenolphthalein (Acid - Alkali)

Colourless - Pink

Methyl Orange (Acid - Alkali)

Red - Yellow

Which chloride arent soluble?

Silver and lead (II)

Which sulphate aren’t soluble?

Barium, calcium and lead (II)

Which carbonates are soluble?

Sodium, potassium, and ammonium

Which hydroxide are soluble?

Sodium, potassium, and calcium

How do you create a pure dry sample of a salt?

Crystallisation

How to test for presence of water

Add anhydros copper sulphate if positive powder turns blue

What’s the isomer of butane (C4H10) ?

2-Methylpropane

Why do simple molecular structure have low MP and BP?

They have weak intermolecular forces which require a small amount on energy to overcome

Why does MP and BP increase with an increase in relative atomic mass?

They have more electrons and string intermolecular forces so require more energy to overcome

Physical properties of DIAMOND

Very hard, high MP, doesnt conduct

Physical properties of GRAPHITE

Very soft, conductor, high MP, layered

List the reactivity series

K, Na, Ca, Li, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au

Oxidation is…

Gain of oxygen and loss of electrons

Reduction is…

Gain of electrons and loss of oxygen

What is Cl, Br, I at room temperature?

Gas, liquid, solid

What’s the composition of air

N (78%), O (21%), Ar (0.9%), CO2 (0.04%)