chemistry - chemical changes

topic 4

What is a metal ore?

A rock that contains enough of a metal compound to make it economically worthwhile to extract the metal.

What is oxidation?

Loss of electrons or gain of oxygen.

What is reduction?

Gain of electrons or loss of oxygen.

How are metals extracted from their oxides?

By reduction using carbon if they are less reactive than carbon.

What is the reactivity series?

A list of elements ordered by their reactivity.

List some metals in order of reactivity (most to least).

Potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, tin, lead, (hydrogen), copper, silver, gold, platinum.

Why are carbon and hydrogen included in the reactivity series?

To compare metal reactivity for extraction methods.

What is a displacement reaction?

A more reactive metal displaces a less reactive metal from its compound.

What happens when metals react with acids?

They form a salt and hydrogen gas.

What happens when metals react with water?

They form a metal hydroxide and hydrogen gas (for more reactive metals).

What is a salt?

A compound formed when the hydrogen in an acid is replaced by a metal or ammonium ion.

How can salts be made?

By reacting an acid with a metal, metal oxide, hydroxide, or carbonate.

What is the general word equation for acid + metal?

Acid + metal → salt + hydrogen

What is the general word equation for acid + metal oxide/hydroxide?

Acid + base → salt + water

What is the general word equation for acid + carbonate?

Acid + carbonate → salt + water + carbon dioxide

What does soluble mean?

A substance that dissolves in water.

How do you make soluble salts from acids?

React with an insoluble base, filter the excess, then crystallise the salt.

What is the pH scale?

A measure of acidity or alkalinity from 0 (acidic) to 14 (alkaline).

What is a neutral solution?

pH 7

What is a universal indicator?

A dye that changes colour to show pH.

What is an acid?

A substance that forms H+ ions in aqueous solution.

What is an alkali?

A soluble base that forms OH− ions in aqueous solution.

What is a base?

A substance that neutralises an acid (includes metal oxides and hydroxides).

What is a strong acid?

Completely ionised in water (e.g., hydrochloric, nitric, sulfuric acids).

What is a weak acid?

Partially ionised in water (e.g., ethanoic, citric, carbonic acids).

How does concentration differ from strength?

Strength refers to ionisation; concentration refers to amount of acid in a volume.

What is the equation for neutralisation?

H+ + OH− → H2O

What is titration used for?

To find the exact volumes of acid and alkali that react together.

What indicator is used in titration?

Phenolphthalein or methyl orange (not universal indicator).

Why is titration repeated?

To ensure results are accurate and concordant.

What equipment is used in titration?

Burette, pipette, conical flask.