C5: Chemical Changes
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What are the two products formed when a metal reacts with water
Hydroxide and hydrogen metal + water = metal hydroxide + hydrogen
What can we say
The more reactive the metal, the more rapid the reaction
What happens when a metal reacts with a dilute acid. Give the equation and the two products formed
Salt and hydrogen acid + metal = salt + hydrogen
What is a displacement reaction
In those reactions, the more reactive metal always takes over the place of a less reactive metal Eg: copper chloride + magnesium = magnesium chloride + copper
What are the two types of reaction
Oxidation and reduction
What is oxidation
Oxidation is a loss of electrons and a gain of oxygen
What is reduction
Reduction is a gain of electrons and a loss of oxygen
What is a redox reaction
Displacement reactions when oxygen is removed from metal oxides Eg: copper oxide + carbon = copper + carbon oxide
What is an ionic equation
When we do a regular balanced equation but involve all the charges of the ions involved in the reaction
What is an acid
Acids form acidic solutions in water and produces hydrogen ions in aqueous solutions Acidic solutions have pH values less than 7
What is an alkali
Alkalis form alkaline solutions in water and produces hydroxide ions in aqueous solutions Alkaline solutions have pH values more than 7
What is a neutral solution
They have the exact pH value of 7, and are not alkaline or acidic
What is the pH scale
It measures the acidity and alkalinity of a solution.
How else can we measure the pH of a solution
Universal indicators
What is a base
A base is any substance reacting with an acid to form a salt and water. This shows metal oxides and metal hydroxides are bases base + acid = salt + water
How do we know if a base is alkaline or acidic
If a base is soluble in water, it is alkaline. If a base is insoluble in water, it is acidic.
What is an acid-alkali neutralisation
The reaction between hydrogen and hydroxide ions, forming water
When do acids take part in reactions
When salts are produced. Hydrogen ions in acids are then replaced by metal ions
What are acids neutralised by
By bases, alkalis and metal carbonates
What is the equation for acids and metal oxides. Give the two products and the equation
Salt and water. Acid + metal oxide = salt + water
What is the equation for acids and carbonates. Give the three products and the equation
Carbon dioxide, water and salt Acid + carbonate = salt + water + carbon dioxide
How do we name salts
When naming a salt, it has two parts. The first part comes from the base, alkali or metal carbonate. The second part comes from the acid