The silver residue obtained on heating mercury (II) oxide is mercury. This is an example of a decomposition reaction.

Give an example of a chemical reaction for the following situation:

(b) A gas is evolved.

Only one substance is formed after a chemical reaction.

Two chemical species $\mathrm{X}$ and $\mathrm{Y}\mathrm{}$combine together to form a product $\mathrm{P}$ which contains both $\mathrm{X}$ and $\mathrm{Y}$, $\mathrm{X}\mathrm{}+\mathrm{}\mathrm{Y}\to \mathrm{P},\mathrm{}\mathrm{X}$ and $\mathrm{Y}$ cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species $\mathrm{X},\mathrm{}\mathrm{Y}$ and $\mathrm{P}$ are correct?

(i) P is a compound

(ii) X and Y are compounds

(iii) X and Y are elements

(iv) P has a fixed composition

A student took a solution of copper sulphate in a beaker and put an iron nail in it and left it for about an hour.

What changes do you observe?

Write the quadrants in which the following points lie:

$\left(-4,7\right)$

Identify the picture given alongside and answer the following question

Name the type of reaction.

Define the following:

Reactants

Give an example of a chemical reaction for the following situation:

(c) Sound is produced.

What is a chemical reaction? What are the conditions necessary for a chemical reaction?