A carbonate was added to an acid to make a salt.potassium chloride. Write the word equation for this.

Deep added an unknown compound (X) to some hydrochloric acid. Bubbles were formed.

Describe how he could find out if the gas was hydrogen or carbon dioxide.

A teacher measured the mass of a piece of iron wool (fine strands of iron) as $3.6$ g. She used tongs to hold the iron in a Bunsen flame. She noticed it turned darker and dull in colour. She let it cool and then measured the mass again. It was now $3.9$ g.

Describe what happened to the mass of the iron when it was heated.

A teacher measured the mass of a piece of iron wool (fine strands of iron) as $3.6$ g. She used tongs to hold the iron in a Bunsen flame. She noticed it turned darker and dull in colour. She let it cool and then measured the mass again. It was now $3.9$ g.

Use the particle model to explain why this happened.

Use the formula below to draw a particle diagram to show the reaction between calcium and sulphuric acid.

Sulphuric acid ${\mathrm{H}}_2{\mathrm{SO}}_4$

Calcium sulphate ${\mathrm{CaSO}}_4$

Jordi makes a pot of fresh coffee in his kitchen. People from other rooms can soon smell the coffee.

What process causes the smell to spread.