- Formation of Salt:

Acids react with metals to form salts. The product of the reaction is a salt and hydrogen gas. For example, when hydrochloric acid (HCl) reacts with iron (Fe), iron(II) chloride (FeCl2) and hydrogen gas (H2) are formed.

$$Fe_{(s)}+ 2HCl_{(aq)} \rightarrow FeCl_{2(aq)} + H_{2(g)}$$

- Liberation of Hydrogen Gas:

During the reaction between acids and metals, hydrogen gas is liberated. This is because acids contain hydrogen ions (H+), which readily react with the metal to form hydrogen gas.

- Effervescence:

The reaction between acids and metals often produces effervescence, which is the bubbling or fizzing due to the rapid liberation of hydrogen gas. The escaping hydrogen gas creates bubbles that rise to the surface of the liquid.

- Heat Evolution:

The reaction between acids and metals is usually exothermic, meaning that it releases heat. This is because the formation of new bonds between the metal and the nonmetal ions releases energy.

- Colour Change:

In some cases, the reaction between acids and metals can result in a color change. For example, when copper (Cu) reacts with nitric acid (HNO3), the solution turns blue due to the formation of copper(II) nitrate.

Overall, the reaction between acids and metals involves the formation of salt, liberation of hydrogen gas, effervescence, heat evolution, and sometimes color change.