Key learning points

1. The pH of rain water is naturally below 7.
2. Chemical reactions between certain pollutants and water in the atmosphere may cause a decrease in the pH of rainwater.
3. Acid rain is not as acidic as vinegar or citric acid that is found in lemons and oranges.
4. Acid rain chemically reacts with carbonates that form many rocks to produce a salt, water and carbon dioxide.
5. Acid rain can have long term effects on habitats and ecosystems.

Keywords

• PH - pH is a measure of the hydrogen ion (H+) concentration in a solution.

• PH scale - The pH scale is a scale of acidity or alkalinity, often shown to be between values of 1 and 14. Below pH 7 are acids; numbers above 7 are alkalis, and pH 7 is neutral.

• Acid rain - Acid rain is rainwater which has been made more acidic by pollutant gases such as sulfur dioxide and nitrogen oxides.

• Chemical weathering - Chemical weathering is when rocks are broken down by a chemical change, for example reactions with acid rain.

Common misconception