When harmful substances get into rain, the polluted water falls on soil and damages living things. Acid rain is a form of environmental pollution where the rain itself becomes acidic enough to stop plants from growing. This project shows that sunflower seeds watered at pH 3 and pH 2 never sprout at all, revealing how polluted rain causes real damage.

The pH scale measures how sour or bitter a liquid is, with lower numbers meaning more sour. In this experiment, sunflower seeds watered at pH 6 and pH 5 grow normally, but at pH 4 growth slows down sharply. At pH 3 and pH 2, the seeds never sprout at all, showing how even small pH changes can have large effects on living things.

How acidic does rain need to get before sunflower seeds stop growing? You water five pots of sunflower seeds with water adjusted to pH levels ranging from pH 6 — close to normal rain — down to pH 2, using sulfuric acid to hit each target. Every two days for two weeks, you measure the average height of three plants per pot. At pH 6 and pH 5, plants grow normally. At pH 4, growth slows down sharply. At pH 3 and pH 2, the seeds never sprout at all.

Plants make new cells using water, light, and nutrients from the soil — but what happens when the water itself becomes acidic? You water five pots of sunflower seeds with water at pH levels ranging from 6 (normal rain) down to 2 (very acidic), then measure average plant height every two days for two weeks. At pH 6 and pH 5, the seeds grow normally. At pH 4, growth slows down sharply. At pH 3 and pH 2, the seeds never sprout at all. The acid disrupts how plants take in water and nutrients, which stops new cells from forming.