Try solubility experiments and see how well salt, sand, chalk and soil dissolve. Measure the solubility and also show the effects of warmth.
Use small scale test tubes for younger pupils. Show how erosion works by agitating lumps of chalk or soil in water. Discuss the effects on the surface area, showing how easily the lumps break up and would wash away. A good demonstration in a large jar, especially with a magnetic stirrer-hotplate, would reveal the ease with which nature can break up land. This helps them understand the larger scale damage done to coastal areas.