1. Burning Wood: When wood burns, it reacts with oxygen in the air. This reaction produces ash, smoke, and carbon dioxide. The wood has been transformed into new substances, making it a chemical change.

2. Rusting of Iron: Iron reacts with oxygen and water in the air to form iron oxide, commonly known as rust. The reddish-brown rust is a new substance, different from the original iron.

3. Baking a Cake: Mixing flour, sugar, eggs, and other ingredients causes a chemical change. The heat from the oven causes the ingredients to react, forming a new substance—the cake—with a different texture and flavor.

4. Digesting Food: The enzymes in our bodies break down complex food molecules into simpler substances that our bodies can absorb. This process is a chemical change that changes the composition of the food.