1. Burning wood: When you burn wood, the wood reacts with oxygen in the air. This reaction produces ash, carbon dioxide, and water. The wood is permanently transformed into different substances, and this change cannot be reversed easily.

2. Rusting of iron: Iron reacts with oxygen in the presence of water to form iron oxide, commonly known as rust. The iron changes its chemical composition and appearance, and this change is irreversible.

3. Baking a cake: When you bake a cake, the ingredients undergo a chemical change. The flour, sugar, eggs, and other ingredients react with each other in the presence of heat. This results in a new substance, the cake, with different properties than the original ingredients. This change is irreversible.