What are some examples of chemical changes?
burning wood, baking bread, iron rusting
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Chemical changes involve the formation of new substances with different chemical properties. Here are some common examples of chemical changes:
1. Burning a candle: The wax of the candle reacts with oxygen in the air to produce carbon dioxide, water vapor, and heat.
2. Rusting of iron: When iron is exposed to moisture and oxygen, it undergoes a chemical reaction to form iron oxide, commonly known as rust. This process is irreversible.
3. Digestion of food: In our bodies, the enzymes in our digestive system break down complex food molecules into simpler ones that can be absorbed by our cells. This process involves the chemical breakdown of substances.
4. Cooking an egg: When an egg is heated, the proteins in the egg coagulate, causing the liquid egg white and yolk to solidify. This irreversible change is a chemical reaction.
5. Tarnishing of silver: Silverware or jewelry can tarnish when exposed to air, sulfur, or certain chemicals. This results in the formation of silver sulfide, which gives it a dull appearance.
To identify chemical changes, one should look for signs such as color change, the production of gas, formation of a precipitate (solid), temperature change, odor change, or irreversibility. Observing these indicators helps recognize when a chemical change has occurred.