A physical change is a change in which a substance undergoes a change in its physical properties, but no new substance is formed.

A chemical change is a change that results in the formation of one or more new substances through a chemical reaction.

Rusting of iron, burning wood, baking a cake, and vinegar reacting with baking soda are examples of chemical changes.

Combustion is a chemical reaction between a substance and oxygen that produces heat and/or light, such as burning wood or magnesium.

Rusting forms iron oxide, a new brown-colored substance, from iron in the presence of oxygen and moisture.

Ignition temperature is the minimum temperature at which a substance catches fire.

Changes like melting ice or boiling water can often be reversed, while changes like chopping vegetables or baking a cake cannot.

Magnesium ribbon burning produces magnesium oxide, a new substance, along with heat and light.

Lime water turns milky in the presence of carbon dioxide, indicating a chemical reaction.

Weathering is the process of breaking down rocks into smaller pieces due to physical and chemical changes.

Erosion is the movement of sediments from one location to another by natural forces like wind or water.

Boiling water shows a physical change as water changes state from liquid to gas without forming a new substance.

Bioluminescence is the production of light by living organisms, often seen in fireflies.

Combustible substances are materials, like wood or paper, that can burn and undergo combustion when exposed to heat and oxygen.

Temperature changes can cause rocks to expand and contract, leading to cracks and breaking in the rocks.

A chemical equation represents a chemical reaction, showing the reactants and products in a concise form, like H2 + O2 → H2O.

The formation of a new substance is indicated by a change in properties, like color, temperature, or the release of gas.

Oxygen is essential for combustion as it reacts with the combustible substance to produce heat, light, and new substances.