What is a Chemical Change?
A chemical change is a process where the chemical composition of a substance is altered. This means the atoms within the substance are rearranged to form new molecules.
Key Indicators of a Chemical Change:
* Formation of a new substance: The resulting substance has different properties (color, odor, melting point, etc.) than the original substances.
* Release or absorption of energy: Chemical changes often involve the release of energy (exothermic, like burning) or the absorption of energy (endothermic, like cooking).
* Production of gas: Bubbles or fumes indicate the formation of a gas.
* Formation of a precipitate: A solid that forms from a solution.
* Color change: A change in color that is not simply due to light reflection.
Examples of Chemical Changes:
* Burning: Wood burning into ash and smoke
* Rusting: Iron reacting with oxygen to form iron oxide (rust)
* Cooking: Transforming raw ingredients into cooked food
* Baking soda and vinegar reacting: Producing carbon dioxide gas
* Photosynthesis: Plants using sunlight, water, and carbon dioxide to create sugar and oxygen
Important Note:
* Physical changes only alter the form or appearance of a substance, not its chemical composition. Examples include melting ice, cutting paper, or dissolving sugar in water.
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