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Physical and Chemical Changes & Law of Conservation of Mass

Chemical formula

chemical symbols that indicate the number of atoms of each of the elements found in a compound

Chemical reaction

a process in which atoms of the same or different elements rearrange themselves to form a new substance - some clues that one is taking place or has taken place may include bubbles, smoke, a strong smell, color change, temperature change, or a sizzling sound

Closed system

a physical system that is not open and does not interact with other systems it cannot exchange matter or energy with its surroundings


a number used to multiply a variable

Law of conservation of mass

a law that states that during a chemical reaction matter cannot be created or destroyed it just changes form

Open system

a physical system that is open and does interact with other systems - it does exchange matter or energy with its surroundings


a substance that is formed as a result of a chemical reaction


the substances that are present before a chemical reaction occurs - they are altered during the chemical reaction and create new products


in a chemical formula, the number written next to the right and slightly below a letter or number - it indicates the number of atoms of the element that are in the molecule

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