Physical and chemical change

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Physical and chemical change

  1. 1. 113. Physical and chemical change Chemistry: Chemical change Grade 10 Everything Science www.everythingscience.co.za
  2. 2. 2Physical changeMatter does not stay the same. It may undergo physical or chemical changes. A physical change is a change that can be seen or felt, but that does not involve the breakup of the particles in the reaction. During a physical change, the form of matter may change,but not its identity. During a physical change, the arrangement of particles may change but the mass, number ofatoms and number of molecules will stay the same.Physical changes involve small changes in energy and are easily reversible. Everything Science www.everythingscience.co.za
  3. 3. 3Chemical changesA chemical change occurs when one or more substances change into other materials.A chemical reaction involves the formation of new substances with different properties. Forexample, hydrogen and oxygen react to form waterA chemical change may involve a decomposition or synthesis reaction. During a chemicalchange, the mass and number of atoms is conserved, but the number of molecules is notalways the same.Chemical reactions involve large changes in energy. Chemical reactions are not easilyreversible. Everything Science www.everythingscience.co.za
  4. 4. 4Chemical change continuedThe law of conservation of mass states that the total mass of all the substances taking partin a chemical reaction is conserved and the number of atoms of each element in the reactiondoes not change when a new product is formed.The law of constant composition states that in any particular compound, all samples of thatcompound will be made up of the same elements in the same proportion or ratio.Gay-Lussac’s Law states that in a chemical reaction between gases, the relative volumes ofthe gases in the reaction are present in a ratio of small whole numbers if all the gases are atthe same temperature and pressure. Everything Science www.everythingscience.co.za
  5. 5. 5For more practice or to ask an expert for help on thissection see:www.everythingscience.co.zaESADS Everything Science www.everythingscience.co.za

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