chemical changes

physical changes

• change in which no new substance is formed

• products have the same chemical properties as before

• changes made are easily reversible

chemical changes

• change in which 2 or more new substances are formed

• reactants do not retain the same chemical properties as products

  • word equations are used to represent chemical changes

    • [reactants}→[products]

• irreversible; requires extreme amounts of heat to reverse chemical changes

rearrangement of atoms

• to from products, the atoms of the reactants are usually rearranged

  • atoms cannot be created or destroyed, only rearranged, therefore, during chemical changes, the atomic mass of the products and reactants remain the same

    • results in the law of conservation of atomic mass

combustion

• chemical reaction in which a substance is heated in the presence of oxygen

  • carbon+oxygen→carbon dioxide

thermal decomposition

• chemical reaction in which an element in heated and breaks down into two or more simpler substances

  • calcium carbonate→calcium oxide+carbon dioxide

oxidisation

• a chemical reaction in which an element gains oxygen

  • glucose+oxygen→carbon dioxide+water

neutralisation

• a chemical reaction between an acid and an alkali

  • nitric acid + calcium hydroxide → calcium nitrate

acid + carbonate

• acid + carbonate → salt, water and carbon dioxide

  • acetic acid → sodium carbonate → water, carbon dioxide and sodium acetate

acid + metal

• acid + metal → hydrogen + salt

  • hydrochloric acid + zinc → hyrdogen + zinc chloride

physical properties of acids

• sour taste

• has a pH level of lower than 7

• turns blue litmus paper red

physical properties of alkalis

• bitter taste

• soapy, slippery feel

• has a pH level of more than 7

• turns red litmus paper blue