4/17/09

Post date: Apr 17, 2009 12:32:36 AM

Bell Ringer: Give two examples of physical properties.

    • Changes of matter - Group presentations

      • Physical changes

        • Affects one or more physical properties of a substance without changing the identity of the substance

          • Melting - change of state, but same substance

          • Cutting - change of size, but same substance

          • Crushing - change of shape, but same substance

        • Dissolving is a physical change

          • Sugar dissolves in water, but you can still taste it

          • Water molecules spread out the molecules of the other substance, but don't alter them

      • Chemical changes

        • One or more substances are changed into entirely new substances with different properties

        • Can be detected by a change in taste, smell, color, etc.

        • Cannot be reversed by physical changes

      • Breaking down mixtures and compounds

        • Mixtures can be physically separated

        • Some compounds can be broken down through chemical changes

    • Signs of a chemical change

      • Different color

      • Gas is produced

      • A precipitant is formed

      • Each sign indicates a new substance is present

    • Observations - physical or chemical change?

      • Ice melting - physical (all changes of state, such as solid to liquid, are physical changes)

      • Baking soda and vinegar - chemical (bubbles form, meaning the new substance is a gas)

      • Milk and lemon juice - chemical (forms a precipitant, meaning it gets chunky)

      • Food coloring and water - physical (dissolving is a physical change, water just spreads the other molecules out)

  • Page 64: 1-8 due Tuesday

  • Chapter 2 Test Wednesday