1. Changes in Matter

2. Matter’s Changes and Properties Physical Change – properties remain the same – changes the form of a substance without changing its identity – All changes in state! (freeze, melt, condense, evaporate, and sublimate) – Examples: Boil, dissolve, break, split, crack, grind, cut, crush, and bend.

3. Matter’s Changes and Properties Chemical Change – changes the identity of a substance – a new substance is produced – Examples: rust, rot, burn, decompose, corrode, oxidize, ferment, and explode! – Evidence of a chemical change: change in color or odor, formation of a gas, formation of a precipitate (solid), change in light or heat

4. Matter’s Changes and Properties A physical change during digestion is the mechanical breaking up of food by teeth. A chemical change during digestion is the chemical breaking down of food in the mouth, stomach and small intestine with the aide of enzymes.

5. Matter and Change Property SolidLiquidGas Shape Volume Definite Indefinite Definite Indefinite Attractive ForcesStrongWeakNone ExpansionVery slightModerateGreat CompressibilityAlmost none Readily Atom MovementVibrationFlowingFree

6. Physical and Chemical Changes In a chemical reaction one or more substances change into new substances. The starting substances are called reactants and the substances formed are called products. iron + sulfur  iron sulfide or Reactants  Products

7. Law of Conservation of Mass The Law of Conservation of Mass states that the mass of all substances present before a chemical change is equal to the mass of all substances after the change. 10 g Before ReactionAfter Reaction

8. Sometimes the mass of the reactants and the mass of the products appears to be unequal. This is usually because some of the mass is lost as a gas. Wood + Fuel ash + released gas 99g + 1 g = 99.5g + 0.5g Total Mass = 100g Law of Conservation of Mass Although it appears mass is lost, 0.5g of mass is released into the air. The sum on both sides of the reaction is equal.