Review
LIQUID SOLID GAS
Vaporization? Deposition? Freezing? Condensation? Sublimation? Adding Energy Removing Energy Melting? Vaporization? Deposition? Freezing? Condensation? Sublimation?
Chemical Change One or more substances changing into new substances with new compositions and properties
Examples: Baking a cake
Examples: rust Iron-oxide
Chemical Changes Starting substances - reactants New substance - product Reactants Product
Evidence of a chemical change Always a change in properties
Evidence of a chemical change Color – statue of liberty
Evidence of a chemical change Odor – sour milk
Evidence of a chemical change Produce heat / light - sparkler
Heat reactions Exothermic reaction – gives off heat Endothermic reaction – takes in heat
Evidence of a chemical change Produce gas – antacid tablets
Evidence of a chemical change Produce solid – precipitate Lead(II) Nitrate Sodium Iodide
Physical vs. Chemical Change when matter undergoes physical change, its shape or form changes, but its identity remains the same. When matter undergoes a chemical change, its identity and properties change.
Can reverse – Physical Change After ice melts into liquid water, you can refreeze it into solid ice if the temperature drops. Freezing and melting are physical changes.
Can’t reverse - Chemical Change As wood burns, it turns into a pile of ashes and gases that rise into air. After the wood is burned, it cannot be restored to its original form as a log.
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change? Rotten Egg
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Physical or Chemical Change?
Measuring Chemical Reactions By measuring mass before and after chemical reactions, it was observed that, although chemical changes occurred, the total mass involved in the reaction remained constant.
Law of Conservation of Mass Mass is neither created nor destroyed during a chemical reaction – it is conserved Mass of reactants = mass of product
Mercury Oxide 1774 Lavoisier
Mercury Oxide 10.00 g of mercury oxide is heated until it becomes liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of the oxygen?
DEMO Baking soda Vinegar Balance Balloon Container
Practice In the complete reaction of 22.99 g of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed? + =
Practice A 12.2 g sample of X reacts with a sample of Y to form 78.9 g of sample XY. What is the mass of Y that reacted?