Pure substances, properties

✗ Matter Contain only one type of particle mixtures Pure substances heterogeneous homogeneous compounds elements Suspension Solution Colloid ✗ ?

Contain only one type of particle Pure substances compounds elements At least two types of atoms, that have chemically combined  Can be separated into constituent elements Only one type of atom (there may be more than one of the same kind!)  Impossible to separate into other substances with chemical separation techniques. Practice page 14 # Hydrogen Oxygen Oxygen

Work book page 14 # 1 together

Periodic table of elements name Mendeleev listed elements according to their atomic weight. He realized that when he kept isting them with atomic wheight that after a certain number of elements there was a repetition in the properties of the element -> he started a new row. Practice finding atomic number Explain, in their book colours indicate state of matter Atomic number Atomic symbol Atomic weight

Notes pure substances Practice page 14 No2 and 3

Identifying pure substances: Using properties that are specific to a substance or a small group of substances. Characteristic Properties Non Characteristic Properties: All substances have these properties Mass - temperature shape - state of matter

Characteristic properties 1. Physical properties 2. Chemical properties No change of the identity / nature of the substance during test process During course of identification process substance reacts with another substance and will change Who can help think of a physical property that might help me identify that this liquid here is water, without destroying the water.

Physical properties: Melting point The temperature at which a solid becomes a liquid (or a liquid becomes a solid) Melting point water: 0 °C Melting point ethanol: - 117 °C

Physical properties: Boiling point The temperature at which a liquid becomes a gas (or a gas becomes a liquid) Boiling point water: 100 °C Boiling point ethanol: 78 °C

Physical properties: solubility Maximum amount of solute, that can be dissolved in a given volume of solvent Expressed in units of concentration  g/L, %m/v, %m/m or %v/v

Physical properties: density Do they have the same weight? air water steel No! Density = Mass per unit volume (in g/mL):  I always indicate how much 1 ml of the substance weighs.

Notes on characteristic physical properties

Practice 1. A rock with the volume of 22 ml weighs 37.4 g; what is its density? 2. The mass of a plastic spoon 7.5 g and its volume is 3 ml; what is its density? 1.7 g/ml 2.5 g/ml 135.2 g 3. The density of silver is 10.4 g/ml. If a sample of pure silver has a volume of 13 ml, what is its mass?

Characteristic Chemical Properties Help us identify a substance but may change the nature of the substance during the process.  Ex: Reaction to litmus paper, Reaction to cobalt Chloride Paper, Reaction to limewater, Reaction to a glowing splint, reaction to a burning splint, reaction to an open flame.

Reaction to litmus paper Can identify if a substance is acidic or basic. Acid Base

Reaction to cobalt chloride paper Turns pink in the presence of water. no water with water Water goes into the crystal and changes the color of the crystal from blue to pink

Reaction to limewater Turns Cloudy in the presence of CO2 CaOH2 – solution – CaCO3 precipitates

Reaction to glowing splint Splint reignites in the presence of oxygen Reignite fire in fireplace through blowing, hair dryer, bellows A pair of bellows uses the same principal to reignite a fire

Reaction to burning splint An explosion will occur in the presence of hydrogen. Magnesium and acid in test tube plus match Hindenburg in 1937 http://www.youtube.com/watch?v=1PLH4H7Mjl8

Reaction to an open flame The color of the flame may indicate the presence of certain substances. K Na Ba

Notes characteristic properties