Pure substances, properties

MIXTURES

heterogeneous homogeneous

Suspension

?✗

ColloidSolution

PURE SUBSTANCES

compounds elements

MATTER

Contain only one type of particle

PURE SUBSTANCES

compounds elements

Contain only one type of particle

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.

At least two types of atoms, that have chemically combined

Can be separated into constituent elements

Hydrogen

Oxygen Oxygen

• Work book page 14 # 1

Periodic table of elements

Atomic number

Atomic symbol

name

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.

All substances have these properties- Mass - temperature- shape - state of matter

Characteristic properties

1. Physical properties• No change of the

identity / nature of the substance during test process

2. Chemical properties• During course of

identification process substance reacts with another substance and will change

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

• Do they have the same weight?

air water steel

No!

Physical properties: density

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?

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?

2. The mass of a plastic spoon 7.5 g and its volume is 3 ml; what is its density?

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

Reaction to limewater

• Turns Cloudy in the presence of CO2

Reaction to glowing splint

• Splint reignites in the presence of oxygen

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.

http://www.youtube.com/watch?v=1PLH4H7Mjl8

Hindenburg in 1937

Reaction to an open flame

The color of the flame may indicate the presence of certain substances.

K Na Ba

• Notes characteristic properties