Chapter 2

How do you identify matter?

•We identify matter by its properties–How it taste, looks,and feels–Its size, shape, and color

Properties of Matter Video Clip

http://www.bozemanscience.com/matter

• Physical properties are those that we can determine without changing the identity of the substance we are studying.

Stretching a rubber band does not change how it looks before and after it is stretched!

• The physical properties of sodium metal can be observed or measured. It is a soft, lustrous, silver-colored metal with a relatively low melting point and low density.

• Hardness, color, melting point and density are all physical properties.

A physical change occurs when the substance changes state but does not change its chemical composition. For example: water freezing into ice, cutting a piece of wood into smaller pieces, etc. The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.)

• Melting point• Boiling point• Vapor pressure• Color• State of matter

• Density • Electrical conductivity• Solubility• Absorption to a

surface• Hardness

DENSITY

or a kilogram of iron?

Q) Which weighs more:

A kilogram of

feathers

What is Density?

Density is the Mass per unit Volume

Wood Water Iron

1 cm3 1 cm3 1 cm3

If you take the same volume of different substances, then they will weigh different

amounts.

0.50 g 1.00 g 8.00 g

Q) Which has the greatest mass and therefore the most dense?

IRON

Density = MassVolume

g or kg

cm3 or ml

g/cm3 or kg/ml

= m

V

Example:

Q) Liquid water has a density of 1000kgm-3, while ice has density of 920kgm-3.

Calculate the volume occupied by 0.25kg of each.

Density Equation:

m

V

V = m = 0.25 = 0.000250m3

1000V = m = 0.25 = 0.000272m3

920

DENSITY OF A REGULAR SOLID

• Find the Mass of the solid on a balance.

• Measure the three lengths and calculate the Volume.

(ie V = l x w x h )• Calculate the

Density.4.0 cm

2.0 cm

3.0 cm

= m = 240 =10.0 g/cm3

V 24

m = 240 g

Material Mass

in g

Length

in cm

Width

in cm

Height

in cm

Volume

in cm3

Density

in g/cm3

DENSITY g/cm3

Aluminium 2.70

Brass 8.50

Iron 7.86

Wood 0.50

Slate 2.80

Glass 2.50

Lead 11.3

Marble 2.70

Wax 0.89

DENSITY OF AN IRREGULAR SOLID

Find the Mass of the Find the Mass of the solid on a balance.solid on a balance.Fill the Measuring Fill the Measuring Cylinder with Water to a Cylinder with Water to a known Volume.known Volume. Add the Object.Add the Object. Work out the Volume Work out the Volume of Water that is of Water that is displaced.displaced. Calculate the Density.Calculate the Density.

50 cm3

80 cm3

m = 360 g = m = 360 =12.0 g/cm3

V 30

DENSITY OF AN IRREGULAR SOLID

• OR use a Eureka Can to find the Volume.

Find the mass of the solid Find the mass of the solid on a balance.on a balance.Add water until just Add water until just overflowing.overflowing. Place a Measuring Cylinder Place a Measuring Cylinder under the spout.under the spout. Add the Object.Add the Object. Collect the Water and read Collect the Water and read off the Volume.off the Volume.Calculate DensityCalculate Density

m = 440 g

40.0 cm3

= m = 440 =11.0 g/cm3 V 40

DENSITY g/cm3

Aluminium 2.70

Iron 7.86

Brass 8.50

Wood 0.50

Slate 2.90

Glass 2.50

DENSITY OF A LIQUID

• Find the Mass of an empty Measuring Cylinder.

• Add a certain Volume of Liquid.

• Find the Mass of the Measuring Cylinder and Liquid

• Calculate the Mass of Liquid.• How?• Calculate Density of Liquid.

Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of empty Measuring Cylinder

25.0 g

20.0 cm3

45.0 g

45 – 25 = 20 g

= m = 20 =1.00 g/cm3 V 20

Liquid Mass of empty

Measuring Cylinder

in g

Mass of Measuring Cylinder

and Liquid

in g

Mass of Liquid

in g

Volume

in cm3

Density

in g/cm3

DENSITY OF A GAS

• Remove the air from a flask of a known Volume, using a vacuum pump.

• Find its Mass.• Add the gas to be

tested.• Reweigh.• The difference is the

Mass of gas.• Calculate Density.

To vacuum flask

1000 cm3

150.0 g170.0 g

= m = 20 =0.0200 g/cm3 V 1000

170 -150 = 20.0g

• Chemical properties describe the way a substance can change or react to form other substances. These properties, then, must be determined using a process that changes the identity of the substance of interest.

• One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens.

• In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

A chemical change occurs when a substance changes into something new. This occurs due to heating, chemical reaction, etc. You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (bubbles forming, mass changed, etc).

• Reaction with acids• Reaction with bases

(alkalis)• Reaction with oxygen

(combustion)• Ability to act as

oxidizing agent

• Ability to act as reducing agent

• Reaction with other elements

• Decomposition into simpler substances

• Corrosion

Signs of a Chemical Change

• Production of an odor

• Change in temperature

• Change in color

• Formation of bubbles

• Formation of a solid

Chemical and Physical Properties Video Clip

http://video.about.com/chemistry/Physical-and-Chemical-Properties-of-Matter.htm

Chapter 2: Section 2Physical Changes

of State

Phase Changes Video Clip

http://www.youtube.com/watch?v=ZnC_IztcTL8

solid liquid gasmelting

freezing

boiling

condensing

Changes of State

Changes in State (phase changes)

1. Melting - solid to liquid

a. Particles get more kinetic energy and begin rotating around each other.

b. There isn’t enough energy to break the inter-particular attractions, so the particles remain close (liquid).

c. The energy required to melt a solid is called the heat of fusion.

2. Freezing - liquid to solid

a. Particles lose kinetic energy

and slow down.

b. Attractive forces between particles become stronger than the particles’ motion, so the particles begin merely vibrating in place.

c. The amount of heat the particles must lose to turn into a solid is called the heat of fusion.

3. Vaporization - liquid to gas

a. Types:

1) Boiling - rapid; gas bubbles are produced throughout.

2) Evaporation - slow; occurs at the surface.

b. Liquid particles gain enough kinetic energy to overcome forces between the particles and they begin translational motion; this energy is called the heat of vaporization.

4. Evaporation is a cooling process.

a. Particles in a liquid gain kinetic energy.

b. They leave as gas particles (taking the energy away with them).

c. This leaves less energy in the liquid, therefore cooling down what is left.

melting

freezing

solid liquid

boiling

condensing

liquid gas

tem

per

atu

re

time

solid

liquid

gas

Changes of state – heating curve

5. Sublimation - solid to gas or gas to solid a. Dry ice - carbon dioxide b. Iodine c. Frost6. During phase changes there is no change of

temperature.

7. Condensation - gas to liquid

a. Particles lose kinetic energy, slow down, and come closer together.

b. Inter-particular forces become strong enough to make particles merely rotate around each other.

c. The energy they lose to turn into a liquid is the heat of vaporization.

Changes of state – cooling curve activity

Changes of state activity

Chapter 2: Section 3

Properties Used to Identify Substances

1. Density- mass per unit of volume

2. Heating Properties- measure the rate at which substances conduct heatExample: iron and aluminum are used in pots and pans

3.Solubility- how much a substance dissolves in a given volume of liquid4. Electric Properties- how electrical charges are allowed to pass through

5. Magnetic Properties-how substances are attracted to

magnets

Techniques for Separating Solutions:

#1. Evaporation: changing

from a liquid to vapor state– leaves behind

the other component.

Example: Water mixed with sugar can be heated until the water evaporates and leaves the sugar behind.

#2. Distillation:–Process used to drive vapor from liquid by heating

–Great for separating two or more liquids which have different boiling points.

Example: Water treatment plants must add chemicals to purify our drinking water.

#3 Separating Solids Mixed with Liquids

Use a paper filter to drain the liquid and the solid remains in the filter

#4 Separating SolidsRecycling centers use magnets to separate cans made of aluminum

from those made of steel; magnets stick to steel!