Physical and Chemical

Properties

Physical vs Chemical

In Chemistry we focus on physical and chemical properties that help us organize Elements, chemicals, compounds, and everything in Chemistry

Physical Change – is when we are able to change the physical appearance of object. Many of these changes can be observed with your senses, through measurements or calculations.

Physical Properties

There are many different types of physical properties that help us to understand physical changes, but here are a few.

Physical Properties:

colour ductility malleability

density boiling point

melting point

conductivity

crystalline structure

magnetism brittleness

solubility viscosity hardness state lustre

Physical Properties

There are three states of physical properties:1) Solid – ex. rock, table, glass, tree and etc…

2) Liquid – ex. water, pop, tea, soup and etc…

3) Gas – ex. oxygen, propane, helium, hydrogen and etc…

The changes of states go from solid liquid gas and can go from gas liquid solids. They can only change in this order.

Thus, the ability to change from one state to another depends on an objects melting and boiling points.

Physical ChangeMelting point – the temperature needed for a substance to change from solid to a liquid. Ex. Pure water melts at 0º Celsius. Thus, it freezes just below 0º Celsius.

Boiling point – the temperature needed for a substance to turn from liquid to gas. Ex. Pure water boils at 100º Celsius and the gas will turn to liquid just below 100º Celsius.

Refer to page 159 to see multiple boiling and freezing points.

Physical ChangeMalleability – the ability to to change its shape. Ex. Playdough, we can flatten it by applying pressure to it, and if we roll it together it can thicken it up.

Ductility – It refereneces the softness of a metal. The ability to strip away, twist, and bend the metal. Ex. Gold is very ductile as it can be squeezed and bent and twisted.

Solubility – The degree to which a substance will dissolve in a given amount of another substance. Ex. Copper Chloride into water.

Physical Properties

Density – the heaviness of a substance is density. We do not have a device to measure density, we can only calculate it.

Density = massvolume

It is measured in g/cm3 or g/ml.

Note, 1 ml = 1 cm3

Density example:

A piece of aluminum has a mass of 20g and has a volume of 7.4 cm3. What is the density of aluminum?

Density = 20 g = 2.7 g/cm3

7.4 cm3

Note, no matter how much aluminum you have the density will stay the same. Thus density is a constant, it never changes.

Density example #2

Glycerol is a liquid and thus we cannot measure its cm3, we have to measure it in ml. If you have 1500 grams of glycerol and a volume of 1190 ml, what is its density?

Density = 1500 g = 1.26 g/ml 1190 ml

Chemical Properties

Chemical Changes – is when you are able to take a substance and completely change it into another substance. Chemical properties are used to group substances that have common chemical reactions.

Flammability, Corrosion and Reactions with Acid will be the three we will look at.

Chemical Properties

Flammability - is the rapid reaction of a substance with oxygen. (Flammability and combustible both are the same thing). Ex. Combustion reactions help heat a house, run the engine of a car, and cause fire and explosions.

Corrosion – is the slow reaction of certain metals with oxygen to form metal oxides. This process is called oxidation. Ex. Iron when it rusts is a reaction between iron and oxygen to produce rust.

Reaction with Acids – Some metals from the periodic table like zinc, magnesium are highly reactive with acid. Ex. Recall the Zinc and Hydrochloric Acid experiment creating hydrogen at a fast rate.

Changes in MatterAs stated earlier, substances can change from solid liquid gas and can go in reverse order from gas liquid solids.

When a substance goes from solid liquid gas heat has to be added at each stage.

When a substance goes from gas liquid solid heat has to be removed.

Chemical and Physical ChangesChemical changes are:

Usually irreversible

Produce new substances (a gas or liquid)

Create a new set of properties (a new colour)

Energy change may occur (releasing heat or absorbing heat)

Physical changes are:Usually reversible

No new substance is formed

Properties do not change

Energy change may occur, but it is really small and usually non-noticeable.

Example of Physical and

Chemical ChangesPhysical Change Chemical Change

When cream is whipped, air puffs up the cream. The substance is still cream.

Baking powder reacts with heat to produce carbon dioxide which makes bread rise.

Boiling water creates a gas, but the gas created is still water.

Gasoline burns to create heat, carbon dioxide and water. New gases are created as well.

Sugar dissolves in water. The sugar may “disappear”, but if you vaporize the water you will be left with sugar crystals. If you drink it the water and sugar you will still taste the sweetness.

Sunlight on the skin creates vitamin D and melanin in the skin.

Tattoo ink is injected into the skin to create a graphic.

Hydrogen peroxide is used to bleach hair to a much lighter colour. The hair colour changes into another substance that has less, or no, colour.

AssignmentPg 164 Questions – 3 – 5, 7 – 9 , 12

Pg 170 Question – 1 – 3, 5 – 9, 14