Physical and Chemical Properties

Lesson 2

Physical Properties

-A physical property describes a characteristic of a substance that can be observed or measured without changing the composition of matter.

Example: Melting Point, Boiling Point

When water freezes it expands due to a special bonding between water molecules. Larger volume with the same mass = Less

dense This is why ice floats

Observing Physical Properties

Property Description Examples What it looks like

Colour and lustre

The light the substance reflects gives it colour and lustre (shine)

The names for somesubstances, such as gold,are also the names of colours. Gold has lustre; concrete is dull

Observing Physical Properties

Property Description Examples What it looks like

Conductivity

Conductivity is the abilityof a substance to conduct electricity or heat. Asubstance that conductselectricity or heat is called a conductor. A substance with little or no conductivity is an insulator.

Most metals are good conductors. Copper is a very good conductor of electricity and so is used to make electric wires. Styrofoam® and glass are insulators.

Property Description Examples What it looks like

Density Density is the amount ofmass in a given volume ofa substance.D = m/v

The density of pure water is 1 g/mL. The density of gold is 19 g/mL. Water is denser than oil, but gold is denser than water.

Observing Physical Properties

Property Description Examples What it looks like

Ductility Any solid that can bestretched into a long wire is said to be ductile.

Copper is a commonexample of a ductile material.

Observing Physical Properties

Property Description Examples What it looks like

Hardness Hardness is a substance’sability to resist being scratched. Hardness isusually measured on the Mohs hardness scale from1 to 10.

The mineral talc is the softest substance on the Mohs hardness scale (1). Emerald is quite hard (7.5). Diamond is the hardest(10).

Observing Physical Properties

Property Description Examples What it looks like

Malleability A substance that can bepounded or rolled intosheets is said to be malleable.

Aluminum foil is an example of a malleable substance.Metals such as gold and tin are also malleable.

Observing Physical Properties

Property Description Examples What it looks like

Viscosity

Viscosity is the resistance of a fluid to flow.

Honey has a high viscosityCompared to water.

Observing Chemical Properties

A chemical property describes the ability of a substance to change into a new substance or substances.

In order to view a chemical property a chemical change must occur. Chemical change - the formation of a new

substance or substances with new properties. A chemical reaction is a process in which a

chemical change occurs.

Chemical Properties

1. Combustibility is the ability of a substance to burn. In order to burn a substance requires Oxygen

Chemical Properties

Light sensitivity is a chemical property that can cause new substances to form when light hits it.

Chemical Properties

3. Reacting with an acid is a chemical property where when acid is poured on a substance it produces a gas and bubbles.

Physical Change

In a physical change, the substance involved remains the same (chemically). The substance may change form or state, however. All changes of state are physical changes.

Examples: Dissolving a substance in a liquid, breaking something.

NOTE: Most physical changes can be reversed.

Chemical changes

In a chemical Change the substance is changed into one or more different substances.

The new substances have different properties from the original substance.

Most chemical changes are difficult to reverse and most cannot be. The new substances are not likely to combine and form the original substance.

Often during a chemical change you cannot see the change that has occurred in the substance, but you can observe the results of the change. There are clues that suggest that a chemical change has taken place.

Clues that a chemical change has occurred

Clue Evidence

Change in colour Final product(s) may have a different colour than the colours of the starting material(s).

Formation of a solid (precipitate)

Final materials may include a substance in a state that differs from the staring material(s): Precipitate

Clues that a chemical change has occurred

Clue Evidence

Formation of a gas Final materials may include a substance in a state that differs from the staring material(s); commonly, a gas

Release / absorption of heat or light

Energy (light, electricity, sound or most commonly heat) is given off or absorbed.

The change is difficult to reverse

The change cannot be reversed or it is difficult to.

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