introduction to 4 -...

Introduction to 4.2

What’s so Special about Paper Clips?

Activity 4-4 p.150

4.2 Physical Properties

Physical Properties

Characteristic of a substance

Can be observed and measured without changing the identity of the substance

Physical Properties

2. Quantitative1. Qualitative

1. Qualitative Physical Properties

Can be observed and described without detailed measurement

Property Examples

Colour colourless, red, black

Odour sweet, pungent, mouldy

State solid, liquid, gas

Texture rough, smooth, bumpy

Lustre shiny, dull

Malleability soft, pliable, hard

2. Quantitative Physical Properties

Can be measured and assigned a particular value

Property Description

viscosity resistance to flow

melting point temperature of melting

boiling point temperature of boiling

solubility ability to dissolve in another substance

hardness ability to scratch another material

conductivity ability to conduct electricity or heat

density ratio of mass to volume

Physical Properties

states of matter

melting and boiling points

solubility

hardness

conductivity

density

States of Matter

A qualitative physical property

Gas

Solid

liquid

Melting and Boiling Points

A quantitative physical property

Melting point is the temperature at which a solid turns into a liquid

Boiling point is the temperature at which a liquid turns into a gas

Solubility

A quantitative physical property

Measures the ability of a substance to dissolve in another substance

The maximum quantity of a substance that can dissolve

in a given amount of solvent

at a particular temperature and pressure

Solubility

Example: sodium chloride (table salt)

39.5 g/100 mL in water at 25 °C and atmospheric pressure

Solubility

Aqueous solution is a solution with water as a solvent

Insoluble means does not dissolve or has a very low solubility

Examples: copper in water

Solubility Fat can be a solvent

Some chemicals dissolve in fats

eg. DDT (dichloro-diphenyl-trichloroethane)

a synthetic pesticide

bioaccumulates and biomagnifies in mammals

Hardness

A quantitative physical property

Ability to scratch another material

Between 1 to 10 on the Mohs scale

Fingernail --- 2

Diamond --- 10 (the hardest natural material)

Conductivity

A quantitative physical property

Ability to conduct electricity or heat

Copper: conducts electric current very well

Aluminum: conducts heat very well

Density

A quantitative physical property

The ratio of the mass of a substance to the volume it occupies

Oil flows on water

Iron nails sinks in water

A cruise ship floats on the sea water

All three phases exists on Earth

Universal solvent

Can absorb a lot of heat before it gets hot

Its solid form is less dense than its liquid form(ice acts as an insulator for water below)

Water’s Unique Physical Properties

Learning Check

What is the difference between qualitative physical properties and quantitative physical properties?

How could knowing the melting points of two pure substances that look alike help you tell the substances apart?

Why do people often check to see if a diamond is real by rubbing it against glass?

DEMO: Density Tube

Density

Unit for density is g/cm3

Density = mass

volume

D = m

V

Sample Problem

A sample of silver has a mass of 5.04 g and a volume of 0.480 cm3. What is the density of silver?

Practice Problems

Page 157 #1-5

Homework

P.159 #1-8