chapter 2: solids, liquids and gases

CHAPTER 2: SOLIDS, LIQUIDS AND GASES

water

rock

air sand

lava

woodoil

What is our world made of ?

liquid

solid

gas

solid liquid gas

1.States of Matter

Properties of Solids

• Definite shape• Definite volume• Hard to compress• Do not flow

Types of solids• Solids that are made up of crystals are

called crystalline solids. • I.e.: salt, sugar, snow…• Amorphous solids:The particles are

not arranged in a regular pattern. • They don’t melt at a distinct

temperature, they may become softer or change into other substances.

• I.e.: plastics, rubber and glass

• The pictures below show the arrangement of solid particles

• Please identify the types of solid.

Properties of Liquids

• No definite shape• Definite volume• Flow easily• Hard to compress

Properties of liquids• Surface tension is the result of an inward pull

among the molecules of a liquid that brings the molecules on the surface closer together.

• Fluid : a substance that flows• Another property of liquids is viscosity .• Viscosity depends on the size and shape of

its particles and the attraction between the particles.

Properties of Gases

• No definite shape• No definite volume• Easy to compress• Spread out to fill all available

space - diffusion

Change of State

Energy

2. Change of State Changes Between Solid and Liquid• The temperature at which the solid melts – melting

point

Vibrating a little

Particles vibrate more

Solid melted to form liquid

o The melting point is the temperature at which the solid and liquid states of a substance exist together

Changes Between Liquid and Gas

Particles in liquid state

Particles move faster

Particles have enough energy to escape

The boiling point is the temperature at which evaporation begins to occur throughout the liquid, i.e. Bubbles of vapour form inside the liquid

Temperature Scale For Water

Change of State - Evaporation

What happens if there are puddles on the road on a sunny day?

Sun gives some particles near surface extra energy

Particles have enough energy to overcome forces holding them together

Break away from liquid & go into the air

Some liquid has evaporated to form a gas

o Evaporation is the changing of a liquid to a vapour that take place only on the surface of a liquid.

Vaporization: The change from a liquid to a gas

Vaporization Evaporation

Boiling

Question

What are the ideal conditions when hanging out clothes to dry?

Dry, warm and windy

Evaporation is helped by the wind

The wind blows away the particles that have already evaporated

This makes room for more particles to evaporate

Evaporation V Boiling Point Liquid doesn’t have to be heated

to its boiling point for evaporation to occur – evaporation from surface of liquid is always taking place

Condensation• When gas cooled.• Particles slow down, become closer to

each other.• Liquid formed eventually.

Changes from the Gas to the Liquid:

Condensation

Questions On a cold morning if

you breath on the window of the car what happens?

What happens to the mirror in the bath room when you have a hot shower?

Why do they happen?

Why does butter spread more easily if it is warmed slightly?

Why do ice cubes added to a glass of lemonade slowly disappear?

Condensation Steam (gas)

cooled when it hits the cold mirror

Particles slow down, become closer to each other

Liquid formed eventually

Math Analyzing Data P53 1.Time on the x-axis, temperature on

the y-axis. 2.The temperature is rising from 0 ℃ to

100 ℃ 3. Segment B: melting point of ice; Segment D: boiling point of water 4. Melting and Boiling 5.Water molecules in segment E have

more thermal energy because they are at a higher temperature.

Sublimation• Some substances when heated change

directly from solid to gas (sublimation)

• Iodine and solid carbon dioxide (dry ice)

Changes Between Solid and Gas:

Solid Liquid Gas

Particle Arrangement

3.GAS BEHAVIOUR• When working with a gas, it is helpful to know its

volume, temperature and pressure– Volume: amount of space that matter fills

(cm3, ml or L)– Temperature: measure of the average energy of

random motion of the particles of a substance. The faster the particles are moving, greater energy and higher temperature.

– Pressure: (particles collide with one another and with the walls of their container). Force of its outward push divided by the area of the walls of the container• Pressure= Force/Area Unit: Pascal (Pa), atmosphere

(atm), mmHg (millimeters of Mercury)

1. PRESSURE AND VOLUME– Boyle’s law

• When the pressure of a gas at constant temperature is increased, the volume of the gas decreases. When the pressure is decreased, the volume increases.

• Relationship between volume and pressure– I.e.: Balloons in the

atmosphere and bicycle pump

– Pressure and volume graph

2. PRESSURE AND TEMPERATURE– When the temperature of a gas at constant

volume is increased, the pressure of the gas increases. And the opposite.• I.e.: Trucks tires in summer (reduce the pressure)• Pressure and temperature graph

3. VOLUME AND TEMPERATURE– Charles’s Law

• When the temperature of a gas is increased at constant pressure, its volume increases. When the temperature of a gas is decreased at constant pressure, its volume decreases

• I.e.: Balloon in the oven and freezer• Volume and temperature graph