Kinetic TheoryApril 18, 2023

ObjectivesHSW: Use the kinetic theory to explain the different states of matter.Candidates should be able to draw simple diagrams to illustrate the

difference between solids, liquids and gases.

HSW: AF1 – Thinking Scientifically

AF4 – Using investigative approaches

Used before in: Will use again in: Lesson 2 –

Energy Transformations

PLTS: Independent enquirers: support conclusions, using reasoned arguments and evidence.

Used before in: Will use again in:

KeywordsBoiling point, condense, evaporate, freezing point, melt, melting

point, sublimation

Learning Outcomes:All students should be able to: • Describe what happens at

melting/freezing and boiling point• Label a general cooling curve.Most students should be able to: • Use the particle model to explain what is

happening at each point on the cooling curve• Describe the difference between the

temperatures of substances at boiling and evaporation point.

Some students should be able to: Explain how evaporation makes a liquid

cooler

At a cold enough temperature, even substances that are normally gases will become solid.

At higher temperatures, solids change to become liquids or gases – as long as they do not catch fire or break down.

Water can be a solid, liquid or a gas

States of matter and temperature

Particles in a solid – animation

Particles in a liquid – animation

Particles in a gas – animation

Each change of state is given a different name:

solid liquid gasmelting

freezing

boiling

condensing

Changes of state

sublimation

reverse sublimation

melting

freezing

solid liquid

boiling

condensing

liquid gas

tem

per

atu

re

time

solid

liquid

gas

Changes of state – heating curve

Changes of state activity

Changes of state – cooling curve activity

Evaporation occurs when the particles in a liquid escape to form a vapour.

Evaporation can occur at any temperature but it occurs most rapidly at a liquid’s boiling point.The particles that escape take some energy from the remaining particles and so the temperature of the liquid falls.

What is evaporation?

Evaporation is another method of heat transfer.

Practical time

• Practical - Stearic Acid practical – follow method teacher has shown you. (method on next slide)

• Draw your own cooling curve in your book and label each change of state

• Now complete a “triangle/arrow summary diagram in books to show all changes of state and Particle diagrams of solids/liquids/gases

AF1 – Thinking ScientificallyAF4 – Using investigative approaches

Method

• Take a boiling tube of molten wax from the water bath

• Place in a boiling tube rack

• Take the temperature of the wax every minute recording the state of matter.

• Stop when the wax has been solid for 2 minutes with no temperature change

• Draw a cooling curve from your results

Plenary - Sublimation

Sublimation, reverse sublimation

OR: AB document link on page 127 opens a CLOZE exercise covering the material on page 126-127. There is also an AT presentation with the answers.

Youtube video of sublimation of dry ice:http://www.youtube.com/watch?v=J8mDGwf-5x0