Kinetic Model of Matter

9.1 The States of Matter

9.2 The Kinetic Model of Matter

9.3 Pressure in Gases

Learning Objectives

• Distinguish between solids, liquids and gases in terms of their physical properties.

States of Matter

States of Matter

• What can you recall from your prior knowledge?• What is matter?• What are the different states of matter?• What are some properties of each state of matter?

States of MatterState of Matter PropertiesSolids •Fixed shape and volume

• Hard rigid• High density• Incompressible

Liquids •Fixed volume but no fixed shape• High density• Incompressible

Gases •No fixed shape and volume• Low density• Compressible

The Kinetic Model of Matter

Learning Objectives• Describe the molecular structure of solids,

liquids and gases• Infer from Brownian motion experiment the

evidence for the movement of molecules • Describe the relationship between the

motion of molecules and temperature

States of Matter at a Molecular Level

• Using an applet, the three various states will be looked at a microscopic level

• Keep these questions in your mind as we explore the applet

1) How are the particles arranged?2) How do the particles move?

States of Matter at a Molecular Level

Solid State Liquid State Gaseous State Particles are closely packed together which explains their high densities Particles are held in place by strong attractive forces and vibrate about their fixed positions which gives them their fixed shape and volume

Particles are arranged randomly and are slightly further apart as compared to the solid state, retaining relatively high densities Particles have strong attractive forces but are not held in fixed positions, allowing them to move freely within the liquid, resulting in a fixed volume but no fixed shape.

Particles are arranged randomly and are very far apart resulting in low densities Weak attractive forces between particles allows them to move about freely. Thus, they have no fixed shape or volume.

Brownian Motion

• It is a random motion of particles suspended in fluids caused by the random movement and bombarding of the suspended particles by the fluid particles

Brownian Motion

• Observe the video and describe Brownian motion

• How does temperature affect Brownian Motion?

Brownian Motion

• Let’s imagine dust particles that are suspended in our atmosphere

• During a hot day, as the temperatures rise, what would happen to the air molecules?

• What would be the resultant effect on the dust particles that are suspended in the air?

Brownian Motion

As the temperature of air , the average of air molecules increases. This causes the number of bombardments of air molecules on the dust particles . As a result the dust particles move faster and change direction more frequently.

Pressure in Gases

Learning Objectives

• Explain the pressure of a gas in terms of the motion of its molecules

• Recall and explain the relationships between pressure, volume and temperature using the kinetic model

Pressure in Gases

• What is Pressure? • How do gases cause pressure?

• Moving gas molecules with the inner wall of the container and a force on it. The force exerted per unit area is thus called gas pressure.

Gay-Lussac's Law

• At a higher temperature, the air molecules have greater speeds (greater average kinetic energy).

• The air molecules will then the walls of their container more forcefully and more frequently.

• This causes an in gas pressure inside the container.

Consider a container filled with air. What would happen if we increased the temperature of the gas (i.e. the air) in the container?

Gay-Lussac's Law

This law relates and pressure together.

The pressure, p, of a fixed mass of gas is directly to its temperature, T, at constant volume.

P Twhen mass and volume are constant

Gay-Lussac's Law

.

P is the pressure of the gasT is the temperature of the gas (measured in Kelvin).k is a constant

Charles’ Law

Charles’ Law

This law relates and temperature together.

The volume,V, of a fixed mass of gas is directly to its temperature, T, at constant pressure.

V Twhen mass and pressure are constant

Charles’ Law

; V/T = K (Constant) ; V1/T1 = V2/T2V T

V is the volume of the gasT is the temperature of the gas (measured in Kelvin).k is a constant

Boyle’s Law

Pressure - Volume Relationship

The pressure p of a fixed mass of gas is inversely proportional to its volume V at constant temperature.

when mass and temperature are constant

P V1

This law relates and volume together.

Boyle’s Law

;PV=Constant(K) ; P1V1 = P2V2P V1

P is the pressure of the gasV is the volume of the gask is a constant

Combined Gas Law