Describe and explain diffusion Describe and explain dependence of rate ofdiffusion on molecular mass Describe qualitatively the pressure andtemperature of a gas in terms of the motionof its particles Describe the heating and cooling curves

1. Presented by: Mrs. Saima

2. Review (last lesson)
 Describe the structure of solids, liquids and gases in
terms of particle separation, arrangement and types
of motion
 State the distinguishing properties of solids, liquids
and gases
 • Describe and explain diffusion (1 core)
 • Describe evidence for the movement of particles in
gases and liquids (1 core)
 Describe changes of state in terms of melting, boiling,
evaporation, freezing, condensation and sublimation
 Explain changes of state in terms of the kinetic
theory

3. terms of particle separation, arrangement and types of
motion

4. Describe and explain diffusion
 Diffusion is the movement of a substance from an area
of high concentration to an area of low
concentration.
 Diffusion happens in liquids and gases because their
particles move randomly from place to place.
 What causes diffusion?
 In gases and liquids, particles move randomly from
place to place. The particles collide with each other or
with their container. This makes them change direction.
Eventually, the particles are spread through the whole
container.
 Diffusion happens on its own, without stirring, shaking
or wafting.

5. OBJECTIVES
 Describe and explain diffusion
 Describe and explain dependence of rate of
diffusion on molecular mass
 Describe qualitatively the pressure and
temperature of a gas in terms of the motion
of its particles
 Describe the heating and cooling curves

6. RATE OF DIFFUSION
AND MOLECULAR MASS
 THINK:
 If you roll a heavy ball and lighter ball with same force,
which will move faster
 If there are two gases, one with lighter molecules and
other with heavier particles/molecules; whose particles
will be moving faster
 Molecular mass of gas A is 17 and gas B is 36.5. which
will diffuse out faster from a container with a pin hole.

7. RATE OF DIFFUSION AND
MOLECULAR MASS
 Molecular mass of HCl is
higher than that of NH3
hence it diffuses to a
smaller distance whereas
ammonia (NH3) which has
lighter molecules

8. Describe the heating and
cooling curves
 A heating or cooling curve is
the graph of temperature and
time when a substances is
heated or cooled.
 It involves state changes and
helps determine the melting
point and boiling point of a
substance
 When a substance changes
state, the temperature of the
substance stays same until all
of it has changed to the other
state. As a result there is a
flat/horizontal section in the
graph when there is a state
change.
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9. Describe the heating and
cooling curves
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