States of Matter, Kinetic Molecular Theory
Read 9.1 (pages 418 – 420)
1. Are there larger attractive forces between
molecules of gases, liquids, or solids? Explain.
2. Which state(s) of matter have these properties:
a) definite shape, b) definite volume, c) takes the
shape its container, d) incompressible.
3. Explain the properties of the three states of
matter by referring to the forces that exist in each
(e.g. “solids have intermolecular forces that are
so strong that molecules are fixed in place. This
gives solids a definite shape and volume. Solids
are incompressible because their strong forces
hold molecules tightly together, eliminating space
between molecules.” Repeat for liquids & gases.)
States of Matter, Kinetic Molecular Theory
4. What factor, in addition to strength of intermolecular forces, affects the state of a substance?
5. Which theory deals with molecular motion?
6. What 3 types of motion can a molecule exhibit?
Simply stated, what do these words mean?
Which types exist in solids, liquids, & gases?
7. What term means “the energy of motion”?
What is an average measure of this?
8. A flask of O2(g) is heated from 10°C to 90°C. Are
all O2 molecules moving faster at 90°C? Explain.
9. Why does evaporation cause the temperature of
a liquid to decrease?
10.Would a gas diffuse faster or slower in a
vacuum? Explain your reasoning.
1. Solids have greater attractions, that’s why
they stay together (whereas gases disperse).
2. a) solids, b) solids & liquids, c) liquids &
gases, d) solids & liquids.
3. Liquids have forces that are strong enough to
keep their molecules together (thus, they are
incompressible with a definite volume).
However, these forces are not strong enough
to fix molecules in place (shape is not fixed)
Gases have forces so weak that, at room
temperature, molecules move freely (shape &
volume change). The large spaces between
molecules makes gases compressible.
4. Temperature affects state.
5. The kinetic molecular theory.
6. 1- vibrational (small motion from side to side),
2- rotational (spinning), 3- translational
(straight line motion).
Solids: vibrational, Liquids: all, Gases: mostly
translational, also rotational (and vibrational).
7. Kinetic energy is the energy of motion.
Temperature = average kinetic energy
8. Not all molecules will be faster. However, the
average speed will increase.
9. Only the fastest moving molecules are able
to overcome the attractive forces of their
neighbors and leave the surface of the liquid.
The slower molecules are left behind. Thus
the average kinetic energy (i.e. temperature)
decreases.
10. Gas particles travel in a straight line until they
hit another particle. A vacuum is devoid of
molecules, so particles of a gas placed in a
vacuum will not bump into anything until they
hit the side of the container. Thus, a gas will
diffuse faster in a vacuum.
Demo 1: Diffusion of KMnO4
Observations: KMnO4
(potassium permanganate)
diffuses faster in hot water.
Cold water
Hot water
Explanation: KMnO4 dissolves
in water. As the KMnO4
dissolves, it collides with H2O
molecules and spreads out.
Because molecules in hot
water are moving faster, the
solid dissolves faster and
diffuses faster.
Demo 2: thermal expansion of a liquid
Glass
tube
Rubber
stopper
Coloured
water in
florence
flask
Hot plate
Observations: coloured water
moves slowly up the tube
Explanation: heat increases
the kinetic energy of liquid
particles. The particles move
faster (greater vibrational,
rotational, and translational
energy). This greater
movement increases the
distance between molecules.
Thus, the volume expands.
Demo 3: Heating Mercury
Air
Glass
tube
Beads
Mercury
Heat
source
Observations: beads are
propelled upwards when
mercury is heated.
Explanation: heat increases
the kinetic energy, so that the
particles move faster. The
fastest moving mercury
molecules (that boil off)
transfer their energy to the
beads, causing them to jump.
Would this work with water?
Pressure and Volume
Read 9.2 (pages 423 – 425)
1. Define pressure. What is the SI unit for pressure?
2. How does a gas exert pressure on the side of a
container? What would happen to the pressure if
a container of gas was heated? Explain with
reference to the kinetic molecular theory).
3. Define and give the conditions of STP and SATP.
4. How was atmospheric pressure first determined?
5. Copy figure 1 into your notes. What would
happen to the the level of mercury if a) the
barometer were at a high elevation (where
atmospheric pressure is lower), b) the tube length
was doubled, c) the air pressure was increased?
6. Solve for question 2 on page 425.
Pressure and Volume
1. Force per unit area. SI unit is Pa (kPa)
2. Pressure is due to collisions of gas particles.
Pressure would increase because the speed of
molecules increases ( collisions per second)
3. STP: standard temperature and pressure (0°C,
101.3 kPa or 1 atm). SATP: standard ambient
temperature and pressure (25°C, 100 kPa).
4. Via an inverted tube of mercury (see fig 1)
5. a) the level of mercury is lower (<760 mm Hg)
b) no change: it’s the air pressure that pushes
mercury up, not the vacuum that pulls it up.
c) the Hg level would rise (“barometer rising”)
Q: how can you get water from a well over 10 m?
Demo 4: Kill da wabbit
Question: what will happen when the air pressure
surrounding a balloon is decreased? Why?
Explanation: A balloon
normally stays the same size
because the pressure inside
the balloon is equal to the
pressure outside the balloon
(rate of collisions with the wall
of the balloon is equal).
Reducing the pressure on the
outside eliminates opposing
collisions, allowing the
balloon to expand.
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