3. Lesson Objective
At the end of this
section, you should be
able to use the kinetic
molecular model to
explain the shape and
volume of liquids and
solids.
4. Review
Recall Kinetic Molecular Theory
1. All matter is made of tiny particles.
2. These particles are in constant motion.
3. The speed of particles is proportional to
temperature. Increased temperature means
greater speed.
5. 4. Solids, liquids, and gases differ in distances
between particles, in the freedom of motion of
particles, and in the the extent to which the
particles interact.
9. Shape and Volume of Liquids and Solids
The common and simple way by which the
solid, liquid, and gaseous phases of matter are
distinguished is by comparison of their shapes
and volumes. We recall the concepts that:
10. 1. Matter in the
gas state has
indefinite shape
and volume.
11. 2. Matter in the
liquid state has
indefinite shape
and definite
volume.
12. 3. Matter in the
solid state has
definite shape and
volume.
13. Shape and volume of matter in the three states are
explained as follows:
1. Shape and volume of gases are not definite
because molecules are widely separated, have
negligible attraction for one another, constantly
moving rapidly in all directions so they can fill
any shape and size of container.
14. 2. Liquid molecules are close enough to
touch one another. Attractive forces keep
them together so that total volume of a
certain amount is definite. Since they can
still move, slipping and sliding over one
another, the liquid continues to conform to
the shape of its container.
15. 3. Solid particles are closely packed
because of strong attractive forces
among them. Their low kinetic energies
cause them to stay in fixed positions,
resulting in definite shape and volume.
At the atomic level, vibrational motion of
the molecules is observed.
16.
17.
18. Roleplay of the three physical states – solid, liquid, gas.
• The activity involves the students acting as particles (or
molecules) and they will present their behavior and
positions relative to each other in the solid, liquid and
gaseous state.
• Divide the class into three groups. Assign one group to
act out the solid, the second as liquid and the third one as
gas.
19. • Give the students 3 minutes to discuss among
themselves how to act the assigned state, and 2 minutes
to act it.
• One member of the group will explain their act.
• Allow the other groups to make comments on the group
acts.
20. Lesson Assessment
1. How do liquids and solids compare with
gases in terms of attractive forces?
2. How are attractive forces related to the
motion and the amount of kinetic energy of the
particles?
