Grade 8 — Maroon (7:30-8:30 am)
Grade 8 — Sienna (9:45-10:45 am) November 20, 2014
Grade 8 — Magenta (10:45-11:45 am)
Grade 8 — Fuchsia (8:30-9:30 am)
Detailed Lesson Plan in Chemistry
I.
Objectives
At the end of the lesson, the students should be able to:
1. Explain the process involve in the changes between a solid and a liquid.
2. Describe some concrete examples that show the process of melting and freezing
3. Illustrate what happens to the particles of water when it is heated and then cooled and
what happens to the particles of ice when it turns to liquid.
II.
A.
B.
C.
D.
E.
Learning Tasks
Subject Matter: What changes take place when water is heated or cooled?
What changes take place when ice turns into liquid water?
Materials: chalk, board, marker, tap water, beaker, watch glass, tripod, wire gauze,
alcohol lamp, matches and ice cubes.
References: Science Grade 8 Student Learning Module by Pia C. Campo et.al p 184189.
Skills: Explaining. Describing, Illustrating
Science Concepts:
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The transformation process in which a solid is changed to a liquid is called
melting.
The transformation process in which a liquid is changed to a solid is called
freezing.
F. Values Integration:
Students will be aware of the two processes they commonly encounter in their
everyday life which is the transition of a solid and a liquid.
III.
Teaching Strategy
TEACHER'S ACTIVITY
A. Motivation
Has anyone ever eaten ice cream on a
hot summer day and during cold days?
What do you observe between the two
conditions?
Have you ever left a glass of ice water
out on the table? What happened to the
ice?
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Very good observation. The state of.
STUDENT'S ACTIVITY
The ice cream melts faster during a hot
summer day than cold days.
The ice melted because of the alteration in
temperature.
TEACHER'S ACTIVTY
matter depends on the pressure and temperature
that are applied to it which allows its transition
from one form or state to another with each
decrease or increase in the pressure or
temperature.
B. Presentation
So for today, we will tackle about the
two processes that depend on the
temperature applied to it — melting and
freezing.
Let us check first your assignment
which is activity 5 and 6 in your
module.
In question number 1 in activity 5,
Describe what you observe in the water
STUDENT'S ACTIVITY
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There are bubbles formed at the bottom of
the beaker and bubbles in the boiling water.
There is also steam observed above the
liquid.
iwnastiedre. the beaker and above the level of
•
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What do you think is inside the bubbles
that form when the water boils? Where
did they come from?
The bubbles are water in the gaseous state.
(It is very common for students to say that
the bubbles formed are air. At the start of
the heating process, however, the tiny
bubbles that form are due to the air
dissolved in the water. This is not boiling.)
If you keep the water boiling for more
than 10 minutes, what do you think will
happen to the amount of water in the
beaker? Why?
The volume of water in the beaker will
decrease if water will be kept boiling for
more than 10 minutes because there will be
rapid evaporation of water.
Where did the water go?
As the water is heated and the temperature
of the water rises, the molecules gain more
kinetic energy and they move faster. More
molecules have the energy to overcome the
forces of attraction of the neighboring
molecules. These molecules escape to the
gaseous phase.
TEACHER’S ACTlVlTY
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Can you explain by illustration how the
water changes from liquid to gas? What
is happening to the particles of water?
Describe what you observe in the water
inside the beaker and at the bottom of
the watch glass.
Where does the water at the bottom of
the watch glass come from?
Can you explain by illustration how the
water changes from gas to liquid?
Describe what is happening to the
particles of water
STUDENT’S ACTlVlTY
Students' drawings will vary. What is
important to note is how students represent
and explain the escape of fast-moving
molecules of water from the surface of the
liquid to the air. Also, their representation or
drawing of water in the gaseous state should
show that the molecules of water are very far
apart.
As the water began to cool, droplets formed
under the watch glass that covered the beaker
containing hot water. There are also drops of
water formed on the inside wall of the
beaker. Some of these drops of water were
observed falling to the water inside the
beaker.
The water droplets at the bottom of the watch
glass are the molecules of water that escape
from the liquid and go into the gaseous
phase. These water vapor rise and some
molecules touch the glass.
Students' drawings will vary. Their
illustrations should show that the particles or
molecules representing water in the gaseous
state should be very far apart and as the
water begins to cool, the particles should be
drawn closer to each other.
When a gas is cooled, the motion of the
particles slows down. If the particles lose
enough energy, their attraction for each other
can overcome their motion and cause them to
come closer with one another to become a
liquid.
Let us proceed in activity 6.
In question no. 1, Explain what is
happening to the particles of water in ice
as it turns to liquid using the particle
model of matter.
•
After one to five minutes (depending on the
room temperature), the ice begins to turn
into a Iiquid. (Some students may write that
“the ice meIted.”) When ice, which is a soIid,
turns into a Iiquid, the particIes or moIecuIes
of soIid water vibrate faster due to the
TEACHER’S ACTlVlTY
STUDENT’S ACTlVlTY
higher temperature in the room compared to
the freezer. Eventually, the particles or
molecules break away from their fixed.
•
Explain what will happen to the liquid
on the watch glass or saucer if it is
transferred into a small container and
left inside the freezer after a few hours
or overnight?
C. Lesson Proper
The activity 6 in your module shows two phase
changes between the states of matter.
The ice cube, which was taken from the
freezer, is at a lower temperature than
the surrounding room temperature.
Probably, after about 15 to 20 minutes,
the ice (solid water) on the watch glass
or saucer turned into liquid water.
If some of the heat energy of the
surroundings is transferred to the water
molecules in the ice. What will happen
to the kinetic energy of the molecules of
the ice?
•
The molecules become excited and
move faster and faster and at some point
have enough energy to overcome the
forces that hold them in their fixed
places in the solid. Then eventually,
break away from their fixed positions.
What happened to the arrangement of
the water molecules in ice?
The liquid will turn into solid when
transferred to the freezer.
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The kinetic energy of the molecules
increases and as the heat transfer continues,
the particles gain more and more kinetic
energy.
The arrangement of the water molecules in
ice gradually becomes disorganized and the
solid where the molecules are in fixed
positions turns to liquid where the molecules
are more free to move.
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Then, what is the process involved in
this phenomenon?
Who can define the process of melting?
On the other hand, when you put liquid
water in a place that has lower temperature
like inside a freezer, the cooling system of
the refrigerator removes heat energy from
the water molecules as a
Melting
Melting is the transformation process in
which a solid is changed to a liquid.
TEACHER’S ACTlVlTY
result of which they have less kinetic energy
and move more slowly.
As more and more heat is removed,
what happened to the arrangement of the
molecules?
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Correct. If the removal of heat
continues, what will happen to the
molecules?
Good. What is the process involved in
this phenomenon?
Right. What is freezing?
STUDENT’S ACTlVlTY
As more and more heat is removed and as
the molecules move more slowly, the forces
of attraction between the molecules cause the
molecules to be aligned.
The molecules lose so much energy that they
are not able to move from place to place but
only able to vibrate in place.
Freezing.
Freezing is the process in which a liquid is
changed to a solid.
Good. Also, take note that liquid water
that freezes is still water. Similarly, ice
that melts is still water. For, melting and
freezing is an example of physical
change in matter which means the
composition of the substance is not
changed.
This ends our discussion about matter. From
activity 1-6 you have learned the four basic
aspects of the particle model of matter. What do
you think are those concepts?
These are: (1) matter is made up of very
small particles; (2) matter is made up of
particles that are constantly moving; (3) there
is empty space between the particles; and (4)
there are forces that act between the
particles.
I hope you learn a lot from our discussion.
Goodbye class.
D. Generalization
The state of matter depends on the temperature that is applied to it which allows its
transition from one form or state to another with each decrease or increase in the temperature.
Melting and freezing are examples of the phase changes that depend on the temperature
applied to it.
E. Evaluation
A. Knowledge
1. The change of state from a liquid to a gas is called:
a. Evaporation b. Melting c. Liquefaction
2. The change of state from a solid to a liquid is termed:
a. Freezing
b. Melting c. Condensation
3. The process when a gas changes to a liquid is called:
a. Evaporation b. Solidification c. Condensation
4.
The melting point of water in degrees Celsius is=
a. 100
b. 0
c. 25
5. The melting point of water is the temperature at which:
a. water freezes from liquid water to solid ice
b. w`tir dints tb d`li sti`d
c. ice changes directly to a gas without making a liquid
B. Give other examples or activities that show the process of melting and freezing.
C. You leave a bowl outside overnight. It snows and fills the bowl. You notice the bowl
in the morning and leave it. The snow melts as the temperature increases. Draw a
diagram what happens to the snow as it melts.
Assignment:
Read about the 3 subatomic particles.