Name:_________________________
Change of Phase
Problem:
Can we demonstrate the changes of state (phase changes) of ice to
liquid water to steam by adding heat energy?
Background:
Water is found everywhere on earth. It may be found in the air as water vapor, in liquid form, or as
a solid if it is frozen. Water undergoes many phase changes. When substances change phase, the physical
properties change (solid, liquid, or gas), but the chemical properties stay the same. For example, water is
made up of two hydrogen and an oxygen atom. When the water freezes, evaporates, or condensates, it is still
made of two hydrogen and one oxygen atom. Melting, freezing, condensation, and evaporation are examples
of phase changes. The phase of a substance depends on temperature and pressure. The pictures below show
how molecules of water look in each phase. Notice how solid water molecules are bunched together and how
far apart the gas molecules are. (edited from http://www.nyu.edu/pages/mathmol/textbook/slg.html)
You are going to investigate how increasing heat energy causes phase changes in water. We will add
heat energy from a hot plate to a beaker of ice to create phase changes. The heat energy will make the
molecules move faster and farther apart. This is a physical change because heating or cooling water does
not change the composition of the water. It is still H20. During this experiment, the water undergoes only
physical changes.
Define the following Key Terms:
State of
Matter
Definition
Examples
1. Solid
Ice
2. Liquid
Water from the tap
3. Gas
Water Vapor in the Air
4. Plasma
Stars
Hypothesis:
If
heat energy is added to ice and to water,
ice state will change to liquid water state and the liquid water
state will change to the steam state.
Then
Experiment:
Experimental Set Up
Control Group:___________
_Ice _______________________________________
Experimental Group:_______
Variable:_____________
Ice with heat added _______________________________________
heat energy ____________________________________________
Materials:
250 ml beaker, Clamp, Hot Plate, Thermometer, Ring Stand, Ice for 250 ml beaker.
Procedure:
1. Fill the 250 ml beaker full of ice.
2. Put the beaker on the wire thingy.
3. Position the thermometer in the middle of the beaker of ice.
Note: It must not touch the sides or the bottom of the beaker.
4. Wait two minutes for the thermometer to register the temperature of the ice.
5. Record this starting temperature at time 0 minutes.
6. Plug in the hot plate.
7. Record the temperature of the beaker each minute for 25 minutes.
8. Shut off the hot plate.
9. Pull up the thermometer.
10. Allow the hot beaker to stay on the hot plate.
Record Data:
1. Record the temperature and state of matter on the data table.
Note: More than one state of matter may be seen at a temperature.
Time in Minutes
Temperature
States of Matter Observed
0
Mostly solid,
some liquid
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Analyze Data:
1. Using the graph paper provided, make a line graph of your data.
1. Time (minutes) is the X-Axis (Horizontal Axis).
Hint: Count by ones on the lines. (0, 1, 2, 3, 4)
2. Temperature ( 0C) is the Y-Axis. (Vertical Axis)
Hint: Count by threes on the lines. (0, 3, 6, 9, 12)
3. Remember to make the spaces between the numbers the same
4. Remember to make the numbers consecutive.
5. Write the title at the top of the page. “Adding Heat Energy to Ice to Show Physical Phase
Changes”
2. What happened to the heat energy from the hot plate when it reached the ice?
The energy was used to make the solid particles move faster. As the
solid particles move faster, they spread farther apart and melt into
liquid.
3. What happened to the temperature of the water while the ice was melting?
The temperature stayed the same until all of the solid ice had melted
into the liquid water.
(This same temperature shows as a short plateau on the graph.)
4. What happened to the temperature of the water when the water was boiling?
The temperature stayed the same until all of the liquid water had
changed into the gas steam (water vapor).
(This same temperature shows as a long plateau on the graph.)
5. What were the states of matter that were present during this experiment?
Solid, liquid, and gas
6. Is phase change an example of chemical or physical change? _
physical change
The water was still water no matter whether it was a solid (ice),
liquid (water), or gas (water vapor – steam). We just changed how
close the particles are to one another.
Explain
Both have heat energy added to
make the particles move faster and spread farther apart.
7. What do melting and evaporation have in common?
All phase changes or changes of state are physical changes.
Compare and Contrast Phase Changes among Ice, Liquid Water , and Water Vapor
Solid
Ice
S
U
B
L
I
M
A
T
I
O
N
Gain
energy
Liquid
Water
Melting –
add energy
Freezing –
Lose
energy
L
i
q
u
i
d
Gas
Water Vapor
1-4 How does matter change state?
Lesson Review
W
a
t
C
O
N
D
E
N
S
A
T
I
O
N
Lose
energy
E
V
A
P
O
R
A
T
I
O
N
Gain
energy
Cross out the term that does not belong in each group.
1. condensation, ice, gas, liquid
5. evaporation, gain energy, leave liquid,
2. solid, water vapor, liquid, freezing
melt
3. gain energy, lose energy, gas particles, 6. freezing, melting, reacting, condensing
condensation
7. gain heat, melt, evaporate, state of matter
4. dry ice, water, moth balls, iodine
8. solid, water, sublimation, gas
Skill Challenge
Skills: interpreting a graph, analyzing, inferring
The graph on the right is called a state-change diagram. It shows what happens
to water as it changes from ice to liquid water and then to steam. Study the
graph. Then, answer the questions that follow.
1. What is being measured along the vertical axis of the graph? Temperature _____
2. What is being measured along the horizontal axis? Increasing
Heat
_________
3. What happens to the temperature of the ice when heat is first added? increases
4. What happens to the temperature of the ice right after the ice reaches 0°C? What is happening
to the ice at this time? The
temperature stops increasing and stays at 0 0 C
because all of the heat energy
is being used to make the
solid particles move faster and
separate to turn into liquid
water. The solid ice is
changing into liquid water. ________________________________________
5. The temperature of the liquid water
steadily increases between what two
temperatures on the graph?
0 0C – 100 0 C____________________________________
6. What happens to the temperature of the water as it changes to steam? Temperature
stays the same.
What is happening to the heat during this time? Heat
is still being added.
7. During the times when the temperature is not changing, what do you think is happening to the
heat that is being added to the water? The
heat energy is making the liquid
particles move faster and spread farther apart to change the liquid
into gas. (evaporation). __________________________________________
Conclusion: Write as a paragraph. Do NOT number the sentence answers. Write your conclusion
on a sheet of notebook paper.
1. Write a thesis statement based on the hypothesis.
2. Accept or reject hypothesis.
3. Use information from the control group data as support for accepting or rejecting the
hypothesis.
4. Use information from the experimental group as support for accepting or rejecting the
hypothesis.
5. List at least one source of error.
6. List at least one improvement that could be made.
7. Write a summary (closing) sentence.
My hypothesis stated ___________________________________
_____________________________________________________.
I _________________ my hypothesis because the data
_____________________________.
The control group was the 250 mL beaker of ice which only melted a
little. The gas state of matter was not seen in the control group
beaker.
The experimental group was ______________________________
and showed ___________________________________________
_____________________________________________________.
A source of error was ____________________________________
_____________________________________________________.
An improvement to the experiment would be _________________
_____________________________________________________.
In conclusion, this experiment showed ______________________
All heat energy goes to make particles move faster and farther apart.