Lesson 2 Changes in Temperature

General SCIENCE
Grade 7

Textbook

Make sure you have the following
before we start:

01

02

03

Notebook

Pencil, Eraser, Ruler
Fully charged laptop

learning Golden Rules
You agree to:

1. Listen to your teacher.

2. Ask questions using the chat box.

3. Be prepared to start the lesson by having

your resources ready.

4. Try your best and be an active learner!

5. Do not interrupt when some one is talking.

—SOMEONE FAMOUS

"Successful people do what

unsuccessful people are not willing to
do. Don't wish it were easier; wish you

were better."

Unit 1 – Understanding matter

Module 1 - Classification and

states of matter

Changes in
Temperature

Lesson 2

•Understand what happens to the volume of a gas when
thermal energy changes.

•Illustrate how does thermal energy transfer between
objects.

•Explain how can air hold up water.

•Analyze how does pressure change when temperature
changes.

•Analyze what happens to states of matter as
temperature changes.

Vocabulary

✓ Thermal Energy
✓ Volume
✓ Temperature
✓ Contraction
✓ Expansion
✓ Heat
✓ Open system
✓ Closed system
✓ Pressure

✓ Collisions
✓ Kinetic energy
✓ Pressure gauge
✓ Melting
✓ Freezing
✓ Vaporization
✓ Condensation

Textbook # 29

Starter Activity

Which statement do you agree with the most?

Write the answer chat.

Activity - Discussion

Textbook # 31

Activity - Discussion

➢ What do you think happens to the

ice during summer? How does it
change during winter?

Textbook # 31

What happens to the volume of a gas when

thermal energy changes?

The ice on Tioga Lake gained energy
from the Sun.
Recall that when energy is added to a
solid, such as ice, the kinetic energy of
the particles increases.

How do you think this affects the
volume of a substance?

Let’s find out.

Activity - Investigation

Textbook # 34

Activity - Investigation

Textbook # 34-35

Activity - Investigation

Textbook # 34-35

The balloon should inflate as the flask heats up.

As the flask cools the balloon should deflate or shrink.

Activity - Investigation

Textbook # 35

As the temperature becomes colder than the air, the balloon
should deflate. The balloon may even invent into the flask.

Activity - Investigation

Textbook # 35

Analyze and Conclude

9. How did heating the flask affect the air inside the flask?

10. Develop a claim about the relationship between temperature and the volume of a

gas. Support your claim with evidence and reasoning.

Activity - Investigation

Textbook # 35

Analyze and Conclude

9. How did heating the flask affect the air inside the flask?

10. Develop a claim about the relationship between temperature and the volume of a

gas. Support your claim with evidence and reasoning.

As the hot plate heated the flask, the balloon inflated. The air in the flask
warmed up the particles moved farther apart and inflated the balloon.

As the temperature rises, the volume of a gas increases. As the
temperature falls, the volume of a gas decreases. This is a proportional
relationship between temperature and volume.

What happens to the volume of a gas when

thermal energy changes?

Volume-Temperature Law

✓Jacques Charles (1746–1823) was a French scientist who described the

relationship between temperature and volume of a gas.

✓Charles’s law states that the volume of a gas increases with increasing

temperature, if the pressure is constant.

✓The opposite is also true. When temperature decreases, the volume of

a gas also decreases.

Charles’s law

Question time:

➢
Is the relationship between temperature and volume
directly or inversely proportional?

Write the answer in the chat

Answer: Directly proportional

✓ The temperature and volume of gas is a directly

proportional relationship.

What happens to the volume of a gas when

thermal energy changes?

Volume-Temperature Law

✓When the balloon is in cold air, the temperature of

the gas inside the balloon decreases.

✓A decrease in temperature is a decrease in the

average kinetic energy of particles.

✓They have less energy to overcome the attractive

forces between them and begin to get closer

together.

✓Thermal contraction is a decrease in a volume as

its temperature decreases.

What happens to the volume of a gas when

thermal energy changes?

Volume-Temperature Law

✓When the balloon is in warm place, the

temperature of the gas inside the balloon

increases.

✓An increase in temperature is a increase in the

average kinetic energy of particles.

✓They have more energy to overcome the attractive

forces between them and begin to move apart

✓Thermal expansion is an increase in volume as its

temperature increases.

What happens to the volume of a gas when

thermal energy changes?

✓ The number of particles does not change during expansion and

contraction.

✓ The object that the particles are in changes size as the thermal

energy changes.

✓ This is due to the space between the particles changing. Each

particle does not change size.

✓ Particle size remains the same during expansion and contraction.
✓ The volume that the particles take up changes.

Multiple Choice

What happened to the balloon when it was taken outside to a snowy area?

• The particles moved away and the balloon decreased in volume.

• The particles moved away and the balloon increased in volume.

• The particles moved closer and the balloon increased in volume.

• The particles moved closer and the balloon decreased in volume.

Activity

Textbook # 37

The day before:

The next morning:

Explain:

As the temperature falls, the particles
inside the basketball lose kinetic energy.
The particles collide with the wall of the
basketball less often and with less energy
so the ball deflates. The volume of the
basketball decreased.

Activity - Discussion

➢
Look at the picture. Where
does the thermal energy for
melting the ice come from?

➢ How do substances gain thermal

energy?

Let’s find out!

How does thermal energy transfer between

objects?

✓ The thermal energy of an object is the total potential

and kinetic energy it possesses.

✓ Heating an object adds thermal energy to the object.

✓ Cooling an object removes thermal energy from the

object.

Activity - Investigation

Textbook # 38

Activity - Investigation

Textbook # 39

Data and Observations

The temperature of the cold water that was connected to the hot
water increased.
The temperature of the hot water that was connected to the cold
water decreased.
The temperature of water in the control beakers changed
significantly less than the temperature of the water in the
connected beakers.

Activity - Investigation

Textbook # 39

Analyze and Conclude

9. Describe what happened to the thermal energy in the beakers.

The thermal energy in the hot water traveled through the aluminum to the cold
water. The thermal energy in the water in the control beakers stayed about the
same.

10. What did the temperature of the two beakers without the foil tell you?

The temperature of the beakers without the foil tells you that the thermal energy did
not just go into the atmosphere. The thermal energy must have moved through the
aluminum foil.

Activity - Investigation

Textbook # 39

Analyze and Conclude

11. Was the rise or fall in temperature equal across all the beakers? Explain

No, there were differences between the beakers with foil and the beakers without
foil. The beakers without foil may have changed slightly.

12. Describe any relationships that you observe in your measurements.

As the temperature of the hot water decreased, the temperature of the cold water
increased. The thermal energy was conserved.

How does thermal energy transfer between

objects?

Heating
✓ Think about a warm cup of hot cocoa on a cold

day. Thermal energy moves from the warm cup to
your hands.

✓ The transfer of thermal energy from a region of

higher temperature to a region of lower
temperature is called heat.

✓ Something is heated when thermal energy

transfers from one object with higher temperature
to another object with lower temperature in
contact.

✓ The material with the higher temperature can be a

solid, a liquid, or a gas.

✓ Heat can also refer to the amount of energy

transferred during a process.

How does thermal energy transfer between

objects?

SYSTEMS

✓The materials or objects involved in a transfer of energy are part of

a system.

✓The cup, coffee, the mug, hands and the surroundings are part of

the system.

What type of system is shown
in the picture?

How does thermal energy transfer between

objects?

SYSTEMS

✓This is considered an open system because energy is released to the

environment.

✓In a closed system, there is no exchange of matter or energy with

the environment. This type of system is only theoretical.

Question time:

➢
When a liquid such as hot soup cools down, what
happens to the thermal energy?

Answer: The thermal energy is transferred to the bowl,
the table the bowl is on, and the surrounding air.

Activity

Textbook # 40

Multiple Choice

How does heat transfer in objects?

• Thermal energy transfers from cold object to hot object in contact.

• Thermal energy transfers from cold object to hot object not in contact.

• Thermal energy transfers from hot object to cold object in contact.

• Thermal energy transfers from hot object to cold object not in contact.

Multiple Choice

Thermal energy transfers from warm object to cooler object.

How can air hold up water?

➢ How does a beach ball get its shape?

The beach ball fills up with air.

➢ You decide to use the ball pump rather than blow

the ball up with your mouth. The beach ball fills
up.

You put in just a little more air and… pop!
How did that happen?

Activity - Lab

Textbook # 41

Write the answer in the
textbook

Activity - Lab

Textbook # 41

Write the answer in the
textbook

Data and Observations

Analyze and Conclude

6. Sketch a model of the glass of water and the air outside the cup to explain your

observations. Include in your model the particles of both the water and the air inside
and outside the cup.

The card held the water in the glass.

Students should sketch more air particles colliding with
the card than particles of water colliding with the card
to show the reason the card stayed in place.

How can air hold up water?

Air Pressure

➢ The air around us is a gas that creates pressure. Pressure is the

amount of force per unit area applied to an object’s surface.

➢ The force caused by the collisions of the air particles around

objects is called air pressure.

➢ The particles in the air collide with the glass and the card.

Textbook # 42

How can air hold up water?

Air Pressure

➢ When you turn the glass upside down, there are fewer air particles

colliding with the water surface than colliding with the card.

➢ Air pressure pushes the card up and keeps the water in the glass.

Textbook # 42

Open ended Question:

➢
Look at the picture below. Why doesn’t the liquid leave
the straw?

Answer

✓ When you place your finger on top of the straw,

you reduce the air pressure on the top of the
liquid.

✓ When the straw is removed from the glass, the

liquid stays in the straw because there is now
more air pressure acting on the bottom of the
liquid than at the top.

✓ The force of the air pressure at the bottom of the

liquid is greater than the force of gravity!

Textbook # 42

How can air hold up water?

Air Pressure

➢Once the finger is removed, there is equal air
pressure at the top and bottom of the straw.

➢These forces cancel each other out.

➢Gravity is no longer the smaller force, and the
liquid falls out of the straw.

Textbook # 42

How can air hold up water?

Units of Pressure

➢ The pressure of gases can only be measured by

the number of collisions of particles with the
container.

➢
➢ The amount of particle collisions is directly

proportional to the pressure.

➢ The higher the number of particle collisions, the

higher the pressure.

Textbook # 43

How can air hold up water?

Units of Pressure

➢ One method of describing pressure is by relating

the pressure of a substance to the pressure that
exists due to the atmosphere.

➢ Sometimes scientists use units of atmospheres

(atm). The pressure at sea level is 1 atm.

➢ If a pressure gauge reads 4 atm, then the

pressure inside the container is four times the
pressure of the atmosphere at sea level.

Textbook # 43

Activity

Textbook # 43

Activity - Discussion

➢
What happen when you
shake and open the coke
can? Explain .

Raise your hand to answer.

Activity - Lab

Textbook # 44

Write the answer in the
textbook

Activity - Lab

Textbook # 45

The bottle completely collapsed.

The bottle regained most of its
original shape.

Activity - Lab

Textbook # 45

Immediately after
ice bath: Sketch
should show slowly
moving particles
close together inside
the bottle.
5 min after ice bath:
Sketch should show
quickly moving
particles farther apart
inside the bottle.

How does pressure change when temperature

changes?

Temperature and Pressure

➢ When you placed the bottle in the ice bath, you decreased the

temperature of the air inside the bottle.

➢ This decreased the speed of the particles, so the particles did not

collide with the walls of the bottle as often.

➢ A decrease in temperature decreases the pressure of a gas.

➢ Air pressure surrounding the bottle was greater than the pressure

inside the bottle and caused the bottle to collapse.

Textbook # 45

Activity – Open Ended Question

What will happen to the crushed bottle when it returns to room temperature or warmer temperature?

✓As the bottle gained thermal energy from the
room and the temperature of the bottle
increased, the particles sped up.

✓As the particles moved faster, they collided
with the walls of the bottle more often,
increasing the pressure.

✓The pressure eventually returned to normal
air pressure and the container almost returned
to its original shape.

Textbook # 45

What happens to states of matter as temperature

changes?

Phase Change

When you melted the ice cube at the
beginning of the lesson, you might have
increased the temperature of the ice cube.
Eventually the ice cube melted.
What happens to the particles in the ice
cube to cause a change in state?

What happens to states of matter as temperature

changes?

Phase Change

➢ Matter can change state when it gains or loses

enough thermal energy.

Add energy

Add energy

Remove energy

Remove energy

Textbook # 47

Phase change : Melting

What happens to states of matter as temperature

changes?

Melting
✓ Matter can change state when it gains or loses

enough thermal energy.

✓ When the temperature of a substance increases,

the particles speed up.

✓ When particles speed up, they start to move

farther away from each other.

✓ The particles in a solid are also held together by

strong attractive forces.

✓ As the particles gain more and more thermal

energy, they gain enough energy to start to
break away from the other particles.

✓ This is the melting point of a substance.

Home

Open in new tab

Copy link

What happens to states of matter as temperature

changes?

Melting

As energy is added, solid
particles vibrate faster and

temperature increases.

As particles move farther
apart, the solid becomes a

liquid. Temperature

remains constant at the

melting point.

Once all particles are in the
liquid state, any additional

energy increases the speed of

the particles. Temperature

increases.

Textbook # 47

What happens to states of matter as temperature

changes?

Melting

✓ At first, both the thermal energy and the

temperature increase.

✓ The temperature stops increasing at the melting

point of the water.

✓The energy supplied to the ice goes to breaking the
attractive forces until all of the ice has melted.

✓ Once all the ice is melted, any additional energy

supplied to the substance goes to speeding up the
particles again

QUESTION: Explain the changes happening during
vaporization.

oThe change in state from a liquid to a gas is vaporization.

oAs thermal energy is added to a liquid, the particles move
faster and faster.

oOnce they are moving fast enough, they overcome the
attractive forces holding them in a liquid state and become
gas particles.

oThe temperature needed for a substance to boil is
called the boiling point.

oA substance’s temperature will remain at its boiling point until
all of the particles have changed from liquid to gas.

oOnce all the particles are a gas, any additional energy will
increase the speed of the gas particles.

What happens to states of matter as temperature

changes?

Question time:

➢
What caused the liquid water in the puddle to vaporize?

Answer: The water is evaporated.

What happens to states of matter as temperature

changes?

Evaporation

✓ Evaporation is vaporization that occurs

only at the surface of a liquid.

✓ When the particles at the surface of the

puddle gained enough energy from the
Sun to overcome the attractive forces
holding them to the rest of the particles
in the puddle, they broke away as a
gas.

What happens to states of matter as temperature

changes?

Pressure and Evaporation

✓ Not only do the particles need to overcome the attractive forces between

the particles, but they must also overcome the force of air pressure.

✓ Air pressure is constantly pressing down on the surface of a liquid.

✓ For a particle to evaporate, it must overcome the force of air pressure to

escape from the surface of the liquid.

Textbook # 48

FREEZIING AND CONDENSATION

FREEZING

•The change of state from a liquid
to a solid.

•Freezing point is same as
melting point.

•Freezing requires the removal of
thermal energy.

•Particles slow down and cannot
overcome the attractive forces.

CONDENSATION

•The change of state from a gas
to a liquid.

•Condensation point is same as
boiling point.

•condensation requires the
removal of thermal energy.

•Particles slow down and cannot
overcome the attractive forces.

Textbook # 49

Multiple Choice

The temperature at which a liquid becomes a gas is the ____ point

• freezing

• boiling

• condensation

• melting

Multiple Choice

The state of matter of a material depends on its _____.

• density

• temperature

• volume

• weight

Fill in the Blank

The evaporation of water is an example of a change in ..............

What happens to states of matter as temperature

changes?

Textbook # 50

Multiple Choice

A change in the state of matter is caused if enough _____ is added to or removed from an object.

• thermal energy

• kinetic energy

• potential energy

• force

Multiple Choice

During a hot shower, water vapor fogs up the cooler mirror when it turns to water. This is an example of _____.

• condensation

• deposition

• sublimation

• vaporization

Multiple Choice

Marco put a pot of water on to boil eggs. After a few minutes, all the water was gone. This is an example of _____

• condensation

• deposition

• sublimation

• vaporization

Multiple Choice

Which model best represents a change that results from adding thermal energy to a substance in a jar?

Multiple Choice

Snow melts after a snowstorm because of the addition of _____.

• thermal energy

• kinetic energy

• potential energy

• force

Activity

Lesson Review

Textbook # 53

Lesson Review

Textbook # 54

Lesson Review

Textbook # 54

Thank You