Unit 3: States of Matter, Phase Changes, Heat Transfer, and Gas

LawsJ. Stevens

Section 1: Adapted from Mr. Jones, http://www.sciencewithmrjones.com/Section 2: Adapted from http://education.jlab.org/index.html

VocabularyTerm Definition Example

Solid Definite shape & volume; particles vibrate & are tightly compact and have strong attraction to each other; low energy

Liquid No definite shape, but definite volume;Particles close together, but can move around freely/slide past each other; moderately attracted to each other; higher energy

Gas No definite shape or volume; particles move around freely; weak attraction; high energy

Plasma Gas-like; very high energy; charged particles

VocabularyTerm Definition Example

Phase change(Physical change of state from one form to another)

Evaporation: liquid to gas

Freezing: liquid to solid

Melting: solid to liquid

Condensation: gas to liquid

Deposition: gas directly to solid

Sublimation: solid directly to gas

Evaporation:

Freezing:

Melting:

Condensation:

Deposition: water vapor directly to ice

Sublimation:

Vocabulary

Term Definition ExampleThermal Energy the total kinetic energy of

the particles that make up a substance

Kinetic Molecular Theory

Theory that describes how atoms move and react to temperature

Endothermic energy is lost, or released in the form of heat

Exothermic Energy is added or absorbed

Conduction The transfer of heat from one particle of matter to another by direct particle to particle contact.

VocabularyTerm Definition Example

Convection the transfer of thermal energy (heat) through the bulk movement of matter (in currents)

Radiation the transfer of (thermal) energy by electromagnetic waves.

Pressure amount of force exerted over a given area

VocabularyTerm Definition Example

Charles’ Law For a fixed amount of gas at a constant pressure, the volume of the gas increases as the gas’s temperature increases.

Boyle’s Law pressure times the volume is a constant, for a given mass in a closed system, as long as the temperature is constant

Gay-Lussac’s Law

The pressure of a gas increases as the temperature increases, if the volume of the gas does not change.

Avogadro’s Law

Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules

Section 1: States of Matter and Phase Changes

• Key Ideas:– What is the difference between solid, liquid, gas and

plasma?– What kind of energy do all particles of matter have?– What happens when a substance changes from one

state of matter to another?• Vocab:

– Solid - plasma - phase change– Liquid - thermal energy– Gas - kinetic theory

Kinetic Molecular Theory

4 Main States of Matter• Solid • Liquid• Gas

• Plasma

Kinetic Molecular Theory (KMT)

• KMT– Tiny, constantly moving particles (atoms) make up all

matter.

– The higher the temperature of the substance, the faster the particles move (more kinetic energy-energy of motion)

– At the same temp, more massive particles move slower than less massive ones.

– These particles are colliding with each other and the walls of their container.

Solid

• Particles:– are tightly compact– vibrate but can’t move

around (low KE)– Strong attraction to

each other• Definite shape and

volume• Solid Animation

Liquid

• Particles:– are still close together,

but can move around (higher KE)

– Moderate attraction to each other

• No definite shape, but definite volume

• Liquid Animation

Gas• Particles:

– can easily spread out or move close together

– move freely and with a lot of energy (high KE)

– Weak attraction to each other

• No definite shape or volume

• Gas Simulation• Bill Nye Video

Plasma

• Very high KE; particles collide with enough energy to break into charged particles (+ / -)

• Gas-like, indefinite shape & volume

• This form is not too common on Earth, however it is the most common form of matter in the universe—makes up ~99% of the universe!!!

• Examples: stars, florescent and neon lights, lightning, aurora borealis

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-

-

Why do you think this is the most common form/state of

matter in the universe?

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+

Energy’s Role• Energy is the ability to change or move matter• Energy of motion is called Kinetic Energy (KE). Since all particles

(atoms) are moving, they all have KE.• Temperature is a measure of the average kinetic energy

– Most matter expands when heated & contracts when cooled. Why?

– The more energy, the higher the temperature. Particles collide with more force & spread out.

• more energy means more movement for the particles and less energy means less movement.

• So which state of matter has the least energy? • Energy/Temperature and Matter Simulations

– PhET– BEC: Temperature and Absolute Zero

If you were to compare an ice cube and the steam created from boiling water, which would you think has more energy?

Thermal Energy

• Thermal energy: the total kinetic energy of the particles that make up a substance– Depends on particle speed and number of particles

• Ex: temp is not determined by how much of a substance you have, a teapot and freshly poured mug of tea is the same temp

• However, the thermal energy in each container is different, because the number of particles is different

States of Matter Continuum

Taken from: http://www.abc.net.au/science/articles/2010/03/16/2840402.htm

Energy and Changes of State (Phase Change)

• Law of conservation of mass and energy:– The identity and mass of a substance does not change during a

change of state– The energy changes forms, but the total amount of energy is still the

same.• As heat (energy) increases, the state of matter changes.

Solids go to liquids, liquids to gases and so on. This is called a phase change. A phase change is a physical change. Some examples are:– Evaporation: liquid to gas below the boiling point– Melting: solid to liquid– Sublimation: Solid to gas, ex: dry ice

• These phase changes can also happen when heat (energy) is lost.

Phase Changes

http://aventalearning.com/content168staging/2007ChemistryB/images/unit7_images/s4_3.jpg

Endothermic vs Exothermic

• For some phase changes, energy is lost, or released in the form of heat is and the temperature of the immediate surroundings rises(exothermic)– Condensation - Freezing– Deposition

• For others, energy is added or absorbed (endothermic):– Sublimation - Melting– Vaporization

Endothermic vs Exothermic TableChange of State Phase change Energy added or

lost? Examples

Melting Solid to a Liquid Endothermic (added) Ice melts to water

Freezing Liquid to a solid Exothermic (lost) Water freezes to become ice

Vaporization(evaporation) Liquid to a gas Endothermic (added)

A puddle on the ground evaporates after a few hours in the sun

Condensation Gas to a Liquid Exothermic (lost)

When a person wearing glasses enters a warm house after being outside on a cold day, their glasses will fog up.

Sublimation Solid to a gas Endothermic (added) Dry Ice

https://gcps.desire2learn.com/d2l/lor/viewer/viewFile.d2lfile/6605/48349/matter/phasechangesofmatter/Phase_Changes_of_Matter_print.html

Practice

• If you pour an object from one container to another and it loses volume, do you have a solid, liquid, or gas?

• Do particles slow down or speed up during the following phase changes?– Freezing– Boiling– Sublimation– Melting.

• What does temperature measure?• Create phase change diagrams.

Section 2 - Heat

• Key ideas:– How does heat energy transfer happen?

• Vocab:– Conduction– Convection– Radiation

The Nature of Heat

Heat moves in only one direction:• Under normal conditions and in nature, heat

energy will ALWAYS flow from the warmer object to the cooler object.

• Heat energy will flow from one substance to another until the two substances have the same temperature (thermal equilibrium)

How is heat transferred?

• What is heat?– movement of thermal energy from a

substance at a higher temperature to another substance at a lower temp

• Heat can be transferred 3 ways:– Conduction– Convection– Radiation

Conduction

• Direct contact of particles

• Solids/liquids/ gases

• Solids: good conductors

• Gases: poor conductors

• Ex: the handle of a cooking utensil in a boiling pot of soup

• Transfer of energy by waves

• Only radiant energy that is absorbed becomes thermal energy

• Shiny/light colors- reflect

• Dull/dark colors-absorb

• Ex: Lightbulb• Ex: Fireplace

• Transfer of energy by bulk movement of matter (fluids)

• Ex: Currents (wind,water)

• Ex: Hot air balloon, air in a room

Radiation Convection

Conduction

CONDUCTION: • The transfer of heat from one particle of

matter to another by direct particle to particle contact.

– Conduction occurs primarily in solids because the particles are tightly packed together.

– The particles themselves DO NOT change positions.

• Can you think of an example of conduction?

Conduction

If you have ever left a silver spoon in very hot soup, you will notice that the whole spoon gets hot. Thermal energy is transferred from the hot end of the spoon through the entire length of the spoon. This is called conduction. • Particles often collide with each other. When this

happens, energy is transferred from the faster (hotter) moving particle to the slower (cooler) moving particle. This makes the slower moving particles increase in speed.

• When molecules in a substance are made to move faster, they get warmer. The warmer an object gets, the more kinetic energy and therefore, thermal energy it contains.

From: https://www.oakland.k12.mi.us/Portals/0/Learning/kmtphasechanges.pdf

Conduction

• In solids (especially metals), electrons in atoms collide with each other inside the object being heated. • Good conductors of heat are metals with loose

electrons – silver, copper, iron, etc. • Poor conductors are called insulators. These

don’t have loose electrons – wool, wood, paper, Styrofoam, etc.

• Air is a poor conductor of heat, so things with air spaces in them are sometimes used as insulators.

From: https://www.oakland.k12.mi.us/Portals/0/Learning/kmtphasechanges.pdf

Conduction

• The rate at which the kinetic or thermal energy is transferred from one particle to another depends on the separation of the particles and their freedom to move. • In a gas, the particles are allowed to move freely, but

their separation distance is great, so heat or energy transfer is slow.

• In a liquid, the heat transfer by conduction is faster because the particles are closer together.

• In a solid, the molecules are constrained into a specific location within the material, which can make for quick conduction. Although the particles are closer together than in liquids, the constraints in some materials actually prevent the transfer of heat energy. A good example of that is in wood. From: https://www.oakland.k12.mi.

us/Portals/0/Learning/kmtphasechanges.pdf

Conduction

Brainstorming: What are other examples of conduction?

Application: Describe the process of conduction when you place a hot spoon into a bowl of ice cream.

Convection

Convection: the transfer of thermal energy (heat) through the bulk movement of matter.

– Convection occurs in FLUIDS (liquids and gases).

– Convection produces CURRENTS in both gases and liquids.

– Thermal Energy heat is carried by the particles as they move from one location to another.

Convection

Example: Heating water:a. When the water at the bottom of the pot (nearest

the burner) is heated, the particles absorb energy by conduction as they touch the hot pot.

b. The water particles vibrate more rapidly.c. The particles also move farther apart and the hot

water becomes less dense than the surrounding cool water.

d. This causes the heated (hot) water to rise.e. The surrounding denser cooler water is forced

downward near the burner by the rising hot water. f. This process continues to repeat.g. This FLOW creates a circular motion known as a

convection current.Application: How do convection currents form in a room when the heater is turned on?

Convection

1.The warm air from the heater vent will rise. Why?

– The warm air is less dense than the surrounding cooler air.

2. The cool air is pushed down by the rising warm air.

What is the best location for a heat vent in a room and why? Near the

ceiling or the floor?Floor: Because the warmair will rise to the ceiling.

Convection

Convection currents occur in the environment as well. They produce:

– Global winds that contribute to Earth’s weather.

– Ocean and lake currents– Currents in the mantle that move

tectonic plates

Convection

Brainstorming: On a hot summer day the breeze near the beach blows toward the water. However, later in the day the breeze reverses direction and blows toward land and will get increasingly stronger. Why?

Convection

Answer:In the morning the water may be warmer than the sand causing the air over the water to rise.

In the afternoon, the sand has become much hotter than the water and the air above it rises. The air over the water rushes in to fill its void causing a wind.

Radiation

• Radiation: the transfer of (thermal) energy by electromagnetic waves.

– Radiation does not require matter to transfer thermal energy. • All the sun’s energy that reaches Earth

travels through millions of kilometers of empty space (a vacuum).

– All matter can radiate energy.• You feel the radiation of thermal energy

from a bonfire, a heat lamp and a light bulb. You don’t need to touch it!

Radiation

• Other examples of the transfer of heat by Radiation:

a. Charcoal grill.b. Hot tin roof.c. Burner on a stove top.d. ?e. ?

Radiation

Key Point: For radiation to be felt as heat it must first be absorbed by a material.

Example: Why do blue jeans feel hotter in the sun than a yellow shirt, even though they are both exposed to the same amount of sunlight?

– The blue jean fabric absorbs more radiant energy from the sun than the yellow shirt because of its dark color.

Conduction, Convection & Radiation

Practice

1. What happens when you put ice in a warm soft drink? (Describe what kind of heat transfer is happening, and how the energy is moving)

– The heat energy moves from the soft drink into the ice by conduction (particle to particle contact) causing the ice to melt.

2. In a swimming pool warm water is pumped into the bottom of the pool to warm it. What kind of heat transfer is happening and how is the energy moving?

– Convection – the warm water has faster moving molecules, that move farther apart making it less dense, and causing it to rise.

3. Outside in summer, my shirt that is black feels hotter than my friends shirt that is white. Why?

- Radiation (black absorbs more sunlight than white)Heat and metal ball

Section 3- Pressure and Gas Laws

• Key Ideas– What causes pressure?– What are some properties of gases?– How can you predict the effects of pressure,

temperature, and volume changes on gases?• Vocab

– Pressure– Boyle’s law– Charles’ law

Pressure

• What is pressure?– The amount of force exerted over a given area– Pressure = Force / Area, P=F/A– Measured in the SI unit pascal– Fluids (like liquids or gases) exert pressure

evenly in all directions• Example: pumping up a bike tire• What do you think is happening with the

molecules when you add air?

Properties of Gases

• Gases expand to fill their containers• They spread out easily and mix with one

another• They have low densities and are

compressible• Unlike solids and liquids, gases are mostly

empty space• Gases exert pressure on their containers,

through collisions

Segment 1 Questions

• What do you think pressure is?

• Use the video to answer the following questions:– What causes pressure?– What causes higher pressure?

• Video Segment 1

Segment 2 Questions

• Use the video to answer the following questions:– Why does the balloon deflate?– Draw the balloon and indicate the pressure differences.– Why does a balloon stay blown up?– What do you think would happen if we put a balloon in the

hot sun? Why?

• Video Segment 2

Segment 3 Questions

• Use the video to answer the following questions:– Describe how pressure works, using air molecules as

an example.

• Video Segment 3

Segment 4 and 5 Questions

• Use the video to answer the following questions:– Why do you think the marshmallow peeps expand when air

is sucked out?– Why do they get smaller when air is put back in?– What’s happening with the regular marshmallows?

• Growing and Shrinking Marshmallows_Steve Spangler

• Marshmallow Masher_Steve Spangler

Gas Laws• How do you measure the volume of a gas?

– The volume of a gas is the same as its container• Gases behave differently than liquids and solids. The gas

laws mathematically describe how the behavior of gases is affected by pressure, volume and temperature.

• Gas laws help us understand and predict the behavior of gases in specific situations.

• Ideal Gas Law: P1V1 = P2V2

T1 T2• General law that describes how gases will behave when

one variable is held constant. More specific laws are Boyle’s Law, Gay-Lussac’s Law, and Charles’s Law.

Boyle’s Law (constant Temp)• What is Boyle’s Law?

– PV=k (pressure times the volume is a constant, for a given mass in a closed system, as long as the temperature is constant)

– To compare the same substance under two sets of conditions, we use the formula:

– Pressure1 * Volume1=Pressure2*Volume2 or P1V1=P2V2• For a fixed amount of gas at a constant temperature, the volume

of a gas increases as the gas’s pressure decreases. Likewise, the volume of a gas decreases as the pressure increases.

• Volume and pressure are inversely proportional• Boyle's Law• Write Boyle’s law in two “If X happens, then Y happens” statements. • What two conditions have to be true to make this happen?

– Constant mass– Constant temperature

Boyle’s Law Practice Problem• The gas in a balloon has a volume of 7.5L at 100.0kPa. In the

atmosphere, the gas expands to a volume of 11L. Assuming a constant temperature, what is the final pressure in the balloon?

• Given: V1=7.5L Unknown: P2= ??? P1=100.0kPa V2=11L• Write equation and solve for P2.

• Equation: P1V1=P2V2

• P2= P1V1 / V2• P2= (100.0kPa)(7.5L) / 11L• P2= 68kPa

• You try: If the pressure exerted on a 300 mL sample of hydrogen gas at constant temperature is increased from .500kPa to .750kPa, what will be the final volume of the sample?

Gay-Lussac’s Law (constant volume)

• The pressure of a gas increases as the temperature increases, if the volume of the gas does not change. The pressure decreases as the temperature decreases.– Pressure and temperature are directly proportional.

• Example: The tire pressure of your bike is lower in winter than it is in summer. This is because as the temperature outside decreases, so does the pressure in your tire…and vice versa. No new air molecules are added.

Charles’ Law (constant pressure)

• For a fixed amount of gas at a constant pressure, the volume of the gas increases as the gas’s temperature increases. Likewise, the volume of the gas decreases as the gas’s temperature decreases.– Volume and temperature are directly proportional

• Example: an inflated balloon will pop when it gets too hot, or will shrink when it gets too cold.

Avogadro's Law

• Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules.

Practice1. Which law does this

graph show?2. What are four

properties of gases?3. Which law does this

graph show?4. Does this graph show

an indirect or direct relationship?

5. Give an example for each ideal gas law.

Review and Study for Test!!