Place the 2 groups of objects below in order from coldest to hottest.

1. Cheese, popsicle, napkin2. Bonfire, napkin, fried egg

What do you think?

So…

• Is the napkin hot or cold?

(Chapter Eleven)

Temperature,

Phases of Matter and

Heat

Back to the hot and cold …

• Using the words “hot” or “cold” can sometimes be confusing…or relative (some of you think the room is too cold…some don’t)

• To reduce confusion, an object should be described by its temperature.

• SUBJECTIVE vs OBJECTIVE

Temperature

• Is a measure of the kinetic energy of the particles in an object.

• The faster the particles move, the higher the temperature

• Temperature is independent of the amount of the substance being measured (a little bit can have the same temperature as a whole bunch)

TemperatureThere are two common

temperature scales. The Celsius scale:

Water freezes at 0 CWater boils at 100 C

(metric)On the Fahrenheit scale:

Water freezes at 32 F Water boils at 212 F.

(English or standard)

The 3rd Temperature Scale (though not so common)

• Kelvin (K) – SI unit – starts at absolute zero

• NO degrees, labelled in “Kelvins”• Fahrenheit (oF) – US unit• Celsius (oC) – metric unit – broken into 100

equal units between freezing and boiling water

Absolute zeroAbsolute zero is -273°C. You cannot have a temperature lower than absolute zero.Think of absolute zero as the temperature at which atoms are “frozen.”

Thermometer

A thermometer is an instrument that measures temperatureThermometers you have likely seen uses colored liquid alcohol to sense temperature- because alcohol stays liquid over a wide range of temperatures.

How does a thermometer work?

• They work due to thermal expansion• As a substance gets hotter, its particles move

faster. The particles do not expand, but they need to spread out…this spreading is called thermal expansion.

• When the thermometer is warmed, the liquid inside expands and rises up in the tube.

Thermal Expansion

1. object is heated up2. particle movement

increases3. particles spread out

Thermal Contraction

1. object cools down2. particle movement

decreases3. Particles stay closer

together.

Converting to KelvinThe Kelvin temperature scale is useful in science because it starts at absolute zero.

To convert from Celsius to Kelvin, you add 273 to the temperature in Celsius

Let’s convert...

• What temperature was it this morning when you got up?

• Let’s convert it to Celcius:

Another temperature conversion…

• Look at the conversion formulas earlier in your notes.

• It is 77 in this room. • What unit would that be in? • Let’s convert that number to the other 2

units.

What temperature really is…

Temperature measures the kinetic energy per atom due to random motion. (how fast the molecules are moving)

What temperature really is…

The back-and-forth jiggling of atoms is caused by thermal energy, which is a kind of kinetic energy- (E an object possesses due to temperature)

BROWNIANMOTION.

Atoms are in constant motion, even in a solid object.

More on temperature (without having to listen to me)!

1. Watch “Brainpop” on Temperature2. Take review quiz on Temp.

Tell your neighbor!

1.) Why can’t there be a temperature lower than

absolute zero?

2.) Explain the scientific meaning of the word

random.

3.) Which is colder, 0 ˚C or 20 ˚F ?

More tomorrow…

What is heat?• Heat is energy of the atom

that is moving.

• Heat flows any time there is a difference in temperature.

• Because your hand has more thermal energy than the chocolate, thermal energy flows from your hand to the chocolate and the chocolate begins to melt.

Soda and Heat

• How does soda get cold in a cooler of ice?

What is Thermal Energy

• Remember, temperature is the measure of particle movement due to temperature )(kinetic energy)…..however, the TOTAL energy in ALL of the particles in a substance is called its thermal energy….

• the more particles there are, the more thermal energy it contains.

What is Temperature again?

Heat, Temperature, and Thermal Energy

• Heat, temperature, and thermal energy are related, but are not the same thing.

• The amount of thermal

energy depends on the temperature but it also depends on the amount of matter you have.

HEAT - TEMPERATURE

and THERMAL ENERGY

Units of heat and thermal energy

• The metric unit for measuring heat is the joule.

• This is the same

joule used to measure all forms of energy, not just heat.

How are calories relatedto heat?

• How can you determine how much “energy” is contained in a substance?

• Use a calorimeter. It uses the amount of heat generated by burning something as a measure of how much energy it contains.

Heat and thermal energy• Thermal energy is often measured in

calories. • One calorie is the amount of energy it

takes to raise the temperature of one milliliter of water by one degree Celsius.

How a calorimeter works:

1. Food to be tested is burned below a container of water.

2. The temperature increase in the water is measured.

3. A calorie is the amount of energy needed to change the temp 1 gram of water by 1oC.

Heat Transfer

There are three ways that heat is transferred:

1.Thermal Conduction2.Convection3.Thermal Radiation

Thermal ConductionHeat conduction is the transfer of heat by the direct contact of particles of matter.

Conduction occurs between two materials at different temperatures when they are touching each other.

Where is the heat energy conducted to and from in this system?

Examples of Conduction

• direct contact

Thermal conductors and insulators

• Materials that conduct heat easily are called thermal conductors and those that conduct heat poorly are called thermal insulators.

Is a down coat a conductor or an insulator?

• Substances that transfer heat easily are called conductors

• The best conductors are metals.

• Substances that do not conduct thermal energy very well are called insulators.

• For years, the plumbing in homes was done in copper piping. Now they are done in PVC. What are some reasons that this change occurred?

Application

Convection• Convection is the transfer

of heat through the motion of matter such as air and water.

• In a container, warmer fluid rises to the top and cooler fluid sinks to the bottom.

• This is called natural convection.

Convection

Convection• Convection is mainly what distributes

heat throughout a room.

Radiation

• Transfer of heat through electromagnetic waves across empty space.

Thermal radiation• Heat from the Sun is

transferred to Earth by thermal radiation.

• The higher the

temperature of an object, the more thermal radiation it emits.

• All the energy the Earth receives from the Sun comes from thermal radiation.

Thermal radiation• Thermal radiation is also

absorbed by objects.

• The amount of thermal radiation absorbed depends on the surface of a material.

• Dark surfaces absorb most of the thermal radiation they receive.

• Silver or mirrored surfaces

reflect thermal radiation

Equilibrium• Thermal equilibrium occurs when two

bodies have the same temperature.

• No heat flows in thermal equilibrium because the temperature is the same in the two materials.

I remember that!1.) What are the three ways heat is transferred?

2.) Heat from the Sun is transferred by _______ _________.

3.) When heat is transferred by two objects touching, it is called _____________.

HEAT TRANSFER VENN DIAGRAM

STATES OF MATTERSolid

Liquid

Gas

AND

?????

The Phases of Matter

Intermolecular forces tend to bring molecules together. Intermolecular forces have to be overcome in order to change phase.

Sing it Baby…. http://www.youtube.com/watch?v=btGu9FWSPtc

Solid

A solid holds its shape and does not flow. The molecules in a solid vibrate in place, but on average, don’t move far from their places

Liquid

A liquid holds its volume, but does not hold its shape—it flows. Liquids flow because the molecules can move around.

GasA gas flows like a liquid, but can also expand or contract to fill a container. A gas does not hold its volume. The molecules in a gas have enough energy to completely break away from each other.

Plasma

• At temperatures greater than 10,000˚C, the atoms start to come apart and become a plasma.

• Atoms are broken apart into separate positive ions and negative electrons

• Conducts electricity and is formed in lightening and inside stars.

I remember that!1.) What are the three phases of matter?

2.) Liquid holds its volume, but does not hold

its ___________ .

3.) The melting point and the freezing

point for water is ___ degrees Celsius.

Phases of Matter

http://www.youtube.com/watch?v=KxtqzApPAfc

9:12

Phases of Matter and Phase Change

• Boiling point• Melting point• Freezing point• Vaporization/evaporation• Condensation• Phase Change Diagram

Boiling Point

The temperature at which a liquid becomes a gas is called the boiling point.

Vaporizaton and Evaporation

• Also known as the boiling point• When liquid turns to vapor (gas)

Melting PointThe melting point is the temperature

at which a substance changes from a solid to a liquid.

Freezing PointThe freezing point is the temperature

at which a substance changes from a liquid to a solid.

CondensationCondensation is the point at which a

substance changes from a gas to a liquid.

Melting and boiling points ofcommon substances

Materials have a wide range of melting and boiling points.

So what?

• So what really is the difference between the boiling point and the condensation point of a substance?

• So what really is the difference between the freezing point and the melting point of a substance?

Phase Change Diagram

DO NOW:Quick Quiz – True/False

1. Heat is the transfer of energy between two objects with different temperatures.

2. Conduction occurs in fluids.3. Convection currents result from

temperature differences in gases and liquids.

4. Radiation is the means by which the energy from the sun is transferred to Earth.