Un i t 3H e a t &

Te m p e r a t u r e

Un i t 3Topic 3- Particle

Model

Particle Model• Wave your hand in the air … is it easy?• Imagine waving your hand under water … harder?• Why is that?

• The Particle Model Theory!

Particle Model• So everything is made of tiny, tiny particles. • How tiny are we talking? • *Drop of water on finger* Look at it closely…• How many particles would you guess are holding

it together … holding that single drop?

1 700 000 000 000 000 000

One thousand seven hundred million million million!

Particle Model• Particle Model has 3 main ideas …1) All substances are made of tiny particles too

small to be seen 2) The particles are always in motion – vibrating,

rotating (liquids/gasses) and moving around3) The particles have space between them

Temperature & Particle Model• If the motion of the particles change the

temperature changes• When something is warmed its particles are moving

quicker than normal • When something is cooled its particles are moving

slower than normal • This leads us to the 4th point of the particle model

4) The motion of the particles increases when the temperature increases. The motion of the particles decreases when the temperature decreases!

Energy• Energy– A measure of something’s ability to do work

(i.e.: to cause change)• When something happens scientists are sure that

energy is transferred from one to another

Thermal Energy• Thermal Energy– Energy associated with hot objects

• When something happens scientists are sure that energy is transferred from one to another

• Classic example … stove top!– Element turns on and

heats up– The heated element

transfers heat (thermalenergy) to the pot

– You get a lovely bowl ofAlphaghetti!

Thermal Energy• What happens to your bedroom at night when it is

cold? • What if you turn on a heater in the room? What

happens to the air in the room? • The heat generated by the heater transfers

thermal energy to the air • Bedrooms are typically small so …– What if we used the same small heater in our school

gym? What would you expect to happen?

Thermal Energy• No way José! • The heater would generate the same amount of

thermal energy to the air in the room BUT the room is much larger

• This means it contains more air particles and each particle only gets a tiny share of the available extra (thermal) energy

• So temperature goes up but not very much … in some cases you would not even fee the difference

• So in a visual …

Thermal Energy

Thermal Energy• There is a direct connection between …

Thermal Energy Temperature• Applying heat (heating) something increases the

total energy of all the particles • This average energy of the particles (it’s

temperature) may increase a little or a lot• So essentially the temperature change depends

on the number of particles (i.e.: amount of material you are heating)

Thermal Energy• So what about cooling something off?• If you put an ice cube into a single glass of warm

iced tea what happens?• The ice cube absorbs the thermal energy as it

melts• With less energy

the average motion of the particles in the lemonade slow down

• Temperature drops!

Thermal Energy• So what about cooling something off?• If you put an ice cube into a single glass of warm

iced tea what happens?• The ice cube absorbs the thermal energy as it

melts• With less energy

the average motion of the particles in the lemonade slow down

• Temperature drops!

CV

CV

What is Energy?

Energy … Cont!• Energy is not a substance!– Not weighed, does not take up space, etc …

• So what is it then?• Describes a quality or condition!• Energy is measured in Joules (J)• Energy is …– The ability to do work, move or cause change(s)

• Thermal Energy– Energy associated with hot objects

Energy … Cont!• Law of Conservation of Energy– Energy cannot be created

or destroyed

– It can only be transformed from one type to another or passed from one object to another

Un i t 3Topic 4-

Expansion & Contraction

Expansion & Contraction• So what do we know about heating & cooling?• Heat = faster moving particles• Cold = slower moving particles• But if we are talking about particles … how does

that affect the space they take up?• If something is heated it tends to expand because

the particles are moving faster and further apart• If something is cooled it tends to contract because

the particles are moving slower and closer together

Expansion & ContractionGOOOOOOOOOAL!

Expansion & ContractionDenied!!!

Expansion & Contraction• You can check if this is true by observing pure

substances (i.e.: gold, oxygen, water)• Solid State– Definite shape, volume & cannot be compressed into a

smaller space• Liquid State– Definite size (volume) but no fixed shape (take shape

of container holding them) … not compressible• Gas State– No definite shape or volume … expand to fill all space

in container

Expansion & Contraction• Solids– Let’s examine steel bars (Page 211 – Table 1)– How does heat/cold affect the length of the bar?– Now that is 100cm

• Liquids– Imagine a thermometer changing

temperatures– As it moves up it takes more spaces

(expands) and vice versa – Would all liquids behave the same way?

Expansion & Contraction• So … were you paying attention yesterday when we

calculated how to measure contraction of steels?• Challenge Time!• I am an engineer, who knew,

and I have been tasked with constructing a building that will be 150M wide by 250M tall. The average winter in the area averages out to -25oC.

• What kind of contraction should I anticipate?

Expansion & Contraction• Gasses– Difficult to observe but possible to make observations– Far apart and moving freely– Putting a balloon on the mouth of the beaker and

heating the beaker will eventually fill the balloon up – Why?– The particles warm, excite

(move faster and father apart expand) and take up more space thereby filling the balloon

Heat Capacity v Specific Heat Capacity

Heat Capacity v Specific Heat Capacity

• So how fast does an object heat up?

Heat Capacity

Specific Heat Capacity

Definition

- amount of thermal energy that warms or cools the object by 1 degree Celsius

- amount of thermal energy that warms or cools one gram of a material by one degree Celsius

Describes- a particular object - material the object is

made of

Depends On- mass of the object and material the object is made of

- material the object is made of

Changing of States• What does “changing of states” mean?• When something goes from either solid/liquid/gas

to another form solid/liquid/gas• Water is a great example…– It can melt (solid ice can melt to liquid water)– It can freeze (liquid water to solid ice) – It can become a gas (from liquid water to water vapour

- gas - when it is boiled)

Changing of States• What does “changing of states” mean?• When something goes from either solid/liquid/gas

to another form solid/liquid/gas• Water is a great example…– It can melt (solid ice can melt to liquid water)– It can freeze (liquid water to solid ice) – It can become a gas (from liquid water to water vapour

- gas - when it is boiled)

There is a change of state where it breaks the natural progression … hops from solid directly to liquidThis is known as sublimation

Change of State• Any pure substance can exist in all 3 states– Often easier said than done but it is doable

• Time for a review!• Find a partner • Write “Thermal Energy” & “Temperature” &

“Energy” on a piece of paper and …• … explain to me the difference between them!

Thermal vs. Temperature Review• Simply put, heat is the flow of thermal energy.

• Temperature represents average thermal energy. Heat goes from objects with high temperature to low temperature, not high thermal energy to low thermal energy. (Like diffusion)

• For example, a massive glacier will have more total thermal energy than a small hot nail (simply because it has more molecules); however, its temperature is lower because it has less average thermal energy. Therefore, energy will be transferred from the nail to the glacier...

• Thermal energy is the total internal energy of the system. i.e. how fast the molecules are vibrating

Evaporation• When you sweat you tend to cool off … why?• Enter Particle Model• Imagine a liquid (we will use water) in a jar …

Top = moving fast (enough to escape)

Top = moving fast (enough to escape)