Unit 3 Heat & Temperature

1. Unit 3 Heat & Temperature

2. Unit 3 Topic 3- Particle Model

3. 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!

4. 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? 000 1 000 000 000 000 700 One thousand seven hundred million millionmillion!

5. Particle Model • Particle Model has 3 main ideas … • All substances are made of tiny particles too small to be seen • The particles are always in motion – vibrating, rotating (liquids/gasses) and moving around • The particles have space between them

6. 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!

8. 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

9. 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 elementtransfers heat (thermalenergy) to the pot • You get a lovely bowl ofAlphaghetti!

10. 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?

11. 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 …

12. Thermal Energy

13. 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)

14. 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!

15. 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

16. What is Energy?

17. 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

18. 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

19. Unit 3 Topic 4- Expansion & Contraction

20. 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

21. Expansion & Contraction GOOOOOOOOOAL!

22. Expansion & Contraction Denied!!!

23. 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

24. 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?

25. 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?

26. 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

27. Heat Capacity v Specific Heat Capacity

28. Heat Capacity v Specific Heat Capacity • So how fast does an object heat up?

29. 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)

30. Changing of States There is a change of state where it breaks the natural progression … hops from solid directly to liquid This is known as sublimation • 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)

31. 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!

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

33. 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)