1. AOHS/Conceptual Physics Heat 1b: Specific Heat Capacity

2. Specific Heat Capacity Hot Pocket Physics Which part of a hot pocket is the hottest?

3. Specific Heat Capacity Hot Pocket Physics Which part of a hot pocket is the hottest? – The entire ‘item’ is the same temperature!! – The entire pocket was in the same oven for the same amount of time. Which appears to hold more thermal energy the crust or the ‘guts’?

4. Specific Heat Capacity Hot Pocket Physics Which appears to hold more thermal energy the crust or the ‘guts’? – The ‘guts’ seem to hold a WHOLE LOT more thermal energy than the crust!! Some materials simply hold more thermal energy than others!!

5. Specific Heat Capacity Consider water, metal and air. – Order each material according to its ability to store thermal energy (greatest first). What kinds of materials hold thermal energy well? animals.desktopnexus.com scottishmist.com lcv.org Air Metal Water

6. Specific Heat Capacity Consider water, metal and air. – Order each material according to its ability to store thermal energy (greatest first). What kinds of materials hold thermal energy well? Water Metal Air animals.desktopnexus.com scottishmist.com lcv.org Air Metal Water

7. Specific Heat Capacity – Order each material according to its ability to lose thermal energy (greatest first). Metal Air Water animals.desktopnexus.comscottishmist.com lcv.org Air Metal Water

8. At-Home Demo Aluminum foil – Lightly ball up a piece of aluminum foil and stick in the oven (200 °F) for a few minutes. – Reach in and pick the piece of foil out of the oven. Be careful to touch ONLY the foil!! – Record your observations: The oven was definitely hot; evident upon opening the door. After a bit of time the foil reached thermal equilibrium with the oven at 200 °F. The foil, although quite warm, was easily picked up without oven mits. While the foil was not cold or even cool it did not seem as hot as one would think coming out of a hot oven. sz-wholesale.com

9. At-Home Demo Which can you withstand? – 120 degree sauna or – 120 degree hot tub? iammyownsweatshop.org rewls.com

10. At-Home Demo Which can you withstand? – 120 degree sauna or 120 degree hot tub? I could withstand the sauna at 120 °F but absolutely NOT the water at the same temperature! Although the same temperature both materials do NOT seem to have the same amount of thermal energy! iammyownsweatshop.org rewls.com

11. Specific Heat Capacity The ability of a material to store thermal energy is defined by the materials Specific Heat Capacity (c). – Specific heat capacity (c) how much thermal energy a substance can transfer through releasing or absorbing per unit of mass. Consider this idea applied to the following situation: – How long does it take these 3 substances to increase in temp 80 °C? 1 kg of water – 5 minutes 1 kg of alcohol – 2.9 minutes 1 kg of mercury – 10 seconds!

12. Specific Heat Capacity If all substances were heated to the same temperature, just call it 80 °C, which substance … … is the ‘hottest’? … holds the most thermal energy? … holds the least thermal energy? 1 kg water 5 min 1 kg alcohol 2.9 min 1 kg mercury 10 sec

13. Specific Heat Capacity If all substances were heated to the same temperature, just call it 80 °C, which substance … … is the ‘hottest’? – All the same temperature, 80 °C … holds the most thermal energy? – WATER holds the most thermal energy; it takes the longest to heat up to 80 °C … holds the least thermal energy? – MERCURY holds the least thermal energy; it takes the least amount of time to heat up to 80 °C 1 kg water 5 min 1 kg alcohol 2.9 min 1 kg mercury 10 sec

14. Specific Heat Capacity Specific heat capacity (c) can be thought of as ‘thermal inertia’ – Inertia recall is a “tendency to resist change” – A substances specific heat capacity is therefore descriptive of the amount of energy required to raise the temperature of 1 gram of substance 1 degree Celsius. Substances with high specific heat capacity values require more energy than do substances with low c-values to raise 1 gram of substance 1 degree Celsius. Consider a mass m of specific heat capacity c experiencing a change in temperature ΔT the quantity of heat ΔQ delivered is then described as…

15. Specific Heat Capacity Again… – ΔQ = quantity of heat required or transferred; measured in JOULES (J) – m = mass; measured in GRAMS (g) – c = specific heat capacity; measured in J/g°C – ΔT = change in temp; measured in CELCIUS (˚C)

16. Specific Heat Capacity Specific heat capacities of some common materials: MaterialJ/g˚C water 4.186 aluminum0.9 clay1.4 copper0.386 lead0.128 olive oil1.97 gold0.23 iron0.448

17. Specific Heat Capacity The specific heat capacity of any substance is determined using a device called a Calorimeter. A calorimeter is an insulated chamber that contains a small amount of water. A heated sample is placed within the chamber and the temperature variance of the water is measured. Knowing the temperature change experienced by the sample and the water and the specific heat capacity of water one can determine the thermal energy transferred to the water ΔQ. The thermal energy gained by the water is equal to the thermal energy lost by the sample. Therefore, ΔQ can be used to determine the specific heat capacity of the sample. vinstan.wikispaces.com

18. Specific Heat Capacity Guided example and practice problems are provided as part of the lesson; not presented here in powerpoint format. vinstan.wikispaces.com

19. Specific Heat Capacity Why is water so special?

20. Specific Heat Capacity Why is water so special? – It has one of the highest specific heat capacities. – It gives up or absorbs large amounts of heat with small changes in temperature