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Heat. Lab 31 Terms. Δ (delta) means change Subtract FINAL – INITIAL. Temperature = average kinetic energy of particles in a substance Measured with a thermometer. Q means HEAT measured in calories or Joules ΔQ means change in heat. HEAT

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Heat

Lab 31 Terms
• Δ (delta) means change
• Subtract FINAL – INITIAL
• Temperature = average kinetic energy of particles in a substance
• Measured with a thermometer
Q means HEAT

measured in calories or Joules

• ΔQ means change in heat.
• HEAT

The flow of thermal energy from HIGH to LOW temperature

Must be calculated

calorie = amount of heat required to raise the temperature of 1 g of water 1oC
• 1 calorie = 4.18 Joules
Calorimeter

Styrofoam cup calorimeter

an insulated container where a reaction can be performed and heat can be calculated

http://www.chem.purdue.edu/gchelp/howtosolveit/Thermodynamics/ThermoArt/Calorimeter.JPG

Flip page over to II. Heat EquationΔQ = m · c · ΔT

Heat = mass x heat capacity x change in temp

cal = g X X ºC

c for water = 1

density of H2O = 1 g/ml

• Find by taking T2 – T1

m

T1

T2

?

1

Try this:

100 ml of water warms from 10 ºC to 30 ºC. What is the heat gained?

m =

ΔT =

c =

ΔQ = m · c · ΔT

ΔQ = 100g · 1 · (20 ºC)

ΔQ = 2000 cal

100 g

30oC – 10oC = 20oC

m

T1

T2

?

Lab 31 Pre Lab Questions

If 10.00 g of water is changed from 70ºC to 85ºC. What is the ΔQ (change in heat)?

ΔQ = m · c · ΔT

ΔQ = 10g · 1 · (85 ºC - 70 ºC)

ΔQ = 150 cal

Lab 31 Pre Lab Questions

300 calories of heat is added to 100 ml of water at 20 ºC.

• What is the mass of water?

100g

• What is the ΔT of the water?
• What would the final temperature be?

23o C

ΔQ = m · c · ΔT300 cal = 100g · 1 · ΔT

ΔT = 3o C

m = ?

T2

∆Q

T1

1

cal

g

Lab 31 Pre Lab Questions

• What mass of water is in a calorimeter if it takes 1500 calories to heat it from 10 ºC to 65 ºC?

DQ = m c DT

1500 cal = m · 1 · (65 ºC - 10 ºC)

m = 27.27 g

cal

g

http://www.skthew.com/upload/image/time_ice_melting.jpg

Heat of Fusion

heat needed to melt 1 g of a solid.

Heat of Fusion =

For ice,

Heat of Fusion = 80

Lab 32 Terms

Law of Conservation of Energy =

Energy is neither created nor destroyed…Only Transferred.

Heat Lost = Heat Gained

http://www2.uni-siegen.de/~pci/versuche/pics/exo4.jpg

http://www.photospin.com/content/photos/thumb/PS012046.jpg

• Exothermic =

a reaction that releases heat…Feels HOT!

Temp Rises

• Endothermic =

a reaction that absorbs heat…Feels COOL!

Temp Decreases

65

35.1

cal

cal

g

g

Heat of Crystallization

Heat of Crystallization

Heat released as 1 g of a substance crystallizes.

For wax =

For napthalene =

Lab 33: Specific Heat Capacity
• Symbol: c
• heat needed to raise 1 g of substance 1oC
• Units:
• cwater = 1
• cAl = 0.21
• cCu = 0.09
• cFe = 0.11
Lab 34
• “Error of the Air”

assuming room temp is about 20 ºC by starting our experiments at 10 ºC and finishing at 30 ºC we can limit the error from heat gained from the room or lost to the room.

finish

30oC

20oC

10oC

start

33,000

7,000

Joules

cal

g

g

Heat of Combustion

Heat of Combustion

Heat released as 1 g of a substance burns.

For candle =

For nut =

Remember, 1 cal = 4.18 J

Cooling Curve

Heat of fusion

Heat of crystallization

Heat of combustion

DQ = mcDT

g

g  l

DQ = mcDT

temperature

l

l s

DQ = mcDT

s

time