1 / 23

# Heat - PowerPoint PPT Presentation

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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Heat' - ursula

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Heat

• 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

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

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

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

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

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

g

Heat of Fusion

heat needed to melt 1 g of a solid.

Heat of Fusion =

For ice,

Heat of Fusion = 80

Law of Conservation of Energy =

Energy is neither created nor destroyed…Only Transferred.

Heat Lost = Heat Gained

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

Heat is released

Heat

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 =

• Symbol: c

• heat needed to raise 1 g of substance 1oC

• Units:

• cwater = 1

• cAl = 0.21

• cCu = 0.09

• cFe = 0.11

2 L H2O at 50º C

2 L H2O at 90º C

Review:Which is holding more heat?

10 L H2O at 50º C

2 L H2O at 50º C

Examples:Which is holding more heat?

2 kg H2O at 50º C

Examples:Which is holding more heat?

• “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

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

Heat of fusion

Heat of crystallization

Heat of combustion

DQ = mcDT

g

g  l

DQ = mcDT

temperature

l

l s

DQ = mcDT

s

time