Temper-Temper-atureature

Specific Specific HeatHeat

LabLab HeatHeat PotpourriPotpourri

100 100 100 100 100

200 200 200 200 200

300 300 300 300 300

400 400 400 400 400

500 500 500 500 500

Final

100 Temperature

Convert a temperature of -233.3 C to Kelvins

Answer

Temp 100

K =C + 273.15

K = -233.3 + 273 = 39.7

Answer = 39.7K

200 Temperature

Convert a temperature of -15.8C to F

Answer

Temp 200

F = 1.8 C + 32

F = 1.8 (-15.8) + 32 = 3.56

Answer = 3.6 F

300 Temperature

Convert a temperature of 105F to Celsius

Answer

Temp 300

C = (F – 32) / 1.8

C = (105 – 32) / 1.8 = 40.55555 C

Answer = 41 C

400 Temperature

Give the definition of temperature.

Answer

Temperature 400 Answer

• Temperature is the average kinetic energy of all particles in a sample.

500 Temperature

Explain what is meant by absolute zero, what is theorized to occur at this temperature, what are the advantages of the Kelvin scale.

Answer

Temperature 500 Answer

• Absolute zero is the lowest theoretical temperature.

• At absolute zero, atomic motion and volume approach zero.

• The Kelvin scale is used in scientific calculations because it has no negative numbers. Its T is also equal to T in Celsius.

100 Specific Heat

Define specific heat and give the SI units for specific heat.

Answer

Specific Heat 100 Answer

• Specific heat is the amount of energy required to raise the temperature of 1 g of a substance by 1oC.

• SI Units are: Joules or Joules

g oC g K

Specific Heat 200 Answer

• Gold will heat to 200 oC first because it has the lowest Cp and therefore requires less energy to increase its temperature.

200 Specific Heat

The Cp values of Gold, Mercury and Lead are 0.129, 0.14, and 0.160 J/g C respectively. Equal masses of the three metals are placed in an oven at a temperature of 200. C. Which metal will reach 200. C first? Explain.

Answer

300 Specific Heat

Determine the mass of a substance if it has a Cp of 0.385 J/g C and it absorbs 345 calories when heated

from 23.5 C to 99.9 C.

Answer

Specific Heat 300

• First convert q to Joules

• ?J = 345 cal x 4.184J = 1443.5 J cal

• Mass = q = 1443.5 JCp x T (0.385J/goC) (99.9-

23.5oC)

Answer: Mass = 49.1 g

400 Specific Heat

Calculate the specific heat of a substance if 44.4g of it releases

7850. cal when cooling from 99.0 C to 23.5 C.

Report answer in SI unitsAnswer

Specific Heat 400 Answer

Cp = q = -7850.cal

mass x T (44.4 g) (23.5-99.0oC)

= 2.3417 cal x 4.184 J = 9.80 J

calg C g C

500 Specific HeatCalculate the specific heat of a metal, in SI units, given the following data for a metal

that is heated in a hot water bath then poured into a calorimeter containing 35.00 g

of water.Mass of metal =12.55 gTemp of water bath = 98.7 C

Ti of water in calorimeter = 26.5 CTf of water in calorimeter = 32.8 C

Answer

Sp Heat 500 Answer

qH2O = 4.184 J/gC x 35.00g x (32.8C -26.5C ) = 922.572J

-q H2O = q metal

Cp = -922.572 J = 1.115

(12.55g) x (32.8 C -98.7 C )

Answer = 1.1 J/g C

100 Lab

Apart from type of material, name the 2 criteria that determine the amount of heat energy in a material.

Answer

Lab 100 Answer

•Mass

•Temperature

200 Lab

• Explain why a candle goes out when a jar is placed over it.

Answer

Lab 200

• CO2 produced from combustion extinguishes the flame by pushing the oxygen away from the wick.

300 Lab

The Cp of silver is 0.0564 cal/goC. What is this

specific heat in J/goC?

Answer

Lab 300 Answer

• ? J = 0.0564 cal x 4.184 J = goC goC 1 cal

Answer = 0.236 J/g oC

400 LabWhat is visual evidence that a

gas is being produced in a chemical change?

Describe a lab test that would determine if the gas produced

is O2 or CO2.Answer

Lab 400 AnswerFizzing and bubbling

indicates production of a gas.

A glowing wood splint inserted into the bubbles will relight if the gas is O2 and will extinguish if the gas is CO2.

500 LabExplain why the tallest candle goes out first when a jar is placed over different sized burning candles. Include density changes in your explanation.Answer

Lab 500

The CO2 produced by combustion is hot, so it rises (it is less dense than surrounding cooler air)

The CO2 hits the top of the jar, cools, becomes more dense and descends.

As the CO2 sinks it successively extinguishes candles from top of cylinder to bottom.

100 Heat

What happens to heat in an exothermic change?

Describe a chemical change that is exothermic.

Answer

Heat 100 Answer

• An exothermic change releasesreleases heat energy.

• Combustion is an exothermic chemical change. Zn + HCl to produce H2 gas, Zn pyrotechnics, KClO3 + sugar are also exothermic chemical changes.

200 Heat

Define the term “Heat”.

Answer

Heat 200 Answer

• Heat is energy that is transferred between samples due to a difference in temperatures.

300 Heat

Define “calorie”

Answer

Heat 300 Answer

• A calorie is the amount of heat required to raise the temperature of 1 g of water by 1 degree Celsius

400 Heat

Six boneless chicken tenders (deep fried) contain 1 448 000 joules of energy. Convert to

calories and to Food Calories.

Answer

Heat 400

? cal = 1 448 000 Joules x 1 cal = 1 4.184 Joules

Answer = 3.461 x 105 cal

? Food Cal = 3.461 x 105 cal x 1 Food Cal = 346.1 Food Cal1000 cal

500 Heat Determine the heat absorbed by

15.00 g of pure iron if it is heated from 25.0 C to 255.5 C.

The Cp of Fe is 0.444J/g C.

Answer

Heat 500

Q = sp ht x mass x T

Q = 0.444 J/g C x 15.00 g x (255.5 C -25.0 C )

Q = 1540 J

100 Potpourri

Define BTU

Answer

Potpourri 100

BTU: The amount of heat required to raise the

temperature of one pound of water by 1oF.

200 Potpourri

Name the following phase changes and tell whether they are

exothermic or endothermic

solid to gasliquid to solidgas to liquid

Answers

Answers for Potpourri 200

solid to gas– sublimation, endo

liquid to solid – freezing, exo

gas to liquid – condensing, exo

300 Potpourri

Explain, in terms of heat, phase change and molecular motion,

why sweating cools you off.

Answer

Potpourri 300

• Sweat evaporates from your skin.• Evaporation is an endothermic process because

the molecules must gain energy to speed up and break free of their attraction to each other in order to go from liquid phase to gas phase.

• The energy that the molecules absorb is taken from your skin.

• When the molecules evaporate to the gas phase and leave your skin surface, they take this absorbed energy away. Your skin has lost energy thus is cooler.

400 Potpourri10. 00 g of water must absorb 3138 J of energy as it heats from 25oC to 100oC. 10. 00 g of water needs 22,600 J of energy to go from liquid to gas at 100oC.

Explain.

Answer

Potpourri 400• A phase change from liquid to gas

requires a much greater amount of energy than a simple temperature change.

• As temp increases yet phase remains same, molecules are speeding up

• As water goes from a liquid to a gas, its molecules must have enough energy to become very spread apart, overcoming the attractions between molecules

500 Potpourri

Give 3 properties of hydrogen.

Explain why it was used in the Hindenburg despite obvious

hazards.

Answer

Potpourri 500 Answer

• Colorless• Odorless• Gas at room temperature• Flammable• Formed from reaction of Zn and

hydrochloric acid• The Americans would not sell He to

Germans because of Hitler’s politics

Final Jeopardy

Convert a ΔT of 10.0oF to a

ΔT in oC.

Answer

Final Jeopardy Answer

ΔT of 10.0oF ÷ 1.8 = ΔT of 5.6oC