Specific Heat Pre – Lab. Specific Heat Different substances require different amounts of heat to...

Specific Heat

Pre – Lab

Specific Heat

• Different substances require different amounts of heat to change their temperature.

• In general the specific heat of a substance indicates how hard something is to heat up or cool down.

• Scientifically speaking the specific heat is the amount of heat required to change the temperature of 1 gram of a substance by 1ºC.

•Which substance is the hardest to heat up or cool down?

Sample Problem 1• A 70.00g sample of metal is heated to 80.0C and placed in

100.00g of water at 22.0C in a styrofoam cup. The temperature of the water in the cup rises to 26.4C as the metal cools. Determine the specific heat of the metal.

Sample Problem 1• A 70.00g sample of metal is heated to 80.0C and placed in

100.00g of water at 22.0C in a styrofoam cup. The temperature of the water in the cup rises to 26.4C as the metal cools. Determine the specific heat of the metal.

What three things must we determine to find the specific heat?

Look at the units for specific heat

Sample Problem 1• A 70.00g sample of metal is heated to 80.0C and placed in

100.00g of water at 22.0C in a styrofoam cup. The temperature of the water in the cup rises to 26.4C as the metal cools. Determine the specific heat of the metal.

What three things must we determine to find the specific heat?

Look at the units for specific heat

J/g °C

Joules (Energy)

Grams (mass)

°C (temperature change)

Sample Problem 1• A 70.00g sample of metal is heated to 80.0C and placed in

100.00g of water at 22.0C in a styrofoam cup. The temperature of the water in the cup rises to 26.4C as the metal cools. Determine the specific heat of the metal.

• Mass of metal = 70.00g ∆T of metal = 53.6°C• Heat gained by water = (mass of water)(T of water)(Cp of water)

• Heat = (100.00g)(4.4°C)(4.184 J/g C) = 1840.96J = 1800J• Heat gained by the water = Heat lost by the metal

• To find specific heat remember the units: Cp = J/g ·°C

Cop

g

J48.0

Cg

J0.4797441 =

C53.6 70.00g

1800J

T x m

H = metal of C

Sample Problem 2

• Calculate the percent error, of this measurement if the true value for the specific heat of the metal is 0.50 J/g C.

Sample Problem 2

• Calculate the percent error, of this measurement if the true value for the specific heat of the metal is 0.50 J/g C.

x100Value True

Value True - Value alExperiment =error %

Sample Problem 2

• Calculate the percent error, of this measurement if the true value for the specific heat of the metal is 0.50 J/g C.

x100Value True

Value True - Value alExperiment =error %

4.0% 4% =100 x

Cg

J 0.50

Cg

J 0.50 -

Cg

J0.48

Sample Problem 3a• A 45.00g sample of metal is heated to 98.0C and placed in

100.00g of water at 21.0C in a styrofoam cup. The temperature of the water in the cup rises to 24.0C as the metal cools. (a) Determine the specific heat of the metal.

Sample Problem 3a• A 45.00g sample of metal is heated to 98.0C and placed in

100.00g of water at 21.0C in a styrofoam cup. The temperature of the water in the cup rises to 24.0C as the metal cools. (a) Determine the specific heat of the metal.

• Heat gained by water = (mass of water)(T of water)(Cp of water)

• Heat gained by the water = Heat lost by the metal• Heat = (100.00g)(3.0°C)(4.184 J/g C) = 1255.2J = 1300J

Cg J

48.0Cg

J0.4797441 =

C53.6 70.00g1800J

T x mH

= metal of Co

p

Co

p g J

39.0Cg

J0.39039 =

C)74.0( (45.00g1300J

T x mH

= metal of C )

Sample Problem 3b

• Calculate the percent error, of this measurement if the true value for the specific heat of the metal is 0.34 J/g C.

x100Value True

Value True - Value alExperiment =error %

%15%705.14100xCg/J34.0

Cg/J34.0Cg/J39.0

Homework

• Lab Summary for Specific Heat of a Metal