**Specific Heat Capacity**

Heat Capacity

The amount of heat energy required to raise the temperature of a certain material by 1˚C

How much energy must be transferred as heat to 420 kg of water in a bathtub in order to raise the water's temperature from 25℃ to 37℃?

What mass of water is required to absorb 4.7 x 10 J of energy from a car engine while the temperature increases from 298 K to 355 K?

A steel bolt gives up 1124 J of energy as its temperature drops 25 K. If the bolt's mass is 0.093 kg, what is its specific heat capacity?

**Review!**

Warm-up (Tuesday, Feb. 11)

You have

a 50g piece of aluminum (at room temperature)

a beaker half-full of water (at room temperature) that you also measure as 50g

You put both of these objects on the same hot plate. 5 minutes later, which object will feel hotter to your hand? Explain.

Directions: 1. Pick up a handout and a calculator;

2. Copy the warm-up question to your journal and answer in complete sentences.

How much energy must be added to a bowl of

125 popcorn kernels

in order for them to reach a popping temperature of

175℃

?

Assume that their initial temperature is

21℃

, that the specific heat capacity of popcorn is

1650 J/(kg.℃)

, and that each kernel has a mass of

0.105g

The initial temperature o 0.150 kg of ethanol was 22℃. What will be the final temperature of the ethanol if 3240 J was needed to raise the temperature of the ethanol?

Specific heat capacity of ethanol is 2440 J/(kg.℃)

Specific Heat Capacity

Demonstration of the Warm-up Activity

Exit Quiz!

216 J of heat energy is required to raise the temperature of aluminum from 15℃ to 35℃. Calculate the mass of aluminum.

Specific heat capacity of aluminum is 900 J/(kg.℃)

Some things

heat up

or

cool down

faster than others

Sand heats up and cools down faster than water

Review: Heat vs. Temperature

Heat:

flow of energy from hotter objects to cooler objects

Temperature:

a measure of the average kinetic energy of the molecules of an object

Post-demo questions:

Record the initial and final temperatures of the aluminum cube and the water.

Do you think the objects absorbed different amounts of heat despite being on the same hot plate?

Introduction

You can think of heat capacity as a measure of the heat energy something can hold

UNITS

for heat capacity:

J / ℃

Specific Heat Capacity Formulas

Q

= heat energy transferred ( J)

m

= mass (kg)

c

= specific heat constant [ J/(kg.℃)]

∆T

= change in temperature (℃ or K)

for specific heat capacity:

What is the sign of

∆T

when heat is

transferred

to the object?

What is the sign of

∆T

when heat is

removed from the object?

When

Q

is positive,

∆T

is positive,

and when

Q

is negative,

∆T

is negative!

J /(kg.℃)

The amount of heat energy required to raise the temperature of 1 kg of a certain material by 1℃

**Problem Solving!**

Concept Question:

Ethyl alcohol has about one-half of the specific heat capacity of water. If equal masses of alcohol and water in separate beakers at the same initial temperature are supplied with the same amount of energy, which will have the higher final temperature?

a

calorimeter

is used to help measure the specific heat of a substance

5

Student Practice!

Don't forget to convert g to kg!

Heat capacity

is the amount of heat energy required to raise the temperature of a certain material by 1˚C

Specific heat capacity

is the amount of heat energy required to raise the temperature of 1 kg of a certain material by 1℃

A

calorimeter

is used to help measure the specific heat of a substance

UNITS

mass of aluminum = _________

specific heat capacity of aluminum = 900 J/(kg.℃)

initial temperature of aluminum = _________

final temperature of aluminum = __________

mass of water = _________

specific heat capacity of water = 4186 J/(kg.℃)

initial temperature of water = _________

final temperature of water = __________

Applying the formula: