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Monday and Tuesday April 16 and 17. Chapter 10: Thermodynamics. What is energy? Is there a difference between heat and temperature?. Heat Energy flow caused by a temperature difference Measured in J or cal 1 cal = 4.184 J. Temperature Measure of random motion of a substance

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Monday and Tuesday April 16 and 17

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## Chapter 10:Thermodynamics

What is energy?

Is there a difference between heat and temperature?

Heat

Energy flow caused by a temperature difference

Measured in J or cal

1 cal = 4.184 J

Temperature

Measure of random motion of a substance

Measured in ̊C, ̊F, or K

### Calculations

• Convert temperature

• Change in temperature

• Convert to grams of a substance

• Q=SM∆T

### Converting T ( ̊F to ̊C)

Fahrenheit to Celsius

T ( ̊C) = ( T(°F) – 32) x (5/9)

Ex: Convert 65 ̊F to ̊C

T ( ̊C) = ( T(°F) – 32) x (5/9)

T ( ̊C) = ( 65 °F – 32) x (5/9)

T ( ̊C) = 18. ̊C

### Change in T (∆T)

∆T = T final – T initial

Ex: If a cup of boiling water is left on the counter until it comes to room temperature (20 ̊C), what is the change in temperature?

∆T = T final – T initial

∆T = 20 ̊C – 100 ̊C

∆T = -80 ̊C

### Convert to grams (from mol)

Convert 6.00 mol of H2O to grams.

108. g H20

### Q = SM∆T

Q = Energy (heat) required in Joules

S = specific heat capacity in J/g̊C

M = mass of the sample in grams

∆T = change in temperature in ̊C

Specific Heat Capacity

The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius.

### Heat transfer

How can people walk on hot coals?

Specific Heat Capacity

The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius.

### Q = SM∆T

How much energy is needed to warm 7.40 g of water from 17.0 ̊C to 35.0 ̊C?

Q = want

S = 4.184 J/g̊C (from table)

M = 7.40 g

∆T = 35.0 ̊C – 17.0 ̊C= 18.0 ̊C

Homework:

Thermo WS 1

10.2 (pg 291 – 292)

10.5 (pg 294 – 300)

Practice Problems

Pg 318 - 320 # 6-10, 22-28, 49-58

Rewrites are due Friday, 4/20

Extra credit assignment due 5/11

### Warm UP

How much energy is needed to warm 3.60 g of lead from 17.0 ̊C to 35.0 ̊C?

Q = want

S = 0.128 J/g̊C (from table)

M = 3.60 g

∆T = 35.0 ̊C – 17.0 ̊C= 18.0 ̊C

### Practice Problem

How much energy is introduced in to 1.0 kg of ice at -20.0°C, to turn it into steam at 110.0°C?

Q = want

S = 2.03 J/g̊C (from table)

M = 1.0 x 103 g

∆T = 110.0 ̊C – -20.0 ̊C= 130.0 ̊C

### Calorimeter

Calorimeter is a heat measuring device.

The calorimeter is generally used to measure the amount of heat energy transferred during a reaction.

Using this information, one can calculate the specific heat of a substance or other heat related information.

Stirrer

Thermometer

Water

Metal pieces

Insulated container

### Calorimeter

A closed system in which energy is maintained.

-(Q 1) = Q 2

### Calorimeter

If a 30.0 g block of iron is put into the calorimeter and -9.87 J of energy is released, how much energy does the water take on?

### Practice Problems

A sample of aluminum (0.895 J/g °C )at 75.0°C was placed in a calorimeter containing 25.0 grams of water at 20.0°C. The temperature stopped changing at 29.4°C. What is the mass of the sample?

-(Q 1) = Q 2

-(SmetalMmetal∆Tmetal )= SwaterMwater∆Twater

### Practice Problems

A 4.57 g sample of metal is heated to 57.8 ̊C and placed in 150. mL of water that is at 20.0 ̊C. The temperature of the water increases to 40.0 ̊C. What is the specific heat capacity of the metal?

-(Q 1) = Q 2

-(SmetalMmetal∆Tmetal )= SwaterMwater∆Twater

### Practice Problems

A 8.13 g sample of iron is heated to 45.4 ̊C and placed in 400. mL of water that is at 23.0 ̊C. What will the final temperature?

-(Q 1) = Q 2

-(SmetalMmetal∆Tmetal )= SwaterMwater∆Twater

### Practice Problems

A 7.01 kg sample of iron is heated to 69.4 ̊C and placed in 6.71 L of water. The final temperature of the water is 39.8 ̊C. What is the initial temperature of the water?

-(Q 1) = Q 2

-(SmetalMmetal∆Tmetal )= SwaterMwater∆Twater

### Homework and Reminders

Homework:

Thermo WS 2

Reminders:

Rewrites are due FRIDAY, 4/20

Extra credit due 5/11

### REWRITES DUE

If you rewrote your Lab 3.21 for proficiency, turn in the highlighted rewrite and the original paper to the turn in bin.

### Warm Up

If 150.0 grams of iron at 95.0 °C, is placed in an insulated container containing 500.0 mL of water at 25.0 °C, and both are allowed to come to the same temperature, what will that final temperature be?

### Quiz Time

Clear desk except a pencil and calculator

### Thermodynamics Lab

Purpose: Determine the specific heat capacity of an unknown metal and identify the metal.

Complete the prelab

assignment

BEFORE class.

Dress appropriately

for lab

### Notes for the lab

• Don’t poke the thermometer through the cups

• Put metal in water and cover as quickly as possible

### Homework and Reminders

Homework:

Thermo WS 3

Thermo prelab

Reminders:

Rewrites are due FRIDAY, 4/20

No exceptions

### Warm Up

In a calorimeter 187 mL of 18.9 ̊C water is mixed with a 4.32 g block of 92.0 ̊F granite. What will the final temperature be?

### Lab Time

• Don’t poke the thermometer through the cups

• Put metal in water and cover as quickly as possible

### Done in lab?

◦Work on write up

Title, purpose, data tables, calculations, analysis

If you finish the lab turn it in to the turn in bin, if not it is your homework

◦Work on practice test if you finish the lab

### Reminders

Homework:

Thermo Lab Write Up

GeneralReminders:

Extra Credit due 5/11

Thermodynamics Test 4/25 and 4/26