Chapter 5 Thermochemistry - Yolaclassfiles.yolasite.com/resources/Week 1_Part 1...27/12/2011 1...

27/12/2011

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Chapter 5

Week 1

Part 1

Thermochemistry

John D. Bookstaver

St. Charles Community College

Cottleville, MO © 2012 Pearson Education, Inc.

Thermochemistry

© 2012 Pearson Education, Inc.

Energy

• Energy is the ability to do _________ or __________ _______.

– Energy used to cause an object that has mass to _______ is called ____________. (W = ____ x ___)

– Energy used to cause the _____________ of an object to _____ is called _________.

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Thermochemistry


Kinetic Energy

Kinetic energy is energy an object

possesses by virtue of its ___________:

Ek = ________

Thermochemistry

Potential Energy

• Potential energy is energy __________,

for example in a _________ or

________ ________.

E = ________

• Where m = mass, h = height and g =

gravity constant


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Thermochemistry


Potential Energy • Potential energy is

energy an object possesses by virtue of its _________ or chemical composition. It is stored energy that arises from ________ and repulsions an object experiences in relation to another object.

• The most important form of potential energy in molecules is __________ potential energy, Eel:

Eel = ___________

Thermochemistry


Units of Energy

• The SI unit of energy is the ______ (_):

• An older, non-SI unit is still in

widespread use: the _______ (___):

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Thermochemistry

What is a BTU?

• BTU (______ ______ ____) – it is

based on the _______ of heat required

to rise the temperature of __ pound of

water to __̊ F.

1 BTU = ____________Joules

You must ___________ these energy

conversions! © 2012 Pearson Education, Inc.

Thermochemistry

Convert the following:

1. ___ BTU to Joules

2. _____ BTU to kcal


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Thermochemistry


First Law of Thermodynamics

• Energy is neither _________ nor _________.

• It can only be _______________ from one form

to another.

Thermochemistry


Conversion of Energy Figure 5.2

• Energy can be converted from one type to

another.

• For example, the cyclist has _______ energy

as she sits on ____ of the _____.

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Thermochemistry


Conversion of Energy

• As she coasts ______ the hill, her potential

energy is converted to __________ energy.

• At the bottom, all the potential energy she

had at the top of the hill is now kinetic energy.

Thermochemistry

Conversion of Energy

• Consider a car in motion

_______ energy

• You suddenly apply the ________, what

happens to the energy?

Kinetic energy is converted to ______

energy (_______ pads heat up, ________

from the road produces ______)


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Thermochemistry


• To understand the movement of energy

we must first define the _______ and its

_________________.

• In the laboratory the _________ is the

________ and _______ of the chemical

mixture (the system is the reaction what

you are investigating)

• The ____________ is the container and

everything beyond


Thermochemistry


Example: System and Surroundings

• The system includes the

molecules we want to

study (here, the hydrogen

and oxygen molecules).

• The surroundings are

_________ _____ (here,

the cylinder and piston).

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Thermochemistry

Types of Systems

1. ______ – matter and energy can be

__________ with the ______________

2. ______ – can exchange energy but

_____ matter with the _____________

3. ______ – _______ energy or matter

can be exchanged with the _________


Thermochemistry



• Energy is neither created nor destroyed.

• In other words, the total energy of the _______ is

a constant; if the system _____ energy, it must

be _______ by the surroundings, and vice versa.

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Thermochemistry


Exchange of Heat between System and

Surroundings

• When heat is ________ by the ________ from

the surroundings, the process is ___________.

• When heat is ________ by the _________ into

the surroundings, the process is ___________.

Thermochemistry


Internal Energy

• The _________ ________ of a system is the

sum of all ________ and ________ energies of

all components of the system; we call it E.

• The internal energy of a substance can be due to

________________, ____________ (kinetic

energy) and ____________ \ _________ forces.

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Thermochemistry


Internal Energy

By definition, the change in internal energy, E,

is the final energy of the system minus the initial

energy of the system:

E = ______ − ______

Thermochemistry


Changes in Internal Energy

• If _____ > ___, _____ > ______

– Therefore, the system __________ energy from the surroundings.

– This energy change is called __________.

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Thermochemistry



• If ____ < __, _____ < _____

– Therefore, the system ________ energy to

the surroundings.

– This energy change is called __________.

Thermochemistry



• When energy is

exchanged between

the _______ and the

____________, it is

exchanged as either

heat (__) or work

(___).

• That is,

E = __ + __.

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Thermochemistry

Internal Energy – Sign of “q”

• Sign reflects the system’s point of view is

energy flowing into or out of the system?

• ___________ Process – energy flows _____

the system:

q is ___________

• ___________ Process – energy flows _____

of the system:

q is ___________

Thermochemistry

Internal Energy – Sign of “w”

• Sign reflects the system’s point of view.

• System _____ _____ on ______________

example, blowing up a balloon, it

_______ into the surrounding:

w is ________ energy flows ____ of

system

• Surroundings do work on the system:

w is ________ energy flows _____

system


http://www.clker.com/clipart-23562.html

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Thermochemistry


Let’s Consider “Work”

Usually in an open

container the only work

done is by a gas

pushing on the

surroundings (or by

the surroundings

pushing on the gas).

Thermochemistry


Determing the Sign for “Work” We can measure the work done by the gas if

the reaction is done in a vessel that has been

fitted with a piston:

w = _____ and ∆V = _______ - _______

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Thermochemistry


E, q, w, and Their Signs

Thermochemistry

Example 1:

• Calculate the change in the internal

energy for a process in which a system

absorbs ____ J of heat from the

surroundings and does ____ J of work

on the surroundings.


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Thermochemistry

Example 2:

• One gram of liquid water absorbs ____J

of heat and is converted to steam. The

steam ______ and does _____J of work

on a turbine blade. Calculate q, w and

∆E.


Thermochemistry

Example 3:

• A balloon is heated by adding _____J of

heat. It ______, doing ____J of work on

the atmosphere. Calculate ∆E.


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Thermochemistry


• 5.13, 5.15, 5.19, 5.25, 5.27


Thermochemistry

References:

• Brown, T.L., Bursten, B.E., LeMay, H.E., Murphy, C.J.

and Woodward, P.M. (2012). Chemistry – The Central

Science. (12th ed.). United States Of America: Pearson

Prentice Hall

• Brown, T.L., Bursten, B.E., LeMay, H.E. and Murphy,

C.J. (2009). Chemistry – The Central Science. (11th

ed.). Upper Saddle River, NJ: Pearson Prentice Hall.

• Zumdahl, S.S. and Decoste, D.J. (2010). Introductory

Chemistry: A Foundation. (7th ed.). Belmont, CA:

Brooks/Cole Cengage Learning.

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