Announcements & Agenda (01/12/07)
Quiz 1 (the CD quizzes) is due Mon.
Solutions to practice problems are at the end of
each chapter (not the end of the book - oops)
Write your clicker number & name on the sheet I
pass around
Good biology/chemistry seminar today @ 4pm in
VWF102: development of new arthritis treatments
Did you get the email from Bob last night
about Quiz 1?
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Today:
Highlight what you need to know in Ch 1
Forms of energy (2.1)
Energy content of foods (2.2, 1.5, 1.6)
Heat and temperature (2.3, 2.4)
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Measurement: Quantitative Analysis
Chapter 1
In chemistry we
Numbers in Measurements
and Problem Solving
•
•
•
•
Will quickly highlight here…
You will practice & get more instruction
on these concepts in lab
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measure quantities.
do experiments.
calculate results.
use numbers to report
measurements.
compare results to
standards.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Units of Measurement:
Metric System (Know These!)
Know How to Use Metric Equalities
An equality
In the metric and SI systems, one unit is used for each
type of measurement:
Measurement
Length
Volume
Mass
Time
Temperature
Metric
meter (m)
liter (L)
gram (g)
second (s)
Celsius (°
(°C)
states the same measurement in two different units.
can be written using the relationships between two
metric units.
SI
meter (m)
cubic meter (m3)
kilogram (kg)
second (s)
Kelvin (K)
Example:
Example: 1 meter is the same as 100 cm and 1000
mm.
1 m = 100 cm
1 m = 1000 mm
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Converting between Units
(No need to memorize for this class)
Metric and SI Prefixes
American: 1 foot = 12 inches; 1 lb = 16 oz
MetricMetric-toto-US
1 inch = 2.54 cm
1 kilogram = 2.2 lb
You don’
don’t need to memorize any of these, but know how
to use them!
By the way, these are called exact numbers – and I will
tend to call them “conversion factors”
factors”
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Some Tools for Measurement:
Have fun in lab ☺
Making Measurements
. l2. . . . l . . . . l3 . . . . l . . . . l4. .
cm
• The markings on the meter stick at the end of the
•
•
orange line are read as
the first digit
2
plus the second digit
2.7
The last digit is obtained by estimating.
estimating.
The end of the line might be estimated between 2.7–
2.7–
2.8 as halfhalf-way (0.5) or a little more (0.6), which gives
a reported length of 2.75
2.75 cm or 2.76
2.76 cm.
Measured #s always need units!
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Known & Estimated Digits
(Significant Figures)
Learning Check
In the length reported as 2.76 cm,
. l8. . . . l . . . . l9. . . . l . . . . l10. . cm
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•
•
The digits 2 and 7 are certain (known
).
(known).
The final digit 6 was estimated (best
(best guess).
guess).
All three digits (2.76) are significant including the
estimated digit.
What is the length of the orange line?
1) 9.0 cm
2) 9.03 cm
Key Point: How well we can make measurements
depends on the instrument we use. Using too many
or too few significant digits can introduce drastic
errors in calculations
3) 9.04 cm
Will practice applying sig. figure rules a lot in lab!!!
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Rounding Off Calculated Answers
In calculations,
•
Here are some numbers written in standard format
and in scientific notation (will practice more in lab).
answers must have the same
number of significant figures
as the measured numbers.
•
often, a calculator answer
must be rounded off.
off.
•
rounding rules are used to
obtain the correct number of
significant figures.
Know Scientific Notation
Number in
Number in
Standard Format
Scientific Notation
Diameter of the Earth
12 800 000 m
1.28 x 107 m
Mass of a human
68 kg
6.8 x 101 kg
Length of a pox virus
0.000 03 cm
3 x 10-5 cm
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Aside: will discuss density (1.7) in lab too!!!
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What is Energy?
What are Some Forms of Energy?
Energy – the ability to do work
1. Kinetic Energy: energy of motion
2. Potential Energy: stored energy
3. Thermal Energy: energy associated w/ heat
content
4. Radiant Energy: energy of light (e.g. from sun)
On to Chapter 2!!!
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Potential Energy
Kinetic Energy
Potential energy is
energy stored for use at
a later time.
Kinetic energy is the
energy of matter in motion.
Examples are
• swimming.
Examples are
• water flowing over a dam.
•
•
•
• working out.
• burning gasoline.
water behind a dam.
a compressed spring.
chemical bonds in
gasoline, coal, or food.
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One Key Form of Potential Energy
Chemical Energy: energy
resulting from attraction of
the electrons and nuclei in
molecules (bond energy)
Important!!!
forming chemical bonds
releases energy
breaking chemical bonds
requires energy
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Units for Measuring Energy
Heat is measured in joules or calories.
4.184 Joules (J) = 1 calorie (cal) (exact)
1 kJ = 1000 J
1 kilocalorie (kcal) = 1000 calories (cal) = 1 nutritional
calorie
Same principle for food: breakdown of food results in the
formation of simpler molecules like carbon dioxide and water
that leads to a net release in energy
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Examples of Energy In Joules
Energy and Nutrition
On food labels, energy is shown as the nutritional
Calorie, written with a capital C. In countries other
than the U.S., energy is shown in kilojoules (kJ).
1 Cal (nutritional) =
1 Cal = 1 kcal
1 Cal = 1000 cal
1 Cal = 4184 J
1 Cal = 4.184 kJ
1000 calories
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Caloric Food Values
Energy Values for Some Foods
The caloric or energy values for foods
indicate the number of kcal(Cal) provided
by 1 g of each type of food.
Carbohydrate:
Fat (lipid):
Protein:
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TABLE 2.2
4 Cal
1g
9 Cal
1g
4 Cal
1g
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Energy Requirements
• The amount of
Learning Check
TABLE 2.3
A cup of whole milk contains 12 g of
carbohydrate, 9.0 g of fat, and 5.0 g of
protein. How many kcal (Cal) does a cup of
milk contain?
energy needed
each day
depends on age,
sex, and physical
activity.
activity.
1)
2)
3)
48 kcal (or Cal)
81 kcal (or Cal)
150 kcal (or Cal)
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The Last Question was an Example of using
Conversion Factors to Solve Problems
Solution
A cup of whole milk contains 12 g of carbohydrate,
9.0 g of fat, and 5.0 g of protein. How many kcal
(Cal) does a cup of milk contain?
To solve a problem
• Identify the given unit
• Identify the needed unit.
Example:
Example:
A person has a height of 2.0 meters.
What is that height in inches?
The given unit is the initial unit of height.
given unit = meters (m)
3) 150 kcal (or Cal)
12 g carbohydrates x 4 kcal/g = 50 kcal (1 SF)
9.0 g fat
x 9 kcal/g = 80 kcal (1 SF)
5.0 g protein
x 4 kcal/g = 20 kcal (1 SF)
150 kcal
The needed unit is the unit for the answer.
needed unit = inches (in.)
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Problem Setup
Heat & Temperature
• Write the given and needed units.
• Write a unit plan to convert the given unit to the needed unit.
• Write equalities and conversion factors that connect the
units.
• Use conversion factors to cancel the given unit and provide
the needed unit.
Unit 1
x
Given
unit
x
Unit 2
Unit 1
Conversion
factor
Particles are always moving.
When you heat water, the water molecules move faster.
When molecules move faster, the substance gets hotter.
When a substance gets hotter, its temperature and total
energy content increases.
= Unit 2
= Needed
unit
measure temperature changes with a thermometer
PRACTICE!
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Fahrenheit Formula
Three Important Temperature Scales
Fahrenheit
Water boils
212°F
180°
Water freezes 32°F
Celsius
Kelvin
100°C
373 K
100°C
0°C
• On the Fahrenheit scale,
scale, there are 180°
180°F between the
freezing and boiling points and on the Celsius scale,
scale,
there are 100°
100°C.
180°F =
9°F =
1.8°F
100°C
5°C
1°C
• In the formula for the Fahrenheit temperature,
temperature, adding
32 adjusts the zero point of water from 0°
0°C to 32°
32°F.
100K
273 K
TF
= 9/5 TC + 32°
32°
TF
= 1.8 TC + 32°
32°
or
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Solving A Temperature Problem
Celsius Formula
A person with hypothermia has a
body temperature of 34.8°C.
What is that temperature in °F?
• TC is obtained by rearranging the equation for TF.
TF =
1.8TC + 32
• Subtract 32 from both sides.
TF - 32
=
1.8TC ( +32 - 32)
TF - 32
=
1.8TC
• Divide by 1.8 = °F - 32
1.8
TF - 32
=
TC
1.8
TF
= 1.8 TC + 32°
32°
TF = 1.8 (34.8°C)
= 1.8 TC
1.8
exact
tenth's
+ 32°
exact
= 62.6 + 32°
= 94.6°F
tenth’s
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Why are we so interested in heat?
Heat (2.4)
Different substances have different capacities for
storing energy
It may take 20 minutes to heat water to 75°C.
However, the same mass of aluminum might require
5 minutes and the same amount of copper may take
only 2 minutes to reach the same temperature.
Chemical reactions
that produce heat
“Exothermic”
Chemical reactions
that absorb heat
“Endothermic”
THINK ABOUT BOB MAKING MAC & CHEESE
Heat is related to whether a chemical or
biological process will happen!
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