CHAPTER 1: CHEMISTRY AND YOU

Explain why a knowledge of chemistry is central to many human endeavors.

List and describe the steps of the scientific method.Explain the basic safety rules that must be followed when working in the

chem lab.Identify the metric units of measurement used in chemistry.

Explain what causes uncertainty in measurements.Compare accuracy and precision.

Explain how to use significant figures and scientific notation.Calculate percent error.

Define density and explain how it is calculated.Explain how dimensional analysis and conversion factors are used to

solve problems in chemistry.

Vocab

Chemistry Scientific method Observation Hypothesis Experiment Conclusion Natural law Theory Variable Experimental control Metric system International System of

Units (SI)

Base unit Mass Volume Metric prefix Precision Accepted unit Accuracy Significant digit Percent error Density Dimensional analysis Conversion factor

Chapter 1: Chemistry and You

Look at the pic on p. 2 and read the caption Name some of the

basic chemical substances that make up your body.

Name some other chemical processes, besides digestion, that occur in your body.

Can you think of an important chemical reaction that occurs in plants and trees?

Section 1-1What is Chemistry?

Chemistry in Action

Chemistry is a broad science that touches nearly every aspect of human life.

What are some ways chemistry affects the 2 careers mentioned in the section? Examining a wetlands habitat Preserving historical artifacts

The Central Science

Chemistry has been called the central science b/c it overlaps so many sciences

Careers that use chemistry Hair stylists Construction Biologists What others?

Possible chemistry careers Police departments (CSI) Perfume companies Research chemists

Why Study Chemistry?

It is involved in many aspects of life Helps you to understand the world

around you

Cleaning Priceless Art

Read the “Connection” box on p. 6 What occupation is using chemistry? What did they do to clean the art? Why are some people upset about their

actions?

Section 1-2The Scientific Method

The Scientific Method

A way of answering questions about the world we live in

Oscar Has Extremely Colorful T-Shirts

Observation

Question

Hypothesis

Experiment

Conclusion

Natural Law

Theory(Model)

Prediction

Experiment

Theory modifie

d as needed

Observation

Seeing a problem or asking a question that you cannot answer

Always leads to a question

Hypothesis

An educated guess Usually asked in a “cause-effect”

statement Must be able to test the hypothesis

Experiment

A test of the hypothesis

Data will be collected and analyzed

Must have 1 variable and at least 1 constant Variable – the

particular factor being tested

Conclusion

The result of the analyzed data May agree or disagree with your

hypothesis

Theory

Answers the original question as well as any others formed during the process

Predicts the results of further experiments

Scientific/Natural Law

Describes how nature behaves but not why

1-2 Section Review

On looseleaf to turn in, page 13 (1-5)

Bikini Bottom Experiments

With your small group, complete the SpongeBob worksheet

SpongeBob Scientific Method.pdf

Section 1-3Safety in the Lab

Section 1-4Units of Measurement

Units of Measurement

Measurement: always includes a number and unit If someone is 7 feet tall, “7” is the number and

“feet” is the unit Saying someone is 7 does not tell you enough

info They could be 7 yrs old, 7 feet tall, 7 inches tall, …

Feet and inches are part of the English system of measurement

In science, we use the Metric system All scientists, no matter their country or

language, use the metric system

United States, Liberia, and Burma

International System of Units

SI units used by all scientists around the world

Based on 7 metric units called base units Length meter (m) Mass kilogram (kg) Time second (s) Count/Quantity mole (mol) Temperature Kelvin (K) Electric Current ampere (A) Luminous Intensity candela (cd)

Derived Units

Area square meter (m2)Volume cubic meter (m3)Force Newton (N)Pressure Pascal (Pa)Energy joule ( J )Power watt (W)Voltage volt (V)Frequency hertz (Hz)Electric charge coulomb (C)

Units

Science is a process, not a collection of rules

The most frequently used units in class that differ than SI: Temperature - Celsius (˚C) Volume – liter (L) Pressure – atmosphere (atm)

millimeters of mercury (mmHg)

Energy – calorie (cal)

Commonly used units

Length A dime is 1 mm thick A quarter is 2.5 cm in diameter Average height of a man is 1.8 m

Mass A nickel has a mass of 5 g A 120 lb woman has a mass of about 55 kg

Volume A 20 oz can of soda has a volume of 360 mL A ½ gallon of milk is equal to 2 L

Metric Prefixes

Prefix Abbreviation

Meaning

kilo- k 1 000

hecta- H 100

deca- D 10

Base Unit 1

deci- d 0.1

centi- c 0.01

milli- m 0.001

KingHenry Died by drinking chocolate milk

Base units include meter, liter, second, gram

How to Use Prefixes

kilo-

hecto-

deca-Base units

deci-

centi-

milli-

Example

kilo-

hecto-

deca-base units

deci-

centi-

milli-

How many millimeters are in a meter?1 meter = mm

1 meter = 1000 mm

Practice Problems

Convert a volume of 16 deciliters into liters 1.6 L

Convert 1.45 meters into centimeters 145 cm

Convert a volume of 8 deciliters into liters 0.8 L

Is 5 centimeters longer or shorter than 8 millimeters? Explain. 5 cm is longer than 8 mm b/c 0.05 m is

greater than 0.008m

Metric ManiaWorksheet

Section 1-5Uncertainty in Measurement

Making Measurements

When making a measurement, write down everything given to you with one uncertain estimated number 5.1 inches is easy to spot but we still

need 1 uncertain number My estimation = 5.12 inches

Measurements are uncertain b/c: Measuring instruments are never completely

free of flaws Measuring always involves some estimation

Reliability in Measurement

Precision: the same result is given over and over under the same conditions

Accuracy: the result is close to a reliable standard

Accepted value: the reliable standard

High PrecisionHigh Accuracy

Section 1-6Working with Numbers

Working with numbers

Measurements are rarely used just by themselves.

Usually used in some form of mathematics (+, -, x, or ÷)

Produces values of mass, temperature, volume, etc.

Significant Figures (Digits)

The certain digits and the estimated digit of a measurement Example: In the # 31.7, there are 3 sig figs

The 3 and 1 are certain digits while the 7 is the uncertain digit

Rules for Sig Figs

Nonzero #: any number that is not a zero 1, 2, 3, 4, 5, 6, 7, 8, or 9

Zeros Never count “leading zeros”

0023 only count the 2 and 3 0.054 only count the 5 and 4

Always count “captive” or “sandwiched” zeros 303 count the 3, 0, and 3

“Trailing zeros”: zeros to the right Only count if used with a decimal point

5400 only count the 5 and 4 5.400 count the 5, 4, 0, and 0

Example

How many sig figs are in 0.057 010 g? Nonzero numbers:

0.057 010 Captive zeros

0.057 010 Trailing zeros when there is a decimal

0.057 010 Final Answer

0.057 010 5 significant figures

Practice Problems

How many sig figs in the following numbers? 0.002 6701 m

5 sig figs 0.002 6701 19.0550 kg

6 sig figs 19.0550 3500 V

2 sig figs 3500 1 809 000 L

4 sig figs 1 809 000 95 600 m

3 sig figs 95 600 520 mL

2 sig figs 520 0.0102 ms

3 sig figs 0.0102

Sig Fig Practice Wkst

Significant Figures in Calculations

Multiplying and Dividing The answer will have the same # of sig

figs as the measurement with the smallest # of sig figs

Volume = 3.052 m x 2.10 m x 0.75 m (4 sig figs) (3 sig figs) (2 sig

figs)

= 4.8069 m3

= 4.8 m3

Sig Figs in Calculations

Adding and Subtracting The answer will have the same # of decimal

places as the measurement with the smallest # of decimal places

951.0 g 1407 g 23.911 g + 158.18 g 2540.091 g Since there aren’t any decimals in 1407, our

answer will not have decimals Final answer = 2540 g

Practice Problems

6.15 m x 4.026 m = 24.7599 m2 = 24.8 m2

1.45 m x 1.355 m x 2.03 m = 3.9884425 m3 = 3.99 m3

0.3287 g + 45.2 g = 45.5287 g = 45.5 g

0.258 mL ÷ 0.361 05 mL = 0.71458246 mL = 0.715 mL

More PracticeWorksheet

Scientific Notation

In science we work w/ very large and very small #s

For example: 1 drop of water contains =

1,700,000,000,000,000,000,000 molecules The mass of 1 proton =

0.000 000 000 000 000 000 000 000 001 672 62 kg

Scientific Notaion

To make it easier for ourselves, we use scientific notation 1 drop of water contains =

1,700,000,000,000,000,000,000 molecules 1 drop of water contains = 1.7 x 1021

The mass of 1 proton = 0.000 000 000 000 000 000 000 000 001 672 62 kg

The mass of 1 proton = 1.67262 x 10-21

How to make # into scientific notation

Write 1700 in scientific notation Write down the full number

1700 Move the decimal until it is right after the first

1-10 number 1700 1700. 1.700

Write down this new number without the zeros 1.7

Place “x 10” after this number 1.7 x 10

Count how many times you had to move the decimal and place that number after the 10 as an exponent

If you move to the right = negative exponent If you move to the left = positive exponent

1.7 x 103

Examples

37 700 3.77 x 104

1 024 000 1.024 x 106

0.000 000 003 901 3.901 x 10-9

8960 8.96 x 103

0.000 23 2.3 x 10-4

Percents

Data will often be given as a percent If it is a fraction,

just divide and multiply by 100

Ex: 900 million kilograms of plastic soft drink bottles are produced each year. 180 million kilograms of them are recycled.180 million

kilograms900 million kilograms

= 0.2 x 100% = 20%

Percent Error

A measurement can be compared to its accepted value by finding the percent error

% error can be positive or negative Positive = measured value is greater than

accepted Negative = measured value is less than

accepted% error = measured value – accepted value

accepted valuex 100%

Example

In an experiment dealing with finding the boiling point of water, you performed 3 experiments and found water to boil at 98.4˚C, 98.9 ˚C, and 97.5˚C. What is the average and % error of your data? (Hint: the accepted value of the boiling point of water is 100˚C)

98.4 + 98.9 + 97.5 = 294.8 / 3 = 98.3 % error = (100 – 98.3) / 100 x 100 = 1.7%

PracticeWork the problems on your “Accuracy Precision and Percent Error” worksheet from a few class periods ago

Density

Density – compares the mass of an object to its volume measured in:

grams per cubic centimeters (g/cm3)

grams per milliliter (g/mL)

Density

Mass

Volume=

Density Problems If a sample of aluminum has a mass of

13.5g and a volume of 5.0 cm3, what is its density?

2.7 g/cm3

Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass of the aluminum sample? (Use the density you found in the problem before this)

8.1 g

A piece of metal with a mass of 147g is placed in a 50mL graduated cylinder. The water level rises from 20mL to 41mL. What is the density of the metal?

7 g/mL

What is the volume of a sample that has a mass of 20g and a density of 4g/mL?

5 mL

A metal cube has a mass of 20g and a volume of 5cm3. Is the cube made of pure aluminum? Explain. (Hint: Pure Aluminum will have a density of 2.7g/cm3.)

4 g/cm3

Dimensional Analysis

Technique of converting between units How many feet are in 86 centimeters?

We know 12 inches = 1 foot We also know 1 inch = 2.54 centimeters

86 cm 1 in 1 ft2.54 cm 12 in= 2.82 ft

Practice Problems

Use Fig 1-29 on page 38 to help you solve the following problems

How many cubic centimeters are in 2.3 gal? 8 700 cm3

How many meters are in 3.5 mi? 5 600 m

How many pascals are in 770 mm Hg? 103 000 Pa

How many seconds are in 10.5 hours? 37 800 s

How many days are in 12 583 seconds? 0.14564 days

Graphing

How to draw a scientific graph Need independent variable (x – axis)

the variable being changed Need dependent variable (y – axis)

the variable being changed by the independent variable

Label each axis Do not connect each dot, use a “line of best

fit” Give the graph a title which tells what it is of

Example

A balloon is filled with air and attached to the bottom of a large container of water. If the water temperature is changed, by heating or adding ice, the volume of the air in the balloon also changes. Data was collected from taking volume measurements at different temperatures. Independent variable: temperature Dependent variable: volume

Sample Graph

20 30 40 50 60 70 8090

95

100

105

110

115

120

Volume (mL)Trial Temperature

(˚C)Volume

(mL)

1 25 101.3

2 30 103.2

3 35 103.4

4 40 105.0

5 45 106.7

6 50 108.4

7 55 110.0

8 60 111.5

9 65 112.9

10 70 114.2