CHEMISTRY-CPCHAPTER 1

CHEMISTRY AND YOU

This chapter will introduce you to chemistry and the uses of chemistry in our world. You will

apply the scientific method to various problems and use experiments to prove hypotheses. You

will also learn the basic mathematical skills needed to succeed in chemistry.

is also known as the central science

• Chemists are employed in dozens of occupations

• Whatever your career choice is, chances are you will need some

knowledge of chemistry!!!!

The Scientific Method

Hypothesis: A Testable Prediction

• If…then… statement

• Narrow—tests one, and only one, thing

Example 1: The static on your radio increases right before it thunders during a storm.

Example 2: People who smoke cough more than people who don’t smoke.

Hypothesis: A Testable Prediction

• If…then… statement

• Narrow—tests one, and only one, thing

Example 3: You sneeze every time you visit your best friend’s house.

Example 4: On a cold morning, the air pressure in the tires of your car measures 34 psi. After several hours of high-speed driving, the pressure measures 38 psi.

EXPERIMENT

Variable: The factor being tested in an experiment

• Independent Variable: The factor that you change/adjust in the experiment

• Dependent Variable: The factor that changes due to changes in the independent variable.

EXPERIMENT

Control: Factor that responds in a predictable way to the experiment

– A control is what the rest of the experiment can be compared to

Constant: Factor(s) that do

not change during the

experiment.

• Independent Variable:• Dependent Variable:• Control:• Constant:

EXPERIMENT

Pea plant clones are given different amounts of water for a 3 week period. The first plant receives 400 mL a day. The second pea plant receives 200 mL a day. The third pea plant receives 100 mL a day. The fourth pea plant does not receive any extra water, the plant only receives natural ways of receiving water. The height of the pea plants is recorded daily.

• Independent Variable:• Dependent Variable:• Control:• Constant:

EXPERIMENT

You want to test which size ball is easiest to juggle. You test a baseball, a softball, a soccer ball and a basketball. You count the seconds you can continuously juggle each type of ball.

You want to determine which classroom is the hottest one in the school.

• Independent Variable:• Dependent Variable:• Control:• Constant:

• Data: Recorded Observations

• Graph: a visual representation of data

Graph: a visual Graph: a visual representation of datarepresentation of data

x-axis: the horizontal axisx-axis: the horizontal axis Independent Variable: The factor in the Independent Variable: The factor in the

experiment that the experimenter experiment that the experimenter changes.changes.

y-axis: the vertical axisy-axis: the vertical axis Dependent Variable: The factor that Dependent Variable: The factor that

changes due to changes in the changes due to changes in the independent variable.independent variable.

Y-a

xis

x-axis

Steps to GraphingSteps to Graphing

Numbering: Make sure the numbers Numbering: Make sure the numbers you put on the axes follow patterns.you put on the axes follow patterns. For example: 2, 4, 6, 8, 10 or 5, 10, 15, For example: 2, 4, 6, 8, 10 or 5, 10, 15,

20 or 0.1, 0.2, 0.3, 0.4 etc.20 or 0.1, 0.2, 0.3, 0.4 etc. Labeling: Make sure you label each Labeling: Make sure you label each

axis with a title and a unit and that axis with a title and a unit and that you title your graph.you title your graph.

TrendsTrends

Best Fit Line: A straight line that Best Fit Line: A straight line that goes through the center of most goes through the center of most points.points.

Trends cont.Trends cont.

Inversely Proportional: As one Inversely Proportional: As one variable increases, the other variable increases, the other variable decreases.variable decreases.

Trends in GraphingTrends in Graphing

Directly Proportional: As one Directly Proportional: As one variable increases/decreases the variable increases/decreases the other does the sameother does the same

Y-a

xis

x-axis

Example: Create a line graph of the following data: Mass (g)Mass (g) Volume Volume (cm(cm33))

2525 100100

3030 115115

4040 134134

5050 160160

5454 163163

Draw Conclusions

Theory: Explains

• States the “Why”

Law: States a Fact

• States the “What”

Base Units: The 7 metric units that SI is built upon

Physical Quantity Unit Name & Symbol Measured using…

Mass

Length

Time

Quantity

Temperature

Electric Current Ammeter

Luminous Intensity Photometer

NON-SI UNITS

Physical Quantity Unit Name Unit Symbol

Volume

Pressure

Temperature

Energy

Derived Units

1. Write the mathematical formula for the quantity.

2. Replace the formula with units and simplify.

Density

Density = Mass Volume

METRIC CONVERSIONS

METRIC PREFIXESPREFIX ABBREVIATION UNIT EQUALITY

mega-

kilo-

deka-

BASE UNIT

deci-

centi-

milli-

micro-

nano-

pico-

DIMENSIONAL ANALYSIS

• What is a conversion factor equal to?

• How do you use conversion factors?

Steps to Dimensional Analysis

1. Start with what you know (number and unit).

2. Times a line.

3. Add a conversion factor so that units cancel and what you are looking for is on top of the ratio.

4. Check your answer.

DIMENSIONAL ANALYSIS

Uncertainty in Measurements

Why are measurements uncertain? Precision of instrumentation varies Human error

Reading Measurements The number of digits you should write

when writing down a measurement depends on the instrumentation you are using.

You should always include a number and a unit when writing down a measurement

When determining a measurement include all the digits you know for certain plus 1 more digit.

Precision Also called reproducibility or repeatibility Measurements are close to each other (getting

the same measurements each time)

Accuracy

Measurements are close to the actual value

Graduated Cylinder

Put the cylinder flat on the table and read at the bottom of the miniscus (bubble)

Triple Beam Balance

OPENERWith your partner, make the following measurements. Be sure

to make the measurements to the proper # of digits. Be sure to include units for all measurements. Write your answers on a sheet of paper and have Ms. Wack check your answers. All materials are in the back of the classroom.

The volume of water in the 100 mL and 10 mL graduated cylinders.

The length of the paper clip. The mass of a 100 mL beaker.

ROUNDING The first significant digit is the first nonzero

number. Count the appropriate # of sig figs, if the

next number is 5 or greater, round the last number up 1. If not, do nothing. Examples:

2.3344(1)1.029 (3)0.00234(2)

SIGNIFICANT FIGURES

The certain digits and the estimated digit of a measurement.

All the known digits of a measurement and the one estimated digit.

SIGNIFICANT FIGURES1. All nonzero numbers are significant.

123 = _____ sig figs

2. All zeroes at the beginning are not significant.0.0025 = _____ sig figs

3. Zeroes between 2 nonzero digits are significant.5007= ______ sig figs

4. Zeroes at the end of a number are only significant if the number contains a decimal point.470 = ____ sig figs, 470.0 = ___ sig figs, 0.00470 = ____ sig figs

5. In scientific notation, all numbers in the coefficient are significant.2.020 x 104 = ____ sig figs

SIGNIFICANT FIGURESEasier Rule: To count significant figures, if there is

a decimal, count all digits including and after the first non-zero

number. If there is not a decimal, start counting at the first

non-zero number but do not count zeroes at the end of the

number.

3.3333 = ______ sig figs 2000.0 = ____ sig figs

3023 = ____ sig figs 0.216 = ____ sig figs72800 = ____ sig figs 0.009030 = ____ sig figs

Round each of the following numbers to 3 significant figures.a) 3.3333 d) 0.009030

b) 3023 e) 0.21653

c) 0.3287 f) 1.99999

SIGNIFICANT FIGURES IN CALCULATIONSMultiplication/Division: The measurement with the

smallest number of significant figures determines how many

significant figures are allowed in the final answer.

Addition/Subtraction: The measurement with the smallest

number of decimal places determines how many decimal

places are allowed in the answer.

SIGNIFICANT FIGURES IN CALCULATIONS0.3287 g x 45.2 g =

0.258 mL 0.36105 mL =

68.32 ns x 1.001 ns x 0.00367 ns =

8.85 cs 333.2 cs =

10 s 5 s =

800.0 mm x 200.00 mm x 10.0 mm =

Scientific Notation

A number is written in 2 parts. The first part is a number between 1 & 10 The second part is a power of ten

Exponent Positive exponents represent numbers

greater than 1 Negative exponents represent numbers less

than 1

Scientific Notation To convert a number to scientific notation:

Count how many places the decimal place must be moved to make the number a number between 1 & 10 (the coefficient) The number of spaces the decimal moved is the value of the

exponent If you moved the decimal to the right, the exponent is negative If you moved the decimal to the left, the exponent is positive Write: Coefficient x 10exponent

To convert a number from scientific notation to regular notation: If the exponent is positive, move the decimal in the coefficient

the number of spaces indicated by the exponent to the right If the exponent is negative, move the decimal in the coefficient

the number of spaces indicated by the exponent to the left.

Scientific Notation Example 1: Express each of the following in

scientific notation.8960 = 36,000,000 =

0.00023 = 0.000 000 025 3 =

Example 2: Express each of the following numbers in regular notation.4.563 x 107 = 2.53 x 10-3 =

6.805 x 108 = 1.33450 x 10-7 =

Scientific Notation

A number is written in 2 parts. The first part is a number between 1 & 10 The second part is a power of ten

Exponent Positive exponents represent numbers

greater than 1 Negative exponents represent numbers less

than 1

Calculating in Scientific Notation(Do not change the numbers out of scientific notation when calculating)

(5.5 x 106) x (1.111 x 10-1) =

(6.23 x 103) x 1 3.33 x 102

(6.026 x 1023) x (2.5 x 102)

(9.896 x 10-34) (3.311 x 10-24) =