Introduction to Science

Chapter 1

The Nature of ScienceScientists try to answerquestions about thenatural world by:• Exploring the unknown• Explaining the known• Experimenting to test

theories or confirm facts

3 Main Branches of Science

• Biological- Botany, Ecology, Zoology, etc.• Physical- Physics (motion), Chemistry (matter)• Earth- Geology, Astronomy, Meteorology

The Way Science Works: Scientific Method

Used to learn about the natural world; includes thefollowing steps:1. Making observations2. Asking questions3. Forming a hypothesis; making a prediction4. Testing the hypothesis through experimentation5. Collecting and analyzing data from experiment6. Drawing conclusion(s) from data7. Communicating data to peers or public

Scientific Method (cont’d)

• Only 1 question investigated at a time.• Controlled experiments- compare

experimental group (variable) to control group (lacks variable).

*independent variable= variable/factor tested

*dependent variable= variable measured quantitatively (numbers)

• Experiments can only disprove an hypothesis.

Scientific Thinking

• Inference= conclusion drawn from previous data, not on direct observation.

• Theory= explains why something happens.• Law= describes how something works.

Units of Measurement-System International (SI) Units

Quantity Base Unit Abbreviation

Length meter m

Mass kilogram kg

Time second s

Temperature Kelvin K

Amount mole mol

Metric System(based on 10)

based on powers of 10

Prefix Symbol Meaning Multiply base unit by...

giga- G billion 1,000,000,000

mega- M million 1,000,000

kilo- k thousand 1000

-------- BASE UNIT ----------------------------

deci- d tenth 0.1

centi- c hundredth 0.01

milli- m thousandth 0.001

pico- u millionth 0.000001 (5 zeros!)

nano- n billionth 0.000000001 (8 zeros!)

BIGGERBIGGER

SMALLERSMALLER

Metric Conversions(Only SI units are used to express scientific data)To convert from 1 unit to another:1. Identify given unit; unknown unit.2. Use dimensional analysis to compare known to unknown unit (factor-label method) Ex. How many pounds are in 1000 grams?

• How many meters is 800 km?Know Want

Don’t want

• An object’s mass is 250 kg. What is its mass in grams?

Organizing Data: Graphs1. Line Graph: for continuous data2. Bar Graph: compare similar data for several things3. Pie Graph: compare parts of a whole

Our Ages

Favorite Stores

Car Speed

Graphing Data• Independent Variable: changed by scientist; x-axis• Dependent Variable: “depends” on independent

variable; y-axis

Time

Distance (m)

How to Make a Line Graph

1.Label x-axis with dependent variable2.Label y-axis with independent variable3.Choose increments to represent data on each

axis.4.Plot points.5.Connect points.6.Name graph.

Time (s)

Dist

ance

(m)

Time Distance

0 s 0 m

30 s 2 m

60 s 5 m

90 s 11 m

Scientific Notation• Reduces # of 0’s in very large or small

numbers.• Expresses simple #’s x power of 10. (simple #- 1 < number < 10)

Writing Scientific Notation

1. Identify first number between 1 and 10.2. Place decimal after that number.3. Count number of places the decimal had to

move- this is the exponent of 10. ex. 210,000,000,000,000,000,000,000 m 2.10,000,000,000,000,000,000,000 m (decimal was moved 23 places to the left) sci notation= 2.1 x 1023

Writing Scientific Notation (cont’d)• If decimal moves to right, exponent is

negative (original number is less than 1)• If decimal moves to left, exponent is positive (original number is 1 or greater) ex. 0.0000000902 cm 0x00000009.02cm (decimal was moved 8 places to the right) sci notation = 9.02 x 10-8 cm

Write 28750.9 in scientific notation.

1. 2.87509 x 10-5

2. 2.87509 x 10-4

3. 2.87509 x 104

4. 2.87509 x 105

Write 2.87509 x 104 in standard notation

1. 287,509.2. 28750.93. 2875.094. 28.7509

Calculating Scientific Notation (Follow math rules for powers of 10) *multiplication= add powers of 10 **division= subtract powers of 10 ex. 7.2 x 10-9

1.2 x 102

7.2 x 10-9

1.2 x 102

sci notation = 6 x 10 -11

Significant Figures

• Number of meaningful digits in a quantity.• Significant figures are: 1. Any # that is not a zero. ex. 1246 (4 SF) 2. Zeros between nonzeros. ex. 1206 (4 SF) 3. Zeros to right of decimal ex. 0.1200 (4 SF)

Significant Figures (cont’d)

• Significant figures are not: 1. Zeroes after nonzeros unless a decimal is present. ex. 80,000 (1 SF) ex. 83,000 (2 SN) ex. 83000. (5 SN) ex. 83.000 (5 SN)

Putting It All Together: Chewing Gum1. I’ve noticed that when I

chew gum, the size changes.

2.How does the amount of time gum is chewed affect the mass?

3.Looking through the literature on gum, I see that others have noticed what I’ve noticed, but no one has done an experiment on this.

4.My hypothesis: I think the gum will get smaller as it gets chewed because the sugar will dissolve.

5. I create an experiment where I time chewing gum and weighing it at different intervals.

6. I perform the experiment and collect data7.YOU will do this in the lab!