Introduction to Science Chapter 1

The Nature of Science Scientists try to answer questions about the natural 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 the following steps: Making observations Asking questions Forming a hypothesis; making a prediction Testing the hypothesis through experimentation Collecting and analyzing data from experiment Drawing conclusion(s) from data 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!) BIGGER SMALLER

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: Graphs Line Graph: for continuous data Bar Graph: compare similar data for several things Pie Graph: compare parts of a whole Favorite Stores Car Speed Our Ages

Graphing Data Independent Variable: changed by scientist; x-axis Dependent Variable: “depends” on independent variable; y-axis Distance (m) Time

How to Make a Line Graph Label x-axis with dependent variable Label y-axis with independent variable Choose increments to represent data on each axis. Plot points. Connect points. Name graph. Distance (m) Time (s)

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. 2.87509 x 10-5 2.87509 x 10-4 2.87509 x 104 2.87509 x 105

Write 2.87509 x 104 in standard notation 287,509. 28750.9 2875.09 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 Gum I’ve noticed that when I chew gum, the size changes. How does the amount of time gum is chewed affect the mass? 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.

My hypothesis: I think the gum will get smaller as it gets chewed because the sugar will dissolve. I create an experiment where I time chewing gum and weighing it at different intervals. I perform the experiment and collect data YOU will do this in the lab!