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**Introduction to Science**

Chapter 1

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**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

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**3 Main Branches of Science**

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

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**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

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**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.

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Scientific Thinking Inference= conclusion drawn from previous data, not on direct observation. Theory= explains why something happens. Law= describes how something works.

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**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

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**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 (5 zeros!) nano- n billionth (8 zeros!) BIGGER SMALLER

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**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?

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How many meters is 800 km? Know Want Don’t want

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

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**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

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**Graphing Data Independent Variable: changed by scientist; x-axis**

Dependent Variable: “depends” on independent variable; y-axis Distance (m) Time

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**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)

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Time Distance 0 s 0 m 30 s 2 m 60 s 5 m 90 s 11 m

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**Scientific Notation Reduces # of 0’s in very large or small numbers.**

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

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**Writing Scientific Notation**

1. Identify first number between 1 and 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

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**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 cm 0x cm (decimal was moved 8 places to the right) sci notation = x 10-8 cm

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**Write 28750.9 in scientific notation.**

x 10-5 x 10-4 x 104 x 105

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**Write 2.87509 x 104 in standard notation**

287,509.

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**Calculating Scientific Notation**

(Follow math rules for powers of 10) *multiplication= add powers of 10 **division= subtract powers of 10 ex x x 102 7.2 x x 102 sci notation = 6 x

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**Significant Figures Number of meaningful digits in a quantity.**

Significant figures are: 1. Any # that is not a zero. ex (4 SF) 2. Zeros between nonzeros. ex (4 SF) 3. Zeros to right of decimal ex (4 SF)

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**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 (5 SN) ex (5 SN)

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**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.

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**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!

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