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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: 1.Making observations 2.Asking questions 3.Forming a hypothesis; making a prediction 4.Testing the hypothesis through experimentation 5.Collecting and analyzing data from experiment 6.Drawing conclusion(s) from data 7.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 Lengthmeterm Masskilogramkg Timeseconds TemperatureKelvinK Amountmolemol

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Metric System (based on 10) based on powers of 10PrefixSymbolMeaning Multiply base unit by... giga-Gbillion1,000,000,000 mega-Mmillion1,000,000 kilo-kthousand BASEUNIT deci-dtenth0.1 centi-chundredth0.01 milli-mthousandth0.001 pico-umillionth (5 zeros!) nano-nbillionth (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? KnowWant 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 1. Line Graph: for continuous data 2. Bar Graph: compare similar data for several things 3. Pie Graph: compare parts of a whole Our Ages Favorite Stores Car Speed

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

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How to Make a Line Graph 1. Label x-axis with dependent variable 2. Label y-axis with independent variable 3. Choose increments to represent data on each axis. 4. Plot points. 5. Connect points. 6. Name graph. Time (s) Distance (m)

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TimeDistance 0 s0 m 30 s2 m 60 s5 m 90 s11 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 10 23

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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 = 9.02 x cm

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Write in scientific notation x x x x 10 5

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Write x 10 4 in standard notation 1.287,

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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. 7.2 x x x x 10 2 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 1. 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.

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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 data 7. YOU will do this in the lab!

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