Physical Science 1

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The Metric System

• Easier to use because it is a decimal system
• Every conversion is by some power of 10.
• A metric unit has two parts
• A prefix and a base unit.
• prefix tells you how many times to divide or
  multiply by 10.

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Base Units

• Length - meter more than a yard - m
• Mass - gram - about a raisin - g
• Time - second - s
• Temperature- Kelvin or ºCelsius- K or ºC
• Energy - Joules- J
• Volume - Liter - half of a two liter bottle- L
• Amount of substance - mole -

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Prefixes

• giga G 1,000,000,000 times or 109
• mega M 1,000,000 times or 106
• kilo k 1000 times or 103
• hecto h 100 times or 102
• deci d 1/10 or 10-1
• centi c 1/100 or 10-2
• milli m 1/1000 or 10-3
• micro 1/1000000 or 10-6
• nano n 1/1000000000 or 10-9

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Everyday Measurements

• kilometer - about 0.6 miles
• centimeter - less than half an inch for 1 inch
  2.56 centimeters
• millimeter - the width of a paper clip wire
• 1 square meter about a washing machine or
  dryer

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Measuring length

• Use a ruler
• Line up from zero not the end of the ruler
• Small divisions are centimeters

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Volume

• 1 L about 1/4 of a gallon - a quart
• 1 mL is about 20 drops of water or 1 sugar cube

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Measuring Volume
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• Use a graduated cylinder.
• The water will curve in the cylinder.
• Hold it level with your eye.
• Read the bottom of the curve.
• Measures in milliliters mL.

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Mass

• weight is a force, is the amount of matter.
• 1gram is defined as the mass of 1 cm3 of water at
  4 ºC.
• 1 kg 1 L of water
• 1 kg 2.5 lbs
• 1 g 1 paper clip
• 1 mg 10 grains of salt or 2 drops of water.

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Measuring Mass

• Use a triple beam balance
• First balance it at zero.
• Then put item on
• Then move one weight at a time
• When balanced, add up the weights

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Metric Conversions

• how far you have to move on this chart, tells you
  how far, and which direction to move the decimal
  place.

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Metric Conversions

• Change 5.6 m to millimeters

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Metric Conversions

• Change 5.6 m to millimeters
• starts at the base unit and move three to the
  right.

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Metric Conversions

• Change 5.6 m to millimeters
• starts at the base unit and move three to the
  right.
• move the decimal point three to the right 5600

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Metric Conversions

• convert 25 mg to grams
• convert 0.45 km to mm
• convert 35 mL to liters
• It works because the math works, we are dividing
  or multiplying by 10 the correct number of times

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Chapter 1 Studying Science

• Comes from the latin word scire which means to
  know
• Answers the questions why? And how?
• Try to explain the world around them.
• Science is
• a study of the universe around you
• a language with its own vocabulary
• a way of thinking.
• A collection of facts and theories

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Science Skills

• Data- the information you gather.
• Observe- using one or more of your senses to get
  information about your surroundings.
• Infer- applying reason to explain an observation
• Usually several are valid
• Estimate- make a careful guess when you cant
  make a measurement

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Science Skills

• Measure- comparing to a standard
• More exact
• Contain a number and a unit
• Predict- state what you might think will happen
  in the future and why
• Classify- group things together.
• Hypothesize- suggest an answer to your problem
  based on information you have.

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Science Skills

• Record and organize- writing down what you see
  and measure
• Often you will want to use a table
• Analyze- look for trends and patterns.
• See if data supports inference, prediction, of
  hypothesis

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Nature of Science

• Science has many branches. The Big 3 are
• 1. Biological Science
• 2. Physical Science
• 3. Earth Science

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Nature of Science

• We will visit mostly Physical Science and some
  Earth Science.
• Physical Science includes
• Chemistry
• Physics

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Nature of Science

• Science is learning for the sake of knowledge
  itself.
• Technology is the application of science for
  practical purposes.

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Nature of Science

• Laws and Theories.
• A law tells how things work.
• A theory is a possible explanation.

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Nature of Science

• Laws and Theories.
• Compare the Law of Gravity to the Theory of
  Evolution.
• Both based on facts
• One is stronger

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Nature of Science

• Many Laws are expressed mathematically
• The Law of Gravity-The closer and more massive
  objects are the more they are attracted to each
  other.
• FG((m1m2)/d2)

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Nature of Science

• Models are a useful tool in science. Examples
  include
• Pictures
• Maps
• Miniatures
• Computer models

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Scientific Method

• A way of solving problems or answering questions.
• Starts with observation- noting an recording
  facts
• Hypothesis- an educated guess as to the cause of
  the problem or answer to the question.

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Scientific Method

• Experiment- designed to test the hypothesis
• only two possible answers
• hypothesis is right
• hypothesis is wrong
• Generates data observations from experiments.
• Modify hypothesis - repeat the cycle

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• Cycle repeats many times.
• The hypothesis gets more and more certain.
• Becomes a theory
• A thoroughly tested model that explains why
  things behave a certain way.

Observations
Hypothesis
Experiment
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Scientific Method

• Theory can never be proven.
• Useful because they predict behavior
• Help us form mental pictures of processes (models)

Observations
Hypothesis
Experiment
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• Another outcome is that certain behavior is
  repeated many times
• Scientific Law is developed
• Description of how things behave
• Law - how
• Theory- why

Observations
Hypothesis
Experiment
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Theory (Model)
Modify
Prediction
Experiment
Law
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Measuring with scientific units

• Length- the basic unit of length is the meter.
• Meter- is the distance between the doorknob and
  the floor.
• Volume- is the amount of space that something
  occupies.

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Measuring

• Cubic meter- is the SI unit for volume.
• Cube one meter on a side
• Liter , is the convenient unit for everyday use
• A little more than a quart
• Mass- is the amount of matter an object contains.
• Kilogram- the basic SI unit for mass.
• About 2 ½ pounds.

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Measuring

• Density- tells you how much matter is packed into
  a given volume.
• How heavy something is for its size
• Calculated by dividing mass by volume
• D M V

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What does density tell us?

• Water has a density of 1 g/cm3 or 1 g/mL
• Anything with a density greater than 1 g/mL
  will sink
• Because it is heavier than the water it is
  pushing up.
• Helium is less dense than air.

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Graphing

• Three kinds of graphs circle graphs, bar graphs
  and line graphs.
• Compares numerical data with a picture.
• Different types have different uses

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Circle Graphs

• Often called a pie chart
• divided into parts
• easy to compare to whole amount.
• Use several to show changes over time

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Bar Graphs

• Bar Graphs- wide columns used things like weight,
  height , and length.
• Compare quantities over a period of time.

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Line Graphs

• Line Graphs- compares sets of data, show change
  and patterns over time.

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Graphs include

• A title
• Labeled axes
• A consistent scale.

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Tools and Technology

• Computer- rapid calculations
• Spectroscope- tells what makes up the matter in
  space.
• Particle Accelerator-studies how energy and
  matter interact.
• Electrophoresis- Studies proteins and nucleic
  acids that build living things.

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• Gas chromatograph- identifies an unknown
  substance.
• Radio telescope- receives radio waves from outer
  space.
• Wind Tunnel- studies the effects of moving
  fluids like water and air.

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A. Accuracy vs. Precision

• Accuracy - how close a measurement is to the true
  value
• Precision - how close a set of measurements are
  to each other

ACCURACY CORRECTNESS PRECISION CONSISTENCY
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B. Percent Error

• Indicates accuracy of a measurement.

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B. Percent Error

• Julie determines the density of copper to be 8.25
  g/cm3. Find the error if the actual density of
  copper is 8.92 g/cm3.

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C. Significant Figures

• Indicate precision of a measurement.
• Recording Sig Figs
• Sig figs in a measurement include the known
  digits plus a final estimated digit

2.33 cm
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C. Significant Figures

• Counting Sig Figs (p.152)
• Count all numbers EXCEPT
• Leading zeros -- 0.0025
• Trailing zeros without a decimal point -- 2,500

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C. Significant Figures
Counting Sig Fig Examples
1. 23.50
1. 23.50
4 sig figs
3 sig figs
2. 402
2. 402
3. 5,280
3. 5,280
3 sig figs
2 sig figs
4. 0.080
4. 0.080
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C. Significant Figures

• Calculating with Sig Figs
• Multiply/Divide - The with the fewest sig figs
  determines the of sig figs in the answer.

(13.91g/cm3)(23.3cm3) 324.103g
(13.91g/cm3)(23.3cm3) 324.103g
(13.91g/cm3)(23.3cm3) 324.103g
324 g
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C. Significant Figures

• Calculating with Sig Figs (cont)
• Add/Subtract - The with the lowest decimal
  value determines the place of the last sig fig in
  the answer.

224 g 130 g 354 g
224 g 130 g 354 g
224 g 130 g 354 g
3.75 mL 4.1 mL 7.85 mL
3.75 mL 4.1 mL 7.85 mL
3.75 mL 4.1 mL 7.85 mL
? 350 g
? 7.9 mL
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C. Significant Figures

• Calculating with Sig Figs (cont)
• Exact Numbers do not limit the of sig figs in
  the answer.
• Counting numbers 12 students
• Exact conversions 1 m 100 cm
• 1 in any conversion 1 in 2.54 cm

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C. Significant Figures
Practice Problems

• 5. (15.30 g) (6.4 mL)

? 2.4 g/mL
2.390625 g/mL
6. (18.9 g) - (0.86 g)
? 18.0 g
18.04 g
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D. Scientific Notation

• Converting into Sci. Notation
• Move decimal until theres 1 digit to its left.
  Places moved exponent.
• Large (gt1) ? positive exponentSmall (lt1) ?
  negative exponent
• Only write sig figs.

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D. Scientific Notation
Practice Problems

• 7. 2,400,000 ?g
• 8. 0.00256 kg
• 9. 7 ? 10-5 km
• 10. 6.2 ? 104 mm

2.4 ? 106 ?g
2.56 ? 10-3 kg
0.00007 km
62,000 mm