Physical Science

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Physical Science

• Chapter 2 Notes

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Chapter 2 Physical Science Methods

• 2-1
• Standards of Measurement

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Unit and Standards

• In order for measuring to be useful, a
  measurement standard must be used.
• Standard exact quantity that people agree to
  use for comparison.

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International System of Units

• SI standard system for all measurements used
  worldwide
• Each type of measurement has a base unit.
• Prefixes are used to indicate the power of ten
• Examples of page 35, Table 2-1

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Please do the following.

• How many liters are in 6 kiloliters?
• How many centimeters are in 15 meters?
• How many milligrams are in 18 centigrams?

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Large distances

• AU astronomical unit distance from the sun to
  the earth
• About 150 000 000 000 meters
• Light year- distance light travels in one year.
• About 9.5 trillion kilometers
• Nearest star is 4.2 light years away.

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• Calculate how many kilometers are in one AU?
• How many miles are in one AU?
• 1 mile 1.61 km

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Section 2-2Using SI Units
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SI Units and Symbols

• 7 base units- all others derived from these
  seven.
• Table 2-2

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• Length- distance between two points
• Meter (m)- SI unit of length
• Please do the practice problems on page 40 1,2

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Choosing a Unit

• Size of the item will determine the unit.
• What is the best unit to measure
• Distance to your house?
• Width of an animal cell?
• Distance to Mars?
• Length of a pencil?

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• Conversions changing between units will
  sometimes be needed.
• One way is to multiply by a ratio that equals one
  like
• 4 quarters1 dollar
• 1 meter 100 centimeters

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Volume

• -the amount of space occupied by an object
• -expressed in distance cubed
• What is the distance cubed of your cube in
• cm3?
• mm3?
• dm3?

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• derived units- found by combining base units
• 1 L 1 dm3
• 1mL1 cm3
• 1 L 1000 cm3
• How many cubic centimeters are in 1.45 L of milk?

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Mass

• Measurement of matter in an object
• Kilogram-(kg) SI unit of mass
• In the lab mass is measured with a balance

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Density

• -mass per unit volume of material
• Density mass
• volume
• Measured in g/ml or g/cm3

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Time and Temperature

• Time- interval between two events
• Second-SI unit for time

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Temperature

• SI unit for Kelvin (K)
• Based on absolute zero (-273 C)
• K ºC 273

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Convert the following

• 100 cm to meters
• 2.3 dm3 to liters
• 27º C to K

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• Explain why density is a derived unit.

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• Chemists sometimes use density to identify a
  sample. What is the density of an unknown metal
  that has a mass of 178.0 g and volume of 20.0 ml?
• Use table 2-3 to help predict the possible
  identity of this metal.

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Section 2-3 Graphing
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• Graph visual display of information or data
• Three types
• Line graph show trends or how data changes over
  time
• Independent variable- plotted on the horizontal,
  x-axis
• Dependent variable plotted on the vertical,
  y-axis

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• Bar Graph useful for comparing information
  collected by counting

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• Circle Graph or pie graph, shows how something
  is broken down into parts

Sources of Electricity
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• All graphs need to be properly labeled and
  titled!!!

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Section 2-4

• SI For All

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SI use in the US

• SI is used in athletics, medicine, packaging,
  and some manufacturing.
• Where is it not used??

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Drawback of Adopting SI

• We know this system.
• Could be costly for industry.

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Benefits of Adopting SI

• Easier to convert
• Easier to trade with other countries.