Section 1-3: Measurement

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Section 1-3 Measurement
Chapter 1 Introduction to Physical Science

• Why do scientists use a standard measurement
  system?
• What are the SI units of measurement for length,
  mass, volume, density, time, and temperature?

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A Standard Measurement System
Chapter 1 Introduction to Physical Science

• Using SI as the standard system of measurement
  allows scientists to compare data and communicate
  with each other about their results.

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SI units are based on multiples of 10. We will
be using SI and other metric units.
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Length
Chapter 1 Introduction to Physical Science

• This year we will measure length using
  millimeters (mm), centimeters (cm) and meters
  (m).
• The basic unit of length in SI is the meter (m).

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WEIGHT vs MASS

• Weight

• Mass

• Your weight is a measure of the force of gravity
  on you.
• The force of gravity may be more or less on other
  planets or moons than on Earth.
• You would weigh about one-sixth of your Earth
  weight on the moon.
• The newton (N) is the SI unit, the pound (lb) is
  the English unit.

• Mass is the measure of the amount of matter an
  object contains.
• Mass is not affected by gravity.
• If you travel to the moon, the amount of matter
  in your body (your mass) will not change.
• Scientists prefer to use mass rather than weight.
• SI unit of mass is the kilogram (kg), but we will
  be using mostly grams (g) in this class.

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Volume
Chapter 1 Introduction to Physical Science

• Volume is the amount of space an object takes up.
• The SI unit of volume is the cubic meter (m3),
  but we will often measure milliliters (mL).

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Volume of a liquid

• Graduated cylinder
• mL
• Meniscus- curved surface at top of liquid, always
  record measurements using bottom of meniscus

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Volume of Rectangular Solid
Volume of Irregular Solid

• Example- Rock
• Submerge object in water in graduated cylinder
  and measure the displacement of the water
• Lets look at the example in your book on page 23
  now
• Example units mL

• Example- Cereal box
• Volume Length x Width x Height
• Remember to multiply numbers and units, so units
  will be cubed
• Example units cm3

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Density

• Two objects of the same size can have very
  different masses. WHY???
• Because different materials have different
  densities!
• Density is mass per unit volume
• So Density Mass/ Volume
• Since density is made up of 2 measurements, it
  always has 2 units.
• SI unit of density is kg/m3.
• We will be using g/cm3 and g/mL.

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Calculating Density
Chapter 1 Introduction to Physical Science

• Suppose that a metal object has a mass of 57 g
  and a volume of 21 cm3. Calculate its density.

• Read and Understand
• What information are you given?
• Mass of metal object 57 g
• Volume of metal object 21 cm3

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Calculating Density
Chapter 1 Introduction to Physical Science

• Suppose that a metal object has a mass of 57 g
  and a volume of 21 cm3. Calculate its density.

• Plan and Solve
• What quantity are you trying to calculate?
• The density of the metal object __
• What formula contains the given quantities and
  the unknown quantity?
• Density Mass/Volume
• Perform the calculation.
• Density Mass/Volume 57 g/21 cm3 2.7 g/cm3

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Calculating Density
Chapter 1 Introduction to Physical Science

• Suppose that a metal object has a mass of 57 g
  and a volume of 21 cm3. Calculate its density.

• Look Back and Check
• Does your answer make sense?
• The answer tells you that the metal object has a
  density of 2.7 g/cm3. The answer makes sense
  because it is the same as the density of a known
  metalaluminum.

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Calculating Density

• Practice Problem
• What is the density of a wood block with a mass
  of 57 g and a volume of 125 cm3?

• 0.46 g/cm3

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Density Continued

• The density of a substance stays the same no
  matter how large or small a sample of the
  substance is.
• So a gold earring and a gold necklace will both
  have a density of 19.3 g/cm3

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Sink or Float?

• Knowing an objects density allows you to predict
  whether it will sink or float.
• If the object is less dense than the liquid, it
  will float.
• If the object is more dense than the liquid, it
  will sink.

Problem Water has a density of 1 g/cm3. Will
an object with a density of 0.7 g/cm3 float or
sink in water?
FLOAT!
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Time

• The second (s) is the SI unit of time and
• we will be measuring time in seconds . ?

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Temperature

• The kelvin (K) is the SI unit of temperature.
• Scientists use the Celsius and Kelvin scales to
  measure temperature.