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Chapter 1, Section 3
Measurement
Section 3:Measurement
Why do scientists use a standard measurement system?What are the SI units of measurement for length, mass, volume, density, time, and temperature?
Chapter 1 Introduction to Physical Science
A Standard Measurement System Using SI as the standard system of measurement allows scientists to compare data and communicate with each other about their results. SI units are based on multiples of 10.
Chapter 1 Introduction to Physical Science
Standard MeasurementUsed worldwide in Science; called the International System of Units, or SI
Minimizes confusion
Based on units of 10Most common SI units
Table Talk: What do you think scientists use SI units to measure?
Length, volume, mass, density, temperature, and time
Length The basic unit of length in SI is the meter (m).
Chapter 1 Introduction to Physical Science
Length Basic unit is the meter (m); also, centimeters (cm), & millimeters (mm)
Common measurement tool is the metric ruler
Common conversions for length:
1 km = 1,000 m1 m = 100 cm1 m = 1,000 mm1 cm = 10 mm
Table Talk: What unit would you use to measure the distance between two cities? Your height? The length of a safety pin?
Try this: 200 m = ? cm
Mass The SI unit of mass is the kilogram (kg).
Chapter 1 Introduction to Physical Science
Weight & MassWeight = a measure of the force of gravity on an object (grams, milligrams, kilograms)
Mass = a measure of the amount of matter an object contains
Standard unit for mass is the kilogram (kg)
Common conversions for mass
1 kg = 1000 g1 g = 1000mg
Table talk: Why do you weigh less on the moon than on Earth? Is your mass the same or different on the moon?
Try this: 1600 g = ? kg
VolumeThe SI unit of volume is the cubic meter (m3).
Chapter 1 Introduction to Physical Science
VolumeVolume = the amount of space an object takes up (liters, millileters, cubic centimeters)
Standard unit for volume is the cubic meter m3
Common conversions for volume
1 L = 1000 mL1 L = 1000 cm3
1 mL = 1cm3
Table talk: How would you measure the volume of a liquid? A box of cereal? A raspberry?
Measuring Volume Of liquidsUse a graduated cylinderRead the bottom of the meniscus
Of Rectangular SolidsVolume = length X width X height
Of Irregular SolidsSubmerge the object in water in a graduated cylinderThe water level rises by the amount that is equal to the volume of the object in milliliters
Calculating Density Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.
Read and UnderstandWhat information are you given?Mass of metal object = 57 gVolume of metal object = 21 cm3
Chapter 1 Introduction to Physical Science
Density Density = __mass__volume
Units are grams per cubic centimeter (g/cm3) for solids and grams per milliliter (g/mL) for liquids
Table talk: Which is denser?
Try It! Suppose that a metal object has a mass of 57 grams and a volume of 21cm3. Calculate its density.
Calculating Density Suppose that a metal object has a mass of 57 g and a volume of 21 cm3. Calculate its density.
Plan and SolveWhat quantity are you trying to calculate?The density of the metal object = __What formula contains the given quantities and the unknown quantity?Density = Mass/VolumePerform the calculation.Density = Mass/Volume = 57 g/21 cm3 = 2.7 g/cm3
Chapter 1 Introduction to Physical Science
Calculating Density 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 metal–aluminum.
Chapter 1 Introduction to Physical Science
Calculating DensityPractice 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
Chapter 1 Introduction to Physical Science
Calculating DensityPractice Problem
What is the density of a liquid with a mass of 45 g and a volume of 48 mL?
0.94 g/mL
Chapter 1 Introduction to Physical Science
Density Because density is actually made up of two other measurements–mass and volume–an object’s density is expressed as a combination of two units. The density of a substance stays the same no matter how large or small a sample of the substance is.
Chapter 1 Introduction to Physical Science
Time The second (s) is the SI unit of time.
Chapter 1 Introduction to Physical Science
Time The second (s) is the SI unit of time
Clocks and stopwatches are used to measure time up to one hundredth of a second! (digital stopwatch)Table Talk: Which of these three tools would be most precise to use when timingan Olympic athlete?
Temperature Scientists use the Celsius and Kelvin scales to measure temperature. The kelvin (K) is the SI unit of temperature.
Chapter 1 Introduction to Physical Science
Temperature Scientists commonly use the Celsius scale (oC)
Water freezes at 0oCWater boils at 100oC
Table Talk: Estimate what normal human body temperature (98.6oF) would be in oC.
end
End of Section:Measurement
Chapter 1 Introduction to Physical Science
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