chapter 1, section 3€¦ · section 3: measurement why do scientists use a standard measurement...

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.


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).


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).


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).


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


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.


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



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.


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


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


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.


Time The second (s) is the SI unit of time.


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.


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, section 3€¦ · section 3: measurement why do scientists use a standard measurement...

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