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Section 1-4 Section 1-4 Pgs. 22-25Pgs. 22-25Measurement and Safety Measurement and Safety
9-16-159-16-15
IN: How do scientists IN: How do scientists measure things?measure things?
SI Measurement SystemSI Measurement System
International System of Units (SI)International System of Units (SI)
Helps all scientists share and Helps all scientists share and compare their observations and compare their observations and results.results.
The US by itself does not normally The US by itself does not normally use the SI system of unitsuse the SI system of units
SI System: EVERYWHERE SI System: EVERYWHERE ELSEELSE
Here in the United States we use Here in the United States we use MILES instead of KILOMETERSMILES instead of KILOMETERS
FARENHEIT instead of CELSIUSFARENHEIT instead of CELSIUS
FEET instead of METERSFEET instead of METERS
KILOGRAMS instead of POUNDS (lbs)KILOGRAMS instead of POUNDS (lbs)
SI Measurement SystemSI Measurement System
LengthLength
LengthLength is the is the long long dimensiondimension of any of any object. object.
Tool Tool meter stick or rulermeter stick or ruler SI UnitSI Unit
Meter (m)Meter (m)
TemperatureTemperature
A measure of A measure of how hot (or cold) how hot (or cold) something is.something is.
Tool Tool thermometerthermometer SI UnitSI Unit
Usually Celsius (Usually Celsius (ooC) C) Kelvin (K) Kelvin (K) K= C + 273.15K= C + 273.15
MassMass
The measurement of The measurement of how much how much matter an object contains.matter an object contains.
Tool Tool triple beam balance or scaletriple beam balance or scale SI UnitSI Unit
Kilogram (Kg)Kilogram (Kg) Gram (g)Gram (g)
1 kilogram = 1,000 grams1 kilogram = 1,000 grams
WeightWeight
The measurement of The measurement of the force of the force of gravity on you.gravity on you.
Tool Tool triple beam balancetriple beam balance SI UnitSI Unit
Kilogram (Kg)Kilogram (Kg) Gram (g)Gram (g)
1 kilogram = 1,000 grams1 kilogram = 1,000 grams
Weight or Mass?Weight or Mass?
An object’s weight will change if you An object’s weight will change if you move it from Earth to the moon or to move it from Earth to the moon or to other planets, but its mass will stay other planets, but its mass will stay the same.the same.
VolumeVolume The The amount of space an object amount of space an object
occupies.occupies.
Tool Tool graduated cylindergraduated cylinder
meterstickmeterstick SI UnitSI Unit
Cubic meter (mCubic meter (m33)) Liter (L)Liter (L) Milliliter (mL)= 1 cc (cmMilliliter (mL)= 1 cc (cm33))
Measuring VolumeMeasuring Volume
Rectangular ObjectsRectangular Objects Volume = Length x Width x HeightVolume = Length x Width x Height
DensityDensity
The measurement of The measurement of how much mass how much mass is contained in a given volumeis contained in a given volume..
It is also referred to how closely It is also referred to how closely packed or crowded an object is.packed or crowded an object is. Solids are the most dense.Solids are the most dense. Gases are the least dense.Gases are the least dense. Liquids are in between.Liquids are in between.
Measuring DensityMeasuring DensityDensityDensity=Mass/Volume (mass divided by =Mass/Volume (mass divided by
volume)volume)
Tools:Tools: balance balance andand
graduated cylinder orgraduated cylinder or
meterstickmeterstick
Units:Units:
g/Lg/L
g/cmg/cm33
Density FactsDensity Facts
Less dense object will “float” Less dense object will “float” on top of more dense on top of more dense objects.objects. For example, oil will float on For example, oil will float on
water.water. Oil is less dense than water.Oil is less dense than water. Most of the time solids are more Most of the time solids are more
dense than liquids.dense than liquids. Except for ice!Except for ice! 1g of water = 1 cc = 1 mL1g of water = 1 cc = 1 mL
(at standard temp and pressure)(at standard temp and pressure)
Density FactsDensity Facts ALLALL samples of pure gold have a samples of pure gold have a
density of 19.3 g/cmdensity of 19.3 g/cm3.3.
Fools gold has a density of 5.0 g/cmFools gold has a density of 5.0 g/cm3.3.
Accuracy and PrecisionAccuracy and Precision
They are not the SAME!They are not the SAME!
What is accuracy?What is accuracy?
AccuracyAccuracy - refers to the - refers to the correctness of a measurement.correctness of a measurement.
You are accurate if you hit the You are accurate if you hit the center of the bulls eye.center of the bulls eye.
What is precision?What is precision?
You are precise if your arrow is close You are precise if your arrow is close to other arrows.to other arrows.
You are accurate if your arrow is You are accurate if your arrow is close to the bulls eye.close to the bulls eye.
Can you be both accurate and precise?Can you be both accurate and precise?
Yes, if all your arrows are close Yes, if all your arrows are close together in the bulls eye.together in the bulls eye.
What is precision?What is precision?
PrecisionPrecision - refers to how - refers to how detailed a measurement is based detailed a measurement is based on the measurement tool used.on the measurement tool used.
Using a meterstick to measure Using a meterstick to measure the thickness of one piece of the thickness of one piece of paper is not going to give a very paper is not going to give a very precise measurement.precise measurement.
OUT:OUT: Explain the Explain the difference between difference between accuracy and precision.accuracy and precision.