Section 1-4 Section 1-4 Pgs. 22-25Pgs. 22-25Measurement and Safety Measurement and Safety

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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.