Metric SystemMetric SystemInternational System of Units (SI)

The Language of Measurement

• StandardStandard: an exact quantity against which comparisons can be made (any number)

• UnitUnit: a label that follows the measurement to give it value (meter, liter)

• Standard of comparison:Standard of comparison: comparing the size of an object with that of a known standard. (2 liters, 10 meters, 5 grams)

Science Uses Metric Units• World scientists use the International

System of Units (SI) because it uses less units and is convenient and universal.

Metric Units

Meter

Length

Liter

Liquid Volume

Gram

Mass

Newton

Force/Weight

Second

Time

Celsius & Kelvin

Temperature

MatterMatter• Everything is made of matter• All matter has properties that can be observed and

described

Physical Properties

Chemical Properties

Color

Shape

Hardness

One way to observe physical properties is to measuremeasure them!

Measured using a meter ruler or meter stick

Basic unit for length:meter - meter - mm

Length - 26 cmLength - 26 cm

• Standard SI Unit – square meter - m²m²

• Formula: Area equals length times width: A = l x w

AREA

Length – 8 cm

Width

3 cm

Area: 8 x 3 = Area: 8 x 3 = 24cm²24cm²

• Standard SI Unit – cubic meter - m³m³

• Volume equals length times width times height: V = l x w x h: V = l x w x h

Length – 10 mWidth = 5 m

Height: 3 m

Volume: 10 x 5 x 3 = Volume: 10 x 5 x 3 = 150 m³150 m³

Usually measured in Liters (L)

Tools:Graduated Cylinder

Beakers

Amount of matter in an object

Standard SI Unit: kilogram and gramTool: Triple Beam Balance

Amount of mass a material has for its volume

Often compared with the density of water

less dense: float

more dense: sink

Frozen water expands

and becomes less dense =

floating ice cubes

D = M/V means Mass divided by Volume

A pushpush or pullpull on an object

Weight is the measure of the force of gravity acting on an object

Strength depends on the mass of the object and the distance between them

SI Unit: Newtons (N)Newtons (N)

Weight measured on a spring scale

Kelvin (K)Celsius (C)

•Measured using a thermometer

2 scales used in science

Note: The Fahrenheit temperature scale still used in U.S. Note: The Fahrenheit temperature scale still used in U.S. weather forecasts.weather forecasts.

A measurement of the period between two events.

Not a property of matter

SI Unit: Second

In one second, light can travel about 7 ½ times around the earth at the Equator. Speed of light: 186,300 per second

Most accurate: atomic clock at the National Bureau of Standards in Washington, DC

““WHY DO I NEED TO KNOW WHY DO I NEED TO KNOW THE METRIC SYSTEM?”THE METRIC SYSTEM?”

All countries in the world use the Metric System… except Burma (Myanmar) and the United States

National Bureau of Standards in Washington, DC sets accurate measurement standards for science, industry and commerce

Industries that sell or buy goods in other countries must use SI units to compete in those countries.

Accuracy, Estimation, and Accuracy, Estimation, and PrecisionPrecision

• ACCURACY: depends on how close your value is to the actual or accepted value

• ESTIMATION: a valuable skill that saves time! – It can be improved with practice.

• PRECISION: the degree of exactness with which the object is measured. – Depends on the measuring instrument. – Can’t improve with practice. – Can only be as precise as the measurement instrument. – Does not guarantee accuracy!