THE SI system and units of measurement

- Units of Measurement

Measurement

- Measurement is used to measure quantities.
- Quantity is something that has magnitude, size,

or amount (volume). - A quantity is not the same as a measurement.

SI system of measurement

- In the late 18th century, scientists used the

metric system. The metric system is a forerunner

to the SI System. - Scientists all over the world use a single

measurement system called Le Systeme

International dUnits, abbreviated SI. - It was adopted in 1960 and has both base units

and derived units.

SI Base units

- The most common base units that we will study

include

Quantity Quantity Symbol Unit name Unit abbreviation

Length l meter m

Mass m kilogram kg

Time t second s

Temperature T Kelvin K

Length

- The SI standard unit for length is the meter.
- A distance of 1m is about the width of an average

doorway. - To express longer distances, the kilometer (km)

is used. One kilometer is equal to 1000 m. - To express shorter distances, the centimeter (cm)

is used. One centimeter is equal to 1/100 of a

meter. - Length can be measured using a meter stick or

rulers.

Mass

- Mass is a measure of the quantity of matter. The

standard unit for mass is the kilogram (kg). - The gram (g), which is 1/1000 of a kg is used for

measuring masses of small objects such as flasks

and beakers. Mass is typically measured using a

balance. - Mass is different from weight. Weight is a

measure of the gravitational pull on matter. The

weight of an object increases as gravity acts on

it. The weight of an object on the moon is about

1/6th of its weight on Earth. So, a human on

Earth who weighed 126 lbs. would weight how much

on the moon?

Time

- The standard unit of measurement for time is the

second (s). - Time can be measured using stop watches, clocks,

count down timers, and other time pieces. - Larger amounts of time are measured in minutes

and hours. - There are 60 seconds in one minute. There are 60

minutes in one hour. Given that there are 24

hours in one day, how many seconds are there in

one day?

Temperature

- The standard unit of measurement for temperature

is degrees Kelvin (K). - Temperature can also be measured in degrees

Celsius (C) and degrees Fahrenheit (F). - To convert degrees Celsius (C) to degrees

Fahrenheit (F) multiply by 1.8 and then add 32.

To convert degrees Fahrenheit to degrees Celsius,

subtract 32 and then divide by 1.8 - K C 273
- Temperature is measured using a thermometer.

(measures the degree of heat or coolness)

Derived units

- Derived units are combinations of base units.

They are produced by multiplying or dividing

standard units. The derived units we will study

include

Quantity Quantity symbol Unit Unit abbreviation

Area A square meter m2

Volume V cubic meter m3

Density D kilograms per cubic meter kg/m3

Area

- Area is length times the width. It is expressed

as square meters. - Area can also be expressed as cubic centimeters.
- What is the area of a rectangle that has an a

length of 6 cm and a width of 16 cm? - 16 cm
- 1 6 cm
- 11111cmam

Volume

- Volume is the amount of space occupied by an

object. The derived SI unit for volume is cubic

meters. The cubic meter is rather large, so a

more common unit of cubic centimeters is more

commonly used. - Non-SI units are also used to measure volume such

as the milliliter (mL) and the liter (L), which

is 1000 cm3. There are 1000 mL in 1 L. - Beakers, flasks, and graduated cylinders are

often used to determine the volume of liquids.

density

- Density is the ratio of mass to volume, or mass

divided by volume. It can be written - densitymass/volume or Dm/V
- Density is a characteristic physical property

of a substance that does not depend on the size

of the sample. As the mass of an object

increases, its volume increases. - Question Are raisins, more or less dense than

soda water? Lets see!

Name Volume (cm3) Mass (kg)

Michael 120384 85

John 77509 59

Colleen 35000 56

Fabrizio 135456 80

Abella 47824 62

Aaron 174096 101

Felicita 95700 63

Travis 89775 102

Franklin 97559 70

Steven 90580 70

Kayla 90180 65

Nicholas 89280 66

Brianna 100200 70

Name Volume X Mass Y

Oscar 109620 cm3 74kg 0.000235

Crystal 69,900 cm3 51kg 0.0002857

Ron 172,900 cm3 79kg 0.000222

Brian 170280 cm3 74kg 0.0002

Chevon 126412 cm3 65kg 0.000211

Amber 94350 cm3 0.0002

Maria 56160cm3 49kg 0.0002

Danielle 115520 cm3

Robert 131760cm3 60kg 0.00021

Emmanuel 129960 cm3 62kg 0.000192

Brittany 95456 cm3 55kg 0.00027

Alyssa 110160 cm3 0.00027

Jaclynne 65490 cm3 50kg 0.0003

Jake 142740 cm3 67kg 0.0003