Ch02b using si units

Using SI Units

Measurement Standard•An exact quantity that people agree to use for comparison.

* helps you get the same answer as other

people

What was used as the earliest measurement standards?

•Body Parts* The question then, is

WHO’S body parts?

The KING’S or QUEEN’S

• Is your hand or a body part a

good standard of measurement?

* no

* people’s hands are not the

same size

* get different answers

•In order for any measurement to MAKE SENSE; two things must be included.

1.) a number2.) a unit

•Every type of measurement has a base or central unit.

* meter (distance or length)

* liter (volume)

* gram (mass)

* second (time)

•Adding a prefix to a base (central) unit, you can create a whole new unit to measure any object.

Prefixes Used When Measuring:

• Large Objects

kilo = 103

hecto = 102

deka = 101

• Small Objects

deci = 10-1

centi = 10-2

milli = 10-3

Measurements that can be made

• Length

• Mass

• Temperature

• Time

• Area

• Volume

• Density

• Weight

Length• The distance between two

points.• Base (central) units of length

* (US) FOOT [ft]

* (SI) METER [m]

Length• Length of an object or the

distance between two points is measured using a METERSTICK.

Mass• “A body of coherent matter.”

* a collection of stuff joined to form an object

• Base (central) units of mass* (US) SLUG [slug]* (SI) KILOGRAM [kg]

sometimes gram [g]

Mass•Mass is measured using a BALANCE.

Temperature

•Measurement of how hot or cold something is.

Temperature• Base (central) units of

temperature

* (US) FAHRENHEIT [oF]

* (SI) CELCIUS [oC]

> (SI) KELVIN [K]

* this is an absolute scale

Temperature• Temperature is measured

using a THERMOMETER.

Absolute Zero• The coldest possible

temperature.* temperature where ALL

motion stops* 0 Kelvin * found by the formula:

K = oC + 273.16

Time• Interval between two

events.•Base (central) units of

time* (US) SECOND [s]* (SI) SECOND [s]

Time•Time can be measured using a CLOCK or a CALENDAR.

Derived Units•Obtained by combining multiple units of measurement.

Area

• The amount of surface

included in a set of boundaries.

• Found by the formula:

* Area = length x width

Area•What is the difference between length and width?

•DIRECTION

Area

• Base units of area

* (US) FEET SQUARED [ft2]

* (SI) METERS SQUARED[m2]

Volume• The amount of space an object

occupies.• Easy with liquids & gases,

harder with solids

* for a solid you may need the formula:

volume = l x w x h

Volume• For a liquid or a gas all you

need is a devise that is designed to measure volume.

* a beaker, a flaskor a graduated

cylinder

Volume• Base (central) units of volume

* (US) GALLON [gal]

* (SI) LITER [L]

sometimes centimeters cubed [cm3]

Volume

•1 milliliter equals

1 centimeter cubed.

* 1 mL = 1 cm3

Density• The measurement of how

thick, compact and solid an object is.

• Relationship between the mass & volume of an object

Density

•Found by the formula:

* Density = mass ÷ volume

• Expressed in g/L or g/cm3

* a mass unit / a volume unit

Weight• Measurement of the force of

gravity pulling on the mass of an object.

• Changes as gravity changes.• Base units of weight

* (US) POUND [lb]* (SI) NEWTON [N]

Weight•Weight is measured using a SPRING SCALE.

•MASS and WEIGHT are NOT the same thing!

Physical Properties• Characteristics of a substance that can be

used to identify it.• Color• Shape• Texture

• State of matter• Size

• All measurements(changing a physical property does NOT change the substance)