measurement systems english system (usa) –based on feet, pounds, gallons –complex metric (si)...

Measurement Systems• English System (USA)

– based on feet, pounds, gallons– Complex

•Metric (SI) system (everyone else)– Simpler– Based on powers of 10

a decimal system of measurement based on 10

Prefixes of SI used in this class:Kilo= 1000Deci= 1/10 or 0.1Centi= 1/100 or .01milli= 1/1000 or .001

Measurements• Must have both a number and

a unit: – Ex: 4m

• Size of object determines size of unit used

Length • Distance between 2 points

1km = 1000m1m = 100cm1cm = 10mm

Mass•Mass: amount of matter in an

object– Measured with a balance– Units = g or kg

Volume•Volume: Amount of space taken

up by an object.

• Units = liters (L), milliliters (mL), cm3

Measuring Volume 3 Methods:1. Volume of Regular solids

(cubes, rectangles). V = length x width x height

Volume = 5 cm x 5 cm x 5 cm

= 125 cm3

5 cm

5 cm

5 cm

2.Volume of a liquid

•Pour and measure– Use graduated cylinders

Reading a Graduated cylinder

Record value at bottomof meniscus

In this case 52.8 ml

Measuring Volume 3. Irregular solid (rock) by water

Displacement

• Volume of water displaced = volume of object

Volume by water displacement

Density

Density•Density = Mass/Volume

• Units = g/ml or g/cm3

M

D V

Buoyancy• Ability of a fluid to exert an

upward force on an object placed in it

Density & Buoyancy• If object is less dense than the

fluid it’s in, it floats

• If object is more dense than the fluid it’s in, it sinks

• Density of water = 1.0 g/mL

Temperature• Measured with a thermometer

• SI base unit is Kelvin

Kelvin vs. Celsius ScaleCelsius Scale: •Water freezes

at 0° C

•Water boils at 100° C

Kelvin Scale• 0 K is called absolute zero. • At 0 K all particles stop moving.

Kelvin/Celsius Conversion

K = °C + 273

Graphing Data

Why use Graphs?• provides easy method of organizing

data (picture)3types of graphs

1. Bar: used for comparing data2. Circle: shows how parts relates to a

whole 3. Line: shows changes that occur

between related variables

Bar Graph

Circle Graphs• Parts always add up to 100%

Line Graphs• Most scientific graphs are line

graphs• Lines can be straight

Line graphs• Lines can also be curved