SI Units

Standard

S8CS2a. Follow correct procedures for use of scientific apparatus.

S8CS4b. Use appropriate tools and units for measuring objects and/or substances.

Essential Question

What is the importance and purpose of the SI system?

https://www.youtube.com/watch?v=U04nHNUMfPA

https://www.youtube.com/watch?v=KfrCaKyhwZk

The International System

The International System of Units, or SI for short, was designed to provide a worldwide standard of physical measurement for science, industry, and commerce.

SI prefixes:

Prefix Multiplier

giga- 1,000,000,000

mega- 1,000,000

kilo- 1,000

hecto- 100

deka- 10

[unit] 1

deci- 0.1

centi- 0.01

milli- 0.001

micro- 0.000001

nano 0.000000001

Length

Length is defined as the distance between two points. The meter is the SI unit of measure for length

One meter is about the size of a baseball bat

The size of rooms or buildings is often measured with a meter, smaller objects such as a book or pencil is measured with either centimeter or millimeter.

Long distances may be measured with kilometers

How many kilometers is a marathon?

Volume

Volume is the amount of space an object occupies. Volume describes the amount of space inside a 3D object, therefore

the unit is cubed

The cubic meter m3 is the SI unit for volume

To measure the volume of a square or rectangle, measure the length, width, and height and multiply them together.

A liter is a measurement of liquid volume (a 2-liter of soda) 1L=1000 cm3

Mass The mass of an object measures the amount of matter in the

object. This is different from weight***

Kilogram is the SI unit for mass

You can determine mass with a triple beam balance.

Weight

Weight is a measurement of force.

The SI unit for weight is newton (N) What force determines our weight?? Hint- if you travel to other

planets you would weight different amounts depending on the amount of this force present.

Temperature

The physical property of temperature is related to how hot or cold an object is. Temperature is a measure of the kinetic energy, or energy of motion, of the particles that make up matter.

Temperature is measures in SI Units with the kelvin (K) scale

Farenhiet and Celsius temperature scales are the most commonly used scales. These scales DO NOT start at zero (hence both having negative numbers) Kelvin starts at ABSOLUTE ZERO

Time and Rates

Time is the interval between two events The SI unit for time is seconds (s), time is also measured in hours (h)

A rate is the amount of change of one measurement in a given amount of time Speed is a common type of rate measured (kilometers per hour

km/h)

DISCLAIMER

Several units we use everyday are NOT used throughout the rest of the world, and are NEVER used in science. For example: miles, pounds, inches