Why do we need to be able to measure things? To make sense, all measurements need both . . . Why do we need to be able to measure things? Suppose we wanted to measure a 2 x 4 for building a house. Units by themselves don’t make sense. Numbers by themselves don’t make sense. A Number and a Unit! A board is meters long . . . . A board is 350 long . . . . Any Ideas?

Precision and Accuracy Precision is a description of how close measurements are to each other. Accuracy is comparing your measurement to the actual or accepted value.

Basic Types of Measurement Length: measures distance between objects Volume: measures the amount of space something takes up Mass: measures the amount of matter in an object Other Types of measurement include: time temperature density PH

Measurement System Comparisons ENGLISH SI SYSTEM LENGTH Yard / Inch Meter / Centimeter MASS Ounce / Pound Gram / Kilogram VOLUME Quart Liter TEMPERATURE Fahrenheit Celsius / Kelvin TIME Second All Measurement systems have standards. Standards are exact quantities that everyone agrees to use as a basis of comparison.

The SI System uses the following prefixes: Kilo 1000 Hecto 100 Deca 10 UNIT 1 Deci 1/10 Centi 1/100 Milli 1/1000 This system works with any SI measurement. The UNIT becomes whichever type of measurement you are making. (mass, volume, or length) It is the same system regardless if you are measuring length, mass, or volume.

centi gram It works for all types of measurement. If you’re measuring . . . Length then it is the meter (kilometer, decameter, etc.) Mass then it is the gram (centigram, milligram, etc.) Volume then it is the liter (deciliter, hectoliter, etc.) centi gram The first part of the term indicates the amount, the second part indicates the type of measurement.

How does converting units work? Unlike the English system converting in the SI System is very easy. For Example in the English system if you wanted to know how many inches in 2 miles what would you do? Take the number of miles (2). Multiply it by the number of feet in a mile (5,280). Multiply that by the number of inches in a foot (12). ANSWER: 126,720 inches in 2 miles

The SI system is much easier. For example in the metric system if you wanted to know how many centimeters were in 3 meters, what would you do? Find the unit you have (meters). Find the unit you are changing to (centimeters). Count the number of units in-between (2). Move the decimal point that many spaces, in the same direction you counted (right). 3 meters = 300 centimeters Kilo Hecto Deca UNIT Deci Centi Milli

Kilo Hecto Deca UNIT Deci Centi Milli More Conversions . . . 2,321.0 millimeters to meters = 2.321 meters 521.0 grams to hectograms = 5.21 hectograms NOTE: The digits aren’t changing, the position of the decimal is. In the English system the whole number changes. Kilo Hecto Deca UNIT Deci Centi Milli

Things to Remember All measurements need a number and a unit! Basic units of Measurement (meter, liter, gram) How to convert metric units

Basic Types of Measurement Length: measures distance between objects Volume: measures the amount of space something takes up Mass: measures the amount of matter in an object In SI the basic units are: Length is the meter Mass is the gram Volume is the liter (liquid) Temperature is Celsius

Measurement Review Measurements need a number and a unit! Basic units of Measurement (meter, liter, gram) How to convert metric units Be able to make basic measurements of volume, length, and mass Vocabulary words

Conversion Factors Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example: 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.

Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel How many minutes are in 2.5 hours? Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

= 29 quarters Sample Problem You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 1 dollar = 29 quarters X

A rattlesnake is 2.44 m long. How long is the snake in cm? a) 2440 cm b) 244 cm c) 24.4 cm

Kilo Hecto Deca UNIT Deci Centi Milli Solution A rattlesnake is 2.44 m long. How long is the snake in cm? b) 244 cm Kilo Hecto Deca UNIT Deci Centi Milli

Amount of People in the World. There are 6,900,000,000 people in the world. What is a better way to write this HUGE value? Scientific Notation 6.9 X 109 People Why are we able to write the number like this?

Significant Figures – long story short, this is how well you measured something. The most confusing parts are the zeros Rules

Decimal ‹ 1 – start from left, count all nonzero + zero between No decimal – trailing 0 – not sig. Ex: 7400 --- 2 sig. figs - zeros between nonzero are sig. Ex: 308562 --- 6 sig. figs Decimal ‹ 1 – start from left, count all nonzero + zero between Ex: 0.00506 --- 3 sig. figs. Ex: 0.001400 --- 4 sig. figs Decimal › 1 – all count Ex: 40.070 --- 5 sig. figs

How many significant figures are in the following: 203.4 7600 0.000035

How many significant figures are in the following: 203.4 --- 4 Decimal › 1 – all count 7600--- 2 No decimal – trailing 0 – not sig. - zeros between nonzero are sig. 0.000035--- 2 Decimal ‹ 1 – start from left, count all nonzero + zero between