Using Numerical Units in Science Honors Biology

Warm Up Questions Think about a pizza: what is the difference between a whole pie and a slice??? What problems could arise from the way different people count pies and slices? Write your answers in your notebook

What is a Unit? A unit is label given to a number that enables us to understand the size and quantity we are talking about Examples of units: pounds, inches, centimeters, grams. . .

In science, we don’t count pizzas. . . . . .but we do count and measure objects as groups and as fractions of a whole item. Examples: How many milliliters are in your water sample? How many grams fit in a 1 kilogram container?

Two Systems of Units International System of Measurements (SI) System of measurement used in Europe and Canada Meters, grams, liters, and seconds are all units of SI English System System of measurement used in the United States Miles, inches, pounds, and gallons are all units of the English system

SI = SCIENCE UNITS Time = seconds (s) Length = meters (m) Mass = grams (g) Volume = liters (l)

Are these measurements ok for science? Andy measures time in seconds. Sarah reports volume in gallons. James collects data on distance in miles. YOUR TURN: Write a correct science measurement scenario.

Science and SI SI is used because it is a decimal system based on tens SI prefixes give the reader a clear relative size when the reader understands the system!!!

Converting Values in SI To change how we talk about a given number, add the correct prefix to the unit Examples: 1000 meters = 1 kilometer 1/100 meter = 1 centimeter

Confused? Remember that we do this all the time without thinking. . . 1 pizza pie = 8 slices 1 dozen = twelve items . . . we are just FORMALIZING the process for science

SI prefixes used for counting GROUPS of items Kilo (k) = 103 (1000) Example: 1 kilometer = 1000 meters Hecta (h) = 102 (100) Generate an example!!! Deca (D) = 101 (10)

SI Prefixes used for counting portions of an item Deci (d) = 10-1 (0.1) Example: 10 deciliters make up one liter Centi (c) = 10-2 (0.01) Generate an example!!! Milli (m) = 10-3 (0.001) Micro (µ) = 10-6 (0.000 001) Nano (n) = 10-9 (0.000 000 001)

Your turn!!! Let’s get thinking about these new vocabulary words. . . “Metric Measurements” Worksheet