Bell Work: Please get a text book and read the following pages silently; page Everyone should be quiet at this time.

Measurements/Calculations Analyzing Data

Objectives:  Define SI Base Units  Explain how adding a prefix changes a unit  Convert between Metric Units  Determine Accuracy/Precision  Determine Significant Figures.  Calculate Significant Figures.

Why do chemists use SI units(do not copy this question)? Chemists use an internationally recognized system of units to communicate their findings.

What are SI Units? Systeme Internationale d’Unites (SI) is an internationally agreed upon system of measurements.

SI Base Units

SI Prefixes

Metric Conversions: Problem Solving 1000gram = _______ kilograms 1 25 milliliters = ______ liters hectograms = ______ centigrams meters = ____ decimeters 4090

What are Accuracy & Precision? Accuracy – how close the measurement is to the true or actual value. Example: Actual Value = 2.50 Which one of these values is accurate? 2.49, 2.30, 2.31, 2.32 Precision – the exactness of measurement

What is a Significant Figure? Significant figure – all the digits know plus one estimated or uncertain number.

RULESRULES FOR DETERMINING SIGNIFICANT FIGURES 1. NON-ZERO NUMBERS ARE ALWAYS SIGNIFICANT. 2. LEADING ZEROS ARE NEVER SIGNIFICANT. 3. IMBEDED ZEROS ARE ALWAYS SIGNIFICANT. 4. TRAILING ZEROS ARE ONLY SIGNIFICANT IF THERE IS A DECIMAL POINT SIG. FIG SIG. FIG SIG. FIG SIG. FIG SIG. FIG.

How many significant Figures…..?(Guided Practice) (What is the Rule?) (What is the Rule?) (What is the Rule?) (What is the Rule?) (What is the Rule?)

Independent Practice Turn to Page 63. Complete Problems 80 & 91.

How would you explain…. Tell me how you would explain to someone you were tutoring the process it takes to convert using the metric system.

Home work Find an item that is measured in metric units of volume….grams. Example – milk 236 mL Example – Rice –a-Roni 192 g

Thought for the Week: Let no corrupt communication proceed out of your MOUTH!