Bell Work:
Please get a text book and read the following pages silently; page 32-33.
Everyone should be quiet at this time.
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.
Metric Conversions: Problem Solving 1000gram = _______ kilograms
1 25 milliliters = ______ liters
.025 35 hectograms = ______ centigrams
350000 409 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.
RULES 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.
4.63 - 3 SIG. FIG
0.000682 - 3 SIG. FIG.
1.072 - 4 SIG. FIG.
300.0 - 4 SIG. FIG. 300 - 1 SIG. FIG.
How many significant Figures…..?(Guided Practice)
1. 1.097800(What is the Rule?)
2. 4.690(What is the Rule?)
3. 0.00785(What is the Rule?)
4. 3000(What is the Rule?)
5. 3000.00(What is the Rule?)
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