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U1D6: Rounding using precision and Sig.figs.Do Now: 1. Correct Practice #2 2. Copy and answer on Sig Fig notes page #S.F. rule, precision
3420 g
200 m
0.0032 km
2003 g
1, no decimal, hundreds
2, less than 1, ten thousandths
4, no decimal, ones
3, no decimal, tens
U1D6: Rounding with Precision and Sig Figs
Agenda: • Review of Precision/Sig Figs• Sig Fig Checkpoint• I will be able to round my answers to the
correct precision or significant figures! • Practice!!!!!!
Reminders:
• ALL Lab safety paperwork MUST be in if you are to participate the the lab Day 7.
Sig Fig Review Practice#2 answers
3) Circle the place where the precision is and underline the significant figures in the measurements below. Write the number of significant figures in the measurement to the right of each measurement.
4) Write the following numbers, precise to the noted precision or number of significant figures:
4) Write the following numbers, precise to the noted precision or number of significant figures:
5) Round each number to the precision or # of sig figs noted:
5) Round each number to the precision or # of sig figs noted:
Todays Goal
I know how to round to the correct precision/sig figsTonight:
1.Finish Rounding Practice (#3)
2.Pre-Lab: Thickness and Density of Al Foil
NumberDoes it have a decimal?
Yes No
Precision is farthest # on right
Precision is right most non-zero or a zero w/a line over it
Count from the left most non-zero
to the precision
What is precision?
• Is 7.0 cm the same thing as 7.00 cm?
Is 7.0 cm the same thing as 7.00 cm?
• No, and here is why;• Think back to the measurement lab. The
precision of your measurement depended on the tool you were using
VS
VS7.0 cm 7.00 cm
Why is precision important?
• Comes into play when you need to do math• For example;– If you added 11 km and .003 km you may be tempted to put 11.003 km as the answer
• THIS WOULD BE WRONG!
• Like a chain that is only as strong as its weakest link……
Answers need to be rounded!
Addition and Subtraction: (ASP) Number with the Least precision
Multiplication and Division: (MDS) Lowest Number of Sig Figs
Why?
• 11km is only precise to the kilometer. It could actually be 11.427 km (or some other measurement) but the instruments could not read that precise.
• 11.???????, don’t know what those numbers are!
11.??????? Km+0.003 km11.??????? km
11km + .003 km
• Least precise place is the ones place, so we will round to the ones.
• 11 km + .003 km = 11.003 km 11 km
• Remember:• Adding and subtracting: unit must be the
same: cm + cm = cm
Why?
• If you put your answer as 11.003 km you are saying that all your measurements were precise to the thousandths place (WHICH THEY WEREN’T!)
What if we multiply/divide?
Remember:• Multiplying and dividing :you can mix units mL * mL = mL2
g ÷ mL = g/mL
g/mL * mL = g
Practice • 20.1 g + 60.33 g = 80.43 g After rounding80.4 g
• 170 ml - 17.0 ml = 153.0 ml after rounding150 ml
• 17 g/ml x 5ml = 85 g after rounding90 g
• 2134 g / 17.6 ml = 121.25 g/ml rounding121 g/ml
Your Turn:
Practice packet #3 Work in pairs! Help each other. Talk through the rules! (inside voices)
Tonight: 1. Practice #3 2. Pre-Lab questions Lab 3
