Transcript DO NOW! - Hall High School

DO NOW!
Take out your SI Conversion notes from last
week. Complete page 1 using this slide.
• Metric system is based on powers of 10
• Standard units in the metric system are meter, liter,
gram
Prefixes
kilo
hecto
deca
meter
liter
gram
deci
centi
milli
• The two methods of converting between units within
the metric system include the ladder method
(moving decimal place), and using conversion
factors.
Ladder Method
1
2
KILO
1000
Units
HECTO
100
Units
3
DEKA
10
Units
Standard
DECI
0.1
Unit
Meters
Liters
Grams
How do you use the “ladder” method?
1st – Determine your starting point.
2nd – Count the “jumps” to your ending point.
3rd – Move the decimal the same number of
jumps in the same direction.
CENTI
0.01
Unit
MILLI
0.001
Unit
4 km = _________ m
Starting Point
Ending Point
How many jumps does it take?
4. __. __. __. = 4000 m
1
2
3
The Conversion Factor Method
The following are common metric system
equations that can be used as conversion factors
to cancel out units.
1 m = 100 cm
1000 mL = 1 L
1 kg = 1000 g
1 g = 1000 mg
Example:
Using Conversion Factors
How many milliliters are in 15.67 L of water?
Given: 15.67 L of water
Needed: mL of water
𝟏𝟓. 𝟔𝟕 𝐋
∙
𝟏
1000 𝐦𝐋
1 𝐋
= 15,670 mL
Significant
Figures
2-3 Scientific
Measurement
Error in Measurement
• Some error or uncertainty always exists in any
measurement.
• The measuring instruments themselves place
limitations on precision.
• All measurements in science should have ONE
uncertain or estimated digit (always the last
number)
Example:
• The following picture represents a
graduated cylinder with water in it.
• The meniscus lies between
44mL- 45mL, therefore an accurate
volume would be 44._ mL
• You would make an estimate as to
what the last digit should be.
• Perhaps 44.5 mL
Example:
• The following picture represents a metric ruler
measuring a pencil.
• The pencil tip lies between
8.2 cm - 8.3 cm, therefore an
accurate length would be
8.2_ cm
• You would make an estimate as to
what the last digit should be.
• Perhaps 8.23 cm.
cm
You Try It! - Practice Problems
SIGNIFICANT FIGURE RULES
1. Any non-zero number is ALWAYS
significant. 28.49
2. Any zero(s) between two significant
numbers is ALWAYS significant.
505.7009
3. Any placeholder zero(s) (leftmost
zeros), is NEVER significant. 0.00896
SIGNIFICANT FIGURE RULES
4.
Any zero(s) at the end of a number
AND to the right of a decimal is
ALWAYS significant. 943.8900
5. Any zero at the end of a number
AND to the left of a decimal is
NEVER significant UNLESS there is
an obvious decimal. 980
980.
SUMMARY OF SIG FIG RULES
• ALL numbers are considered significant EXCEPT:
Zeros that start a number
Zeros that end a whole number (no decimal)
0.008764
6,745,000
YOU TRY IT!
How many significant figures are
in the following measurements?
Put the Rule #(s) that you followed to get to your answer.
1. 15.39
2. 9.078003
3. 4.0800
4. 23190
Practice Problems
45.8736
6
•All digits count
0.000239
3
•Leading 0’s don’t
0.00023900 5
•Trailing 0’s do
48000.
5
•0’s count in decimal form
48000
2
•0’s don’t count w/o decimal
3.982106
4
•All digits count
1.00040
6
1.50 x 103
•0’s between digits count as well as trailing in
decimal form
3
•Trailing 0’s do
MULTIPLYING AND DIVIDING
WITH SIGNIFICANT FIGURES
2
1
1
a. 4.0  5 =
3
2
2
b. 4.00  5.0 =
4
c.
3
4.000  5.00 =
3
MULTIPLYING AND
DIVIDING RULE
• The final answer should be
rounded to the same number of
significant figures as the
measurement with the least
number of significant figures in
the problem.
ADDING AND SUBTRACTING
WITH SIGNIFICANT FIGURES
1
0
0
a. 4.4 + 5 =
2
1
1
b. 4.02 + 5.0 =
3
c.
2
4.006 + 5.00 =
2
ADDING AND
SUBTRACTING RULE
• The final answer should be
rounded to the same number of
decimal places as the
measurement with the least
number of decimal places in the
problem.
CONVERSION FACTORS
• Conversion factors are exact numbers and
therefore have an infinite number of
significant figures.
• When doing conversions, your final
answer should have the same number of
significant figures as the given number.