U1D9: HOW DO WE CONVERT FROM ONE UNIT TO
ANOTHER ALGEBRAICALLY?
Do Now: 1. Check HW #4
2. Chemistry reference Tables (CRT) out on desk
Agenda:
1. HW Qs
2. Review of Sci notation and Sig Fig. /check
3. Dimensional Analysis notes and practice
4. Ticket to Leave
PERIOD 2 ONLY TAKE OUT PRACTICE PACKET
A) Convert each of the following into scientific notation:
Number
250.
Scientific Notation
200 000
0.000 55
602 300 000 000 000 000 000 000
0.000 000 000 000 000 000 160
2
B) Convert each of the following into
standard decimal notation:
Scientific Notation Standard Decimal Notation
7.982 X 1011
7.02 X 10-4
2.030 X 10-18
4.3 X 10-5
3
C) Ksp is a measurement of the solubility of a salt. The
larger the value of Ksp is, the more salt can dissolve in
water.
1)4.3 X 10-6
2) 5.7 X 10-7
3) 9.8 X 10-8
4) 3.2 x 10-9
a) Which of the following Ksp values would indicate the
salt with the highest solubility? _______
b) Which of the following Ksp values would indicate
the salt with the lowest solubility? _______
c) Explain how you answered a and b.
4
USING UNITS TO SOLVE PROBLEMS
Yes, algebra is actually used in the real
world to do stuff! Like the stuff you’re
about to learn here.
WHAT DO YOU KNOW?
• EXPLAIN HOW to rearrange the
equation q = m C DT to solve for DT,
ending with a correctly rearranged
equation.
PROBLEM-SOLVING STRATEGY
• Identify the GIVEN and the TARGET
• Write down the GIVEN, including the units
• Multiply or divide the GIVEN by a CONVERSION FACTOR that will
give you your TARGET. Use the units to decide whether to
multiply or divide.
• Record your TARGET, including units.
EXAMPLE OF CONVERSION
• How many minutes are there in 2.3 hours?
GIVEN: 2.3 hours
TARGET: minutes
CONVERSION FACTOR: 60 minutes/hour
2.3 hours
X
60 minutes/hour
To cancel out hours, MULTIPLY.
=
138 minutes
140
Round your answer to the
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
EXAMPLE OF CONVERSION
• How many feet are there in 34.3 inches?
GIVEN: 34.3 inches
TARGET: feet
CONVERSION FACTOR: 12 inches/foot
34.3 inches
/
12 inches/foot
To cancel out inches, DIVIDE.
=
2.8583333
2.86 feet feet
Round your answer to the
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
EXAMPLE OF CONVERSION
• How many nickels are there in $42.25?
GIVEN: 42.25 dollars
TARGET: nickels
CONVERSION FACTOR: 20 nickels/dollar
42.25 dollars
X
20 nickels/dollar
To cancel out dollars, MULTIPLY.
=
845
845.0
nickels
nickels
Round your answer to the
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
METRIC CONVERSIONS
• Look up Reference Table C.
• Add the following to the
table:
• Metric system: uses
prefixes to stand in for
powers of ten of measured
units
• 45 thousand grams = 45 kg
• 32 thousandths of a gram =
32 mg
CREATING METRIC CONVERSION FACTORS
• Write down the GIVEN and
TARGET.
• Write above it the FACTOR for
the units of each.
• Take the difference in power of
ten between the two factors.
This is the conversion factor, in
terms of powers of ten.
• Smaller unit / larger unit
10-2
103
How many cm in 45.2 km? 105 difference
target given
= 100000 cm/km
CREATING METRIC CONVERSION FACTORS
• Write down the GIVEN and
TARGET.
• Write above it the FACTOR for
the units of each.
• Take the difference in power of
ten between the two factors.
This is the conversion factor, in
terms of powers of ten.
• Smaller unit / larger unit
10-9
100
How many nm in 18.9 m?
target given
109 difference
= 1 000 000 000 nm/m
CREATING METRIC CONVERSION FACTORS
• Write down the GIVEN and
TARGET.
• Write above it the FACTOR for
the units of each.
• Take the difference in power of
ten between the two factors.
This is the conversion factor, in
terms of powers of ten.
• Smaller unit / larger unit
10-1
10-6
How many dm in 2.33 mm? 105 difference
target given
= 100 000 mm/dm
CREATING METRIC CONVERSION FACTORS
• Write down the GIVEN and
TARGET.
• Write above it the FACTOR for
the units of each.
• Take the difference in power of
ten between the two factors.
This is the conversion factor, in
terms of powers of ten.
• Smaller unit / larger unit
100
103
How many m in 1.73 km?
target given
103 difference
= 1000 m/km
PUTTING IT TOGETHER
10-3
100
A chemical reaction takes 0.000350 seconds. How many msec is this?
given
target
PUTTING
TOGETHER
10 difference = 1000 msec/sec
THE CONVERSION FACTOR
THE CONVERSION
0.000350USING
sec
1000 msec/sec
0.350
msec
0.35 msec
FACTOR
To cancel out sec, MULTIPLY.
Round your answer to the
3
X
=
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
PUTTING IT TOGETHER
10-3
10-1
A batch of medication has a volume of 2.30 dL. How many mL is this?
given
target
PUTTING TOGETHER
10 difference = 100 mL/dL
THE CONVERSION FACTOR
USING THE CONVERSION
2.30 dL
100 mL/dL
230
mL
230.
mL
FACTOR
2
X
To cancel out dL, MULTIPLY.
=
Round your answer to the
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
target
given
PUTTING IT TOGETHER
10-2
100
9.34 cg of KCl are needed for a reaction. Your balance measures in g.
How many g of KCl need to be weighed?
PUTTING TOGETHER
10 difference = 100 cg/g
THE CONVERSION FACTOR
2
100 cg/gTHE CONVERSION
USING
0.0934 g
To cancel out cg, DIVIDE. FACTOR
Round your answer to the
9.34 cg
/
=
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
PUTTING IT TOGETHER
103
10-1
The distance between two points is 54.3 km. How many dm is this?
given
target
PUTTING TOGETHER
10 difference = 10 000 dm/km
THE CONVERSION FACTOR
USING THE CONVERSION
54.3 km
10 000 dm/km
543000
000dm
dm
543
FACTOR
4
X
To cancel out km, MULTIPLY.
=
Round your answer to the
number of sig figs in your
measurement. The conversion
factor is NOT a measurement so
sig figs don’t apply.
YOUR TURN! (CONVERSION WS AND HW #5)
For each of the problems on p. 24:
1)
2)
3)
4)
Identify the given and target
Write the factors
Create the conversion factor
Multiply or divide the given by the
conversion factor so that the units
cancel out to give you your target
units
5) Round your answer off properly
ALL UNITS NEED TO BE INCLUDED. IF
THERE IS A NUMBER, THERE MUST BE A
UNIT AFTER IT.
TICKET OUT: ON INDEX CARD
Name:
Date:
Period :
• Explain, step by step, how to convert
43.2 mg to kg, ending with the correctly
converted answer.