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

U1D9: HOW DO WE CONVERT FROM ONE UNIT TO ANOTHER ALGEBRAICALLY?

2

PERIOD 2 ONLY TAKE OUT PRACTICE PACKET

Number Scientific Notation

250.

200 000

0.000 55

602 300 000 000 000 000 000 000

0.000 000 000 000 000 000 160

A) Convert each of the following into scientific notation:

3

Scientific Notation Standard Decimal Notation

7.982 X 1011

7.02 X 10-4

2.030 X 10-18

4.3 X 10-5

B) Convert each of the following into standard decimal notation:

4

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 10-62) 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.

Yes, algebra is actually used in the real world to do stuff! Like the stuff you’re

about to learn here.

USING UNITS TO SOLVE PROBLEMS

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 60 minutes/hour

To cancel out hours, MULTIPLY.

X = 138 minutes

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.

140 minutes

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 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.

2.86 feet

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 20 nickels/dollar

To cancel out dollars, MULTIPLY.

X = 845 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.

845.0 nickels

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

How many cm in 45.2 km?giventarget

10310-2

105 difference 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

How many nm in 18.9 m?giventarget

10010-9

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

How many dm in 2.33 mm? giventarget

10-610-1

105 difference 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

How many m in 1.73 km?giventarget

103100

103 difference 1000 m/km=

PUTTING IT TOGETHER

A chemical reaction takes 0.000350 seconds. How many msec is this?given target

10-3100

103 difference 1000 msec/sec=PUTTING TOGETHER

THE CONVERSION FACTOR

0.000350 sec 1000 msec/sec

To cancel out sec, MULTIPLY.

X = 0.35 msec

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.

0.350 msecUSING THE CONVERSIONFACTOR

PUTTING IT TOGETHER

A batch of medication has a volume of 2.30 dL. How many mL is this?given target

10-310-1

102 difference 100 mL/dL=

PUTTING TOGETHERTHE CONVERSION FACTOR

2.30 dL 100 mL/dL

To cancel out dL, MULTIPLY.

X = 230 mL

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.

230. mL

USING THE CONVERSIONFACTOR

PUTTING IT TOGETHER

9.34 cg of KCl are needed for a reaction. Your balance measures in g. How many g of KCl need to be weighed?

given target10010-2

102 difference 100 cg/g=

PUTTING TOGETHERTHE CONVERSION FACTOR

9.34 cg 100 cg/g

To cancel out cg, DIVIDE.

/ = 0.0934 g

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.

0.0934 gUSING THE CONVERSIONFACTOR

PUTTING IT TOGETHER

The distance between two points is 54.3 km. How many dm is this?given target

10-1103

104 difference 10 000 dm/km=

PUTTING TOGETHERTHE CONVERSION FACTOR

54.3 km 10 000 dm/km

To cancel out km, MULTIPLY.

X = 543 000 dm

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.

543 000 dmUSING THE CONVERSION

FACTOR

YOUR TURN! (CONVERSION WS AND HW #5)For each of the problems on p. 24:

1) Identify the given and target2) Write the factors3) Create the conversion factor4) 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.