Chapter Two -Measurement and Conversions-

Chapter Two

-Measurement and Conversions-

CHM1033 Introductory General, Organic, and Biochemistry -Applications to HIV Treatment and Prevention –

Prof. Larry Mailloux Miami Dade College

Our Very Big and Very Small World

https://www.youtube.com/watch?v=uaGEjrADGPA https://youtu.be/W47M-gumtno

HIV Image from: http://representingaids.org/artifacts/items/show/38

Hubble Image from: https://en.wikipedia.org/wiki/Hubble_Deep_Field

Scientific Notation – dealing with zeros

• 1,670,000,000,000,000,000,000 H ₂ O molecules in one drop of water!

• 0.0000079 inches – typical length of a bacteria

• Viruses are even smaller!

• For these kinds of numbers scientists use scientific notation

Multiple Choice Example

• There are about 250,000,000,000 stars in the MilkyWay Galaxy. What is this number in scientific notation?

a) 2.5 x 10 ^-11 b) 25 x 10 ¹⁰ c) 2.5 x 10 ¹¹ d) 25 x 10 ^-10

e) None of the above

Factor Label Method

• Two equal things  Conversion factor

• 1 year = 365 days

• 1 day = 24 hours

• 1 hour = 60 minutes

• 1 minute = 60 seconds

• Io was 9 years old when this picture was taken in 2019. How many second is this?

Citation

Standard/Imperial/American Units

Units of Volume Units of Mass Units of Length

Gallon (gal) Pound (lbs) Mile (mi)

Quart (qt) Ounce (oz) (a.k.a. ounce mass) Foot (ft)

Pint (pt) Inch (in)

Cup Yard (yd)

Ounce (oz) (a.k.a. fluid ounce) Teaspoon (tsp)

Tablespoon (tbsp)

Standard Units – Conversion Factors

Volume Conversions

Mass

Conversions

Length Conversions 1 gal = 4 qts 1 pound = 16 oz 1 mi = 5,280 ft

1 qt = 2 pts 1 ft = 12 in

1 pt = 2 cups 1 yd = 3 ft

1 cup = 8 oz

1 tbsp = 3 tsp

1 tsp = 5 mL

Standard Units – Conversion Examples

a) Every year Prof Mailloux does the SMART Ride to raise money for HIV charities in South Florida. The bicycle ride to key west is 165 miles. How many inches is that?

b) When Prof Mailloux tie dyed T-shirts for pride week he used 8

gallons of dye. If each cup of dye required 2 tsp of dye powder, how

many teaspoons of dye did he need?

Metric Units

Unit Symbol Used to Measure Approximate Size Meter m Distance Prof Mailloux is about 2 m tall

Gram g Mass A 15 oz can of beans weighs 425 grams

Liter L Volume A large soda at McDonals is about one liter

Metric Units - Prefixes

Prefix Symbol Meaning Example of Usage

kilo k 1,000 (or 10 ³ ) x base unit 265 km, dist. from Miami to Key West deci d 1/10 ^th (or 10 ^-1 ) x base unit 1 dm ≈ width of a fist

cent c 1/100 ^th (or 10 ^-2 ) x base unit 1 cm ≈ width of pinkie finger

milli m 1/1,000 ^th (or 10 ^-3 ) x base unit 1 mm ≈ thickness of few sheets of paper micro μ or mc 1/1,000,000 ^th (or 10 ^-6 ) x base unit 1-10 μm ≈ size of a bacteria cell

nano n 1/1,000,000,000 ^th (or 10 ^-9 ) x base unit 120 nm ≈ with of an HIV virus particle

Metric Prefixes – Do you suffer from upside down conversion factor

syndrome?

•Which is it?

a) 1 kL = 1,000L or 1,000 kL = 1 L b) 1 cm = 100 m or 100 cm = 1 m

c) 1,000,000 μs = 1 s or 1 μs = 1,000,000 s

Metric-Metric Conversions

• 1 ^st prefix  base unit  2 ^nd prefix

• Examples:

• A bacteria is 6.5 μm long. Convert this to nm

• A European bottle of soda is 15.0 cL. How many mL is this?

Citation

Metric - Standard Conversions

• Examples:

• A bacteria is 6.5 μm long. Convert this to inches

• A European bottle of soda is 15.0 cL. How many ounces is this?

Mass Volume Distance

1 kg = 2.2 pounds 0.946 L = 1 quart 2.54 cm = 1 inch

Fractional Conversions

a) 60 miles per hour to feet per second

b) 2.25 euros/liter to dollars/gal (exchange rate: 1 euro = $1.12)

Citation

Dosage Calculations – errors cost lives!

a) Example from CHM1033L Lab Manual, Exp 3*

• A patient needs 0.50 grams of a medication two times per day. How many 250 mg tablets must the patient take per day?

b) Another Example**

• The recommended dosage of ketamine is 10 mg/kg body weight. If the

ketamine is supplied as a solution with a strength of 50 mg/mL, how many mL should be given to a 180 pound patient?

*Dosage problem from: Exploring Chemistry, General, Organic, & Biochemistry, 12

ed by Eileen Johann, ana Cierezko, Dorma Gottlieb

** Ketamine Dosage Information from: https://reference.medscape.com/drug/ketalar-ketamine-343099

Temperature Scales and Conversions

• Temperature conversion formulas (memorize)

• F = C (1.8) + 32

• K = C + 273.15

• Where do these formulas come from?

Water Boils 212 - 100 - 373.15 -

Water Freezes 32 - 0 - 273.15 -

Absolute Zero -459.67 - -273.15 - 0 -

°F °C K

Temperature Scales and Conversions Example

• A patient is running a 103.5°F fever. What is this in °C and K?

Citation

Reading Lab Equipment

• Estimate Between Smallest Marks

Reading Lab Equipment Cont.

• Read at eye level  avoids Parallax Error

• Estimate Between Smallest Marks

cm

Reading Lab Equipment Cont.

• If right on the line  put zero!

Density

• Density – ratio of mass to volume of a substance

• D = m/v

• Important fact to memorize

• Density of water = 1 g/mL = 1 g/cm3

• Objects more dense  sink

• Objects less dense  float

• Ways you can be asked

• Simple formula D = m/v

• Volume via

• Water displacement

• V object = V f -V i

• D = m / (V f -V i )

• Geometry

• V box = L x w x h

• As conversion factor between mass and volume

Density Example – simple formula

• An object has a density of 3.21 g/mL and a mass of 37.41 g. What is the volume in mL?

Citation

Density Example – Water Displacement

• A toy dinosaur is placed into water causing the volume of the water to change as shown below. If the mass of the dinosaur is 2.643 grams,

what is the density of the dinosaur ?

Picture from: http://cstephenmurray.com/onlinequizes/chemistry/measuring/displacementmethod.htm

Density Example – Geometry

• The actual width and height of a “two by four” is 1.5 inches by 3.5

inches. If a two by four is made out of pine (density = 26 lbs/ft ³ ), how many pounds would a 12 foot long two by four weigh?

Picture from: https://en.wikipedia.org/wiki/Lumber#Dimensional_lumber

Density Example – Conversion Factor

• Gasoline has a density of 0.789 g/mL. Given this fact, how many

pounds would an 18 gal tank of gas weigh?

Specific Gravity – density without units

• Specific gravity - density of an object compared to the density of water

• =

• Is simply density without units

• By comparing to the density of water, specific gravity is the same regardless of the units used.

• Makes measurement more universal

• A healthy person’s urine has a specific gravity between 1.002 and 1.030. If one liter of a patients urine has a mass of 1032 grams, what is the specific gravity of this patients urine? Is the patients’ urine within the healthy range?

•