M.I.T. C.P. CHEMISTRY Introduction to Measurement

Science is based on measurements.

All measurements have: Units

Length Foot = Length of Hercules’s Foot Mile = 1000 Soldiers’ Paces

1790

SI Units QuantityBase UnitSymbol LengthMeterm MassKilogramkg VolumeLiterl TemperatureKelvinK TimeSeconds

Meter 1 Meter Light travels in a vacuum during 1/299,792,458 of a second

Kilogram

2.5 grams 5.0 grams

Liter 1 Liter Volume occupied by 1 kilogram of H 2 O

All measurements have: Magnitude Units

Metric Prefixes

Powers of Ten

Very Large Measurements k (kilo) means “one thousand of” M (mega) means “one million of” G (giga) means “one billion of”

Very Small Measurements c (centi) means “a hundredth of” m (milli) means “a thousandth of” n (nano) means “a billionth of”

What is a “Nanometer”?

What is “Nanotechnology”?

Ceramic “Nano” Pores

How Small Am I? Bacterium Red Blood Cell Carbon Buckyball DNA Molecule Strand of Human Hair

Strand of Human Hair60,000 nanometers Bacterium10,000 nanometers Red Blood Cell7,000 nanometers DNA Molecule2 nanometers Carbon Buckyball (C60)1 nanometer

How Many Nanometers?

Lab: Measurements That Make ¢!

Lab: Laboratory Procedures

Density

Lab: Interactive DensityInteractive

Scientific Notation Scientific notation is used to express very large or small numbers. 10,300,000,000,000,000,000,000 carbon atoms A carbon atom’s mass = 0.000,000,000,000,000,000,000,020 grams

Scientific notation consists of a coefficient multiplied by 10 raised to an exponent. 10,300,000,000,000,000,000,000 = 1.03 x 10^22 = 1.03 E ,000,000,000,000,000,000,020 = 2.0 x 10^-23 = 2.0 E-23

All measurements have: Magnitude Units Uncertainty

Accuracy & Precision AccuratePrecise Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured. Precision refers to the closeness of a set of measurements of the same quantity made in the same way.

Percent Error Observed Value-Accepted Value/Accepted Value x 100%

Sample Problem You complete a lab and your product has a mass of 90 grams. You should have made 130 grams. What is your % error? Step 1: Step 2: Step 3: Observed – Accepted (Absolute Value)40 Error/Accepted0.308 Answer X 100%30.8%

Lab: Accuracy & Precision

Significant Figures

The numbers 1,2,3,4,5,6,7,8,9 are always significant! Rules for “0” Rule #1: Zeros between numbers are significant! 5063 Significant Figures Significant Figures

Rule #2: Zeros to the right of a number are NOT significant unless the are to the left of a decimal point! Significant Figures Significant Figures

Rule #3: Zeros to the right of a number & to the right of a decimal point are significant! 8.02 Significant Figures Significant Figures

Rule #4: Zeros by themselves to the left or right of a decimal point are NOT significant! Significant Figure Significant Figure

Math with Significant Figures Multiply or divide as you normally would! 2, X 3,200 = Since 3,200 has only 2 “Sig Figs” 640,000 Your answer can only have as many “Sig Fig’s” as the number with the fewest significant figures!

Lab: Pipette Calibration

Dimensional Analysis Factor Label Method Unit Factor Method

How many seconds are there in a day? Step 1:What units do I know and I need in the answer? I’m starting with DAY and ending in SECONDS. Step 2:Choose CONVERSION FACTOR(S) that get rid of your starting unit and end with you desired unit.

1 Day24 Hours 1 Day 60 Min.60 Seconds XX 1 Hour X 1 Min 1 X 24 X 60 X 60 = 86,400

If you are going 50 mph, how many feet/second are you traveling? Step 1:What units do I know and I need in the answer? I’m stating with MILES/HOUR and ending with FEET/SECOND. Step 2:Choose CONVERSION FACTOR(S) that get rid of your starting unit and end with you desired unit. There are 5280 feet in a mile!

If you are going 50 mph, how many feet/second are you traveling?

Your car's gas tank holds 18.6 gallons and is one quarter full. Your car gets 16 miles/gal. How far can you drive without running out of gas?

Your car's gas tank holds 18.6 gallons and is one quarter full. Your car gets 16 miles/gal. How far can you drive without running out of gas?

Power of the Graph! ChartGraph Organizes Data ☺ ☺ Displays Data ☺ ☺ Predicts Data ☺

Lab: Graph This!

Proportional Relationships Direct ProportionIndirect Proportion

Lab: It’s All in the Graph!

Unit Review Game Rags-to-Riches