Welcome to the World of Chemistry
The Language of Chemistry
CHEMICAL _____________ -
pure substances that cannot be decomposed by ordinary means to other substances.
The Language of Chemistry
The elements, their names, and symbols are given on the PERIODIC TABLE
How many elements are there?
The Periodic Table
Dmitri Mendeleev (1834 - 1907)
Glenn Seaborg (1912-1999)
Discovered 8 new elements.
Only living person for whom an element was named.
Branches of Chemistry
Many major areas of study for specialization
Several career opportunities
Also used in many other jobs
1. Organic Chemistry
Organic is the study of matter that contains carbon
Organic chemists study the structure, function, synthesis, and identity of carbon compounds
Useful in petroleum industry, pharmaceuticals, polymers
2. Inorganic Chemistry
Inorganic is the study of matter that does NOT contain carbon
Inorganic chemists study the structure, function, synthesis, and identity of non-carbon compounds
Polymers, Metallurgy
3. Biochemistry
Biochemistry is the study of chemistry in living things
Cross between biology and chemistry
Pharmaceuticals and genetics
4. Physical Chemistry
Physical chemistry is the physics of chemistry… the forces of matter
Much of p-chem is computational
Develop theoretical ideas for new compounds
5. Analytical Chemistry
Analytical chemistry is the study of high precision measurement
Find composition and identity of chemicals
Forensics, quality control, medical tests
Types of Observations and Measurements
We make QUALITATIVE observations of reactions — changes in color and physical state.
We also make QUANTITATIVE MEASUREMENTS, which involve numbers.
Use SI units — based on the metric system
SI measurement
Le Système international d'unités
The only countries that have not officially adopted SI are Liberia (in western Africa) and Myanmar (a.k.a. Burma, in SE Asia), but now these are reportedly using metric regularly
Metrication is a process that does not happen all at once, but is rather a process that happens over time.
Among countries with non-metric usage, the U.S. is the only country significantly holding out. The U.S. officially adopted SI in 1866.
Standards of Measurement
When we measure, we use a measuring tool to compare some dimension of an object to a standard.
What is Scientific Notation?
Scientific notation is a way of expressing really big numbers or really small numbers.
For very large and very small numbers, scientific notation is more concise.
Scientific notation consists of two parts:
A number between 1 and 10
A power of 10
N x 10x
To change standard form to scientific notation…
Place the decimal point so that there is one non-zero digit to the left of the decimal point.
Count the number of decimal places the decimal point has “moved” from the original number. This will be the exponent on the 10.
If the original number was less than 1, then the exponent is negative. If the original number was greater than 1, then the exponent is positive.
Examples
Given: 289,800,000
Use: 2.898 (moved 8 places)
Answer: 2.898 x 108
Given: 0.000567
Use: 5.67 (moved 4 places)
Answer: 5.67 x 10-4
To change scientific notation to standard form…
Simply move the decimal point to the right for positive exponent 10.
Move the decimal point to the left for negative exponent 10.
(Use zeros to fill in places.)
Example
Given: 5.093 x 106
Answer: 5,093,000 (moved 6 places to the right)
Given: 1.976 x 10-4
Answer: 0.0001976 (moved 4 places to the left)
Learning Check
Express these numbers in Scientific Notation:
405789
0.003872
3000000000
2
0.478260
Stating a Measurement
In every measurement there is a
Number followed by a
Unit from a measuring device
The number should also be as precise as the measurement!
UNITS OF MEASUREMENT
Use SI units — based on the metric system
Length
Mass
Volume
Time
Temperature
Mass vs. Weight
Mass: Amount of Matter (grams, measured with a BALANCE)
Weight: Force exerted by the mass, only present with gravity (pounds, measured with a SCALE)
Some Tools for Measurement
Learning Check
Match L) length M) mass V) volume
____ A. A bag of tomatoes is 4.6 kg.
____ B. A person is 2.0 m tall.
____ C. A medication contains 0.50 g Aspirin.
____ D. A bottle contains 1.5 L of water.
Learning Check
What are some U.S. units that are used to measure each of the following?
A. length
B. volume
C. weight
D. temperature
Metric Prefixes
Kilo- means 1000 of that unit
1 kilometer (km) = 1000 meters (m)
Centi- means 1/100 of that unit
1 meter (m) = 100 centimeters (cm)
1 dollar = 100 cents
Milli- means 1/1000 of that unit
1 Liter (L) = 1000 milliliters (mL)
Metric Prefixes
Metric Prefixes
Learning Check
1. 1000 m = 1 ___ a) mm b) km c) dm
2. 0.001 g = 1 ___ a) mg b) kg c) dg
3. 0.1 L = 1 ___ a) mL b) cL c) dL
4. 0.01 m = 1 ___ a) mm b) cm c) dm
Units of Length
? kilometer (km) = 500 meters (m)
2.5 meter (m) = ? centimeters (cm)
1 centimeter (cm) = ? millimeter (mm)
1 nanometer (nm) = 1.0 x 10-9 meter
Learning Check
Select the unit you would use to measure
1. Your height
a) millimeters b) meters c) kilometers
2. Your mass
a) milligrams b) grams c) kilograms
3. The distance between two cities
a) millimeters b) meters c) kilometers
4. The width of an artery
a) millimeters b) meters c) kilometers
Conversion Factors
Fractions in which the numerator and denominator are EQUAL quantities expressed in different units
Example: 1 in. = 2.54 cm
Factors: 1 in. and 2.54 cm
2.54 cm 1 in.
Learning Check
Write conversion factors that relate each of the following pairs of units:
1. Liters and mL
2. Hours and minutes
3. Meters and kilometers
How many minutes are in 2.5 hours?
Conversion factor
2.5 hr x 60 min = 150 min
1 hr
cancel
Steps to Problem Solving
Write down the given amount. Don’t forget the units!
Multiply by a fraction.
Use the fraction as a conversion factor. Determine if the top or the bottom should be the same unit as the given so that it will cancel.
Put a unit on the opposite side that will be the new unit. If you don’t know a conversion between those units directly, use one that you do know that is a step toward the one you want at the end.
Insert the numbers on the conversion so that the top and the bottom amounts are EQUAL, but in different units.
Multiply and divide the units (Cancel).
If the units are not the ones you want for your answer, make more conversions until you reach that point.
Multiply and divide the numbers. Don’t forget “Please Excuse My Dear Aunt Sally”! (order of operations)
Sample Problem
You have $7.25 in your pocket in quarters. How many quarters do you have?
7.25 dollars 4 quarters
1 dollar
You Try This One!
If Jacob stands on Spencer’s shoulders, they are two and a half yards high. How many feet is that?
Learning Check
A rattlesnake is 2.44 m long. How long is the snake in cm?
a) 2440 cm
b) 244 cm
c) 24.4 cm
Solution
A rattlesnake is 2.44 m long. How long is the snake in cm?
b) 244 cm
2.44 m x 100 cm = 244 cm
1 m
Learning Check
How many seconds are in 1.4 days?
Unit plan: days hr min seconds
1.4 days x 24 hr x ??
1 day
Wait a minute!
What is wrong with the following setup?
1.4 day x 1 day x 60 min x 60 sec
24 hr 1 hr 1 min
English and Metric Conversions
If you know ONE conversion for each type of measurement, you can convert anything!
You must memorize and use these conversions:
Mass: 454 grams = 1 pound
Length: 2.54 cm = 1 inch
Volume: 0.946 L = 1 quart
Learning Check
An adult human has 4.65 L of blood. How many gallons of blood is that?
Unit plan: L qt gallon
Equalities: 1 quart = 0.946 L
1 gallon = 4 quarts
Your Setup:
Equalities
State the same measurement in two different units
Steps to Problem Solving
Read problem
Identify data
Make a unit plan from the initial unit to the desired unit
Select conversion factors
Change initial unit to desired unit
Cancel units and check
Do math on calculator
Give an answer using significant figures
Dealing with Two Units – Honors Only
If your pace on a treadmill is 65 meters per minute, how many seconds will it take for you to walk a distance of 8450 feet?
What about Square and Cubic units? – Honors Only
Use the conversion factors you already know, but when you square or cube the unit, don’t forget to cube the number also!
Best way: Square or cube the ENITRE conversion factor
Example: Convert 4.3 cm3 to mm3
Learning Check
A Nalgene water bottle holds 1000 cm3 of dihydrogen monoxide (DHMO). How many cubic decimeters is that?
Solution
1000 cm3 1 dm 3
10 cm
Temperature Scales
Fahrenheit
Celsius
Kelvin
Temperature Scales
Calculations Using Temperature
Generally require temp’s in kelvins
T (K) = t (˚C) + 273.15
Body temp = 37 ˚C + 273 = 310 K
Liquid nitrogen = -196 ˚C + 273 = 77 K
Fahrenheit Formula – Honors Only
180°F = 9°F = 1.8°F 100°C 5°C 1°C
Zero point: 0°C = 32°F
°F = 9/5 °C + 32
Celsius Formula – Honors Only
Rearrange to find T°C
°F = 9/5 °C + 32
°F - 32 = 9/5 °C ( +32 - 32)
°F - 32 = 9/5 °C
9/5 9/5
(°F - 32) * 5/9 = °C
Temperature Conversions – Honors Only
A person with hypothermia has a body temperature of 29.1°C. What is the body temperature in °F?
°F = 9/5 (29.1°C) + 32
= 52.4 + 32
= 84.4°F
Learning Check – Honors Only
The normal temperature of a chickadee is 105.8°F. What is that temperature in °C?
1) 73.8 °C
2) 58.8 °C
3) 41.0 °C
Learning Check – Honors Only
Pizza is baked at 455°F. What is that in °C?
1) 437 °C
2) 235°C
3) 221°C
Precision is how close together the measurements are
Accuracy is how close to the real measurement
Significant Figures
The numbers reported in a measurement are limited by the measuring tool
Significant figures in a measurement include the known digits plus one estimated digit
Counting Significant Figures
RULE 1. All non-zero digits in a measured number are significant. Only a zero could indicate that rounding occurred.
Number of Significant Figures
38.15 cm 4
5.6 ft 2
65.6 lb ___
122.55 m ___
Leading Zeros
RULE 2. Leading zeros in decimal numbers are NOT significant.
Number of Significant Figures
0.008 mm 1
0.0156 oz 3
0.0042 lb ____
0.000262 mL ____
Sandwiched Zeros
RULE 3. Zeros between nonzero numbers are significant. (They can not be rounded unless they are on an end of a number.)
Number of Significant Figures
50.8 mm 3
2001 min 4
0.702 lb ____
0.00405 m ____
Trailing Zeros
RULE 4. Trailing zeros in numbers without decimals are NOT significant. They are only serving as place holders.
Number of Significant Figures
25,000 in. 2
200. yr 3
48,600 gal ____
25,005,000 g ____
Learning Check
A. Which answers contain 3 significant figures?
1) 0.4760 2) 0.00476 3) 4760
B. All the zeros are significant in
1) 0.00307 2) 25.300 3) 2.050 x 103
C. 534,675 rounded to 3 significant figures is
1) 535 2) 535,000 3) 5.35 x 105
Learning Check
In which set(s) do both numbers contain the same number of significant figures?
1) 22.0 and 22.00
2) 400.0 and 40
3) 0.000015 and 150,000
Learning Check
State the number of significant figures in each of the following:
A. 0.030 m 1 2 3
B. 4.050 L 2 3 4
C. 0.0008 g 1 2 4
D. 3.00 m 1 2 3
E. 2,080,000 bees 3 5 7
Significant Numbers in Calculations
A calculated answer cannot be more precise than the measuring tool.
A calculated answer must match the least precise measurement.
Significant figures are needed for final answers from
1) adding or subtracting
2) multiplying or dividing
Adding and Subtracting
The answer has the same number of decimal places as the measurement with the fewest decimal places.
25.2 one decimal place
+ 1.34 two decimal places
26.54
answer 26.5 one decimal place
Learning Check
In each calculation, round the answer to the correct number of significant figures.
A. 235.05 + 19.6 + 2.1 =
1) 256.75 2) 256.8 3) 257
B. 58.925 - 18.2 =
1) 40.725 2) 40.73 3) 40.7
Multiplying and Dividing
Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures.
Learning Check
A. 2.19 X 4.2 =
1) 9 2) 9.2 3) 9.198
B. 4.311 ÷ 0.07 =
1) 61.58 2) 62 3) 60
C. 2.54 X 0.0028 =
0.0105 X 0.060
1) 11.3 2) 11 3) 0.041
Reading a Meterstick
. l2. . . . I . . . . I3 . . . .I . . . . I4. . cm
First digit (known) = 2 2.?? cm
Second digit (known) = 0.7 2.7? cm
Third digit (estimated) between 0.05- 0.07
Length reported = 2.75 cm
or 2.74 cm
or 2.76 cm
Known + Estimated Digits
In 2.76 cm…
Learning Check
. l8. . . . I . . . . I9. . . .I . . . . I10. . cm
What is the length of the line?
1) 9.6 cm
2) 9.62 cm
3) 9.63 cm
How does your answer compare with your neighbor’s answer? Why or why not?
Zero as a Measured Number
. l3. . . . I . . . . I4 . . . . I . . . . I5. . cm
What is the length of the line?
First digit 5.?? cm
Second digit 5.0? cm
Last (estimated) digit is 5.00 cm
What is Density???
DENSITY - an important and useful physical property
Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).
Strategy
1. Get dimensions in common units.
2. Calculate volume in cubic centimeters.
3. Calculate the density.
SOLUTION
1. Get dimensions in common units.
2. Calculate volume in cubic centimeters.
3. Calculate the density.
DENSITY
Density is an INTENSIVE property of matter.
does NOT depend on quantity of matter.
temperature
Contrast with EXTENSIVE
depends on quantity of matter.
mass and volume.
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg?
Strategy
1. Use density to calc. mass (g) from volume.
2. Convert mass (g) to mass (lb)
Need to know conversion factor
= 454 g / 1 lb
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg?
1. Convert volume to mass
Learning Check
Osmium is a very dense metal. What is its
density in g/cm3 if 50.00 g of the metal occupies
a volume of 2.22cm3?
1) 2.25 g/cm3
2) 22.5 g/cm3
3) 111 g/cm3
Solution
2) Placing the mass and volume of the osmium metal into the density setup, we obtain
D = mass = 50.00 g =
volume 2.22 cm3
= 22.522522 g/cm3 = 22.5 g/cm3
Volume Displacement
A solid displaces a matching volume of water when the solid is placed in water.
33 mL
25 mL
Learning Check
What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?
1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3
33 mL
25 mL
Learning Check
Which diagram represents the liquid layers in the cylinder?
(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL)
1) 2) 3)
Learning Check
The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane?
1) 0.614 kg
2) 614 kg
3) 1.25 kg
Learning Check
If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given?
1) 0.548 L
2) 1.25 L
3) 1.83 L
Learning Check
A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans?
1) 1.0 L 2) 2.0 L 3) 4.0 L
Scientific Method
State the problem clearly.
Gather information.
Form a _______________.
Test the hypothesis.
Evaluate the data to form a conclusion.
If the conclusion is valid, then it becomes a theory. If the theory is found to be true over along period of time (usually 20+ years) with no counter examples, it may be considered a law.
6. Share the results.
