Introduction to Chemistry and Measurement

Introduction to Chemistry and Measurement

Welcome to the World of Chemistry Honors: Ch. 1 and 5 Regular: Ch. 1 and 3 ICP: Ch. 1 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck

"Background Printing")! 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 Systme international d'units 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. Information from U.S. Metric Association Chemistry In Action On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars atmosphere 100 km lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N This is going to be the cautionary tale that will be embedded into introduction to the metric system in

elementary school, high school, and college science courses till the end of time. Standards of Measurement When we measure, we use a measuring tool to compare some dimension of an object to a standard. For example, at one time the standard for length was the kings foot. What are some problems with this 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: 1) 2) 3) 4) 5) 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 Meter, m

Mass Kilogram, kg Volume Liter, L Time Seconds, s Temperature Celsius degrees, C

kelvins, K 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)

Can you hear me now? Some Tools for Measurement Which tool(s) would you use to measure: A. temperature B. volume C. time D. weight Learning Check Match

L) length M A. ____ L ____ B. M ____ C. V

____ D. M) mass V) volume A bag of tomatoes is 4.6 kg. A person is 2.0 m tall. A medication contains 0.50 g Aspirin. 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 OH OH distance distance == -11

9.4 x 10 9.4 x 10-11m m -9 9.4 9.4 xx 10 10-9cm cm 0.094 0.094 nm nm 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: Factors: 1 in. = 2.54 cm 1 in. 2.54 cm and

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

1 hr = 150 min cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers! Steps to Problem Solving 1. Write down the given amount. Dont forget the units! 2. Multiply by a fraction. 3. 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. 4. Put a unit on the opposite side that will be the new unit. If you dont 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. 5. Insert the numbers on the conversion so that the top and the bottom amounts are EQUAL, but in different units. 6. Multiply and divide the units (Cancel). 7. If the units are not the ones you want for your answer, make more conversions until you reach that point. 8. Multiply and divide the numbers. Dont 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 X 4 quarters 1 dollar = 29 quarters You Try This One! If Jacob stands on Spencers 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) b) c) 2440 cm 244 cm 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 1m = 244 cm Learning Check How many seconds are in 1.4 days? Unit plan: days hr

1.4 days x 24 hr 1 day x min ?? seconds Wait a minute! What is wrong with the following setup? 1.4 day x 1 day

24 hr x 60 min 1 hr x 60 sec 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 Equalities: 1 quart = 0.946 L 1 gallon = 4 quarts

Your Setup: gallon Equalities State the same measurement in two different units length 10.0 in. 25.4 cm 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, dont forget to cube the number also! Best way: Square or cube the ENITRE conversion factor Example: Convert 4.3 cm3 to mm3 (

4.3 cm3 10 mm 1 cm ) 3 = 4.3 cm3 103 mm3 13 cm3 = 4300 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 10 cm 3 = 1 dm3 So, a dm3 is the same as a Liter ! A cm3 is the same as a milliliter. Temperature Scales Fahrenheit Celsius Kelvin Anders Celsius

1701-1744 Lord Kelvin (William Thomson) 1824-1907 Temperature Scales Boiling point of water Freezing point of water Fahrenheit Celsius

Kelvin 212 F 100 C 373 K 180F 100C 32 F

0 C Notice that 1 kelvin = 1 degree Celsius 100 K 273 K Calculations Using Temperature Generally Generally require require temps temps in in kelvins

kelvins TT (K) (K) == tt (C) (C) ++ 273.15 273.15 Body Body temp temp == 37 37 C C ++ 273 273 == 310 310 K K Liquid

Liquid nitrogen nitrogen == -196 -196 C C ++ 273 273 == 77 77 K K Fahrenheit Formula Honors Only 180F 5C = 9F =

1C Zero point: 1.8F 0C = 32F F = 9/5 C + 32 100C Celsius Formula Honors Only Rearrange to find TC

F = 9/5 C + 32 F - 32 = 9/5 C ( +32 - 32) F - 32 =

9/5 C 9/5 (F - 32) * 5/9 9/5 = C Temperature Conversions Honors Only A person with hypothermia has a body temperature of 29.1C. What is the body temperature in F?

F = 9/5 (29.1C) + 32 = 52.4 + 32 = 84.4F Learning Check Honors Only The normal temperature of a chickadee is 105.8F. 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 455F. What is that in C? 1) 437 C 2) 235C 3) 221C Can you hit the bull's-eye? Three targets with three arrows each to shoot. How do

they compare? Both accurate and precise Precise but not accurate Neither accurate nor

precise Can you define accuracy and precision? 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. . First digit (known) =2 cm 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 Known digits 2 and 7 are 100% certain The third digit 6 is estimated (uncertain) In the reported length, all three digits (2.76 cm) are significant including the estimated one 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 neighbors answer? Why or why not? Zero as a Measured Number . l3. . . . I . . . . I4 . . . . I . . . . I5. . What is the length of the line? First digit Second digit Last (estimated) digit is cm 5.?? cm

5.0? cm 5.00 cm Always estimate ONE place past the smallest mark! What is Density??? DENSITY - an important and useful physical property Density Density mass mass (g)

(g) volume volume (cm (cm33)) Mercury Aluminum Platinum 13.6 g/cm3 21.5 g/cm 3

2.7 g/cm3 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). mass (g) Density volume (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. 1cm 0.95 mm = 0.095 cm 10 mm

2. Calculate volume in cubic centimeters. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3 Note only 2 significant figures in the answer! 3. Calculate the density. 57.54 g 3 = 9.0 g / cm

6.4 cm3 PROBLEM: PROBLEM: Mercury Mercury (Hg) (Hg) has has aa density density 3 of of 13.6 13.6 g/cm g/cm3.. What What is is the

the mass mass of of 95 95 mL mL of of Hg Hg in in grams? grams? In In pounds? pounds? PROBLEM: PROBLEM: Mercury

Mercury(Hg) (Hg)has hasaadensity densityof of 33 13.6 13.6g/cm g/cm .. What What is isthe themass massof of 95 95mL

mL of of Hg? Hg? First, note that 1 cm3 = 1 mL Strategy 1. Use density to calc. mass (g) from 2. Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb

volume. PROBLEM: PROBLEM: Mercury Mercury(Hg) (Hg) has has aadensity densityof of13.6 13.6 33 g/cm g/cm .. What Whatis isthe

themass massof of95 95mL mLof of Hg? Hg? 1. Convert volume to mass 3 95 cm 2.

13.6 g cm3 3 = 1.3 x 10 g Convert mass (g) to mass (lb) 1 lb 1.3 x 10 g = 2.8 lb 454 g 3

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 DENSITY DENSITY Density is an Styrofoam INTENSIVE property of matter. does NOT depend on quantity of matter. temperature Contrast with EXTENSIVE depends on quantity

of matter. mass and volume. Brick 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) V W K K W K V V

W 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)

2) 3) 0.548 L 1.25 L 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 1. 2. 3. 4. 5. 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.

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