Chemistry

Three targets with three arrows each to shoot. Can you hit the bull's-eye? Both accurate and precise Precise but not accurate Neither accurate nor precise How do they compare? Can you define accuracy and precision?

The numbers reported in a measurement are limited by the measuring tool 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 Significant figures in a measurement include the known digits plus one estimated digit

RULE 1. All non-zero digits in a measured number are significant. Only a zero could indicate that rounding occurred. Number of Significant Figures cm4 5.6 ft lb___ m m___

RULE 2. 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 min lb____ m m ____

 Rule 3 – Final zeros to the right of the decimal are significant.    ___  ___

RULE 4. Place holding zeros are NOT significant. Number of Significant Figures mm oz lb____ mL mL ____

RULE 4. Place holding zeros are NOT significant. They are only serving as place holders. Number of Significant Figures 25,000 in. 2 25,000 in yr1 200 yr1 48,600 gal____ 48,600 gal____ 25,005,000 g ____

Rule 5 -To indicate a zero as significant that otherwise would not be considered one you can place a bar above that zero. *This rule is usually used for numbers greater than one and varies from one Chemistry class to another. UTK uses this rule.*

A. Which answers contain 3 significant figures? 1) ) ) 47.0 B. All the zeros are significant in 1) ) ) x 10 3 C. 534,675 rounded to 3 significant figures is 1) 535 2) 535,000 3) 5.35 x ) 535 2) 535,000 3) 5.35 x 10 5

In which set(s) do both numbers contain the same number of significant figures? 1) 22.0 and ) 22.0 and ) and 40 3) and 150,000

State the number of significant figures in each of the following: A m B L C g D m E. 2,080,000 bees 3 5 7

A calculated answer cannot be more precise than the measuring tool. A calculated answer cannot be more precise than the measuring tool. A calculated answer must match the least precise measurement. A calculated answer must match the least precise measurement. Significant figures are needed for final answers from Significant figures are needed for final answers from 1) adding or subtracting 1) adding or subtracting 2) multiplying or 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. See handout for clear rule **

A X 4.2 = 1) 9 2) 9.2 3) B ÷ 0.07 = 1) ) 62 3) 60 C X = X ) 11.32) 11 3) 0.041

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 king’s foot. What are some problems with this standard?

 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.

 A number between 1 and 10  A power of 10 N x 10 x

 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.

 Given: 289,800,000  Use: (moved 8 places)  Answer: x 10 8  Given:  Use: 5.67 (moved 4 places)  Answer: 5.67 x 10 -4

 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.)

 Given: x 10 6  Answer: 5,093,000 (moved 6 places to the right)  Given: x  Answer: (moved 4 places to the left)

 Express these numbers in Scientific Notation: 1) ) ) ) 2 5)

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!

What are some U.S. units that are used to measure each of the following? A. length B. volume C. weight D. temperature

 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)

Select the unit you would use to measure 1. Your height a) millimeters b) meters c) kilometers 2. Your mass a) milligramsb) grams c) kilograms 3. The distance between two cities a) millimetersb) meters c) kilometers 4. The width of an artery a) millimetersb) meters c) kilometers

Two part units with a per relationship. Aka Ratios, fractions, parts, decimal numbers. examples 65 miles/hr 28 meters/second 28 meters/second 100 cm/meter 100 cm/meter 12 eggs/dozen 12 eggs/dozen

Write conversion factors that relate each of the following pairs of units: 1. Liters and mL 2. Hours and minutes 3. Meters and kilometers

 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: L = 1 quart

Read problem Read problem Identify data Identify data Make a unit plan from the initial unit to the desired unit Make a unit plan from the initial unit to the desired unit Select conversion factors Select conversion factors Change initial unit to desired unit Change initial unit to desired unit Cancel units and check Cancel units and check Do math on calculator Do math on calculator Give an answer using significant figures Give an answer using significant figures

 1. A paper clip is 3.2cm long. What is its length in mm?  2. There are 1.609km in 1 mile. How many cm are there in 1 mile?  3. One hundred fifty milliliters of rubbing alcohol has a mass of 120g. What is the density of rubbing alcohol?

 1.06 x 10 5 X 6.25 x x 10 9 X 9.24 x m 1km 60 sec 60min sec 1000m 1 min 1 hr 20km 1hr 1min 1000m hr 60 min 60 sec 1km