Do Now: Working only with the people at your table, measure the length, width, and height of the room. DO NOT discuss your results with other groups. Record your data.

Group Length Width Height 1 2 3 4 5 6 7 8

Measurements and Mathematics in Chemistry

Precision refers to the degree of reproducibility of a measured quantity, that is, the closeness of agreement when the same quantity in measured several times

Accuracy Refers to how close a measured value is to the accepted or “real” value. High precision numbers are not always accurate. But it is more likely that measurements of high precision are more accurate.

Homework Read pages 51 – 57 & 63 – 67 in your textbook Answer Questions: 14, 15, 16 on page 62 17, 18, 21 on page 67

Metric Units Basic units The basic metric unit for the measurement of length is known as the meter. The basic metric unit of volume is the liter. Volume can also be measured using cm. 1 cm3 = _____ mL   a. Tool used to measure volume is the graduated cylinder Smallest increment marked: __________________________________ c. Measurements should be read to the nearest: ______________________

The basic metric unit of mass is the _____________.   Tool used to measure mass is the _________________________________ Smallest increment marked: __________________________________ Measurements should be read to the nearest: _______________________

The basic metric unit for temperature is ________________________.   Tool used to measure temperature is the ______________________________ Smallest increment marked: __________________________________ Measurements should be read to the nearest: _______________________- The temperatures in this scale can easily be converted to the Kelvin scale, or the absolute scale, by the following formula: ****K =

Prefixes Prefix symbol numerical value 10x Mega M 1,000,000 106 (times greater than base)   Mega M 1,000,000 106 Kilo k 1,000 103 Hecto h 100 102 Deka da 10 101 Basic unit (grams, liters, meters)

Prefixes Prefix symbol numerical 10x value (times greater than base) Deci d 0.1 10-1   Cent c 0.01 10-2 Milli m 0.001 10-3

Conversion Factors (factor label method) 1 kilogram = ______grams Rearranged: OR   1 millimeter = ____________ meters Rearranged: OR How do you know which set up is correct? - the unit that you start with goes on the bottom, the unit that you need to solve for is on the top - It may be necessary to use more than one conversion factor to solve a problem

Do Now: .0063 m = ____________ mm 390,000 g = ____________ kg 0.0018 kL = ____________ L 22.4 mL = ____________ cm3 25 °C = ____________ K 377 mm = ____________ cm 275 K = ____________ °C 42,000 cm = ____________ km 250cm = ____________ m 432 cm3 = ____________ L

Page 62 #14 Determine the number of significant figures in each of the following 12 basketball players 0.010 square meter 507 thumbtacks 0.070020 meter 10800 meters 5.00 cubic meters

# 15 Express each of the following in scientific notation. (5.3x104) + (1.3 x 104) (7.2x10-4) ÷ (1.8x103) 104 x 10-3 x 106 (9.12x10-1) – (4.7x10-2) (5.4x104) x (3.5x109) (1.2x102) x (8.9x102) 6.6 x 104 4.0 x 10-7 107 8.65 x 10-1 1.9 x 1014 1.1 x 105

#16 A technician experimentally determined the boiling point of octane to be 124.1 °C. The actual boiling point of octane is 125.7 °C. Calculate the error and the percent error. Error = 1.6 °C Percent Error = 1.3%

#17 Name the quantity and give the symbol. Mole Kilogram/cubic meter Second Pascal Meter Kilogram Amount of substance, mol Density, kg/m3 Time, s Pressure, Pa Length, m Mass, kg

#18 State the difference between mass and weight. Mass is a measure of the amount of matter in an object. Weight is a measure of the force due to gravity on an object.

#21 What is the volume of a paperback book 21 cm tall, 12 cm wide, and 3.5 cm thick Answer: 8.8 x 102 cm3

Percent Error Example) You measure the mass of oxygen in a sample to be 25.0 grams and the theoretical value is 30.0 grams, what is the percent error in the experiment?

What is the length of the following?

Significant Figures Definition: all the known values from a measurement including a last estimated digit

Determining the # of Sig Figs in a measurement Is the decimal present or absent? Begin at the appropriate ocean side of the measurement Move to the first non-zero digit Count all digits moving across

Recall the measured value from earlier: How many significant digits are there in our measured value?

Practice Indicate the number of significant figures in the following measurements: 0.00734 cm3 _____ 510 mL _____ 510. mL _____

More Practice: Indicate the number of significant figures in the following measurements and identify the estimated digit: 20200 g _____ 0.0050 atm _____ 22.4 L _____ 101.3 kPa _____ 5000 mol _____

Addition and subtraction with Sig Figs The answer has only as many decimal places as the measurement having the least number of decimal places. Procedure: 1. line up all measurements by decimal points 2. perform the calculation on your calculator 3. draw a line down next to the least decimal place 4. round your answer off the answer to the digit to the left of the line

Example: Given: 2 H2 + O2 → 2H2O If 4.0318 g of H2 are combined with 32.0 g of O2, how many grams of H2O are formed? 4.0318 + 32.0____

Multiplication and Division Rule: The solution to a multiplication or division problem can only have as many significant figures as the starting measurement with the least number of significant figures. Procedure: 1. perform the calculation on your calculator 2. count the number of significant figures in the starting measurements 3. round your answer off the answer to the least number of significant figures

Example: A student found the mass of an object to be 50.11 grams and the volume of the object to be 22.0 mL. What is the density of the object?

Example: Gold has a density of 19.320 g/mL. If a piece of gold has a volume of 14.8 mL, what is the mass of the object

Example: What is the mass of 75.2 mL of mercury? (density of mercury is 13.546 g/cm3)

How much space does a 85. 32 g sample of platinum occupy How much space does a 85.32 g sample of platinum occupy? (density of platinum is 21.450 g/cm3)

What is the density of zinc, according to the students data? A student that was trying to find the density of a sample of zinc collected the following data: Volume of water in graduated cylinder before object added = 22.01 mL Volume of water in graduated cylinder after object added = 50.9 mL Mass of object = 206.14 g  What is the density of zinc, according to the students data?

Do Now: The speed of light is 186,000 miles per second. Convert the speed of light to miles per hour. Convert the speed of light to meters per second. (1 mile = 1.609 km)