Measurement and Calculations. Mr. Glavan Riverside Local school District Chemistry 1 Fall 2014. Chapters 1 & 2: Measurement and Calculations. Learning Targets Identify a given substance as an element or compound Classify properties and changes as chemical or physical
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Learning Targets
Identify a given substance as an element or compound
Classify properties and changes as chemical or physical
Explain the structure of the periodic including properties of elements based on their location (metal, nonmetal, etc.)
Determine the amount of heat transferred in a process
Express data and results of calculations with appropriate significant figures, units, and in scientific notation
Calculate percent error from lab data and use this to evaluate the quality of lab data
Perform density calculations and apply density conceptually (e.g. identifying substances or determining if an object will float
Properties of Matter
Properties of Matter
Signs of a Chemical Change
Classification of Matter
Classification of Matter
Periodic Table
Scientific notation is a ay of taking very large numbers and/or very small numbers and writing them more simply
For example, an important number in chemistry is
602,000,000,000,000,000,000,000which suck to write…but in scientific notation it is6.02 x 1023
Exercise: Use the examples below to come up with a set of rules for converting from scientific to regular notation.Sci. NotationReg. NotationSci. NotationReg. Notation 4.521 x 105 452,100 8.2 x 108 .0000000823.8862 x 102 388.62 6.447 x 104 .0006447
Exercise: Use the examples below to come up with a set of rules for converting from regular to scientific notation.Sci. NotationReg. NotationSci. NotationReg. Notation 817 8.18 x 102 0.00456 4.56 x 103 0.000006 6 x 106 48260000 4.826 x 107
When are nonzero numbers significant? (circle one) Always Sometimes Never
When are leading zeros significant? (circle one) Always Sometimes Never
When are captive zeros significant? (circle one) Always Sometimes Never
When are trailing zeros significant? (circle one) Always Sometimes Never
X
&
÷
2.0 x 4 = 89.166 x 3.2 = 292.66543 x 0.0032 = .00850.02 ÷ 0.00606894 = 3
2.44 x 8.629 = 21.1199.2 ÷ 4.05 = 49.20.026 x 0.00449 = .00012(5.4 x 102)(6.39 x 106) = 3.5 x 103
Determine the number of significant figures in each answer above.
Determine the number of significant figures in each number in the questions above.
How is the number of significant figures in the answer determined? (write in space below)
+
&

8.663 – 2.1 = 6.61.00036 + 0.2 = 1.28.365434534385 + 1 = 968.633 + 7.9343 = 76.567
14.2 + 2 = 169.887467 – 2.003 = 7.8846.22 + 2.1 = 8.34.0 + 12.98373 = 17.0
Determine the number of decimal places in each answer above.
Determine the number of decimal places in each number in the questions above.
How is the number of decimal places in the answer determined? (write in space below)
A key skill in chemistry is being able to convert from one unit of measurement to another
For example, converting from one unit of distance to another such as feet to miles
Using conversion factors is done using the same approach taken to multiplying fractions
Determine the answers to following problems:
In each case, notice how a common numerator and denominator cancelled each other
This same idea is the key idea to using conversion factors
With conversion factors, the difference is that you select the fraction to the answer you want
To convert one unit to another, e.g. pounds to grams, the same principles as above are used
Arrange units as needed to get the desired unit
The fraction used to convert one unit to another is known as a conversion factor
pounds x  = grams
Set up the appropriate conversion factor for the following:
Inches to centimeters
Miles per hour to meters per minute
A. Feet
Inches
Feet
inches minutes
B. Inches x minutes
feet seconds
C. Feet x minutes
inches seconds
D. Inches x seconds
minutes feet
The numerical relationship between units must be taken into account as well
For example, to convert feet to inches, you need to know that there are 12 inches in one foot
Once the units are in place, the final step is to put each number with its unit
Potentially Useful Information
1 ft3 = 28.32 L 1 mi = 1.609 km 1 in3 = 16.38 cm3 1 in = 2.54 cm
1 kg = 2.2 lbs 1 oz = 28.35 g 1 lb = 16 oz 1 gallon = 3.785 L
1 lb = 453.59 g 1 ft = 12 in 1 ft3 = 1728 in3 3 ft = 1 yd
1 m = 3.281 ft 1 mi = 5280 ft 1 cal = 4.184 J
Determine the answers to following problems:
a) How many inches are there in 2.0 feet?
b)How many seconds are in 3 hours?
Pay special attention to any unit containing the word “per”; for example:miles per hour – mi/hr meters per second – m/s
grams per mole – g/mol grams per liter – g/L
These units are always determined by dividing the two units
grams per mole = grams ÷ moles
When a measurement has a unit with the word “per” in it, it is a conversion factor
For example, speed in mi/hr is the number of miles driven in 1 hour
25 miles per hour means 25 miles in I hour, so….25 miles = 1 hour
Determine the answers to following problem:
a) If your drive for four hours at a speed of 25 miles per hour, how many miles will you drive?
Sample: The molar mass of a substance is measured in the unit of grams per mole. If a sample of a substance is found to contain 3.55 moles and a mass of 79.2 grams, what is its molar mass?
Metric conversions (mL to L, g to kg) can be performed without the use of conversion factors
To convert these unit, just move the decimal the appropriate number of places
This works because the metric prefixes always change the value of a number by a factor of 10, which is what you do when you move a decimal point
Kangaroos Have Dandruff But Don’t Care Much
Sample: What is the volume in mL of a substance that has a mass of 5.00 grams and a density of 2.1 g/mL?
1. What formula is used to find the volume of a cube?2. What units are used to measure a cube’s dimensions?3. Therefore, what are possible volume units?
•What are some possible units for density?
Sample: A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct value is 1.36 g/mL. What is the student’s percent error?