homework read pgs. 11-13 chapter 1 problems 20, 24, 26,30 worksheet scientific measurement (2a extra...
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Homework
Read Pgs. 11-13Chapter 1 Problems 20, 24, 26,30Worksheet Scientific Measurement (2A
Extra Practice Problems)
Significant figures
Addition and SubtractionThe answer must have the
same number of decimal places as the factor with the least number of decimal places.
Significant Figures
Example of Addition:
1250
+ 23.98
1273.98 (this is what a calculator will show)
1274 (this is the answer corrected for significant figures, rounded to the 1’s place)
Significant figures
Multiplication and divisionThe answer must have the
same number of significant figures as the factor with the least number of significant figures.
Significant figures
Example of Division:
15.375 / 5.0 = 3.075(this is what a calculator will show)
Since the denominator only has 2 significant figures the answer is rounded to 3.1
Significant Figures
8.654 m x 0.34 m =2.10 cm x 0.50 cm =
10.4815 ml ÷ 8.4 ml = 0.365 m ÷ 0.050 m =
textbook HW20a. 3 26a. 132.5 g
b. 4 b. 298.69 cm
c. 4 c. 13 lb
d. 1 d. 350 oz
e. 5 30. only c is exact
24a. 0.5
b. 401.4
c. 0.2684
d. 7.8
Scientific Measurement1 a. 3 2 a. 133 g e. 50.8 dm
b. 4 b. 109 mL f. 2.86x103 cal
c. 7 c. 13 cm
d. 2 d. 14 g/mL
e. 3 f. 63 a. 1.0 e. 740. 4a. 145g e.
1.30x102dm
b. 40.1 f. 80 b. 64mL f. 16 cm
c. 6.2x10-5 c. 91.7 cm2 g. 6000cal
d. 1.5 d. 4.3g/cm3
Unit 1
Read pages 8-9Unit 1 Sci. Notation and % ErrorChapter 1 Problems 20, 24, 26,30Quiz: Oct 18/19 (Thursday / Friday)
Numbers and Measurement
Chemistry requires us to make accurate measurements that are often very small or very large.
To more easily handle these very large and small numbers, we use scientific notation.
Scientific Notation
Measurements are written as the product of two numbersA coefficient – number between 1 and 1010 raised to a power – the exponent
indicates the number of times the coefficient must be multiplied or divided by 10.
Scientific Notation
Write the following in scientific notation:6,954,000175.983
Write the following in standard numerical form:6.75 x 10-3
1.865 x 102
Calculations in Scientific Notation
MultiplicationMultiply coefficientsAdd exponents
Perform the following calculations:7.2 x 102 · 5.02 x 10-3
1.0 x 102 · 2.6 x 108
Calculations in Scientific Notation
DivisionDivide coefficientsSubtract the exponent of the denominator
from the exponent of the numerator.Perform the following calculations:
8.4 x 103 / 2.1 x 10-2
7.25 x 104 / 5.0 x 102
Calculations in Scientific Notation
Addition and subtractionMake the exponent of both numbers the
sameAlign decimal points, and add coefficientsThe exponent of the result will be the same
as for the measurements
Calculations in Scientific Notation
Perform the following calculations:1. 6.3 x 104 + 2.1 x 10-3
2. 7.563 x 102 - 1.77789 x 10-3
Calculations in Scientific Notation
1. 1.5 x 106 + 2.7 x 103
2. 6.38 x 10-3 – 3.8 x 10-4
International System of Units
Units of Measurement
Quantity SI base unit or derived unit Symbol
Length meter m
Volume cubic meter m3
Mass kilogram kg
Density grams per cubic centimeter g/cm3
Temperature Kelvin K
Time second s
Pressure Pascal Pa
Energy joule J
Amount of Substance mole mol
Luminous Intensity candela cd
Electric Current ampere a
SI Units
103 for kilo- k 106 for mega- M 109 for giga- G 10-1 for deci- d 10-2 for centi- c 10-3 for milli- m 10-6 for micro- μ 10-9 for nano- n 10-12 for pico- p
Accuracy: Evaluations of Measurements
Accepted value: True or correct value based on reliable source
Experimental value: measured by you during the experiment
Error
Difference between the accepted value and the experimental value
Take the absolute value
% Error
% Error = Error / accepted value * 100
% Error = Actual – Experimental x 100
Actual
What is the % error?
A student measures a volume as 25.0mL, whereas the correct volume is 23.2mL.
Density
Which is heavier – a pound of popcorn or a pound of cheese?
They would have the same mass!!
However, if you had equal VOLUMES of popcorn and cheese, the cheese would have more mass.
Density
A cube of gold-colored metal with a volume of 64 cm3 has a mass of 980. grams. The density of pure gold is 19.3 g/cm3. Is the metal pure gold?
Unit 1
HW: Read pages 9-10Unit 1: Density and TemperatureMore Conversion Problems
Temperature
The temperature of an object determines the flow of heat transfer.
Celsius scale uses the freezing point of water as 0 and the boiling point of water as 100.
Kelvin scale uses 273 for the freezing point of water, and 373 as the boiling point.
(Gabriel) Fahrenheit Scale
German physicistDeveloped scale in 1714Hg was used in thermometerFreeze pt. water = 32˚FBoiling pt. water = 212˚F0˚F = freeze pt. of water, salt and
dry ice (CO2)
Why use Hg in a thermometer?
For every degree the mercury’s temp. increases, the difference in which the Hg expands is NOTICABLE and CONSTANT.
Alcohol thermometer used in Alaska because Hg will freeze!
(Anders) Celsius Scale
Developed in 1742Swedish AstronomerFreezing pt. of water = 0˚CBoiling pt. of water = 100˚CUses Hg in thermometer
325
9 CF
(Lord William) Kelvin ScaleDeveloped in 1848Based on absolute zero = zero heat energy
= all motion stops0 Kelvin = -273.15˚CNo degree on scale (Kelvin units)Kelvin is a theoretical scale because it does
not compare the temp. to FP or BP of water.Based on lowest temperature possible – No
negative numbers on scale
Compare the 3 temperature scales