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Homework Answers. 1. 4.17 m/s 2. 22.36 m 2 3. 13.5 g/L 4. 5712 cm 3 5. 60 kg·m/s 6. 66.86 7. 2.76 N·m/s 8. 32.73 kg/cm 2. 9. 0.1071 mm 3 10. 25 kg·m/s 2 11. 140 N·m 12. 22.81J/g· o C 13. 208 J/g 14. 38 mol/L 15. y/2 16. 152.8 17. 3d 3. More answers…. 18. X=11.5 - PowerPoint PPT Presentation
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Homework Answers
1. 4.17 m/s2. 22.36 m2
3. 13.5 g/L4. 5712 cm3
5. 60 kg·m/s6. 66.867. 2.76 N·m/s8. 32.73 kg/cm2
9. 0.1071 mm3
10. 25 kg·m/s2
11. 140 N·m12. 22.81J/g·oC13. 208 J/g14. 38 mol/L15. y/216. 152.817. 3d3
More answers…
18. X=11.522. X=3.523. X=224. X= H/WQ25. X= T+6/Y26. X=23FG-827. X=EF2/18KR28. X=T/LS29. X= -w+15G30. X= T3KE4R/B2H5Y
31. 520032. 0.00096533. 0.08534. 7.8x105
35. 4.22x10-6
36. 1.0x107
37. 3.28x1027
38. 468,00039. 0.5840. 0.0244941. 5.17x10-7
42. 2.56x10-15
43. 4.7144. 4.69x102
45. 1.1037x104
46. 1.70x10-15
47. 1.43x10-3
48. -2.30x1012
Meter
Liter
Gram
deca
dc
hecto
h
kilo
k
deci
d
milli
m
centi
c
1
0.001
0.01
0.1
10
1001,000
Staircase Rule: The direction you slide your finger is the direction the decimal place goes!
Density
A ratio that compares the mass of an object to its volume
The units for density are often g/cm3
Formula: )(cm volume
(g) mass density
3
Example Problem
Suppose a sample of aluminum is placed in a 25-mL graduated cylinder containing 10.5mL of water. The level of the water rises to 13.5mL. What is the mass of the sample of aluminum? Volume: final-initial13.5mL-10.5mL= 3.0mL Density: 2.7 g/mL (Appendix C) Mass: ????
Temperature
Kelvin is the SI base unit for temperature Water freezes at about
273K Water boils at about 373K
Conversion: 0C +273 =Kelvin
Using and Expressing Measurements
A measurement is a quantity that has both a number and a unit.
Measurements are fundamental to the experimental sciences. For that reason, it is important to be able to make measurements and to decide whether a measurement is correct.
Dimensional Analysis *Very Important*
A method of problem solving that focuses on the units to describe matter Conversion factor- a ratio of equivalent values
used to express the same quantity in different units
Example: 9.00 inches to centimeters Conversion factor: 1 in = 2.54 cm cm 9.22
1in
cm 2.54in x 9.00
We often use very small and very large numbers in chemistry. Scientific notation is a method to express these numbers in a manageable fashion.
Definition: Numbers are written in the form M x 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.
5000 = 5 x 103 = 5 x (10 x 10 x 10)
= 5 x 1000 = 5000
Numbers > one have a positive exponent.
Numbers < one have a negative exponent.
Ex. 602,000,000,000,000,000,000,000
Ex. 0.001775
In scientific notation, a number is separated into two parts.
The first part is a number between 1 and 10.
The second part is a power of ten.
6.02 x1023
1.775 x10-3
ANSWERS
0.000913 9.13x10-4
730,000 7.3x105
122,091 1.22091x105
0.00124 1.24x10-3
0.0000000001259 1.259-10
Your success in the chemistry lab and in many of your daily activities depends on your ability to make reliable measurements. Ideally, measurements
should be both correct and reproducible. Accuracy: a measure of how close a
measurement comes to the actual or true (accepted) value of whatever is being measured.
Precision: a measure of how close a series of measurements are to one another
Good AccuracyGood Precision
Poor AccuracyGood Precision
Good AccuracyPoor Precision
Poor AccuracyPoor Precision
Error- the difference between the accepted value and the experimental value
Accepted Value: referenced/true value Experimental Value: value of a
substance's properties found in a lab.
%100accepted
error
Example
A student takes an object with an accepted mass of 150 grams and masses it on his own balance. He records the mass of the object as 143 grams. What is his percent error?
Accepted value: 150 grams Experimental value: 143 grams Error= 150grams – 143 grams = 7
grams
% ERROR %100
accepted
error
error %67.4100grams 150
grams 7x
The significant figures in a measurement include all of the digits that are known, plus the last digit that is estimated.
Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.
Instruments differ in the number of significant figures that can be obtained from their use and thus in the precision of measurements.
1. Every nonzero digit in a reported measurement is assumed to be significant.
The measurements 24.7 meters, 0.743 meter, and 714 meters each express a measure of length to 3 significant figures.
2. Zeros appearing between nonzero digits are significant.
The measurements 7003 meters, 40.79 meters, and 1.503 meters each have 4 significant figures.
3. Leftmost zeros appearing in front of nonzero digits are NOT significant. They act as placeholders. The measurements 0.0071 meter,
and 0.42 and 0.000099 meter each have only 2 significant figures.
By writing the measurements in scientific notations, you can eliminate such place holding zeros: in this case 7.1 x10-3 meter, 4.2x10-1 meter, and 9.9x10-5 meter.
4. Zeros at the end of a number to the right of a decimal point are always significant. The measurements 43.00 meters, 1.010 meters,
and 9.000 meters each have 4 significant figures.
5. Zeros at the rightmost end of a measurement that lie to the end of an understood decimal point are NOT significant if they serve as placeholders to show the magnitude of the The zeros in the measurements 300 meters, 7000
meters, and 27,210 meters are NOT significant.
6. There are two situations in which numbers have unlimited number of significant figures. The first involves counting. If you count 23
people in the classroom, then there are exactly 23 people, and this value has an unlimited number of significant figures.
The second situation involves exactly defined quantities such as those found within a system of measurement. For example, 60 min= 1 hour, each of these numbers have unlimited significant figures.
Rounding Rules: Addition/Subtraction When you add/subtract measurements, your
answer must have the same number of digits to the RIGHT of the decimal point as the value with the FEWEST digits to the right of the decimal point
Example: 28.0 cm23.538 cm+ 25.68 cm77.218 cm
Rounded to 77.2 cm
Fewest Decimal places
Rounding Rules: Multiplication/Division When you multiply or divide numbers,
your answer must have the same number of significant figures as the measurements with the FEWEST significant figures
Example: 3.20cm x 3.65cm x 2.05cm=
= 23.944 cm3
Rounded = 23.9 cm3Each has 3 sig fig’s