General Chemistry Atoms First, 2e John McMurry, Ro
General Chemistry Atoms First, 2e John McMurry, Ro
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General Chemistry Atoms First 2nd Edition By John McMurry, Robert Fay (Instructor Manual)
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General Chemistry Atoms First, 2e John McMurry, Ro
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General Chemistry Atoms First, 2e John McMurry, Ro
General Chemistry Atoms First, 2e John McMurry, Robert Fay (Instructor Manual)
General Chemistry Atoms First, 2e John McMurry, Robert Fay (Instructor Manual)
,Chapter 0—Chemical Tools: Experimentation and Measurement
Lecture Outline
0.1. Experiment → Hypothesis → Theory: Approaching Chemistry
A. Scientific Method – systematic approach to research
1. Experimentation
2. Hypothesis – interpretation explaining results of many experiments
3. Theory – consistent explanation of known observations; logical interpretations of
experimental results
0.2. Experimentation and Measurement in Chemistry
A. International System (SI) of Units – seven base units (and units derived from them) that suffice
for all scientific measurements (textbook Table 0.1)
B. Common prefixes used to modify SI units (textbook Table 0.2)
6
1. mega (M); factor = 10
3
2. kilo (k); factor = 10
–1
3. deci (d); factor = 10
–2
4. centi (c); factor = 10
–3
5. milli (m); factor = 10
–6
6. micro (); factor = 10
–9
7. nano (n); factor = 10
C. Scientific notation – exponential format for very large or very small numbers (textbook
Appendix A)
D. All measurements of physical quantities contain a
1. number.
2. unit label.
0.3. Fundamental Units: Measuring Mass
A. Mass (SI unit = kg) – amount of matter in an object
B. Matter – anything physically real
C. Weight – pull of gravity on an object
D. Mass of an object
1. Measured on a balance
2. A comparison of the weight of the object to the weight of a reference standard of known
mass
0.4. Fundamental Units: Measuring Length
A. Meter
1. Standard SI unit of length
2. Distance traveled by light in a vacuum in 1/299,792,458th of a second
0.5. Fundamental Units: Measuring Temperature
o
A. Common unit – Celsius degree ( C)
B. Scientific unit – Kelvin
C. Celsius and Kelvin scales –100 degrees between the freezing point and boiling point of water
Temperature in K = temperature in C + 273.15
Temperature in C = temperature in K – 273.15
D. Fahrenheit scale –180 between the freezing point and boiling point of water
1. 180 F encompasses the same range as 100 C
180 o C 9
1 oC = oF
100 o F 5
E. Conversion from Celsius to Fahrenheit
1. Size correction
2. Followed by zero-point correction
, Chapter 0—Chemical Tools: Experimentation and Measurement
F. Conversion from Fahrenheit to Celsius
1. Zero-point correction
2. Followed by a size correction
9 oF
o
F = o oC 32 o F
5 C
5 oC o
o
C= F - 32 o F
9 oF
0.6. Derived Units: Measuring Volume
A. Derived quantities – quantities expressed in terms of one or more of the seven base units (See
textbook Table 0.3.)
B. Volume – amount of space occupied by an object
1. Measured in SI units by the cubic meter (m3)
2. Commonly used measurements:
a. Cubic decimeter (dm3) = metric liter (L)
b. Cubic centimeter (cm3) = metric milliliter (mL)
0.7. Derived Units: Measuring Density
A. Density – intensive property relating mass to volume
1. Typically expressed in units of g/cm3 or g/mL for solids and liquids; gases often use g/mL
2. Temperature dependent property
3. Useful property – allows conversion of a liquid’s volume to mass
0.8. Derived Units: Measuring Energy
A. Energy
1. Capacity to do work or supply heat
2. Energy = work + heat
B. Joule
1. SI unit for energy
2. 1 J = 1(kgm2)/s2
3. Small unit of heat, chemists often use kJ.
C. Calorie
1. Amount of energy necessary to raise the temperature of 1 g of water by 1C
2. 1 cal = 4.184 J
3. Nutritional calorie (Calorie)
4. 1 Cal = 1000 cal = 1 kcal = 4.184 kJ
0.9. Accuracy, Precision, and Significant Figures in Measurement
A. Accuracy – how close a measurement is to the true value
B. Precision – how well a number of independent measurements agree with one another
1. To indicate the precision of a measurement use all the digits known with certainty, plus one
additional estimated digit.
2. Number of digits in the measurement = number of significant figures
C. Determining the number of significant figures – see rules in textbook on page 13
D. Using scientific notation – helpful in determining number of significant figures
E. Exact numbers – infinite number of significant figures
0.10. Rounding Numbers
A. In carrying out a multiplication or division, the answer can’t have more significant figures than
either of the original numbers.
B. In carrying out an addition or subtraction, the answer can’t have more digits to the right of the
decimal point than either of the original numbers.
C. Rules for rounding off numbers
1. See text pages 14-15
, Chapter 0—Chemical Tools: Experimentation and Measurement
2. Doing calculations
a. Use all figures, significant or not
b. Only round off final answer
0.11. Converting Measurements from One Unit to Another
A. Dimensional analysis method
1. Quantity described in one unit converted into an equivalent quantity described in a
different unit
2. Conversion factor used to express relationship between units
3. Units
a. Treated like numbers
b. Can be multiplied and divided
4. Equation
a. Set up so that all unwanted units cancel
b. Leave only desired units
c. Correct answer obtained only if equation set up so unwanted units cancel
5. Method:
a. Start with given information, including units
b. Identify information needed, including units
c. Find relationship between known information and unknown answer
d. Plan a strategy to get from known information to unknown answer
e. Solve
i. Use conversion factor that allows units in given information to cancel
ii. Continue conversion factor use to cancel the previous unit until desired unit
remains
f. Consider whether answer obtained is reasonable (Refer to Ballpark Check in textbook.)
6. Number of significant figures in answer determined from given information
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