1. Chapter 2 The Chemist’s Toolbox
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2. Curious About Oranges Why should nonscience majors study science?
Consider an orange tree that produces oranges with different levels of sweetness
Why are oranges sweet? Page 27

3. Measurement
Allows to distinguish between small differences existing within larger classifications, differences which might otherwise go unnoticed

4. Uncertainty
Scientists report measured quantities in a way that reflects the uncertainty associated with the measuring device used
Figure 2.2; page 30

5. Concept Check 2.1
A fisherman describes his latest catch as a 61.5 cm rainbow trout with a mass of 2.35 kg. What is the uncertainty of each measurement?

6. Concept Check 2.1 Solution
The uncertainty in the length is ±0.1 cm because the last digit measured is in the first decimal place.
The uncertainty of the mass measurement is ±0.01 kg because the last digit measured is in the second decimal place.

7. Scientific Notation
Offers a solution for writing very large and very small numbers
Numbers written in scientific notation have two parts
Decimal part
Exponential part
A scientific calculator accepts numbers in scientific notation; page 32

8. Concept Check 2.2
Express the following numbers in scientific notation:
4531

9. Concept Check 2.2 Solution
The following numbers are expressed in scientific notation:
2.32 × 10−4
4.531 × 103

10. Units in Measurement
Unit: Fixed, agreed-upon quantity by which other quantities are measured
A number in association with a unit is a representation of a measurement

11. International System of Units (SI units)
Used by scientists around the world to minimize confusion
Based on the metric system
Each is a combination of a basic unit and prefix multiplier

12. Important SI Standard Units
Length: Meter (m)
Mass: Kilogram (kg)
Time: Second (s)
Temperature: Kelvin (K)

13. Basic SI Units Length: Meter (m)
Redefined in 1983 as the distance that light travels in 1/2999,792,458 seconds
When length is expressed in meters, a human has a height of about 2 m, while the diameter of a dust particle is about m

14. Basic SI Units (continued 1)
Mass: Kilogram (kg)
Measure of the quantity of matter
Standard SI unit is a block of platinum and iridium kept at the International Bureau of Weights and Measures at Sevres, France
Figure 2.3; page 34

15. Basic SI Units (continued 2)
Weight and mass are different
Mass - Quantity of matter
Weight - Measure of force exerted by the gravitational pull on an object

16. Basic SI Units (continued 3)
Time - Second (s)
Originally defined as 1/60 of a minute
Second is defined by an atomic standard using a cesium clock
Figure 2.4; page 34

17. Table 2.2: SI Prefix Multipliers
Table 2.2; page 34

18. Derived SI Units Volume Composed of other units multiplied together
Expressed in units such as cubic meters (m3) or cubic centimeters (cm3 )
Figure 2.5, page 34

19. Unit Conversions Some unit conversions are intuitive
60 minutes = 1 hour
12 inches = 1 foot
Algebraic expression of unit conversions requires one or more conversion factors
Conversion factors can be constructed from any two quantities known to be equal
Formula
(Quantity given) × (Conversion factor(s)) = (Quantity sought)

20. Table 2.3: Some Common Units and Their Equivalents
Table 2.3; page 35

21. Concept Check 2.3
Convert 85.0 kg to pounds.

22. Concept Check 2.3 Solution
Converting 85.0 kg to pounds (lbs) requires unit conversion factors for mass.
Using Table 2.3, we find the unit conversion factors that are necessary to solve the problem. The unit converted from is in the denominator and the unit converted to is in the numerator.

23. Concept Check 2.4
Convert the length 5.00 m to yards.

24. Concept Check 2.4 Solution
Converting 5.00 m to yards involves two steps. Starting with conversion factors provided on Table 2.3, we begin with converting meters to inches, then from inches to yards.
If we stop here, the answer will be in inches
By adding the conversion factor from inches to yards at the end of the first step, we get:

25. Reading Graphs
Graphs allow for the visualization of trends in numerical data
Figure 2.7; page 38

26. Concept Check 2.5
Using data from the previous graph, calculate the average increase in carbon dioxide concentration per year from 1996 to 2006.

27. Concept Check 2.5 Solution
The data from the previous graph shows that the CO2 concentration in 1996 was 360 ppm and steadily increased to 380 ppm in 2006, an increase of 20 ppm over 10 years. Dividing the increase of CO2 concentration by the 10 year time period gives the average increase of CO2 concentration per year.

28. Reading Graphs (continued 1)
Representation of graphical data can influence the information extracted from that data
Figure 2.6; page 38

29. Reading Graphs (continued 2)
Sulfur dioxide concentration (ppb) (Source: US EPA: page 40

30. Concept Check 2.6
Using data from the previous graph, what is the total decrease in sulfur dioxide from 1990 to 2006 and the total percentage decrease from initial levels?

31. Concept Check 2.6 Solution
Change in SO2 concentrations:
ppb
ppb
8.6 ppb − 3.3 ppb = 5.3 ppb decrease in SO2 concentration
From 1990 to 2006, the SO2 concentration decreased 5.3 ppb, which translates to a 62% decrease from initial levels.

32. Steps to Solve Basic Introductory Chemistry Problems
Write all quantities given with their associated units under the heading "Given"
Write the quantity that is sought, including its units under the heading "Find"
Write all known conversion factors

33. Steps to Solve Basic Introductory Chemistry Problems (continued)
Multiply the given quantity by the appropriate conversion factors and canceling units such that the desired units are the algebraic result
Round off the answer so that the number of digits in the answer is approximately the same as the number of digits in the given quantities

34. Density A measure of how much mass is in a given amount of space
Which weighs more, a ton of bricks or a ton of feathers?
Both weigh the same, 1 ton
The ratio of its mass to its volume is m/V
Figure 2.8; page 42

35. Table 2.4: Density of Common Substances
Table 2-4; page 43

36. Density as a Conversion Factor
Density (d): Measure of how much mass is in a given amount of space
Volume (V): Measure of the amount of space that is occupied
Mass (m): Measure of the quantity of matter present

37. Concept Check 2.7
What is the mass of a 125 mL-sample of a liquid with a density of g/mL?

38. Concept Check 2.7 Solution
Density is expressed using the equation: d = m/v. Rearranging the equation to solve for mass gives us:
m = d × v

39. Chapter Summary Molecular concept Societal impact Measurement tools
Neither science nor technology could advance very far without measurements
The standard SI units
Decisions about which units of measurement need to be used are societal
Understanding graphs
Be cautious when reading data (scientific or informal)
Conversions and conversion factors
Carefully evaluate units in data tables and on graphs