1. Chem 106 Practical Everyday Chemistry
CALCULATIONS
Dr. Ron Rusay
Diablo Valley College
Spring 2004

2. Unit Conversion

3. Systematic Problem Solving Dimensional/Unit Analysis (Conversion)
How many mL of milk are in a1/2 gallon carton?
0.50 gal
? mL
1 gal = 4 qt
1 qt = 946 mL Or
0.50 gal | 4 qt | 946 mL
| 1 gal | 1 qt
= ? mL

4. Complete the following Units & Conversions
Number Scientific Notation Named unit
1.3 x 1010 yrs
13,000,000,000 yrs. ________________ __? gigayears
13 gyrs
546
5.46 X 10 2
___________ mL ______________ mL Liters
0.546 L
0.845
____________ kg __8.45 x kg___ _? grams__
845 g

5. Percent A comparison based on normalization to 100.
George Washington University, 1995: 64 unsealed addressed envelopes with $10 in each were dropped on campus in different classrooms.
In economics 18 of 32 were mailed back, in [business, history and psychology] 10 of 32 were mailed. What is the percent for each of the 2 groups of students?
18/32 x 100 =
10/32 x 100 =
56.25%
© Copyright R.J. Rusay
31.25%

6. Percent Continued
The Professor conducting the study received 43.75% of the original $640 in the mail. How much did he receive?
How many of you would mail the envelop presuming no one knows you found it?
One student mailed an empty envelop with the return address: Mr. IOU, 1013 Indebted Lane, Bankrupt City, MS (WSJ 1/18/95)
43.75% /100% x $ 640 =
$280
© Copyright R.J. Rusay

7. Mass and Volume Measurement
Mass / Volume (g/ml) = Density
Liquid
Solid

8. UN
Title:
Example 1.8
Caption:
Calculation of iron density with voice balloon. Note that the units are expressed when given values are substituted into the general equation. The answer is also expressed in the proper units.
Notes:
Proper units for density are mass per unit volume.

10. Volume of an object (any shape) by displacement
If the mass were 28.8 g, what is the density?
28.8 g/10.5 ml=
2.74 g/ml
60.5 mL
-50.0 mL
10.5 mL
What is the volume of the jade?

11. Density http://www.density.com/what.htm
Density = Mass / Volume [g/mL or g/cm3; g/L]
Least dense man-made solid substance: Aerogel, D = x 10-3 g/cm3
Dair = 1.22 x 10-3 g/cm3 (1.22 g/L)
Densest known substance: a White Dwarf
© Copyright R.J. Rusay

12. Conversion Factor Method (Dimensional Analysis)
Qualitative Descriptions vs. Quantitative
Use exact numbers / “scale factor” UNITS
A Bookkeeping Method: Example
___ ft___in > ? m
(1 ft = 12 in; 2.54 cm = 1 in; 100 cm = 1 m)
___ft x 12 in/ft + ___in = ___in
___in x 2.54 cm/in x 1 m/100cm = ___m 5 9 5 10 70
1.78 70
© Copyright R.J. Rusay

13. Volumes of regular shapes
V = s 3 h
V = l x w x h
V = 4/3  r 3

14. (1 T = 1,000 kg; 1 kg = 1000g; tsp = 14.8 mL; 1 mL = 1 cm3 )
Calculate the density [D = ? g/cm3 ] of a White Dwarf.
1.0 teaspoon has a mass of 3.0 T (metric tons).
(1 T = 1,000 kg; 1 kg = 1000g; tsp = 14.8 mL; 1 mL = 1 cm3 )
Conversion Factors in red are among the ones that you must know from memory.

15. Popcorn & Science How good is it?
Expansion
Kernel Size
Moisture Content
cm3 / g
Kernels / 10 g
Percent H2O
How would you experimentally determine these values?

16. Popcorn & Science How good is it?
Would a single trial be as good as three?

17. Popcorn & Science How good is it?
The average of 3 or more trials is common.

18. Popcorn & Science How good is it?
The average of 3 or more trials is common.

19. Popcorn & Science How good is it?
The average of 3 or more trials is common.

20. Popcorn & Science How good is it?
Calculations:
MWVT Number: cm3/g
Lite Movie Theater Corn on the Cob
Kernel Size: kernels/10g
Percent Water: %
Which would you rate the best and why?