South Pasadena • Chemistry



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TIME PROBLEMS & DIMENSIONAL ANALYSIS – Worksheet #1

These problems may not have much to do directly with chemistry, but they are designed to help you understand the methods of thinking about and solving problems in chemistry.

As chemistry students you will need to convert units and solve for different variables in equations. You can use dimensional analysis to solve these problems.

Any mathematical fact can serve as a conversion factor. 1 hour = 60 minutes ( [pic] or [pic]

Ex. Convert 1.0 years into seconds.

[pic]=31,536,000 sec

Now your try

Convert how old you are into seconds? Show your work.

1. Convert 2.83 days into seconds.

2. Convert 7.72 years into days.

3. Convert 0.0035 weeks into seconds.

4. Convert 180 days into minutes.

Unit Conversions Practice

Do the following conversions: show all work:

1) Convert 16.7 inches to feet. 12 in = 1 ft

2) Convert 25 yards to feet (there are 3 feet in a yard)

3) Convert 90 centuries to years. 100 years = 1 century

4) Convert 84 miles to kilometers (there are 0.6 miles in a kilometer)

5) Convert 4.75 centimeters to meters. 100 cm = 1 meter

6) Convert 48,987 minutes to days

Name________________________________

TIME PROBLEMS & DIMENSIONAL ANALYSIS – Worksheet #1 teacher

As chemistry students you will need to convert units and solve for different variables in equations. You can use dimensional analysis to solve these problems.

Any mathematical fact can serve as a conversion factor. 1 hour = 60 seconds ( [pic] or [pic]

Ex. Convert 1.25 years into seconds.

[pic]

1. Convert 2.83 days into seconds.

2.45 x 105 s[pic]

2. Convert 7.72 years into days.

2.82 x 103 days

3. Convert 0.0035 weeks into seconds.

2.1 x 103 s

4. Convert 180 days into minutes.

2.6 x 105 minutes

Unit Conversions Practice – Answer Key

1) Convert 16.7 inches to feet

1.39 feet

2) Convert 25 yards to feet (there are 3 feet in a yard)

8.3 yards

3) Convert 90 centuries to years

9,000 years

4) Convert 84 miles to kilometers (there are 0.6 miles in a kilometer)

140 km

5) Convert 4.75 centimeters to meters

0.0475 meters

6) Convert 48,987 minutes to days

34.019 days

5. Convert your age into seconds

Density is often used as a conversion factor between the mass and volume of a sample. For example, the density of liquid mercury is 13.6 g/mL.

6. What is the volume of a 175 gram sample of mercury?

12.9 mL

7. What is the mass of 1.00 gallon of mercury? [1 cup = 236.588 mL] [16 US cups = 1 US gallon]

5.15 x 104 g

8. When Joe carries in a 5-gallon container of water from his car, he always wonders its weight. He looked up on the web and found that 1 lb = 0.453542 kg and 1 qt = .946353 Liter. Calculate its weight in pounds.

40 lbs

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16.7 in ____ __ = ft

25 yds ____ __ = ft

90 centuries ____ __ = years

[pic]

84 miles ____ __ = Km

[pic]

4.75 cm ____ __ = meters

[pic]

48,987 min ____ __ = days

[pic]

7.72 yrs ____ = days

[pic]

0.0035 wks____ __ = days

2.83 days ____ = sec

180 days____ __ = min

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