CK-12 Chemistry Concepts - Intermediate
Answer Key
Chapter 3: Measurements
3.1 SI Base Units Practice QuestionsUse the link below to answer the following questions: http://physics.nist.gov/cuu/Units/history.html
1. When was the metric system created?
2. What was deposited in the Archives de la République in Paris? 3. What was the CGS system based on?
4. When was the name International System of Units (SI) assigned? Answers
1. During the time of the French Revolution.
2. The platinum standards for the meter and the kilogram. 3. Centimeter, gram, and second.
4. 1960.
Review
Questions
1. What does SI stand for?
2. When was this system adopted by the international community? 3. Which of the units are commonly used in chemistry?
Answers
1. Le Système International d’Unité 2. 1960
3. Meter, kilogram, kelvin, second, mole.
3.2 Metric Prefixes
Practice
Do the online metric system crossword puzzle at http://education.jlab.org/sciencecrossword/index.html Click on “metric system” to get to the puzzle
Answers
Answers will be apparent within the puzzle.
Review
Questions
1. What is the prefix for “thousand”? 2. What is the prefix for 0.01?
3. How would you write 500 milliliters? 4. How many decimeters in one meter?
5. You have a mass that weighs 1.2 hectograms. How many grams does it weigh? Answers 1. kilo 2. centi 3. 500 mL 4. 10 5. 120 grams
3.3 Scientific Notation in Chemistry
Practice
Questions
Practice scientific notation using the link below:
http://www.mathsisfun.com/numbers/scientific-notation.html Answers
On web site
Review
Questions
2. What do we use scientific notation for? 3. What is a leading zero?
4. Express 150, 000, 000 in scientific notation. 5. Express 0.000043 in scientific notation. Answers
1. It is a way to express numbers as the product of two numbers: a coefficient and the number 10 raised to a power.
2. To express very large or very small numbers in a convenient fashion. 3. A zero placed to the left of the decimal.
4. 1.5 x 108.
5. 4.3 x 10-5
3.4 SI Length and Volume Units
Practice
Questions
Read the section of length and volume in the link below and answer the following questions: http://www.montgomerycollege.edu/Departments/biotp/Metric.html
1. What are some units of length in the metric system? 2. Do the first three length conversions.
3. Where on the meniscus do you measure volume in a graduated cylinder? 4. Do the first two conversion examples for volume.
Answers
1. Meter, centimeter, and millimeter. 2. 100 mm, 2.5 cm, 0.95 m.
3. At the lowest point.
4. 0.65 L, 87,000 µL or 8.7 x 104 µL.
Review
Questions
1. Define length. 2. Define volume.
3. An object measures 6.2 cm x 13.7 cm x 26.9 cm. Which value is the length of the object?
4. How big is a mL? Answers
1. Length is the measurement of the extent of something along its greatest dimension.
2. Volume is the amount of space occupied by a sample of matter. 3. 26.9 cm.
4. It is a volume of one cm on a side.
3.5 SI Mass and Weight Units
Practice
Questions
Use the link below to answer the following questions: http://hyperphysics.phy-astr.gsu.edu/hbase/mass.html
1. The mass of an object is a __________ measure of its inertia. 2. What is the SI unit for mass?
3. How is weight different from mass?
4. What is the unit of weight in the United States? Answers
1. Numerical. 2. Kilogram.
3. Weight is a force and is affected by gravity. 4. The pound.
Review
Questions
1. Define mass. 2. Define weight.
3. If I weigh 180 pounds on Earth, what will I weigh on the moon? Answers
1. Mass is a measure of the amount of matter that an object contains.
2. Weight is a measure of force that is equal to the gravitational pull on an object. 3. I will weigh 1/6 as much, or 30 pounds.
3.6 SI Kinetic Energy Units
Questions
Use the link below to answer the following questions:
http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Kin etic_Energy
1. What is kinetic energy dependent upon?
2. Do molecules at a higher temperature move faster or slower than molecules at a lower temperature?
3. What happens when a chemical reaction releases energy? 4. What happens when a chemical reaction absorbs energy? Answers
1. Mass and velocity. 2. Faster.
3. Potential energy is converted into kinetic energy. 4. Kinetic energy is converted into potential energy.
Review
Questions
1. What is kinetic energy?
2. What is the mathematical equation for kinetic energy? 3. What is potential energy?
4. What is the SI unit for energy? Answers
1. Energy due to motion. 2. KE = ½ mv2.
3. Energy stored in matter and released during a chemical reaction. 4. The joule.
3.7 Temperature and Temperature Scales
Practice
Questions
Use the link below to answer the following questions:
http://www.visionlearning.com/library/module_viewer.php?mid=48
1. What mixture did Fahrenheit use to set his thermometer at zero degrees? 2. Why is the Celsius scale preferred in scientific work over the Fahrenheit scale?
3. What was the idea behind the establishment of the Kelvin temperature scale? 4. What is the advantage of using the Kelvin scale at low temperatures?
Answers
1. Ice-water-salt.
2. It is more compatible with the bases ten units of the SI system. 3. It is based on the idea of absolute zero.
4. All temperature values are positive.
Review
Questions
1. What is absolute zero on the Celsius temperature scale?
2. What are the freezing and boiling points of water in the Celsius scale? 3. Convert the following Kelvin temperatures to degrees Celsius.
a. 188 K b. 631 K
4. Temperature in degrees Fahrenheit can be converted to Celsius by first
subtracting 32, then dividing by 1.8. What is the Celsius temperature outside on a warm day (880F)?
5. Why is the Celsius scale sometimes called “centigrade”? Answers
1. -2730C
2. 00 C and 1000 C respectively.
3. a. -850C b. 3580C.
4. 310C.
5. There are 100 degrees between the freezing and boiling points of water.
3.8 Scientific Dimensional Analysis
Practice
Questions
Use the link below to answer the following questions:
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/units.html 1. What do we always need to express measurements correctly?
2. What does dimensional analysis tell you?
3. How do you know that you have set the problem up incorrectly? 4. How do you know that you have set the problem up correctly?
Answers
1. Units for the numbers.
2. When to multiply and when to divide. 3. When the final units make no sense. 4. The units are the ones you are looking for.
Review
Questions
1. What is a conversion factor? 2. What is dimensional analysis? 3. How many meters are in 3.7 km? 4. How many kg in 12980 g?
Answers
1. A ratio of equivalent measurements.
2. A technique that uses the units (dimensions) of the measurement in order to correctly solve problems.
3. meters 3.7 km x1000 m 37000 m km 4. kg 12908 g x 1 kg 12.9 kg 1000 g
3.9 Metric Unit Conversions
Practice
Questions
Use the link below to answer the following questions: http://www.purplemath.com/modules/metric.htm
1. Why are metric units nice to work with? 2. What are the basic metric units?
3. To move to a smaller unit, which direction do you move the decimal? Answers
1. They are all multiples of ten. 2. Meters, grams, and liters. 3. To the right
Review
Questions
1. Perform the following conversions. a. 0.074 km to m b.24,600 μg to g c. 4.9 × 107 μg to kg d. 84 dm to mm Answers a. 0.074 km x1000 m 74 m km b. 24,600 g x g6 0.246 g 1x10 g c. 4.9 x 107 g x g6 x kg 0.049 kg 1 x 10 g 1000 g d. 84 dm x m x1000 mm 8400 mm 10 dm m 3.10 Derived Units Practice Questions
Use the link below to answer the following questions: http://www.unc.edu/~rowlett/units/siderive.html
1. How many derived units are there? 2. Who established these units?
3. What derived unit gives rise to the definition of the watt? 4. What derived units are defined by the newton?
Answers
1. Twenty-two.
2. The General Conference on Weights and Measures. 3. The joule.
4. The pascal and the joule.
Review
Questions
1. What is a derived unit? 2. Convert 0.00722 km2 to m2
3. Convert 129 cm3 to L
4. Convert 4.9 × 105 μm3 to mm3.
Answers
1. A derived unit is a unit that results from a mathematical combination of SI base units. 2.
2 2 2 6 2 6 2 3 2 3 2 2 1 km 1000 m 1 km 1 x 10 m 1x10 m 7.22 x 10 km x 7.22x10 m km 3. 129cm x3 1L 3 0.129L 1000cm 4. 3 3 9 3 3 5 3 4 3 9 3 1mm (1000 m) 1x10 mm 1mm 4.9x10 m x 4.9x10 mm 1x10 m 3.11 Density Practice QuestionsYou can perform a density experiment to identify a mystery object online. Find this simulation at http://phet.colorado.edu/en/simulation/density
Answers
See web site
Review
1. Define “density”
2. Are gases more or less dense that liquids or solids at room temperature? 3. How does temperature affect the density of a material?
4. A certain liquid sample has a volume of 14.7 mL and a mass of 22.8 grams. Calculate the density.
5. A material with a density of 2.7 grams/mL occupies 35.6 mL. How many grams of the material are there?
6. A certain material has a density of 19.3 g/mL. What is the material? Answers
1. Density is the ratio of the mass of an object to its volume. 2. Gases are less dense.
3. As the temperature increases, density generally decreases. 4. D= (22.8 g)/(14.7 mL) = 1.55 g/mL
5. mass = density x volume m = (2.7 g/mL)(35.6 mL) = 96.12 grams 6. from the table, gold has a density of 19.3 g/mL.
3.12 Accuracy and Precision
Practice
Questions
Take the quiz at the link below:
http://www.quia.com/quiz/1863743.html?AP_rand=980502951 Answers
Get score from computer exercise.
Review
Questions
1. Define accuracy. 2. Define precision.
3. What can be said about the reproducibility of precise values? Answers
1. Accuracy is a measure of how close a measurement is to the correct or accepted value of the quantity being measured.
2. Precision is a measure of how close a series of measurements are to one another.
3. Precise measurements are highly reproducible, even if the measurements are not near the correct value.
3.13 Percent Error
Practice
Questions
Read the material at the link below and then do “Your Turn” questions to see how well you did. http://www.mathsisfun.com/numbers/percentage-error.html Answers On web site. Review Questions
1. Define accepted value. 2. Define experimental value
3. What happens as the accuracy of the measurement decreases? Answers
1. The true or correct value based on general agreement with a reliable reference 2. The value that is measured during the experiment.
3. The percent error increases.
3.14 Measurement Uncertainty
Practice
Questions
Read the material at the link below and answer the questions on the web site: http://www2.southeastern.edu/Academics/Faculty/rallain/plab194/error.html Answers
Review
Questions
1. What is uncertainty in measurements?
2. Why is the top ruler more reliable in measuring length than the bottom ruler? 3. How could the top ruler be made more accurate?
Answers
1. The level of variation possible in the measurement. 2. The division on the ruler are closer together.
3. There could be divisions between the millimeter markings.
3.15 Significant Figures
Practice
Questions
Take a quiz at the link below:
http://www.sciencegeek.net/APchemistry/APtaters/sigfigs.htm Answers
See answers on quiz site.
Review
Questions
1. What does a significant figure tell us? 2. What is a left-end zero?
3. What is a right-end zero?
4. What does an insignificant zero do? Answers
1. All the certain digits in that measurement plus one uncertain or estimated digit. 2. A zero that appears in front of all of the nonzero digits.
3. A zero that appears after all nonzero digits.
3.16 Rounding
Practice
Questions
Practice rounding numbers using the following link:
http://www.mathscore.com/math/practice/Rounding%20Numbers/ Answers
See web site for answers.
Review
Questions
1. Why do we round numbers?
2. What do we need to know before we round a number? 3. What is “rounding up”?
4. What is “rounding down”? Answers
1. To reflect accurately the correct number of significant digits. 2. How many significant digits we can use.
3. Adjusting a value to more than the original value 4. Adjusting a value to less than the original value.
3.17 Uncertainty in Multiplication and Division
Practice
Questions
Read the information and work the problems on the following web site: http://sigfigscalculator.appspot.com/tutorial/multiply_and_divide
Answers
See answers on the web site.
Review
1. What is the basic principle involved in working with multiplication and division? 2. What happens to units in multiplication and division problems?
Answers
1. The answer should be rounded to the same number of significant figures as the measurement with the least number of significant figures.
2. The nits are multiplied together just as the numbers are.
3.18 Uncertainty in Addition and Subtraction
Practice
Questions
Read the information and work the problems on the following web site: http://sigfigscalculator.appspot.com/tutorial/add_and_subtract
Answers
See answers on the web site.
Review
Questions
1. What is the basic principle to use in working with addition and subtraction? 2. What do you pay attention to when working with whole numbers?
Answers
1. The answer should be rounded to the same number of decimal places as the measurement with the least number of decimal places.
