Chapter I. Chemical Foundations

Transcription

1 Chapter I. Chemical Foundations Upon successful completion of this unit, the students should be able to: 1.1 Distinguish among observations, laws, theories, and hypotheses in the scientific approach to knowledge. 1. Which statement below is a theory and which is a law? a. The temperature and volume of a gas are directly proportional. b. The volume of a gas increases as the temperature increases because the molecules that make up the gas move farther apart. 2. Which of the following most closely matches the correct order of the scientific method? a. Conducting experimental work, collecting observations, making a hypothesis, establishing a theory. b. Establishing a theory, conducting experimental work, collecting observations, making a hypothesis. c. Making a hypothesis, collecting observations, establishing a theory, conducting experimental work. d. Collecting observations, making a hypothesis, conducting experimental work, establishing a theory. 3. A friend tells you that he will believe in the theory of evolution when it becomes the law of evolution. Is this possible? ( Yes or No ) (Circle one) If yes, describe how a theory becomes a law. If no, tell why a theory can not become a law. 1.2 State and apply rules for taking measurements and significant figures. 1. Read the volume on the buret to the correct number of significant figures

2 2. Read the volume on the graduated cylinder to the correct number of significant figures. 3. Express the following number in scientific notation to 5 significant figures: 4,590, For the following number, underline the zeroes that are significant and draw an x through zeroes that are not Round the following number to four significant figures: x Perform the following calculations to the correct number of significant figures: a x b. (1.7 x x 10 5 ) Calculate the following and express your answer in scientific notation and to the correct number of significant figures. a x x 10-4 b x x 10-2 (8.67 x ) 8. Carry out the following calculation and express the answer to the correct number of significant figures /4.23

3 1.3 Identify the common SI units for mass (kg), length (m), and time (s) and know the meaning of the following metric prefixes (i.e. memorize and be able to apply): giga, mega, kilo, deci, centi, milli, micro, nano, pico. Students should also memorize and be able to apply 1 cm 3 = 1 ml. See sample questions under objective Perform conversions among different units using dimensional analysis (note: students should be able to apply English to metric and English to English conversion factors, but they do not need to memorize them). 1. Convert 12.0 x 10-7 mg to ng. 2. Because of the high heat and low humidity in the summer in Death Valley, California, a visitor requires about one quart of water for every two miles traveled on foot. Calculate the approximate number of liters required for a person to walk 39 kilometers in Death Valley. 3. Convert 25 m to dm. 4. Which quantity is larger: x 10 3 pg or mg? 5. An atom of oxygen is moving with a speed of 482 m/s. What is its speed in miles/hr? 6. What is the SI unit for length? 7. A picometer is a. greater than a micrometer b. equal to a micrometer c. less than a micrometer d. twice as large as a micrometer 8. In 1999, NASA lost a $94 million orbiter because one group of engineers used metric units in their calculations, while another group used English units. Consequently, the orbiter pushed too far into the Martian atmosphere and burned up. Suppose that the orbiter was to have established orbit at 155 km and that one group of engineers specified this distance as 1.55 x 10 5 m. Suppose further that a second group of engineers programmed the orbiter to go to 1.55 x 10 5 ft. What was the difference (in kilometers) between the two altitudes? 9. Batrachotoxin, the active component of the South American arrow poison obtained from the golden frog, Phyllobates terribilis, is so poisonous that a single frog contains enough toxin (1100 µg) to kill 2300 people. Expressed in scientific notation, how many grams does it take to kill one person? 10. If the area of a telescope lens is 4786 mm 2, what is the area in square feet (ft 2 )? 11. A Honda Insight gets 70 miles / gallon. Convert this to kilometers / liter. 12. In the United States, land area is commonly measured in acres: 640 acre = 1 mi 2. In most of the rest of the world, land area is measured in hectares: 1 hectare = 1 hm 2 [1 hectometer (hm) = 100 m]. Which is the larger area, the acre or the hectare? 13. How many cubic feet are there in a cube whose edge is 6.0 x miles in length? 14. How many square miles are there in 456 km 2?

4 1.5 Interconvert temperatures among Celsius, Fahrenheit and Kelvin scales. 1. Which of the following represents 128 K in o C. a. 401 o C b. 145 o C c. 103 o C d o C 2. Helium has the lowest boiling point of any liquid, o C. What is this temperature in o F? 3. Convert 150 o F to K. 4. Convert 158 K to o F? 1.6 Solve problems involving density. 1. The density of aluminum is g/cm 3. What is the final liquid level of water if lbs. of aluminum is dropped into a graduated cylinder containing ml of water? 2. A sample of motor oil with a mass of 440 g occupies 500 ml. What is the density of the motor oil? 3. The density of an object is 1.63 g/ml. Its volume is 0.48 L. What is the mass of the object in grams? 4. A worker at the United States Mint wants to know if a batch of 100 pennies was minted before 1982 (100% copper) or after 1982 (3% copper and 97% zinc). Assuming both groups of pennies have the same dimensions, would she get her answer by weighing the coins? Explain. 5. Which of the following is less: 4 x 10-2 kg/cm 3 or 4 x 10-1 mg/cm 3? 6. An object having a density of 2.45 g/cm 3 has a mass of 48.0 g. What is the volume of the object in cm 3? 7. An aluminum ball has a density of 2.70 g/ml. If the mass of the ball is kg, what is the volume of this ball in milliliters? (Express your final answer in scientific notation.) 8. A liquid has a density of 18 g/ml. What volume will 9.6 g of this liquid have? 1.7 Differentiate between pure substances and mixtures, and correctly use specific terms such as elements, compounds, homogeneous, heterogeneous, states (phases), and solutions. 1. Define heterogeneous mixture. 2. Identify the following as an element, compound, homogeneous mixture, or heterogeneous mixture: a. Co b. iced tea

5 3. Identify each of the following as an element, a compound, or a mixture. a. blood b. table salt c. aluminum d. brass 4. Which of the following is a mixture? a. chlorine gas b. copper c. calcium chloride d. air 5. A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids A and B and the gas C are elements or compounds. Explain your conclusions for each substance. (Brown, LeMay, and Bursten, 2003) 6. Using the key below as a guide, make a molecular level drawing which shows a homogeneous mixture of carbon monoxide (CO) and carbon dioxide (CO 2 ) gas. Draw 8-10 molecules of carbon monoxide and 2-4 molecules of carbon dioxide. Key: 7. Is C 6 H 12 O 6 an element, compound or mixture? 8. Identify the following as element, compound, homogeneous mixture, or heterogeneous mixture. a. chunky peanut butter b. salt water (assume salt is completely dissolved) 9. Circle the mixtures. chlorine gas saltwater calcium chloride air 1.8 Differentiate between chemical and physical properties and changes. 1. Is the following an example of a chemical change or physical change: An overgrown lawn is manicured by mowing it with a lawn mower. 2. Identify each of the following as either a physical (P) or a chemical (C) change. a. boiling water b. iron rusting c. sugar dissolves in water d. gasoline burns in air 3. Describe the difference between a physical property and a chemical property. Give an example of each. 4. How is a chemical change different from a physical change? Give one example of both a chemical change and a physical change.

6 5. Circle the chemical changes. rusting iron crushing rock melting ice painting a board 1.9 Describe how distillation, filtration, and chromatography can be used to physically separate substances. 1. Describe the differences between distillation, filtration, and chromatography. 2. Sand, candle wax, and table sugar are placed in a beaker and stirred. Design an experiment in which all three can be separated and isolated.