Introduction to Mastering Chemistry

Introduction to MasteringChemistry 1 of 32 Introduction to MasteringChemistry A message from your instructor... The purpose of the following exercises is to familiarize you with the system you will be using for the rest of your course. These exercises are not intended to teach or test your knowledge of any specific subject material. Therefore, you will not be penalized for using hints or submitting incorrect answers. Welcome! Mastering presents homework items assigned by your instructor and works with you to answer them. Homework items typically have an introduction, possibly figures, and one or more parts for you to answer. Type of help offered Mastering tells you immediately whether or not your answers are correct. Usually, you will have multiple chances to arrive at the correct answer. Your instructor will determine how many tries you have available. In many items, hints are available to help you if you get stuck. If you don't need the hints to solve the problem, you can still use them for review later on. If you submit an incorrect answer, Mastering often responds with specific, helpful feedback. Mastering is forgiving of many typos and formatting mistakes. If it can't figure out what you entered, it will let you know and give you another chance. These exercises were chosen specifically to lead you through the key features of Mastering and are not intended to test your knowledge of any specific subject material. Therefore, on this item you will not be penalized for using hints and submitting incorrect answers. In fact, you should submit incorrect answers and use the hints to see what happens! Part A How many squares are in this grid ? Note that the figure link lets you know that a figure goes along with this part. This figure is available to the left. Enter your answer as a number in the box below and then submit your answer by clicking Submit. ANSWER: Number of squares = Correct What you are reading now is called a "follow-up comment." These comments typically offer more information or provide an interpretation of the answer you just obtained. Before you move on to a slightly more challenging question, have a quick look at the other buttons available around the answer box. Give Up allows you to complete the question if you can't solve it on your own. Your instructor controls whether or not the correct answer is displayed to you. My Answers brings up a new window that lists all of the answers you have submitted for this question, along with any helpful feedback you received for incorrect submissions. Grading See the help file available by clicking the Help link at the top right corner, if you want to know more about how grading works in general. Here is the most important information you'll need. You must complete every part to get credit for an item. To complete a part, either answer the main part question correctly or click the Give Up button. Introduction to MasteringChemistry 2 of 32 In a graded homework item, each part counts equally toward your score on the overall item. If you get full credit on each part, you will receive full credit for the problem. You may lose a fraction of the credit for a part when you submit an incorrect answer. Whether you do lose credit and how much you lose are set by your instructor. However, you won't lose credit for most types of formatting mistakes or for submitting a blank answer. As you might expect, you will receive no credit for a part if you use the Give Up button. If you just can't figure out a question, there is a way to get partial credit by using hints, as the following part will illustrate. Part B What is the magic number? Note that there is a figure also associated with this part. However, the figure for Part A may still be visible on the left. To view the figure associated with Part B, click on the figure link. A new figure should appear on the left. You could try to guess the magic number but you would probably use up all your tries before getting the answer. Notice the new Hints button underneath the answer box for this question. Clicking this button will open up a list of hints that will guide you to the correct number. Hint 1. Different types of hints and their impact on grading Notice that there are three hints for this question. You are not required to use all of the hints or to use them in order. Each hint has a tagline that describes its contents. Based on the tagline you can decide whether or not a particular hint will be useful to you. There are two kinds of hints. Some hints, such as Hint 2 below, just provide you with information. Other hints, such as Hint 3 below, give you an opportunity to answer a simpler question that is related to the main question you are solving. These hints either have questions in the tagline or tell you to do something (e.g., Find..., Determine..., Identify..., etc.). There are two ways that this type of hint can help you: Answering the simpler question gives you a chance to check that you are on the right track. If you correctly answer the simpler question, you will receive partial credit for the part even if you are unable to answer the main question. Your instructor may choose to give you a bonus for not using hints or to deduct a small penalty for using hints. If you are stuck, using the hints will usually result in a higher score than simply trying to guess because you may lose fewer points for opening a hint than for getting the answer to the main question incorrect. There is a more detailed explanation of how hints are graded in the help available by clicking the Help link at the top right corner of your screen in the main Mastering window. In this problem, however, you will not lose any credit for using the hints. Now, open up the second hint for some help finding the magic number. Hint 2. How to approach the problem Although you could try to guess the magic number you would most likely exhaust your tries before getting the correct answer. To help you, the magic number is , where is a number between 1 and 10. Hint 3. What is ? Recall that the previous hint stated that the magic number is between 1 and 10. Try to guess the value of . , where is a number between 1 and 10. Specifically You may submit as many guesses as you need. Enter each guess into the answer box that follows. ANSWER: = Correct Now that you have determined , compute ANSWER: magic number = to find the magic number. is an even number Introduction to MasteringChemistry 3 of 32 Correct Your instructor may choose to give you a bonus for not using hints or to deduct a small penalty for using hints. If you are stuck, using the hints will usually result in a higher score than simply trying to guess because you may lose fewer points for opening a hint than for getting the answer to the main question incorrect. Note that you are never required to use the hints; if you want to figure the question out on your own, go ahead! Notice that a new button, Review Part, appears when you correctly answer a part with hints. This button allows you to review all of the hints for that part, even if you didn't need them to get the answer. This is a useful way to review the question when studying for a test. You do not lose any credit for reviewing the hints after you have answered the question. If you didn't look at all of the hints while answering the last question, you should read through them now for some important information about hints and hint grading. Part C Multiple-choice questions have a special grading rule determined by your instructor. Assume that your instructor has decided to grade these questions in the following way: If you submit an incorrect answer to a multiple-choice question with options, you will lose of the credit for that question. Just like the similar multiple-choice penalty on most standardized tests, this rule is necessary to prevent random guessing. If a multiple-choice question has five answer choices and you submit one wrong answer before getting the question correct, how much credit will you lose for that part of the question? ANSWER: 100 50 33 25 20 Correct Your instructor may choose not to deduct of the credit for a multiple-choice question with you, click your instructor's Grading Policy on your assignment page. options. To see how your instructor is grading If you click on the Continue button before finishing all the Parts, you will see a message reminding you that you need to complete each Part to get credit. If you have completed the item, clicking Continue will take you to the next item on the Assignment. At any time you may click on the Provide Feedback link to access a survey page without losing your work. Once you have completed an item, you may access your score from the assignment. Your score will display below the item title. Introduction to Numeric Answers This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for using hints or submitting incorrect answers. Overview When an assignment question requires that you enter a numeric answer, you will see an answer box like the one illustrated here. To answer this type of question, you will need to type the numeric value for distance in the rectangle between the quantity you are solving for (distance) and the units (meters). In addition to typing alphanumeric values from your keyboard, you can enter non-numeric information by using either the menu tabs above the rectangular answer box (for more information click the equivalent key strokes. (click Grading Tolerance (Keyboard shortcuts) button for the list) (Help) button) or Introduction to MasteringChemistry 4 of 32 For grading, your numeric answers often (but not always) can be within a tolerance range of the official answer. For example, if the answer to a numeric problem with a tolerance of 2% were 105, answers between 103 and 107 would be graded as correct. If you submit an answer that is rounded to within the grading tolerance but is not the exact answer, you will receive full credit. If this value is needed in future parts use the full precision value for subsequent parts. Significant figures Most questions with numeric answers will require your answer to be given to at least three digits or significant figures. Your answer may be graded as incorrect if you have calculated correctly but then rounded your final answer to too few digits. If a different number of significant figures is required, this will be part of the question's answer instructions. When you need to do multiple calculations to get an answer, use more significant figures than required in each calculation and round at the end only. Rounding too early can cause your final answer to be outside the tolerance range. Part A For most answers, you will simply enter your numeric answer directly into the space provided to the right of the equal sign. Answer the following question by typing the numeric answer into the answer box. If you have a gross of items, you have 144 items. If you buy a gross of eggs, how many dozen eggs do you have? Express your answer in dozens. Do not enter the units; they are provided to the right of the answer box. Hint 1. How many items are in a dozen? If you have a dozen items, how many items do you have? ANSWER: 6 items 12 items 13 items ANSWER: number of eggs = 12 Correct Part B When entering large numbers in the answer box, do not use commas. For example, enter 1276400 for the number 1,276,400. Do not enter 1,276,400. If you accidentally enter commas, you will get a message that your answer has the wrong number of terms. Answer the following question by typing the numeric answer into the answer box. What is the sum of 9260 and 3240? Express your answer numerically to at least three significant figures. Hint 1. How to compute the sum Recall that the sum of two numbers is the result you obtain by adding the two numbers together. ANSWER: sum = 12500 Correct Note that you can always review exactly what you typed in the answer box by clicking My Answers. Scientific notation You may want to enter 367,000,000 in scientific notation as To use a template, click the To use the keyboard, button found under the . There are two ways to do this. menu. Introduction to MasteringChemistry 5 of 32 Instead of the symbol, use a multiplication dot ( ) by typing the keyboard multiplication symbol * (Shift + 8). To input the exponent for numbers written in scientific notation, do either of the following: Click the button found under the Type ^ (Shift + 6) from your keyboard. menu. can be entered in the answer box by typing 3.67*10^8. For example, Part C Practice entering numbers that include a power of 10 by entering the diameter of a hydrogen atom in its ground state, answer box. , into the Express the diameter of a ground-state hydrogen atom in meters using a power of 10. Do not enter the units; they are provided to the right of the answer box. ANSWER: = 1.06×10−10 Correct In some computer programming languages and software, a shorthand scientific notation for a number such as would be 3.0E12. This notation should be avoided when using the math answer box, because the E will be interpreted as a variable. To correctly enter as an answer, follow the advice given above. Value that are equivalent, such as or would also be marked correct here. Part D If you are asked to provide a set of two or more numeric answers, separate them with commas. For example, to provide the year that Sputnik (the first satellite to be sent into orbit around the Earth) was launched and the year humans first walked on the Moon, you would enter 1957,1969 in the answer box. A rectangle has a length of 5.50 and a width of 12.0 . What are the perimeter and area of this rectangle? Enter the perimeter and area numerically separated by a comma. The perimeter should be given in meters and the area in square meters. Do not enter the units; they are provided to the right of the answer box. Hint 1. How to find the perimeter The perimeter of a two-dimensional shape is the distance around the outside edge of the shape. In the case of a rectangle, there are two sides of length and two sides of width . Therefore, if you were to walk around the outside of a rectangle, you would walk a distance of or . Hint 2. How to find the area The area of a rectangle is given by the product of its length and width : . ANSWER: perimeter, area = 35.0,66.0 , Correct Introduction to Numeric Answers with Units This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for using hints or submitting incorrect answers. Overview When an assignment question requires that you enter an answer consisting of a numeric value and its units, you will see an answer box like the one illustrated here. Introduction to MasteringChemistry 6 of 32 To answer this type of question, you will need to type the numeric value and the appropriate units in the boxes provided. To enter a numeric value, click in the Value box and then type in the value. You can enter only numeric values, including scientific notation. You can’t enter calculations or algebraic expressions. The same grading, tolerance, and significant figure rules apply to the numeric value of your number and units answer as apply to numeric answers. To enter units, click in the Units box and then enter the abbreviated unit. You can enter any of the following: A single unit such as , , , , or . A single unit with a prefix such as or . A compound unit such as or . Note that you must use explicit multiplication in compound units. For example, newtonmeters can be entered as either or , but not . A compound unit with a prefix such as . To undo your work, click . To redo your work, click To clear your work (restart), click . . To view a list of keyboard shortcuts, click . Here are some of the most common shortcuts: Compound unit multiplication: Type * (Shift + 8) or Type - (a hyphen). Exponent: Type ^ (Shift + 6). Fraction: Type / (a forward slash). Degree symbol: Type \deg. For more information, click ( ). To identify the purpose of any icon, simply place your cursor over it. For instance, here is an example showing the degree symbol: Part A Answer the following question by entering the numeric value with appropriate units. If the length of one side of a square is 12.0 , what is the perimeter of the square? Express the perimeter with the appropriate units. Hint 1. Definition of a perimeter The perimeter of a square is the sum of the lengths of all four sides of the square. ANSWER: perimeter = 48.0 Correct Because a square has four sides of equal length, the perimeter is You could also express the perimeter in equivalent units using prefixes such as or (i.e., 4800 or 0.0480 ) Part B When numbers are very small or very large, it is convenient to either express the value in scientific notation and/or by using a prefix with the unit. A pain-relieving pill has a mass of 0.005 . Express the pill’s mass in grams using scientific notation or in milligrams. Express your answer in scientific notation to one significant figure or use a prefix on the unit. Introduction to MasteringChemistry 7 of 32 Hint 1. How to interpret the prefix milli The prefix (milli) implies multiplication by ; thus, a milligram is . ANSWER: mass = 5×10−3 Correct Because , you can enter your answer as or 5 . Part C You can also enter units that are combinations of other units. Keep in mind that you have to indicate the multiplication of units explicitly either with a multiplication dot or a dash. You can add a multiplication dot by selecting the dot The weight of an object is the product of its mass, its weight? , and the acceleration of gravity, from the symbol (where menu. ). If an object’s mass is , what is Express the weight with the appropriate units. Hint 1. The units for weight To calculate the weight of an object, you must multiply its mass by the acceleration due to gravity: Because you are multiplying a value with the units by a value with the units , find the resulting units by multiplying both units together: . ANSWER: weight = 98 Correct The weight of the object is . Because notation as , or with a prefix as 0.098 . (1 newton), you can also express the answer as 98 , in scientific Part D You can enter units that are combinations of units with prefixes. However, you must maintain the same unit system given in the problem. For example, this question uses the SI unit system. Therefore an answer in U.S. customary units, such as miles per hour would not be accepted as correct. A car traveling with constant speed travels 150 in 7200 . What is the speed of the car? Express the speed with the appropriate units. Hint 1. The equation for computing speed If an object is moving with constant speed, its speed is given by ANSWER: 2.1×10−2 Introduction to MasteringChemistry 8 of 32 Correct You can enter your answer in any equivalent combination of SI units representing a distance over any period of time. For example, you could also enter 21 using two significant figures. Part E You can enter compound units that are combinations of other units that are multiplied together. To enter the explicitly, type (shift + 8) on the keyboard, or use the template in the Symbols menu. Torque can be calculated by multiplying the force ( ) applied at to the lever arm at a distance ( ) from the pivot point (point of rotation), the compound SI unit for the torque is . If the force (at to the lever arm) applied is and it is applied at from the pivot point (point of rotation), what is the torque on the lever? Express the torque with the appropriate units. Hint 1. The equation for computing torque If a lever has a constant force applied at given by to the lever arm at a fixed distance from the pivot point (point of rotation), the torque on the lever is ANSWER: 30 Correct Introduction to Significant Figures Many questions in Mastering require you to enter your answer to a specified number of significant figures. For grading purposes, some numeric answers must be exact. Suppose you are asked "How many days are in a week?" The answer must be "7." Other numeric answers may be graded as correct not only when they match the exact answer but also if they fall within an acceptable range of the exact answer. This range is known as the grading tolerance. Suppose you are asked "How many days are in a year?" The precise answer is 365.24 days. However, a calendar contains 365 days, so the Mastering system will also accept that as correct. An answer that falls within the Mastering grading tolerance will also be marked as correct and you will be given full credit. You will see a feedback box that looks like the one below: Because you rounded differently than the system did, your rounded answer might affect your work on further calculations in the same item and could cause your next answer to fall outside of the tolerance. To prevent this, you will be asked to use the unrounded answer for all future parts. Part A Suppose you are asked to find the area of a rectangle that is 2.1wide by 5.6long. Your calculator answer would be 11.76 . Now suppose you are asked to enter the answer to two significant figures. (Note that if you do not round your answer to two significant figures, your answer will fall outside of the grading tolerance and be graded as incorrect.) Enter your answer to two significant figures and include the appropriate units. ANSWER: 12 Introduction to MasteringChemistry 9 of 32 Correct This is your final answer, rounded to two significant figures. To calculate an answer to the correct number of significant figures, you must complete all calculations first and then round your final answer as the very last step. In Part C, you are asked to calculate the volume of a rectangular prism that has a length of 5.6 , a width of 2.1 , and a height of 6.6 . You can calculate the volume of a prism by multiplying the area of the base times the height. You already calculated the area of the base as in Part A. Part B What value should you use as the area of the base when calculating the answer to Part C? ANSWER: 11.8 12 11.76 Correct 11.76 is the correct, unrounded value of the area of the base. It is correct to round to the requested number of significant figures in Part A because calculating the area is your final step. If you want to use that information in further calculations you must use the unrounded value. Part C Using the correct answer from Part B, calculate the volume of a rectangular prism with a length of 5.6 Enter your answer to two significant figures and include the appropriate units. ANSWER: 78 Correct Part D Would an answer that generated the response below be considered correct and give you full credit? ANSWER: , a width of 2.1 , and a height of 6.6 . Introduction to MasteringChemistry 10 of 32 No. It is impossible to tell. Yes. Correct Introduction to Chemical Answers This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for submitting incorrect answers. Overview When a question requires that you enter a chemical formula or a chemical equation as your answer, you will see the following answer box: To insert a template, such as a subscript, superscript, fraction, or reaction arrow click To insert a Greek letter ( , , , or To undo your work, click ), click and then select the appropriate letter. . To redo your work, click To clear your work (restart), click and then select the appropriate template. . . To view a list of keyboard shortcuts, click . Here are some of the most common shortcuts: Subscript: Type _ (an underscore). Superscript: Type ^ (Shift + 6). Isotope template (stacked super/subscripts): Type \stack. Forward reaction arrow: Type \->. For more information, click . To identify the purpose of any icon, simply place your cursor over it. Entering chemical expressions To enter chemical formulas, equations, and expressions using correct formatting, use the menu tabs above the answer space or use the keyboard shortcuts. For example, to enter the subscript 2 in , go to the Templates menu and select the Subscript template . When you enter your answer, keep in mind that the order of the elements in each chemical formula is important. Enter elements in the order you are taught in your chemistry textbook. Part A Enter the molecular formula for butane, . Express your answer as a chemical formula. ANSWER: Introduction to MasteringChemistry 11 of 32 Correct Some questions may ask you to enter the condensed structural formula of a compound instead of a molecular formula. A condensed structural formula reveals how the atoms are bonded together without explicitly showing the bonds, whereas a molecular formula shows only the number of each type of atom. For example, the butane molecular formula and condensed structural formula in this part can be represented as follows: Molecular formula Condensed structural formula Entering more complex expressions To enter an ion such as use a subscript followed by a superscript. In general, use the stacked super/subscript use it for adding a single subscript or superscript. For example, when entering you should see , not only for entering an isotope. Do not . Part B Enter the symbol of a sodium ion, , followed by the formula of a sulfate ion, . Separate the ions with a comma only—spaces are not allowed. Express your answers as ions separated by a comma. ANSWER: Correct Notice that when entering you will need to click out of the subscript or arrow over before entering the superscript. As a rule, you should look at your answer before clicking Submit to make sure that it is formatted correctly and that all subscripts and superscripts are properly placed. Part C Enter the expression , where is the lowercase Greek letter alpha. Express your answer as a chemical expression. ANSWER: Correct Offset prescripts, such as mass numbers. , are not the same as stacked prescripts, such as . Make sure you use stacked prescripts when entering atomic and Part D Enter the chemical equation . Express your answer as a chemical equation. ANSWER: Correct When adding a character within a superscript, choose the superscript template (or its keyboard shortcut) and then type the character. If the cursor is in the superscript area and you want to enter a minus sign, do not press the Shift key at the same time that you type the minus sign. This key combination will cause the next character you type to display as a subscript within the superscript, which will be graded as incorrect. Introduction to MasteringChemistry 12 of 32 Introduction to Symbolic Answers This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for submitting incorrect answers. Overview The type of answer box illustrated here lets you build a symbolic expression just as it would look in your textbook or as you might write it by hand. You use the same answer box and menu tabs to enter numeric and symbolic answers. To insert a formatting template, such as an exponent, square root, or fraction, click To insert Greek letters, (hbar) and To undo your work, click (EMF), click . To redo your work, click To clear your work (restart), click and then select the appropriate template. and then select the letter you want. . . To view a list of keyboard shortcuts, click . Here are some of the most common shortcuts: Subscript: Type _ (an underscore). Exponent: Type ^ (Shift + 6). Fraction: Type / (a forward slash). Square root: Type \sqrt. Greek letters: Type a backslash (\) and the name of the Greek character. For example, to display , you would type \delta. For uppercase Greek letters, begin the name with a capital letter. For example, you would type \Delta to display . For more information, click ( ). To identify the purpose of any icon, simply place your cursor over it. For instance, here is an example showing the Greek letter Omega: . Grading Your answers are graded according to the standard order-of-operations conventions for evaluating mathematical expressions, as follows: 1. Perform any calculations inside parentheses. 2. Perform all multiplications and divisions, working from left to right. 3. Perform all additions and subtractions, working from left to right. For example, in the expression , first you should multiply by and then add to the total. In other words, the correct expression is . Part A Similar to what you see in your textbook, you can generally omit the multiplication symbol as you answer questions online, except when the symbol is needed to make your meaning clear. For example, is not the same as . When you need to be explicit, type * (Shift + 8) to insert the multiplication operator. You will see a multiplication dot ( ) appear in the answer box. Do not use the symbol . For example, for the expression m a would be correct, but mxa would be incorrect. Enter the expression , typing . ANSWER: = Correct When entering algebraic expressions, such as ma, you can enter it using explicit multiplication m a or implied multiplication ma. Both will be accepted as correct. Introduction to MasteringChemistry 13 of 32 All trigonometric functions assume angles are in radians by default, unless the use of degrees is specified. Part B Enter the expression , where is the lowercase Greek letter theta. ANSWER: = Correct To identify a variable displayed in a specific part, place your cursor over it. For instance, here is an example showing the Greek letter theta used in this problem: . Part C Enter the expression , where is the inverse sine function. ANSWER: = Correct Use the same notation to enter other inverse trigonometric functions, for example respectively. and for the inverse cosine and tangent functions Part D Enter the expression , where is the uppercase Greek letter Delta. ANSWER: = Correct Part E Enter the expression , where is N-naught (an N with a subscript zero) and is the lowercase Greek letter lambda. ANSWER: = Correct Introduction to Drawing Lewis Structures This exercise is not intended to test your knowledge of any specific subject material. Therefore, on this problem you will not be penalized for using hints or submitting incorrect answers. Overview When an assignment question requires that you answer by drawing molecules or species, you will see a canvas with buttons for bonds, electrons, charges, and atoms, such as the sample shown: