Step on the gas! p. I. Observable properties of gases. A. Gases are compressible (liquids and solids aren t) Evidence?

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1 Truth is tough. It will not break, like a bubble, at a touch; nay, you may kick it about all day, like a football, and it will be round and full at evening. Mark Twain -Macbeth by William Shakespeare. I. Observable properties of gases A. Gases are compressible (liquids and solids aren t) Evidence? B. Gases have low densities (very low compared to solids, and even low compared to liquids) Evidence? C. Gases mix thoroughly on their own Evidence? Fancy words: diffusion effusion Relationship:

2 D. Gases are fluids (flow under stress, i.e. can be poured) E. Gases fill their container completely (neither liquids nor solids can) Evidence? F. Gases exert pressure Evidence? II. Based upon these observations, what conclusions can we make? A. The conclusions are called the kinetic-molecular theory remember a theory is a statement that is supported by facts; as new facts are gathered, a theory may be modified (or even eliminated). B. Gases must 1. consist of particles that are in constant motion. Which explains which properties? 2. have lots of space between the particles. Which explains which properties?

3 Homework (Use pencil!) 1. a. High altitude baking directions always tell the baker to reduce the quantity of baking soda added to the batter. Given that the baking soda reacts with acids in the batter to produce carbon dioxide bubbles that make the batter rise, explain why those directions are given. Be sure to mention the properties of gases that we have just been studying. b. What happens if the directions are ignored? 2. Is it easier or harder to drink from a straw at the top of a mountain? Remember that air pressure decreases with increasing altitude and that the first stage of sipping through a straw is to swallow air. 3. A tank is shown below with 10 particles of gas in it. Redraw the tank and particles of gas as it would look if there were only 5 particles of gas in it. 4. It is harder to move your arms in water than in air. Explain based on the properties of gases. 5. Arrange the following gases in order of increasing average speed of effusion at the same temperature: CO 2 SO 2 N 2 SF 6 N 2O H 2 Reading at Home p (section 9-1) III. More on gas pressure A. Two of the instruments that measure it 1. barometers What are the units for our room barometer?

4 2. manometer B. How it s caused and calculated C. Other units D. Example: What is 485 torr expressed in kpa? Homework (Use pencil!) 1. Scuba divers are instructed not to hold their breath when rising to the surface? Why? (Don t confuse this question with the one about not coming to the surface too quickly that answer is about solutions.) 2. Why do you suppose mercury is used in manometers and barometers as opposed to some other liquid? 3. You can pump up a bicycle tire to an air pressure of 30 psi pretty easily. If you try putting the same pressure in your car s tires, using the same pump, you find that you re not strong enough. Why? 4. What is a sphygmomanometer? Hint: It has to do with your body. Is it more closely associated with a barometer or a manometer? 5. The pressure inside an auto tire is the same regardless of the location of the nozzle. Explain. **********more Homework on next page*************

5 6. A sunbeam forms when light is reflected from dust suspended in the air. Even if the air is still, the dust particles can be seen to bounce around randomly. Explain. 7. Compare the rate of effusion of N 2 molecules compared with Ar atoms at the same temperature. 8. The kinetic-molecular theory assumes that the volume of molecules and their interactions are inconsequential for gases. Why would the assumptions not be as valid at very high pressures and very low temperatures? 9. Make the following conversions: a torr to atm [2.17 atm] b X 10-5 atm to torr [ torr] c. 185 lb/in 2 to torr [9560 torr] d kpa to atm [ atm] e. 190 torr to lb/in 2 [3.7 lb/in 2 ] f. 85 torr to kpa [11 kpa] Reading at Home (p (section 9-2) Websites Theory/BasicConcepts.html Learn By Doing: Too Much Pressure Our purpose here is to derive an equation that relates pressure of a gas to its volume. As you should know by now, science isn t just a compilation of facts; it is a process, an investigation, of relationships in nature. Yes, there s more to science, but that s the basic premise. So our purpose here is to derive an equation that relates pressure and volume of a gas. This is a relationship that affects you and everything else. First we will determine what type of data we need, then the manner in which we will record the data. Then we will collect the data and record it. As with most relationships, we can determine the correlation between the two variables (pressure and volume) by graphing them. It is from this graph that we will determine the exact relationship, i.e. the formula that exists between pressure and volume. So let s begin. Since pressure is a relationship between force and area and force is related to mass and gravity (remember this from physics last year!!!), let s calculate the pressure that is caused by a variety of masses (weights). Then we will take the masses and place them on an enclosed volume of gas and see how much the gas compresses (how much the volume changes).

6 The pressure: P = F/A (we just showed this with the pencil and weight demonstration) F = mg (from physics: force is a product of mass and acceleration due to gravity) So.. P = mg/a A = area in which the force is being applied; let s apply the force to a circular area So A = π r 2 ; the radius will be measured in centimeters because it s a small circle m = mass; let s use kilogram (kg) masses g = 9.8 m/s 2 (remember that g is acceleration due to gravity) With the formula P = mg/a So P masses = kg 9.8 m = s 2 π cm cm kg m / s 2 cm 2 this is the area Now we haven t seen those units for pressure, so instead of using that calculation, let s add to our dominoes and try to put the pressure units in Pa, pascals. Pa = N / m 2 : domino = Pa_ = Pa m 2 N N m 2 P masses = kg 9.8 m Pa m 2 N s cm 100cm s 2 π cm cm N kg m 1m 1m = Pa that s the radius of our circle N = kg m / s 2 : domino = N = N s 2 (recall: r = d/2) kg m kg m If you look at the Pascal unit you will realize that one needs to cancel the m 2 unit, thus the area is converted to m 2 using two dominos for conversion of cm to m. Additionally, the remaining units need to cancel. That s why the N = kg m / s 2 domino is used. So we finally have the pressure figured out, don t we????? s 2

7 Let s apply kg masses to a syringe. A syringe has marked units for volume, so we can easily compare pressure to volume. Also, the top of the syringe is the area where the pressure is applied. Look at the previous sample calculation. Notice that box for the radius of the circle that s the radius of the circle at the top of the syringe. We need to realize that the syringe will have pressure applied from the masses AND from the atmosphere. Therefore the total pressure will be: P total = P atm + P masses Now this is getting to be a pain. Using the barometer in the room to obtain the atmospheric pressure is fine however, its units are in inches of Hg. We will first need to convert those units to the same units that we used for the pressure obtained from the masses, then obtain the total pressure. This one however should be a bit easier. P atm = in Hg 2.54 cm 10 mm 1.01 X 10 5 Pa = 1 in 1 cm 76Ō mm Hg P total = Pa + Pa = Pa Pa Collecting, recording, and graphing the data: (let s begin with a sample of 50.0 ml of air (30.0 ml if your syringe is small), then apply 1.0 kg mass one at a time (recording the volume each time a mass is added) until we have a total of 5.0 kg. Design and draw a table (it will include some calculations) that has the applied mass in kilogram; the applied, atmosphere (room), and total pressure-all in Pascals; and the volume in milliliters. So how many columns & sub-columns did you get? Do the experiment and record the data in your newly drawn data table. Use just a tiny bit of glycerin to lubricate the sides of the rubber part of the plunger. With the cap of the syringe REMOVED, push the plunger up and down in the syringe to coat the inside of the syringe with glycerin this helps to eliminate any friction which can skew our results. Then place the cap on the syringe and assemble as shown in the diagram to the right. Beginning with a 1.0 kg mass, add masses to the platform (push down then let the plunger come back up) and record the volume of the syringe after each mass addition. Try to get a total of 5.0 kg masses it may be difficult to balance that many masses on the platform be careful. Now that we have the data, let s do our calculations from the previous page and record them in our table. Then, we finally get to graph the data. What s the independent variable? Remember, that goes on the x- axis. Use a correctly written title. Only put in a trendline (regression line) IF the graph shows a proportion. How do you know if it is a proportion. In order for a proportion to exist between variables, a straight line must exist between them and further, the line must go through the origin with a positive slope. This is a math concept. Did you learn this in math?

8 Is your graphed line a proportion? If not, try graphing the square or the inverse of one of the variables, i.e. try graphing volume vs. pressure 2 or volume vs. 1 / pressure, etc.. Does that help? Does that line show a proportion? Print the original graph (volume vs. pressure) and then any graphs that show a proportion. Do NOT print graphs that you were using to try to obtain a proportion but did not work. Writing the proportion: The proportion is written using this format: What to turn in: A α B (where A and B are the graphed variables that showed a proportion) Your sample calculations (the P masses =, the P atm=, and the P total = previously mentioned) Your data table Your graphs (2) Your proportion Back to notes.. IV. Boyle s Law (sometimes known as Boyle s-mariotte s Law) So by now you should realize, science isn t just a compilation of facts; it is a process, an investigation, of relationships in nature. Yes, there s more to science, but that s the basic premise. So you, as scientists, derived an equation that related pressure of a gas to its volume. This equation was first published by Robert Boyle (independently realized by Edme Mariotte). It is a relationship that affects you and everything else. You graphed the relationship. A. So what does Boyle s Law mean: B. The formula: C. Example: The volume of a gas is 475 ml when the pressure is 1.05 atm. When the gas is compressed, the pressure increases to 5.65 atm at the same temperature. What is the volume of the compressed gas?

9 Homework (Use pencil!) 1. If a gas has a volume of 1560 ml at a pressure of 81.2 kpa, what is its volume if the pressure is increased to 2.50 atm? [502 ml] 2. A gas has a volume of 125 ml at a pressure of 62.5 torr. What is the pressure if the volume is decreased to 115 ml [67.9 torr] 3. A gas in a piston engine is compressed by a ratio of 15:1. If the pressure before compression is atm, what pressure is required to compress the gas? (Assume constant temperature.) [14.2 atm] Reading at Home (page ; section 9-3) Websites Learn By Doing: It s too Hot! Our purpose here is to derive an equation that relates temperature of a gas to its volume. 1. Design and draw a raw data table that will show the relationship between temperature and volume. We will use a syringe and heat the gas within it by surrounding it with hot water in a 1L beaker and record temperature and volume five times during the heating process. 2. Remember, in order to find the relationship between variables, we will graph them. We do this in our pre-lab by drawing a small L for the axes and writing the axes labels and title for the graph in the appropriate places. 3. Have the pre-lab graded. Collecting and recording the data 4. Use a tiny amount of glycerin to lubricate the SIDES of a syringe plunger. Place the plunger in the syringe and draw in 15 ml of air. Cap the syringe. Place a test tube holder at the top of the syringe (not the plunger). 5. Fill a 1 L beaker to the 1L mark with tap water. Set it on a stirrer/hot plate. Place a stir bar in the beaker. 6. Assemble a thermometer clamp and thermometer on a ring stand. Arrange it so that the thermometer is in the middle of the water in the beaker. Place the syringe (with the test tube holder attached) in the water. Be careful. You want the gas in the syringe to be submerged but not the top part of the plunger, i.e. you do not want water leaking in the plunger area.

10 7. Turn the stirrer to setting #2 (this allows for a gentle mixing of the water to maintain an even temperature throughout). Turn the hot plate to the 6.5 setting. Every few minutes, push down on the plunger and let it pop back. If the volume has changed, record the new volume and the temperature of the water (we have to assume that the air and the surrounding water are at the same temperature). Repeat until you have your five sets of data. 8. Graph your data. Set the horizontal margins lower limit to be -350 o C. Include a trend line (regression line) and an equation of the line. Just so you know, in Excel, key in Alt0176 to make a o sign. 9. Now, use the equation of the line to calculate the coldest possible temperature in our universe. You may know what it is, but use your own data to see how close you come! 10. Does your graph represent a proportionality, linearity, both, or neither? Use your lab techs with this (there is an area in the graphing section that discusses this). 11. Imagine what would have happened if we had varied the number of moles of gas that we had in your syringe, and measured the corresponding volume. Sketch what the graph of moles as a function of volume would have looked like. You don t have to put numbers on the graph, but DO make it clear whether your line goes through the origin or not. What to turn in: Your data table Your graph Your answers to numbers 9, 10, and 11 Back to Notes V. Charles s Law So scientists also derived an equation that relates temperature of a gas to its volume. This relationship, like that between volume and pressure of a gas, affects you and everything else. Since, as shown with Boyle s Law, relationships between variables can be determined by graphing. You graphed the temperature and volume of a gas. The relationship is known as Charles s Law. A. So what does Charles s Law say? B. The formula C. The special temperature unit that must be used with this formula

11 D. Example: A sample of gas has a volume of 185 ml at a temperature of 52 o C. What is the volume if the temperature is lowered to 17 o C? Homework (Use pencil!) 1. A sample of gas has a volume of 677 ml at 63 o C. What is the volume of the gas if the temperature is decreased to 46 o C? [643 ml] 2. How does the kinetic molecular theory explain Charles s law? 3. The temperature of a sample of gas is 0 o C. When the temperature is increased, the volume increases by a factor of 1.25 (i.e., V 2 = 1.25 V 1). What is the final temperature in degrees Celsius? [68 o C] Back to Notes VI. All together now A. The last quantity to be considered.the number of moles (the amount of gas present in the sample). B. The equation NOTE: If one or more of the variables is not mentioned at all, cross it out of the equation. Its value must not have changed, therefore the variable can have no effect on the equation.

12 C. Example: A quantity of gas has a pressure of 760 torr at 25 o C. What is the pressure in the container if the temperature is increased to 50 o C? D. Example: A 25.8-L quantity of gas has a pressure of 690 torr and a temperature of 17 o C. What is the volume if the pressure is changed to 1.85 atm and the temperature to 345 K? E. Example: A balloon partially inflated with air has a volume of 275 ml and contains mol of air. Without letting any of the air escape, a 1.00-g piece of dry ice (solid carbon dioxide that turns into a gas without melting first, even at room temperature and pressure) is inserted into the balloon, and the neck is tied. What will the volume of the balloon be after the carbon dioxide is completely gaseous? Homework (Use pencil!) 1. A quantity of gas has a volume of 3560 ml at a temperature of 55 o C and a pressure of 850 torr. What is the temperature if the volume remains unchanged but the pressure is decreased to atm? [190 K 2. An aerosol spray can has gas under pressure of 1.25 atm at 25 o C. The can explodes when the pressure reaches 2.50 atm. At what temperature will this happen? (Do not throw these cans into a fire!) [596 K] *****more homework on next page*****

13 3. A mol quantity of gas has a volume of 2.54 L at a certain temperature and pressure. What is the volume of mol of gas under the same conditions? [1.70 L] 4. A balloon has a volume of 75.0 ml and contains 2.50 X 10-3 mol of gas. What mass of N 2 must be added to the balloon for the volume to increase to 164 ml at the same temperature and pressure? [ g] Reading at Home pages Websites VII. STP A. Definition B. Example: A 5850-ft 3 quantity of natural gas measured at STP was purchased, but only 5625 ft 3 was received. Assuming that no one cheated, what was the temperature at the receiving location if the delivery pressure was 1.10 atm? VIII. The ideal gas law A. Formula

14 Learn by Doing: Pirate s Language Your goal is to determine the value of the gas constant, R, by graphing. 1. Rearrange the ideal gas law formula to solve for R. 2. The slope of a line is commonly defined as rise over run. Comparing this definition to R, one can realize that R is the slope of a line when two mathematical products are graphed. What are they? 3. Complete the following data table for the temperature (K) then the X and Y values that need to be graphed. Watch sig figs! 4. Graph the X and Y values (watch sig figs) using the Excel graphing program. Be sure to ask for the regression line on your graph. The formula of the line should be printed on the graph. You should see the value of R in that formula. 5. Turn in the graph. Below the graph, write and complete this statement: The value of R was determined to be. pressure (atm) volume (L) quantity (mol) temperature ( o C) temperature (K) X value Y value B. Example: What is the pressure of a 1.45-mol sample of a gas if the volume is 20.0 L and the temperature is 25 o C? C. Example: What mass of NH 3 gas has a volume of 16,400 ml at STP?

15 D. Example: What is the volume of 1.00 mol of ANY gas at STP? Homework (Use pencil!) 1. A quantity of gas has a volume of 16.5 L at 32 o C and a pressure of 850 torr. How many moles of gas are present? [0.74 mol] 2. What is the pressure (in torr) exerted by g of O 2 in a 250-mL container at 29 o C? [590 torr] 3. What mass of Ne is contained in a large neon light if the volume is 3.50 L, the pressure 1.15 atm, and the temperature 23 o C? [3.34 g] 4. A good vacuum pump on Earth can produce a vacuum with a pressure as low as 1.00 X 10-8 torr. How many molecules are present in each milliliter at a temperature of 27.0 o C? [3.22 X 10 8 molecs/ml] Reading at Home pages Websites IX. Density and molar mass A. The method: use R! B. Example: What is the density of helium at STP?

16 C. Example: A sample of gas has a mass of 3.20 g and occupies 2.00 L at 17 o C and 380 torr. What is the molar mass of the gas? Homework (Use pencil!) 1. A 6.50-L quantity of a gas measured at STP has a mass of 39.8 g. What is the molar mass of the compound? [137 g/mol] 2. What is the density in g/l (STP) of B 2H 6? [1.23 g/l] 3. A gas has a density of 1.52 g/l (STP). What is the molar mass of the gas? [34.1 g/mol] Reading at Home pages (section 9-8) Websites X. Dalton s Law of Partial Pressures A. The logic B. The equations

17 C. Example: Three gases, Ar, N 2, and H 2, are mixed in a 5.00-L container. Argon has a pressure of 255 torr, nitrogen a pressure of 228 torr, and hydrogen a pressure of 752 torr. What is the total pressure in the container. F. Over water inside gas pressure inside gas pressure inside gas pressure outside air pressure (atmospheric pressure outside air pressure (atmospheric pressure outside air pressure (atmospheric pressure Vapor Pressure of Water at Various Temperatures Temperature ( o C) Pressure (mmhg) Temperature ( o C) Pressure (mm Hg)

18 Homework (Use pencil!) 1. The total pressure in a cylinder containing a mixture of two gases is 1.46 atm. If the partial pressure of one gas is 750 torr, what is the partial pressure of the other gas? [360 torr] 2. A sample of oxygen is collected in a bottle over water. The pressure inside the bottle is made equal to the barometric pressure, which is 752 torr. When collected over water, the gas is a mixture of oxygen and water vapor. The partial pressure of water (known as the vapor pressure) at that temperature is 24 torr. What is the pressure of the pure oxygen? [728 torr] 3. A volume of gas is composed of N 2, O 2, and SO 2. If the total pressure is 1050 torr, what is the partial pressure of each gas if the gas is 72.0% N 2 and 8.00% O 2? [21Ō torr SO 2, 756 torr N 2, 84.0 torr O 2] Reading at Home pages ; section 9-7 Websites XI. Gas stoich A. You still cross the bridge in the balanced equation, BUT, if you are a gas, you can turn yourself into a mole by using R B. Example: Aluminum reacts with hydrochloric acid (HCl) to produce aluminum chloride and hydrogen gas. What mass of aluminum is needed to produce 50.0 L of hydrogen at STP?

19 C. Example: Ammonia gas, NH 3, reacts with oxygen gas to produce nitrogen monoxide gas and liquid water. What volume of nitrogen monoxide measured at atm and 25 o C will be produced from 19.5 L of oxygen at STP? Homework (Use pencil!) 1. Magnesium in flashbulbs burns according to the equation 2Mg(s) + O 2 (g) 2MgO(s) What mass of Mg combines with 5.80 L of O 2 measured at STP? [12.6 g] 2. Acetylene (C 2H 2) is produced from calcium carbide as shown by the reaction CaC 2 (s) + 2H 2O(l ) Ca(OH) 2 (s) + C 2H 2 (g) What volume of acetylene measured at 25 o C and 745 torr would be produced from 5.00 g of H 2O? [3.46 L] 3. In March 1979, a nuclear reactor overheated, producing a dangerous hydrogen bubble at the top of the reactor core. The following reaction occurring at the high temperature (about 1500 o C) accounted for the hydrogen. (Zr alloys hold the uranium pellets in long rods.) Zr(s) + 2H 2O(g) ZrO 2(s) + 2H 2 (g) If the bubble had a volume of about 28,000 L at 250 o C and 70.0 atm, what mass (in kg) of Zr had reacted? [2100 kg] 4. Nitric acid is produced according to the equation 3NO 2 (g) + H 2O(l) 2HNO 3(aq) + NO(g) What volume of NO 2 measured at 73 o C and 1.56 X 10-2 atm would be needed to produce 4.55 X 10-3 mol of HNO 3? [7.18 L] 5. Natural gas (CH 4) burns according to the equation CH 4(g) + 2O 2 (g) CO 2 (g) + 2H 2O(l) What volume of CO 2 measured at 27 o C and 1.50 atm is produced from 27.5 L of O 2 measured at 23 o C and 825 torr? [11.9 L] Reading at Home pages ; section 9-9 Websites

20 Lab: Hydrogen Bubbles We will use gas stoich and gas collection over water to determine the initial mass of a reactant. Pre-lab/chemistry 1. Magnesium reacts with hydrochloric acid, HCl(aq), in a single replacement reaction. Write and balance the reaction. Watch for diatomics. Include phases. 2. The gas produced will be collected over water, so it will be part of a gas mixture. Refer back to the collection over water procedure for the quantities that must be measured or determined from other sources.. Draw a raw data table for the experiment. If you get stuck deciding the column headings, do the sample calculations first, then look at the empty boxes. Ask yourself where do I get the values that go in these boxes. Column headings reflect measured items; do these boxes represent measured items? Each group will have a different sample of magnesium, so only one trial can be done. Be sure to have units that show what YOU measured (perhaps you could look at the instruments to determine these units). 3. Show the partial pressure sample calculation necessary to obtain the pressure of hydrogen without water vapor. Be careful! You must have units that YOU can MEASURE (look at the instrument to determine the units). Be sure to show the formula, then rearrange it if necessary, then rewrite it with boxes and units. 4. Show the stoichiometry sample necessary for determining the initial mass of magnesium from the volume of hydrogen produced. From this statement, you should realize how to start and end the sample calculation. Remember to put in boxes for values you do not yet have. Pre-lab/science 5. What is the major independent variable? What is the major dependent variable? What are the other factors that are influencing the dependent variable? Put these answers in a 3-column format. 6. Make 3 columns. In the first column, write the necessary equipment, materials and safety items. In the second column, write the amount of each item needed and in the third column write the size. Some items can be inferred from the procedure. 7. If this experiment were repeated many times, with varying quantities of the independent variable, would there be a positive, negative, or no relationship between the variables. 8. Have your pre-lab graded. Lab Safety: goggles, aprons, closed toe shoes,gloves NO GUM, FOOD, DRINK 9. Fill a beaker about ½ full of deionized water; set it aside so it comes to room temperature.

21 10. Obtain your assigned piece of magnesium ribbon. Record the number of your magnesium in your data table. 11. Roll the ribbon into a flat coil (like a sideways view of a snail--- ) with a diameter small enough to fit into a eudiometer. Be careful the metal can break. Tie the coil together with a piece of thread about 10 cm long. Then pour approximately 10 ml of hydrochloric acid into the eudiometer GLOVES!!! Be very careful this is one powerful acid. If you spill it on you, wash it off immediately and call me over! 12. Hold the eudiometer in a slightly tipped position, and very slowly pour deionized water from the beaker into the eudiometer. Let the water overflow. The idea is to layer the water over the acid rather than to let them mix. Think, but don t answer yet: What physical property of these substances allows layering? Fill your beaker again to approximately ½ full with deionized water. 13. Lower the magnesium coil into the water to a depth of about 5 cm, and insert the rubber stopper so that it holds the string in place. Do this over the sink, because water should overflow, ensuring that no air remains in the eudiometer. 14. Cover the hole of the stopper with your index finger, and invert the eudiometer in the beaker of water. Once the eudiometer is in the water, remove your finger from the hole in the stopper. Do NOT let the eudiometer sit on the bottom of the beaker. You may now remove your gloves. 15. When the reaction is complete (see note), reach into the beaker, cover the hole of the stopper, and transfer the eudiometer to a big jar of water--don t allow gas to enter or escape. Equalize the water levels inside the tube and outside (so that we know the inside pressure is equal to the atmospheric pressure) and record the volume of gas that was produced. Also..record today s room temperature and pressure. When finished, place your finger over the hole in the stopper and empty the remaining contents of the tube down the drain. Allow the eudiometer to set in the sink, upside down. NOTE: If the hydrogen fills the tube beyond the scale or completely escapes it, a new trial with a smaller quantity of magnesium will be necessary. Get a new piece!! 16. Complete your calculation. 17. You will now write a completed, formal lab report. In college, these reports can be many, many pages in length. Ours will be limited to one or two pages. To write our first formal report of the year, we will simply use a hand-out format whereby you will fill-in-the-blanks. See the helpful hints below. a. Write a good title for this lab. Remember, capitalize correctly and no punctuation at the end as a title is not a sentence. b. Abstract i. What is the type of lab and the general method of analysis used in the lab? (see lab techs) ii. Write the purpose of the lab in a good, past tense sentence. iii. Write a good, past tense (no pronoun) summary of the procedure; use complete sentences. No numbers or values. Use 4-5 sentences. Usually, we do not mention types of equipment used unless it is an germane to the lab. This lab is one of the few times, if not the only time, this year that we will mention a piece of equipment. iv. Write the result in a good, past tense sentence. This means state the value (use numbers). v. List one reasonable limitation of this lab. State whether this limitation causes the final result to be higher or lower than expected? A limitation is something over which you have NO control. It causes the results of the lab to be skewed. Make sure that I can understand what you are saying. In other words, explain what you are talking about. This may take 2-3 sentences.

22 vi. List a topic that one can explore more as a result of the type of lab. Do not simply say to do the lab with a different type of metal. Rather, we look at the type of experiment we have done and ask ourselves how this could apply to real life OR how could we take this information and extend it to do more research. c. Analysis One first needs a transition sentence introducing the lab s data table. I wrote it for you in this lab. Below this sentence, place your data table by simply cutting it out and taping it NEATLY in place. d. Results Once again, we first needs a transition sentence introducing each of the lab s sample calculations. I wrote them for you in this lab. Below these sentences, place your sample calculations (cut and tape be neat) in the proper place. 18. Turn in the completed lab report. 19. Take the lab quiz.