OTHS Academic Chemistry Lab Notebook

Transcription

1 Name Period 2 nd Six Weeks OTHS Academic Chemistry Lab Notebook An expert is a person who has made all the mistakes that can be made in a very narrow field. Table -Niels of Contents Bohr-

2 Page Table of Contents Lab 1.. Vegium 4.. Half-Life with M&Ms 7.. Flame Test: Bone Tales 10...Create a Table Activity 12...Periodic Trends with Straws Would you like your own pair of goggles? Order from Flinn Scientific, Models AP3306 and AP3309 are both approved. Lab Protocol: Electronic devices are not appropriate in a laboratory setting and may not be used or in sight during labs. Lab safety rules must be followed at all times. Negligence (not wearing goggles or closed toe shoes), not following instructions, purposeful horseplay, and harmful behavior will not be tolerated in the lab. Clean-up: In a chemistry lab, students are expected to take care of the equipment and lab stations. Each lab period, 10 points are allocated for lab clean-up. If the lab is left in disarray, 10 points will be deducted from the lab grade. Lost notebooks: Students are given one lab notebook each six weeks. If lost, students may print labs from the course website, but 5 points will be deducted for each occurrence. Late labs: 1 day late= Maximum 75, 2 days late= Maximum 50, 3+ days late= zero Unless specified otherwise, violation of lab protocol will result in a 20 point deduction from the lab grade and/or a discipline referral to the student s grade level principal.

3 Vegium Lab Isotopes and Average Atomic Mass Introduction In this lab you will use a sample of the fictitious element vegium to learn about isotopes and average atomic mass. Vegium is composed of 3 isotopes: cornium, beanium, and peasium. Each kernel of corn, bean, and pea represent one atom of that particular isotope. As in real elements, each of the three isotopes of vegium is a different size. You will calculate an average atomic mass of vegium, based on your experimental data. Objectives 1. Determine the average mass of each isotope of the fictitious element vegium. 2. Determine the relative and percent abundance of the isotopes of vegium. 3. Use your experimental data to calculate the average atomic mass of vegium. Materials -Sample of vegium in a container -Digital balance Procedure 1. Sort your sample of vegium into the 3 isotopes of cornium, beanium, and peasium. 2. Find the total mass of each isotope separately. Record the masses in your data table. 3. Count all the beans, all the peas, and all the corn. Record the total number of atoms of each isotope in your data table. 4. Add up the counts from step 3 to get a grand total of all atoms of vegium and record in your data table. 5. Divide the mass of each isotope (beans, peas, and corn) by the number of each isotope to get the average mass of one atom of each isotope. Record in your data table. Use the correct number of significant figures; you can assume your counted numbers have infinite significant figures. 6. Divide the number of each isotope by the total number of particles to get the relative abundance of each isotope. Record in your data table to four significant figures. 7. Calculate the percent abundance of each isotope by multiplying the relative abundance by Calculate an average atomic mass for the element vegium by using the formula provided on your lab sheet. 1

4 Name Date Period Data Table Total mass of each isotope (g) Number of atoms of each isotope Beans Peas Corn Total number of all atoms of vegium: Calculations ***SHOW WORK!!! Box answers and include units where applicable. Average mass of an atom of each isotope (with correct SF) Beans Peas Corn Relative Abundance of each isotope (4 SF, ex ) Percent Abundance of each isotope (multiply above answer by 100, ex %) Calculation of average atomic mass for vegium: Avg atomic mass = (avg mass x rel abundance for isotope 1) + (avg mass x rel abundance for isotope 2) + (avg mass x rel abundance for isotope 3) Show work!!! Box answer and include unit below: Average atomic mass= 2

5 Questions and Conclusions: Answer in complete sentences. 1. What is one similarity between the isotopes of vegium and the isotopes of a real element? What is one difference? 2. Compare your average atomic mass of vegium with that of another lab group. Write the other group s result here: Give one reason for any difference you see. 3. If you wanted the most accurate results possible, would you choose to use a Circle: large sample or small sample of vegium? Why? HINT: would you want your teacher to base your chemistry average on one grade or several grades? 4. Select three beans (brown) from your sample: a large bean, a small bean, and a medium size bean. Using a digital balance, determine the mass of each and calculate the average mass of the three: Mass of large bean Mass of medium bean Average mass of 3 beans: Mass of small bean Consider the methods you used for finding: 1) the mass of the medium bean above 2) the average mass of the three beans above 3) the average mass of a bean from your calculation table (top left box) Which of these 3 methods is the most accurate way to find the average mass of a bean, and why are the other ways not as good? Explain thoroughly. best method because: okay method because: worst method because: 5. Calculate the average atomic mass of this mystery element, given the following data: Isotope #1 has a mass of amu and a percent abundance of 92.23% Isotope #2 has a mass of amu and a percent abundance of 4.67% Isotope #3 has a mass of amu and a percent abundance of 3.10% Use the Periodic Table to identify the element by its atomic mass: Mystery element is 3

6 Half Life Lab with M&Ms Purpose To introduce the concept of radioactive decay by using m&ms to represent atoms of a radioactive isotope. Materials Package of m&m s Mini marshmallows Plastic cups Paper towels Procedure 1. Take a package of m&m s (about m&m s), and pour them onto a paper towel. Count the m&m s, recording the number next to 0 decay cycles in your data table. 2. Remove from the pile any m&m s that landed with the m s facing up. (M facing up represents a decayed atom) Dispose of those m&ms in an appropriate way. 3. Replace the removed m&ms with mini marshmallows. For example, if you removed 6 m&ms, put 6 mini marshmallows in to replace them. What do the marshmallows represent? 4. Count how many m&m s are left. Record this # in the data table next to decay cycle Put the m&m s that were left (those with the m s down, i.e. undecayed) in the cup. Cover the cup with your hand and gently shake the cup several times. 6. Pour the m&m s from the cup onto the paper towel and repeat steps #3-5 until only one m&m is left. If you are down to only a few m&ms and they all flip, change one so that it has the m down, and make that your final entry in the data table. 7. Graph your data on the graph paper provided. Make sure to add a line of best fit. Data Table Number of Decay Cycles/Half- Lives (x) Number of m&m s undecayed (y) 4

7 Questions 1. How is this lab activity similar to the process of radioactive decay? Explain. 2. What does an m&m represent? 3. What does a mini marshmallow represent? 4. According to your data, in which half life cycle were there 17 m&ms remaining (at some time during the cycle)? 5. According to your data, estimate how many particles would remain after 1.25 halflives? 6. Why might your group s graph not be identical to another group s graph? 7. What could be done to get more accurate results (more similar data among lab groups)? Hint: would you want your teacher to base your chemistry average on one grade or several grades? 5

8 6

9 Flame Test: Bone Tales! Introduction A flame test is a method used in chemistry to visually determine the identity of an unknown metal or metalloid ion. When metallic elements are heated to high temperatures, some of their electrons absorb energy and are therefore excited to higher energy levels. These excited electrons then fall back to the original lower energy levels, releasing the excess energy in packages of light called photons. The color of the emitted light depends on its energy. Different elements absorb and release different amounts of energy when heated; therefore, the color of the light emitted is characteristic for a particular element. Scientists can then compare the color of the unknown substance to known substances to aid in its identification. At a crime scene there may be unknown substances present that have to be identified to assist in determining foul play or the nature of a crime. Forensic investigators are able to compare the properties of unknown substances to that of known substances for identification. During this lab activity, you will participate as a forensic investigator and use the flame test and observation skills to aid in the identification of the composition of a bone sample found at a crime scene. Read the following passage and conduct the investigation. Background In the small community of New Water, Ohio, new construction of a mini mall has begun on what used to be a large wooded area near the edge of town. The construction company has cleared the trees from the area, and is digging up the soil to lay the building's foundation. Soon after the digging begins, one of the workers notices what appear to be bones. Upon closer inspection the bones appear to be human. The construction is stopped and the local police are called in to investigate. The condition of the skeletal remains suggests they have been buried for quite some time. Police know in the past 20 years there have only been three cases of missing persons reported who have not been found. Approximately 18 years ago Mr. Hadley, a gentleman in his early thirties, disappeared but the investigation revealed no evidence of foul play. It was assumed he left town. Five years after Mr. Hadley's disappearance, a young local woman, known as Jean, did not show up for work at a local real estate office and her co-workers contacted the police. Like Mr. Hadley, no foul play was detected and she was assumed to have left the small town. In more recent years, a well-known woman in her 80s, Mrs. Crawford, disappeared from her home one morning. Her home showed signs of forced entry and many items were missing, suggesting a burglary had taken place. Mrs. Crawford has never been heard from again and her body has never been recovered. Instructions You will be taking on the role of the forensic investigator employed to analyze the bones at the construction site. You will need to conduct a flame test to determine the consistency of the bone tissue. You will test a series of known salts to determine the color given off in a flame and then compare the known salts to the bone sample from the construction site to identify the composition of the bone sample. Lastly, answer the conclusion and analysis questions to determine whose bones are at the construction site. Materials -Bone sample (unknown) -Sodium chloride -Copper (II) nitrate -Strontium nitrate -Bunsen burner -Calcium nitrate -Lithium nitrate -Potassium nitrate 7 -Barium nitrate -Wood splints

10 Procedure 1. Wear safety goggles 2. Lay a paper towel in the sink and dampen with water. Tie back hair and loose clothing. Light your Bunsen burner according to your teacher s directions. 3. Wet the tip of a dry wooden splint and put it in the dry salt. Burn the sample using tongs, and observe/record the color emitted. Extinguish the splint and place in the sink on top of the wet paper towel. 4. For the remainder of the samples (solutions), obtain a split that has already been soaked in the solution. 5. Burn the sample using tongs and observe/record the color. Dispose of used splints on the wet paper towel in the sink. 6. Test the bone sample from the construction site. 7. Compare the bone sample with the known samples to determine the substance in the bone. 8. Clean up by throwing away the paper towel and all splints in the trash. 9. Wash your hands. Data Table Substance Flame Color Substance Flame Color Sodium chloride solid Sodium chloride solution Sodium nitrate solution Copper (II) nitrate solution Strontium nitrate solution Calcium nitrate solution Lithium nitrate solution Potassium nitrate solution Barium nitrate solution Bone sample (unknown) Conclusion and Analysis 1. What kind of element are flame tests used to identify? (read intro) 2. Why do metal ions exhibit different colors in the flame? (read intro) Explain. 3. The energy of colored light increases in the order red, orange, yellow, green, blue, violet. Arrange the following metallic ions used in the flame test in order from lowest to highest energy: copper (II) nitrate, sodium nitrate, and strontium nitrate. (lowest) (highest) 8

11 4. Of the colors of visible light, which color has the highest frequency? Hint: energy is proportional to frequency (E = hν) 5. Which color has the longest wavelength? Hint: wavelength is proportional to frequency (c = λν) 6. What substance is present in the bone sample based on your investigation? Explain. 7. Stable strontium is one of the most abundant elements on Earth and has proven to be medically beneficial. Since the late 1800's it has been used in medical treatments of osteoporosis, bone cancer treatment, tooth decay, and arthritis. Osteoporosis is the deterioration of bone increasing the likelihood of facture. It is a common disease in the elderly, and patients suffering from osteoporosis are often prescribed medications containing strontium. The strontium works by adding additional strength to bones and teeth. It tends to accumulate in areas of the bone or teeth that are undergoing active remodeling. a. Based on the information provided, which missing person do the bones in the construction site most likely belong to? b. Explain: 9

12 Name Per. Create-a-Table Activity Questions 1. What characteristics did you use for sorting the cards? 2. Where did you put H and He? What was your reasoning for their placements? 3. Did you notice any cards that didn t fit, or that seemed out of order? Explain. 4. Below are 5 possible cards for the element germanium. Which seems most accurate, based on the table you created? Explain your reasoning. 5. What would you add to the three empty corners to complete this card? 6. Which of the following elements would not be found in the same group with the others? Explain your thinking. 10

13 7. What trend do you notice for the size (radius) of the atoms across a period (left to right)? Down a group? 8. Note that for metals, down a group, the color intensity increases. What does that represent? 9. How is state of matter (solid, liquid, or gas) symbolized on the atom models? 10. What detail on the atom models is different for metals compared to metalloids and nonmetals? 11. What do the pegs on the atom models symbolize? 11

14 Periodic Trends Introduction: In this activity, you will model three properties of the elements that show trends across a period and down a group on the periodic table. These properties are: Atomic Radius: a measure of the size of one atom of an element Ionization Energy: the measure of the energy required to remove an electron from the outermost energy level of an atom Electronegativity: the tendency of an atom to attract electrons to itself when it is chemically bonded with another element Straws cut to specific lengths will be used to represent the values of these properties for selected elements (see chart on last page). Straws will be placed vertically in well plates, with each well corresponding to a chemical element. Once the model is assembled, the student will have a visual representation of the trends in the properties, across the periods and down the groups of the periodic table. Procedure: 1. Obtain supplies: 1) a bag of straws labeled with one of the above properties; 2) a well plate with periodic table attached to the back; 3) a ruler. 2. Take out your straws and lay them in order of length on the lab table. 3. Using the chart on the last page and a ruler, find the straw that has been cut to the appropriate length for hydrogen. Make sure you are looking at the column that matches the property on your baggie! 4. Place the straw in the well that corresponds to hydrogen. 5. Repeat steps 2-3 for the rest of the elements in the chart. 6. Keeping your model assembled, answer the questions on the back of this page for your trend. 7. Rotate to another lab station and view the completed model for the second property. Answer the questions on the back for that trend. 8. Rotate to a third lab station and view the completed model for the third property. Answer the questions on the back for that trend. 12

15 Name Per. Questions on Periodic Trends Trend 1: Atomic Radius 1. From top to bottom down a group, this trend (circle one) increases / decreases. 2. WHY do we observe this group trend? SEE CLASS NOTES 3. Which element has the larger atomic radius, (circle one): beryllium or radium 4. From left to right across a period, this trend (circle one) increases / decreases. 5. WHY do we observe this periodic trend? SEE CLASS NOTES 6. Which element has the larger atomic radius, (circle one): cesium or astatine? Trend 2: Ionization Energy 7. From top to bottom down a group, this trend (circle one) increases / decreases. 8. WHY do we observe this group trend? SEE CLASS NOTES 9. Which element has the greater ionization energy, (circle one): lithium or francium? 10. From left to right across a period, this trend (circle one) increases / decreases. 11. WHY do we observe this periodic trend? SEE CLASS NOTES 12. Which element has the greater ionization energy, (circle one): strontium or iodine? Trend 3: Electronegativity 13. From top to bottom down a group, this trend (circle one) increases / decreases. 14.WHY do we observe this group trend? SEE CLASS NOTES 15. Which element has the greater electronegativity, (circle one): carbon or lead? 16. From left to right across a period, this trend (circle one) increases / decreases. 17. WHY do we observe this periodic trend? SEE CLASS NOTES 18. Which element has the greater electronegativity, (circle one): potassium or bromine? 13