Final Chance To Make Back Points On The Mole Test

If you did not take advantage of the opportunity to make back points on the mole test from prior to Thanksgiving break, you have one more chance. After finals on Friday, December 16th, you can earn back 1/3rd of the points on the mole test. The activity will take 45 minutes to complete.

WHAT TO STUDY FOR THE FINAL TEST OF THE FIRST SEMESTER.

Below is a listing of concepts that you need to be familiar with for the final test. The test will consist of mostly multiple choice questions and some short answer questions. Though the book is not used much, this covers most of chapter 10(sections 10.5 through 10.11) and a lot of chapter 11 (sections 11.1, 11.2, 11.4 through11.7) in the book.

• Know the general concept of quantum mechanics. Orbitals are areas of highest probability (90%) of the location of an electron.



• Know that all matter moves in a wave pattern. This is especially true for electrons traveling in an orbital. The direction of the electron traveling is not known, but the path length is. The path length around the nucleus must be a multiple of an integer of the wavelength. An example of this is as follows: If an electron has a wavelength of 20 nanometers (nm), two possible path lengths could be 100 nanometers (nm) and 120 nm. Both path lengths are integers of the path length: (100 nm / 20 nm) = 5 (120 nm / 20 nm) = 6. Since the electron travels as a wave, the path lengths given would cause a crest to meet a crest and a trough to meet a trough. If the path length was 110 nm, the electron could not exist at this path length. The 110 nm path length in not an integer of wavelength ((110 nm / 20 nm) = 5.5). This would cause a crest to meet a trough and destructive interference would occur. The knowledge that the electrons travel as a wave gives credibility to the idea that electrons must exist in certain locations. This is supported by the emission spectrums of elements giving off very specific wavelengths of light when excited.
  


• Know the order of filling orbitals by using a periodic table. You will be supplied with a periodic table for the test.



• Be able to properly write electron configurations and/or orbital diagrams for elements in the ground (lowest energy) state. Also, be able to recognize if an electron is excited from an electron configuration or orbital diagram. This was covered in the electron configuration quiz given in class and can also be found in the notes package. An example of this: electron configuration of sodium (11 electrons) in the ground state is 1s^2 2s^2 2p^6 3s^1 - sodium in the excited state could be 1s^2 2s^2 2p^6 3s^0 4s^1



• Know the concept of penetration by an electron to lower principle energy levels and how this concept dictates the order on how the sub-levels and orbitals of different energy levels are filled. This concept is why the 4s sub-level is filled before the 3d sub-level and the 5s sub-level is filled before the 4d sub-level.



• Know the shape of an "s" orbital (sphere) and a "p" orbital (dumb bell)



• Know the sub-levels that are in each principle energy level. 1st - s only; 2nd - s and p; 3rd - s, p, and d; 4th (and on) s, p, d, and f.



• Know how many orbitals are in each sub-level. You should be able to calculate how many electrons could be held in a particular principle energy. For example: How many electrons could be in the 4th principle energy level? The 4th principle energy level is the first time all of the sub-levels are present. Therefore; 1 orbital for the s, 3 orbitals for the p, 5 orbitals for the d, and 7 orbitals for the f will be a total of 16 orbitals. Each orbital can hold 2 electrons for a total of 32 electrons in the 4th principle energy level.



• Know how to write orbital diagrams (show orbitals with arrows representing the electrons), complete electron configurations, and noble gas electron configurations.



• Know the abnormalities for the electron configurations of chromium and copper.



• Know para-magnetism and di-magnetism based upon unpaired and paired electrons in an orbital. An orbital diagram with many unpaired electrons in orbitals would exhibit magnetic character while an orbital diagram with all paired electrons in orbitals would show little to no magnetic character.



• Know that valence electrons are the electrons in the outer-most s and p sub-levels. Any electron that is not a valence electron in an atom is known as a core electron.



• Know the concept of shielding by the core electrons to minimize the effect of the protons in the nucleus on the valence electrons.



• Know all of the general periodic trends of atomic radius (size), 1st ionization energy, electron affinity, and electronegativity. Be able to define what all periodic trends are. Be able to explain in detail the factors that attribute to a periodic trend. Example #1 - Size of atoms across a period (horizontal row on the periodic table) decrease from left to right. The reason is the number of protons in the nucleus increase as you move to the right across the periodic table, but the number of core electrons remains the same. The increased positive charge of the protons and the shielding staying the same allows the protons to attract the valence electrons in closer to the nucleus. Example #2 - 1st ionization energy of atoms decreases going down a group (vertical columns on the periodic table). The reason is the atoms get larger as successive energy levels are added. The greater distance between the nucleus and valence electrons and increase in the amount of shielding due to more core electrons causes the protons in the nucleus to have less effect on the valence electrons. Because of the diminished effect, less energy is needed to remove an electron from the atom.
  


• Know why successive ionization energies get larger and larger. Know that a substantial increase in an ionization energy value from one electron to the next would be an indication of the removal of a core electron.




• Know that chemical bonds are made to lower the potential energy of the atoms involved in the bond. The lowering of the potential energy of the system makes the atoms in the molecule more stable. An example of this was done numerous times in class looking at the system of the energy input (ionization energy) to take the one valence electron away from a sodium atom compared to the energy release (electron affinity) of a fluorine atom gaining an electron to complete its outer valence level. The total process would be exothermic because the energy release from fluorine would be greater in magnitude than the energy consumption of sodium. Be able to apply this concept to other scenario in which the relative values of ionization energy and electron affinity are known.






• Know why the mole concept is important for comparison of ionization energy values and electron affinity values. Both values are reported in kilojoules per mole. The mole concept allows for equal comparisons because the number of atoms and electrons involved with the either process have been counted using the mole concept.






• Know that valence electrons are the electrons involved in bonding.






• Know how to define the two types of chemical bonds: Covalent bonds - sharing of electrons between atoms to achieve (in most cases) an octet (8 valence electrons) or a duet (2 valence electrons - hydrogen most of the time). Occurs between non-metal and non-metal elements (most of the time). A covalent bond is technically defined as an electronegativity difference between the two elements in the bond of less than or equal to 1.7. Ionic bonds - transfer of electrons between atoms to achieve an octet (or duet) for both atoms. Occurs between metal and non-metal elements (in most cases). An ionic bond is technically defined as an electronegativity difference between the two elements in the bond of greater than 1.7.






• An electronegativity table will be supplied to you for bond type determination.






• An electronegativity difference of less-than or equal to 1.7 does not mean electrons are always shared between the elements. It means the electrons are shared a majority of the time and some transferring of electrons does occur. An electronegativity difference of greater than 1.7 does not mean a complete transfer of electrons from one atom to another. It means electrons are transferred from the less electronegative atom to the more electronegative atom a majority of the time and some sharing of the valence electron(s) does occur.






• Know the term / concept of isoelectronic. This is covered in the second VODCast for the Chemical Bonding / Lewis Dot Diagram worksheet.






• Know how the relative sizes of ions compared to their original atom sizes. Cations (positive ions) will always be smaller than their original atoms and anions (negative ions) will always be larger than their original atoms. The reasoning for the trends is givenin the second VODCast for the Chemical Bonding / Lewis Dot Diagram worksheet.






• Know how to show in a Lewis dot diagram and define: a single covalent bond, a double covalent bond, and a triple covalent bond.






• Know how to draw a Lewis dot diagram and structural diagram of a chemical compound. This is covered in the first and second VODCasts for the Chemical Bonding / Lewis Dot Diagram worksheet.

The test will take roughly 50 minutes of the 90 minute testing period. The point value of the test will be that of some of our larger tests this semester - 50 to 60 points. With the remaining time in the testing period, we will do a lab. Please bring pennies for the lab. You will be converting the copper of the pennies to "gold". (Actually, you will be making brass that looks like gold.)

Electromagnetic Spectrum

Below is an image for the electromagnetic spectrum. You may need to use it to complete your the EM / Bohr model work packet.

Test and Quiz Reminder

Tomorrow, Wednesday, November 9th, 2011, you will have a quiz covering the hydrate lab that was completed today in class. The calculations for the quiz will mimick the calculations done for the lab and pre-lab. Also, start preparing for the mole test which will be given on Thursday, October 10th, 2011. There is a review packet and key posted a a pdf. on today's date on the class events calendar.

MOLE DOLL

Below is the cut-out image to be used to make your mole doll, if you choose. You will get 10 points extra credit for making just the regular sized doll with no extras. You can get 20 points extra credit if you give your doll a theme. Examples are "Holy Moley" and have your mole dressed as an angel, priest, nun,..... You get the idea. Have your theme deal with the word "mole", or just dress it up in some neat, but tasteful way. You can also get 20 points extra credit by taking the image below and enlarging it and make a super-sized mole. Super-sized is anything over 1 and a half feet in length. I would be totally impressed if a couple of people got together and made a life sized mole. You can save the image of the cut-out below and then print it. You will have to show some sewing skills (or you parents sewing skills) to make this. Involve your mom. Mom's love this stuff. The mole will be due next Friday, the 11th of November, 2011.

Empirical and Molecular Formulas / Flipped Classroom

You are going to be taking part in a teaching experiment. The experiment is known as the "Flipped Classroom". The idea of the flip will be that you will learn about the concepts outside of class and then do your "homework" in class. You will be "lectured" on the new concepts via a series of three VODCasts (Video On Demand) from the comfort of your own home or the computer lab in the HHS library. I have made minnie movies to introduce the new concepts and to guide you through the first seven problems of the packet that you were given in class on Percent Composition, Empirical and Molecular Formulas. The VODCast files can be found on the Events Calendar of the class website under the date, Wednesday, November 2nd, 2011. It is your responsibility to view the videos, write notes on the material, and complete the example problems prior to class on Thursday, November 3rd, 2011. On that Thursday, you will come to class and work on the remaining problems of the packet in small groups. Below is a list of concepts that you need to be familiar with after viewing the VODCasts and doing the example problems in the work packet that was given to you.

• Be able to define percent composition, empirical formula, and molecular formula.
• Know the process of how to find the percent composition of individual elements in a compound.
• Know that empirical formulas are the ratios of elements in a compound based upon the counted unit of the mole.
• Know how to treat the amounts of elements in a compound when percentages are given.
• Know how to deal with a situation where the ratio of an empirical formula does not work out to be whole numbers, but rather one or more of the elements in the compound has a subscript that is a decimal / fraction number.
• Know how to determine a molecular formula by comparing the molar mass of a molecular formula to the molar mass of an empirical formula.
• Know how experimentation is needed to determine the "real" molar mass of a molecular formula. Know how relative molar masses are determined using a mass spectrometer.

Before you come to class on Thursday, November 3rd, 2011, you must have all seven example problems completed in the work packet and notes taken from the VODCasts. You will be graded on this preparation work.

Mole Worksheet

Below is a solutions guide to the Mole Worksheet table that was given out in class today. I realized during 6th hour today that there was not information to work with for CH4 and NH3. Do not worry about finishing the chart for those two substances. The answers for the worksheet are given on the back of the worksheet at the bottom of the page. You may also want to view the VODCast that is posted on today's date, Tuesday, November 1st, 2011 on the class calendar. Remember, you need Quicktime on your computer to view the movie file. You will have a quiz over the material covered on the mole worksheet, so make sure that you try and master the material. The quiz will be going into the homework category of your grade. Also, all questions on the Bean Lab must be completed for tomorrow. The lab will be collected at the beginning of class.

Chapters 4 and 18 Test - Wednesday, October 26th, 2011

On Wednesday, October 26th, 2011, you will be taking a test covering the material covered in Chapters 4 and 18 of the chemistry textbook for the class. The sections of one through seven will be tested in Chapter 4 and sections one through four will be tested in Chapter 18. You may want to read those sections specified, but know that all material that is covered by the exam is presented in the handouts and worksheets of the unit. The test will consist of both multiple choice questions and short answer / written questions. On the short answer portion, you may be asked to draw on diagrams to illustrate concepts within the unit of study. A practice test is available on the class calendar on the date Monday, October 24th, 2011. Realize the practice test only covers some of the concepts that are testable. Please use this blog post as the definitive listing of what you will be expected to show proficiency at on the exam. You will be given all equations that need to be utilized, a periodic table, and you will be able to use a calculator on the exam.

The history of the atom starting with John Dalton and the concept of the atom in the early 1800's to JJ. Thomson discovering the electron with a Crooke's tube to Ernest Rutherford discovering nucleus of the atom using the gold foil experiment are what many questions will center around. Know the significance of Dalton developing the atomic theory by using the laws of definite composition and multiple proportions as proof that atoms exist. Example: Water (H2O) and hydrogen peroxide (H2O2) both contain the elements hydrogen and oxygen. Both have different chemical and physical properties, so the concept of atoms allows for the building of these different chemical out of the same elements (Law of Multiple Proportions). The fact that water has two hydrogens and one oxygen gives it very specific chemical and physical properties. When water is poured on your head, a chemical property of water is that it will only wet your hair. It also has a very specific freezing poin, a very specific boiling point and a very specific density. All of these are physical properties of water that come from the two hydrogen to one oxygen ratio. To have these properties, the two to one ratio of hydrogen to oxygen must be, no other ratio will give the identical chemical and physical properties (Law of Definite Composition). Know about Thomson's Crooke's tube experiment for discovering the electron. Be able to diagram / discuss that the particle beam seen inside of the Crooke's tube could not be a charged atom of the lightest known element in the late 1800's (hydrogen), but rather, a particle with less mass based upon the amount of deflection the particle endured when subjected to a magnetic field. Know that Thomson's discovery of the electron and the subsequent discovery of the proton allowed the plum pudding model of the atom be developed. Be able to diagram / discuss the plum pudding model of the atom. Know about Rutherford's gold foil experiment for determining that the protons were located in the center of the atom in the nucleus and the electrons were outside of the nucleus. Be able to diagram / discuss how the plum pudding model predicted that the alpha particles would pass through the thin piece of gold foil. Be able to discuss / diagram the results that Rutherford actually saw from the gold foil experiment. Be able to cite the evidence of 4 out of 10,000 alpha particles were reflected / deflected as proof that the volume occupied by the nucleus is 1/100,000 of the volume of the rest of the atom.

Be able to diagram the number of protons, neutrons, and electrons in an atom or ion (charged atom) of a particular isotope. This is coved by the Atomic Structure worksheet and also the Atomic History / Isotopes Quiz given earlier in the unit of study. Be able to calculate the average atomic mass of an element when percent abundance and atomic mass of each isotope is given. The Isotopes and Average Atomic Mass worksheet covers this along with the Atomic History / Isotopes Quiz. Be able to calculate the percent abundances of an element when the atomic masses of the isotopes is given and the average atomic mass. You will need to use multiple equations (two) to solve for the multiple variables (two) of the percent abundances. You can use which ever method is most effective for you (substitution, elimination, matrices) to solve for the variables. The Isotopes of Pennium activity and Isotopes / % Abundance Problems worksheet cover this topic. Along with isotopes (which you will need to be able to define), you must also know how a mass spectrometer would be used to detect and quantify the different isotopes or chemical compounds in a sample. Remember, the particles must be charged the same (negative or positive) to have their path direction changed in the same way by a magnetic field. The separation occurs when the masses of the different isotopes / compounds dictate that they take different radii paths. The heavier particles will take the wider radius turn and the lighter particles will take the smaller radius turn. This is covered in the notes and in the Atomic History / Isotopes Quiz.

Know about radioactive decays (alpha, beta, gamma, neutrons, positrons) and how to balance the atomic numbers (bottom numbers) and atomic masses (top numbers) on each side of a nuclear decay reaction. This is covered in the nuclear radiation packet and the by the worksheet on the very back of that packet labeled "Nuclear Decay". Know how to designate a parent isotope and a daughter isotope. Know that a nucleus of a isotope is unstable because the ratio of protons and neutrons in the nucleus is too large and particles must be released from the nucleus to attain stability to the nucleus. Know about how nuclear decay of uranium in soil can lead to the formation of radon (Rn) gas that can enter a home through cracks in the foundation of a home. Know that the radon gas is a heavier than air gas, thus it will collect in the low point of a home, which is usually the basement. Know that radon gas can be breathed in and once in a persons lungs, can udergo a nuclear decay. Know the biological effects of radiation on tissues and DNA. This all can be found in the radiation packet.

Know the concept of half-life and how it can be utilized to determine the age of a material. Know that nuclear decays are random / spontaneous events. The reason that nuclear decays happen at a consistent rate is that the population is large enough to cause random events happen at a constant rate. Refer to the baby being born in Littleton in the next minute (maybe) versus a baby being born in the United States in the next minute (definite) example used in class. Know that a number of decays (y-axis) over time (x-axis) graph is exponential. The reason that the graph flattens out is the population of the parent isotopes has decreased, thus the instantaneous rate of decays goes down. The reason natural logs (ln) were used in class was to take the exponential graph of number of decays versus time and straighten it out to a linear relationship. You will not be asked to determine any values from a graph like what was done in class. That was merely to show you that the use of natural logs was necessary. You will be expected to isolate and solve for any variable in the general equation: ln[X] = -kt + ln[X]o. This is covered by the notes package on radiometric dating and the Half-Life / Radiometric Dating worksheet. Remember, if you are asked to solve for ln[X] or ln[X]o, you must find the value then find the inverse ln (e^x) of that value to find the true value. If percentages are used in a problem, the original amount (ln[X]o) is always 100%. You will be asked questions about dating the ash layer that was a focal point of the discussion of radiometric dating. Know that the ratio of unstable U-238 to the stable isotope of Pb-206 was central to dating the ash layer. You must also know the process of carbon-14 dating. Know that carbon-14 is created in the upper atosphere by neutrons from outerspace bombarding nitrogen-14 in the upper atmosphere. Know that the creating of carbon-14 and its demise to nitrogen-14 via beta decay both happen at the same rate, thus the percentage of carbon-14 in the environment stays constant. Know that when a living organism dies, it stops incorperating carbon-14 in its bio-mass. The level of carbon-14 in the bio-mass decreases from the point of death and the ratio of carbon-14 to the daughter isotope of nitrogen-14 will be what can be used to determine how long the organism has been dead. All concepts dealing with carbon-14 dating are presented in the radiometric dating notes packet.

Please do not let the length of this blog post be daunting. You probably know most of this material, I just want to make sure that you are not surprised by any material on the test. That is why the detail of this post is so involved. Study hard and see me outside of class if you have any questions.

Half-Life / Radiometric Dating Worksheet

Below is a picture of North Tabletop Mountain, which is a theme for problem #6 of the Half-Life / Radiometric Dating worksheet. If you look carefully, you can see the interface line between two of the four lava flows that occured over the one million year period that created the geologic formation. The solutions to problems #2, #3(c), and #6 are presented in a VODCast as a Quicktime movie. The movie file is posted under the date, October 21st, 2011 on the class Events Calendar.

Quiz Tomorrow - Friday, October 7th, 2011

Please remember that you will have a quiz tomorrow in class covering all of the material in the notes package being used in class over the history of the atom. Know the names of the scientists, what they discovered about the atom, and the time frame that the discoveries were made. You will also be held accountable for know how to calculate average atomic mass and know how to determine the component parts (protons, neutrons, and electrons) of an atom (neutral) or ion (plus or minus charge). You will also be required to know how a particle (charged or neutral) will behave in a magnetic field. Know that opposite charges will turn opposite directions in the magnetic field and that the radius of the turn is mass dependent. There will be no questions from the reading that was completed this last Wednesday.This quiz will go in your assessment grade.

Atomic Structure Power Point

A file of the Atomic Structure Power Point can be found on the class calendar on today's date, Monday, October 3rd, 2011.

Test Reminder - Study Guide Solutions

Below is the key for the study given out in class today. If you are having a hard time reading the images, click on the images to enlarge them. Come in and see me before the test if you have any questions.

Below are the solutions to problems #6 and #8 of the calorimetry worksheet. Please finish the worksheet and the calorimetry lab for tomorrow, Friday, September 22nd, 2011.

Dance, Dance, Dance

I hope that everyone enjoyed the little dance lesson offered in class today. Remember, when I D.J. the homecoming dance, I had better see all my students movin' and groovin'. Let's review the parts of the "Molecular Motion / States of Matter Dance" or if you prefer "States of Matter / Molecular Motion Dance".
Part 1 - "The Solid" - Fists together and an ever so slight motion showing the molecules vibrating. The fists cannot move around one another nor can they move apart from one another. This shows the "vibrational motion" that all solid molecules have when subjected to energy.

• Definition - Energy - the ability to cause change. Changing the position of a molecule due to movement requires energy.

Part 2 - "The Liquid" - Fists are still touching one another, but they can now move around each other in a circular motion. Vibrational motion is still retained and movement of the fists around each other illustrates the "rotational motion" now afforded to the molecules. Rotational motion is achieved because enough energy is absorbed by the material to cause the vibrational motion of the solid to become so intense, the bonds that once held the molecules in place as a solid are broken.

• Definition - Temperature - the direct measure of molecular motion. A substance's melting point (solid to a liquid; vibrational motion to rotational and vibrational motion) is the molecular motion rate (temperature) that causes the bonds between the solid particles (atoms, molecules) to be broken.

Part 3 - "The Gas" - Fists are no longer touching and are moving in all directions in three dimensional space. Vibrational and rotational motion are still retained and the movement of the fists in all directions illustrates the "translational motion" now afforded to the molecules. Translational motion is achieved because enough eneryg is absorbed by the material to cause the rotational motion of the liquid to become so intense, the bonds that once held the molecules together as a liquid (touching, but able to move around each other) are broken.

• Analogy - "The Mean Uncle" - You are at a family outing and you are a young child. You go to your uncle, "Please swing me!" Your uncle abliges you, but before he grabs your hands to swing you around in a circle, he puts grease all of you hands and arms and his hands and arms. As he spins you round and round and picks up more speed, the weak bond that exists between you and him (greasy hands) is broken quite easily. You end up flying off into a bush. This is just like a liquid. The molecular motion becomes so great (high enough temperature), the bonds holding the liquid molecules together are broken and a gas is formed.

Just as energy can be placed into a material to increase molecular motion and break bonds, thus changing states of matter, energy can be removed (or lost) from a material. As energy is removed, the molecular motion decreases. The decreased molecular motion does not allow the particles (atoms or molecules) to overcome the attractive forces between them, thus bonds are formed between the particles.

**Molecular motion exists as long as there is energy. What is the name of the theory when no energy exists, thus no molecular motion exists in matter.

***Absolute Zero is the theoretical point when all energy has been removed from matter and no molecular motion exists for atoms of an element.

Book work for Monday, 9/12/2011

For homework, you are to read pages 55 - 65 (sections 3.1 through 3.5) in the textbook. At the back of the chapter, starting on page 74, answer the following questions: 1 through 5, 13, 14, 18, 21, 22, 25, 29, 33, and 34. The question #1 to start with is - How, in general, do we define matter?

Answers for Homework Questions Assigned on 9/12/2011

Below are the answers to the problems assigned from the book on Monday, September 12th, 2011.









1. Matter is the "stuff" that occupies space and has mass.




2. Physical states of matter are solid, liquid, and gas.




3. Gases are very compressible.




4. Liquids have a definite volume, but can take on the shape of the container that hold them.




5. Solids are held together the most rigid and can only vibrate next to each other. Liquid molecules touch one another, but can move around each other. Gases can move around and apart from one another.




13. Before question 13 is answered, I want to define the term aqueous. An aqueous is a type of state of matter when a substance is dissolved in water. A physical property of nickel (II) sulfate in solution is a bright green color.




14. A chemical property of nickel (II) sulfate is that it will react with barium form a barium chloride solution to form a white precipitate of barium sulfate. Precipitate is a scientific way of saying a solid was formed.




**The answers to question 18 have explainations with them. You are not required to give the reason for either physical or chemical change, only indicate the type of change. I just added the explainations for the sake of understanding.




18. a. chemical change - the burnt fabric of the shirt will change colors and gases will be released by the burning of the fabric.




18. b. physical change - the gas does not change within the tire, but rather just occupies a smaller volume due to the cold temperatures.




18. c. chemical change - the silver reacts with oxygen in the air to produce a new compound (silver oxide) that appears black in color.




18. d. chemical change - the alcohol in the wine reacts with oxygen to for vinegar (or also called acedic acid).




18. e. chemical change - the physical properties of the grease change. Also, the soapy material would have bubbles within it, indicating the production of a new state of matter, gas.




18. f. chemical change - the leaking of the battery is not in itself a sign of chemical change. The fact that it cannot be recharged (charging is a chemical change) is an indicator that a chemical change has occured. The leaking is probably the result of a new state of matter being produced by the chemical reaction and the design of the battery cannot contain the new substance.




18. g. chemical change - tooth decay is a change in the chemical make-up of the tooth. The acids from the bacterial cause this change.




18. h. chemicale change - related to the sulfuric acid / sugar demonstration done in class. The charring is a result of the sugar burning. Anything that burns undergoes a chemical reaction.




18. i. chemical change - the hydrogen peroxide fizzing (effervescing) is a result of a gas being released from a chemical reaction. This reaction described in 18 i is the reaction for elephant toothpaste done on the first day of class.




18. j. physical change - the term dry ice comes from the fact that solid carbon dioxide (dry ice) goes directly from the solid phase to the gas phase, skipping any liquid that could be produced. This process is called sublimation. The chemical composition of carbon dioxide never changes.




18. k. chemical change - the color change of the fabric is the indicator of the chemical reaction occuring.




21. Elements form compounds.




22. Compounds can be broken down into the component elements by chemical change.




25. A pure substance is a element or compound with a fixed composition. Only that element or compound is in the container. A mixture is not a fixed composition. A mixture can have any number of elements or compounds in the same container.




29. a. The air that you breathe is a mixture. Air consists of different elements in compounds. The main component of air is elements nitrogen (N2), which makes up roughly 75% of the gases in the atmosphere. Elemental oxygen (O2) is roughly 20% of the atmosphere. The remaining percentage are small amounts of carbon dioxide, argon gas, sulfur dioxides, etc, etc.




29. b. A soda is a mixture. The carbon dioxdie dissolved in the soda is a visible component of the mixture as it bubbles out. The sugar that is dissolved in the water could be separated by evaporating away the water. All components of soda can be separted from each other into pure substances.




29. c. Water is a pure substance. It is the chemical combination of two hydrogen atoms and one oxygen atom. Water has consistent properties and cannot be changed as long as the two to one ration of hydrogens to oxygen exist.




29. d. A diamond is pure carbon (not quite an accurate statement). A diamond is considered to be one very large molecule. Therefore; diamond is a pure substance.




33. Distillation can be used to separate two liquids in a mixture. The two liquids must have different boiling points in order to achieve this. An example would be to separate ethanol from watere. Ethanol will boil at a lower temperature thatn water. This concept was covered in the demonstration given on Tuesday, September 13th, 2011.


34. Filtration can be used to sepate anything that can dissolve in a solvent (i.e. salt in water) and a substance that will not dissolve in the same solvent. An example would be to separate ground up glass from sugar. The sugar could dissolve in water but the ground glass could not. The mixture could be passed through filter paper. The ground glass would stay in the filter paper and the dissolve sugar would pass through. The water could be evaporated to collect the solid sugar again.

Test Reminder

Below is a summary of all of the concepts that will be covered by the first major exam of the semester. You received back from me all of your work materials, so you have material to study from. On the calendar for the chemistry class, I have posted a key for the data analysis worksheet. You will not be performing any calcuator skills, only your comprehension of your data analysis skills will be assessed. Good luck and I will be at school early tomorrow moring, Friday, September 9th, 2011 if anyone has questions prior to the exam.

Partial Solutions Guide for the Conversions Packet

A pdf file for the conversions packet can by found on the class calendar under the date September 7th, 2011.

Density Lab Practical

On Friday, September 2nd, 2011, you will be taking your first assessment of the semester. The grade that you earn on the lab practical will have a big impact on your grade. You will be tasked to find the density of a material. The material will be given to you as objects. I am going to outline the expectations that you need to follow to do well.

• You will not write out a purpose, theory, procedure, SEE's, or conclusion statement. You will only be creating a data table and doing your calculations in an analysis section. All tables and work should be neat and orderly. Remember to label all measured and calculated values.


• Even though you are not going to write out a procedure, certain aspects of good laboratory design need to be followed and will be graded. You will be expected to do more than one trial to help ensure accuracy and precision.


• You will be expected to maximize the number of significant figures in your measurements and calculations, so having a larger sample size will be required.


• Adherence to significant figure rules for calculations will graded.


• The density of the material is known, so you will be graded on the accuracy of your calculated density value.


• You will be collecting your data BY YOURSELF WITH NO LAB PARTNER. You must know how to read both the scale and graduated cylinder. You must know the proper procedure on how to operate the scale (use of weighing dish). You will only have roughly 15 minutes to collect all of the data for your trial, so you must be quick but also precise.

While half of the class performs the lab to obtain the measurements for the density determination, the other half of the class will be working on the second half of the test. You will be given a scenario that gives a lab procedure that is performed by a chemistry student. You will be asked to answer questions based upon the scenario. All of the questions are written and you will be required to critique calculations done by the student.

The lab practical is roughly 30 points and will go towards the assessment category of your grade, which is 60% of your overall grade. Please take doing well on this assessment seriously.