Honors Chemistry - Chapters 1-5 Short/Long Answers
Lavoisier proposed that the fundamental truth of the same amount of matter exists before and after each experiment.Therefore, the fact that calx was heavier than the metal even though phlogiston had left the metal bothered him. He conducted his experiments in public using a huge burning lens that focused the sun's rays to produce intense heat. He placed the calx of lead mixed with charcoal inside a glass vessel partially filled with water.Phlogiston means that heat, smoke and light are released as fire burns. He found that a portion of air was absorbed into the solid material when burning and that was why the calx was heavier than the metal. He finished the theory of phlogiston.
Briefly outline how Lavoisier was able to prove the conservation of matter and ultimately disprove phlogiston.
Energy levels: 1, 2, 3, 4 Number of Sub-levels: n=1: 1 (s) n=2: 2 (s, p) n=3: 3 (s, p, d) n=4: 4 (s, p, d, f) Number of Orbitals n=1: 1 n=2: 3 n=3: 5 n=4: 7 Number of Electrons: n=1: 2 n=2: 6 n=3: 10 n=4: 14 Orbital Shape/Orientation: n=1: sphere shape (around nucleus) n=2: double dumbbells (around x,y,z) n=3: double dumbbells with dumbbell with donut (various position around x, y, z) n=4: too complex shape (similar to flower) with orientation around x, y, and z axis'
Develop a table listing the sub-levels, # of orbitals, shapes of orbitals, and total # of electrons in the orbitals for n=1-4 energy levels:
In his experiment Rutherford used a lead box with a particle source to shoot positively charged particles at a 1 atom thick sheet of gold foil surrounded by a fluorescent screen. During this time, he observed the deflection of particles helping to develop an understanding of the structure of an atom.
Ernest Rutherford radically changed the concept of the atom with his interpretation of the gold foil experiment. Briefly describe the experiment that led to this development.
2 unpaired
Give the orbital filling diagram of Polonium: How many unpaired electrons does Polonium have?
Bohr's model demonstrates how the electrons are in a fixed orbit around the nucleus. It shows how the negatively-charged electrons orbit a small, positively-charged nucleus similar to the planets orbiting the Sun, except the orbits are not planar. He developed his model in 1913 as a student of Rutherford's. This model was concocted as he proposed the electrons orbited in a concentric circular shape around the nucleus, which he later summarized in his four main principles and postulates.
How did Bohr develop his model of the H-atom?
Shrodinger treated the electron (which is a particle) as a wave function or quanta and by using some mathematics he was a able to plot probability clouds of electron positions, instead of simply basing electron position on the idea of a concentric circular orbit. He then drew 90% probability volume around theses clouds, developing the orbital (which there are 4 types s, p, d, f in the ground state of an atom). Orbital - regions of space around the nucleus of an atom where an electron is likely to be found
How did Shrodinger use Planck's idea to change the proposal that an electron orbits the nucleus? What is the definition of an orbital?
a. 6 are essential for life functions (SPONCH) but 20 elements are considered common b. macro-minerals (are involved in the formation of bones/teeth, and the maintenance of essential body functions) vs. micro-minerals (involved in other bodily processes) c. Arsenic surprises me because typically it is toxic to the body
How many element are considered essential for a healthy human body? What is the difference between macro and micro minerals, and are there any examples of micro minerals that surprise you?
Dalton was able to form the first atomic theory without performing any experiments himself because he based it off of Lavosier's conservation of matter and Joseph Priestly's law of definite proportions. His four postulates are... 1. All matter is made up of tiny particles called atoms 2. all atoms of the same element are identical to each other and different from atoms of other elements 3. Two or more atoms of different elements can combine to form compounds 4. particular compounds are made up of the same kinds of atoms and the same numbers of each atoms and in chemical reactions compounds can be separated, combined, and rearranged
How was Dalton able to formulate the first atomic theory without performing any experiments himself? What are the four postulates of his atomic theory?
1.Electrons orbit around the nucleus like planets around the Sun, this was later shown to be wrong because it's more complex than just concentric circular orbits. 2.These orbits are energy levels and are absolute. Electrons can't be between levels. 3.When electrons are in their lowest energy level, there are in their ground state which means they're grounded and can't leave. 4.When an electron absorbs energy, it moves up. The energy absorbed must be the exact difference between the levels that the electron moves between. (Absorbs photons)
What are Bohr's 4 postulates?
1. The atom is mainly empty space. He discovered this because 98 % of the positively charged alpha particles passed straight through without deflection. 2. The protons reside in the nucleus in the center of the atom. He discovered this due to 1/8000 of the alpha particles shot straight back... because of the fact the nucleus is positive and thus there must be repulsion between protons 3. The electron surround the atom in some way, this explains how the atom is still "neutral". 4. If you expanded the atom to a size we could see, the nucleus would be the size of a golf ball on the 50 yd. line of a football stadium. Each electron would be the size of the eye on a dime on the 50 yd. line and would occupy the space of the stadium.
What are the four postulates of Rutherfords model and how did he come up with these postulates?
METALS: ductile, malleable, good conductors of electricity, high melt temp; solids @ room temp (iron) METALLOIDS: better conductors of heat/electricity than nonmetals but worse than metals, good semiconductors - can be modified to be both conductors and insulators (boron, silicon) NONMETALS: not shiny, not malleable, not ductile, poor conductors, low melting point, low density (oxygen)
What are the properties of metals, nonmetals, and metalloids? Give an example of a metal, a nonmetal, and a metalloid.
Planck saw a horse shoe being formed and noticed that the Iron went from black to orange to white. He wondered where the rest of the visible spectrum was and he proposed the idea that energy was released in tiny packets called quanta. He develop ed the E=h*frequency showing that the E was directly related to frequency. His skeptics said that was crazy. E in our macroscopic world is smooth not "choppy" thus water warms to a boil not an instantaneous boil and they used the dual slit experiment to prove him wrong.
What caused Planck to develop his quanta theory? Why did his colleagues have problems with his ideas? How did they disprove his idea?
The iceberg contains the greater amount of energy because it has a greater amount of mass contributing to the overall total energy.
What contains a greater amount of energy, an iceberg or a cup of boiling water? Why?
Temperature measures the average heat energy created by molecular motion in an object. This differs from "heat" which is the total energy created by molecular motion, but not measured
What does temperature truly measure? How is it different from "heat energy"?
Mendeleev's problem was that a few of the elements on the periodic table needed to have the mass reversed. Moseley redefined the periodic table. He found all the x-ray spectrums of the elements and arranged the films with wavelengths on them according to their frequency. The dominant x-ray lines rose in frequency step by step like a staircase. He attributed this to the amount of positive charge in the nucleus. And all the elements appeared to be where they should be. Moseley proved that the periodic table is actually arranged by atomic numbers, not atomic mass. Chemical properties of elements are dependent on proton numbers.
What interesting thing did Moseley discover with his x-ray experiments? What did he attribute the pattern to? How did this change Mendeleev's arrangement of the elements?
Absolute zero is the coldest point on the Kelvin scale at 0K and or -273.15 degrees celsius, as well as the point at which all particle motion stops. Scientists are interested in studying this point because it is the point at which particle motion stops, and near this point atom's present unique properties such as moving in wavelike patterns causing the atomic movement to "blend" together.
What is Absolute Zero? What does this point represent? What are scientists interested in studying the atom's behavior near this theoretical point? Give an example of this behavior.
Density compares the mass of an object to its volume in an inverse relationship. You would be able to tell which fluid is rubbing alcohol by comparing its density to that of the alcohol's chemical compositions density, as density is a unique property of matter. To do this, measure the mass of the empty graduated cylinder and the mass of the full graduated cylinder with the rubbing alcohol. Measure the volume of the rubbing alcohol in the graduated cylinder and then divide the mass (full-empty) by the volume to find the density.
What is Density? How would you be able to determine which fluid was rubbing alcohol in our density lab? (describe all steps)
Hund's rule states that an equal energy orbital must be singly occupied before it is doubly occupied. An electron will not pair if there is an equal energy orbital available. Ex: ↑↓ ↑↓ ↑↓ 1s^2 2s^2 2p^2 Violation of Hund's Rule
What is Hund's rule? Give an Example
A natural law is something that occurs in nature that we can describe, analyze, and discuss but we cannot explain why it occurs. An example would be gravity. This differs from a theory which is instead an explanation that unifies a broad range of observations and hypotheses.
What is a natural law and how does it differ from a theory? Give an example of a natural law.
Accuracy is how close it is to the original measurement vs. Precision is the ability for it to reproduce the same measurement more than once. A good measurement is both accurate and precise because you are able to produce similar results that are closer to the correct measurement.
What is accuracy and how does it differ from precision? Why is a good measurement considered both accurate and precise?
An equivalency fraction is an arithmetic multiplier used to convert numbers between units without changing the value of those numbers. They are created by placing two numbers of equivalent value in a ration (or fraction) that when divided equals 1. They are used to convert units, such as those in the metric system. Ex. 1 cow = 12 goats; 1 goat= 92 chickens so... 12 x 92 = 1104 so... 1 cow = 1104 chickens
What is an equivalency fraction? How is it created and used? If a cow costs the same amount as 12 goats and a goat costs the same as 92 chickens, what are the equivalency fractions that you would use to see how many chickens you could acquire by selling a cow?
An exact number is a number obtained by counting and has infinite significant figures as well as no inaccuracy. An example of this would be 12 eggs which correlates to one dozen. This differs from a measured number which is obtained by using a measuring tool and contains estimated digits in addition to the condition of possible inaccuracy.
What is an exact number? How does this differ from a measured number? Give an example of an exact number.
The EM Spectra is both a particle and a wave. At our normal perception it is a wave, but at the subatomic level it is a particle due to tiny size of quanta.
What is meant by the wave particle duality of nature? When does light behave as particle, a wave?
The Celsius scale is an 100 increment scale developed by Andrés Celsius in 1742. It was based upon the freezing and boiling points of water at 0 degrees celsius and 100 degrees celsius. One advantage of this scale is that it is easier to use because it is based on a base of 10.
What is the Celsius scale? What is it based upon? Name one advantage that this scale has over the Farenheit scale?
Heisenberg proposed that it is impossible to know both an electron's position and momentum simultaneously. Electrons absorb energy so easily the best we can say is where it was. Just in the process of detecting electrons, we can give them enough energy to move up a level. He developed this concept to explain why we cannot know both an electron's position and momentum at the same time and to explain why we cannot know an electron's location.
What is the Heisenberg Uncertainty Principle? Why did he develop this concept?
The Kelvin scale is the SI scale used for heat. It was derived based on the discovery of the relationship between the volume and temperature of gas. Scientists believed that gas should have a value of 0 at -273.15 degrees Celsius, so they used this scale to claim that fact. It was necessary to derive this scale, as Lord Kelvin recognized the need for a temperature scale without negative numbers, and this scale helped to determine the temperature at which molecular motions stops.
What is the Kelvin scale? How was it derived? Why was it necessary to derive this scale?
The Pauli Exclusion Principle states that an orbital can hold a maximum of 2 electrons. In an orbital with 2 electrons, the electrons must have opposite spins while all orbitals singly occupied, the electrons would have to spin the same way. Ex: ↑↓ ↑↓ ↑↑ 1s^2 2s^2 2p^2 Violation of Pauli Exclusion Principle
What is the Pauli Exclusion Principle? give an example
(KNOW HOW TO MAKE DIAGRAM) Def: The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner can be called photo electrons Einstein said that if light were truly a wave then given enough time the energy should build up and the electron should be released (this does not happen) The violet light instantly cause a current which caused Einstein to correctly surmise that the quanta packets of violet light had enough energy to release the electron. using a analogy, an elephant (electron) can be hit all day by ping pong balls (red photons) and nothing happens. However when the elephant is struck by a cannonball (violet photon) the elephant is knocked down (released as a current). Einstein then went on to say that E from the EM spectra was both, a save and a particle in the wave particle duality of nature.
What is the photoelectric effect and how did Einstein use this to prove Planck's idea? How did Einstein argue that light could b acting as a wave in this experiment? Using the ping pong ball vs. cannon ball analogy describe how light must be "quanticized"?
a. He applied electricity to a glass tube, which would produce streams of particles called cathode rays. Due to the fact that the rays were attracted to a positive charge, he concluded that the stream of particles must be negatively charged. b. It's relevance to chemistry is that it helped to discover the electron, which in later experiments were found to be much smaller than the atom and found to have an extremely small mass. Because scientists also knew that atoms were neutral, they could determine that the atom also had positively charged particles called protons which were much heavier than electrons. With this information Thompson would later propose his plum-pudding model to give a "structure" to the atom. c. He was also able to establish the ration of the angle of deflection being represented by charge over mass.
What was Thompson able to prove about Dalton's atomic theory using cathode rays? How did he know that the rays were actually "particles"? What ration was he able to establish?
a. He used small oil drops suspended between two metal electrodes (or plates) by balancing downward gravitational force with upward drag and electrical forces. He then put a charge on the tiny droplets, using an x-ray, and measured how strong an applied electric field had to be in order for the drop to stop falling. Since he was able to work out the mass of the oil drop he could also calculate the gravity on one drop, and this determines what electrical charge the drop must have. He then could find the mass of the electron using Thompson's charge/mass ratio. But, the statement means essentially that the mass and charge of an electron are so small, that he measured what could only be measured idirectly.
Which apparatus did Millikan use to find the charge on a single electron? What does that statement that he measured indirectly what can not be measured directly mean? How was he able to use this information to find the mass of a single electron?
Example Answer: a. Silicon - and I learned that it is an important semiconductor and is being used in the development of computer technology b. Come up with your OWN opinion
Which element was your favorite in the element of the year project, excluding your own element. What information did you learn that was most interesting? Should the honor's level class repeat this project next year? Why?
The first idea of the atom can be attributed to the Greek philosopher Democritus, who proposed in 400 BC the idea of a "smallest particle." The word atom comes from the word "atomos" in Greek. This idea was easily shot down his ideas because they questioned why they did not fall apart like sand castles if they were all made up of small particles.
Who proposed the first atomic theory? When did he propose this theory? Why was it so easily dismissed?
Mendeleev look for an organization scheme for his textbook. He organized the 60 known elements according to increasing mass and grouped them based on shared physical and chemical properties. He came to a problem when some of the masses didn't fit in his table but seemed to need to be placed in a particular spot based on their properties. His organization is still universally accepted due to his leaving of spaces in his table to include newly discovered elements and how that preceded to help scientists to predict characteristics of unknown elements.
Why did Mendeleev look for an organization scheme for his elements? How did Mendeleev organize his periodic table? What did he get wrong when he organized his elements? Why was his organization of the elements accepted despite this problem?
Rutherford predicted the presence of the neutron because from his experiment he knew there was a positively charged center of the atom called the nucleus, he knew that the mass of the nucleus was larger than the mass of the protons, so he knew there had to be another subatomic particle in the nucleus that wouldn't interfere with the positive charge (NEUTRON!). James Chadwick, eventually found the neutron. His finding advanced atomic theory because it was now known that in an atom the mass of the protons and neutrons in the nucleus equal the nucleus' mass. They believe that the purpose of the neutron in the nucleus is to shield from same charge repulsion of the protons.
Why did Rutherford predict the presence of the neutron? Who eventually found the neutron? How did finding the neutron advance atomic theory? What do you believe is the purpose of the neutron in the nucleus?
a. The lab table felt less warm because it is a better conductor than the textbook, thus the textbook is a better insulator. Insulators do not take energy away from us quickly, thus it feels warmer than a conductor which removes more energy from us b. The term cold is the absence of heat thus, it is measured based on how much heat energy is absent from the original temperature of the object. Specific heat has a direct relationship with objects conductivity. If an object has a lower specific heat it is a better conductor, and if it has a higher specific heat the object is a better insulator. Thus, if given a table of elements, those with lower specific heats would be the better conductors.
Why did the lab table feel colder to your hand than your textbook? What does the term cold truly mean? How do we measure cold? How does specific heat relate to whether a material is a good insulator or conductor of heat? If you were given a list of specific heats, how would you tell which material was the best conductor?
Fahrenheit was the first glass blower, thus he was able to make the bore the most accurate, so it was universally adopted due to its high accuracy. Daniel Fahrenheit wanted to discover a temperature lower than the 0°C on the Celsius scale, which is simply the freezing point of water. So, he established 0°F by creating a solution of equal parts water, salt, and ice to determine a lower temperature. One advantage of his scale is that the scale is more accurate due to the fact that it has more and smaller increments.
Why was the Fahrenheit scale the first temperature scale universally adopted? What is the scale based upon? What is one advantage that this scale has over the Celsius scale?
There are 4 significant figures in the first measurement and 3 in the second. The accuracy for smaller objects is greater in the second tool because it is more accurate to for measurements going below single digit numbers, as it reaches to the hundreds place. The second measurement is more accurate for larger numbers, which is why it is preferred due to the fact it can develop more on point representations of greater quantities, and would be more cost efficient than the more accurate and in depth measuring tool that is presented in the first measuring tool.
You are given two measurements, 203600 and 2.03. How many significant figures are there in each measurement? What can you tell me about the accuracy of each measuring device? Why would use the first device be preferred to the other?
