60 terms

General SAGE REVIEW 2017-2018


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How do the atoms and elements on earth compare those on the far side of the universe? We say that all matter in our universe has a "common origin". What does that mean?
Elements and matter are consistently the same throughout the universe. Matter is theorized to have originated in an initial explosion where the simplest element, hydrogen, was formed. As hydrogen spread out through empty space gravity "clumped" the hydrogen gas into large massive clouds. When the clouds were massive enough, and pressure in the center of the clump was sufficient, hydrogen atoms began to fuse together in a nuclear fusion reaction to create helium. A star is born. When all the hydrogen has fused into helium, the fusion reactions stop, cooling and collapse occurs, and when pressure is sufficient helium then begins to fuse into other elements. Lithium elements to Iron elements are formed in this second stage. As helium is used up and elements are created and thrown into space, the star cools and collapses again. This final stage creates so much pressure as it cools that the star rebounds and explodes, creating the remaining elements found in the universe and sending them out into space traveling near the speed of light. Elements are formed from the stars, a "common origin."
What is the current theory for the origin of our universe? What evidence do we have to support this theory?
Big Bang Theory. Evidence supporting the big bang includes 1) the disproportionately large amount of hydrogen found in the universe 2) the universe is expanding, as shown by the shift in light frequencies due to the Doppler Effect, or the red shift and 3) vast amounts of gamma radiation (also called "cosmic background radiation") are found in space, which may have originated from an initial explosion, or "bang".
What is the most abundant element in our universe? Where do all the other elements come from? What is the element of life?
Hydrogen is the most abundant element in the universe. Other elements can be formed by fusion, etc. Carbon is the element of life.
Light elements are those with small nuclei. Where are these elements located on the periodic table? Heavy elements are those with big nuclei. Where are these elements located on the periodic table? The universe is composed mostly of __________ (light /heavy) elements. Why?
The periodic table is ordered by atomic number or the number of protons. Increasing the number of protons and neutrons found in an atom increases its mass. Light elements are found at the beginning of the periodic table with hydrogen-1. Heavy elements are found toward the end of the periodic table.
How did the following scientists contribute to our current understanding of the atom. (Democritus, Dalton, Thomson, Millikan, Rutherford, Bohr, Chadwick). Is our current model "perfect "?
Democritus: Idea of the atom, cannot be cut smaller. Did not have access to instrumentation to further his model.

Dalton: Solid sphere model, Father of Atomic Theory.

Thomson: Used cathode ray to determine existence subatomic particles and the charge/mass ratio of the electron. "Plum pudding" model.

Millikan: Used oil drop experiment to measure the charge on an electron.

Rutherford: Used the gold foil experiment to discover the nucleus of the atom. Proved "Plum pudding" model incorrect. Didn't account for lack of electron collisions.

Bohr: Improved Rutherford's planetary model and included emission spectra from hydrogen gas to explain electron energy levels.

Chadwick: Discovered the neutron and its location in the nucleus of the atom.
Describe the location, size, and charge of each of the major particles in an atom. DRAW a simple picture of an atom.
Protons and neutrons are in the nucleus, while electrons are in orbits. (See chart for more info).
Describe the general structure of the atom.
Atoms are made up mostly of empty space, however most of the mass is concentrated in the nucleus, as proven by Rutherford's gold foil experiment.
If an atom with no charge has 12 protons, how many electrons will it have? What do we call an atom that is no longer neutrally charged? If an atom gains an electron, it becomes which type of ion with what charge?. If an atom loses an electron, it becomes which type of ion with which charge?. How can you predict how many electrons an atom will gain or lose?
12 protons would provide 12+ charge, you would need 12 electrons providing 12- charge to make the atom neutral. Atoms that gain charge are called ions. Gaining electrons gives negative charge (anion formation). Losing electrons leaves an atom with positive charge (cation formation). The number of electrons in this outer energy level is normally 8 and atoms will gain or lose electrons to try to have a full octet.
What is "mass number"? How do you calculate it? If an atom has 6 protons and 6 neutrons, then the what is the atomic number and what is the atomic mass? What is this element? Write the correct symbols.
The element is carbon. Mass number = total number of protons + neutrons. Atomic number is the number of protons.
How many objects are in a dozen? How many in a pair? How many objects are in a mole?
12 is a dozen, 2 in a pair, and 6.02x10^23 is a mole.
What does amu stand for? One water molecules has a mass of 18 amu. Since this is way too small to measure in the lab. How much would one mole of water molecules weigh in grams?
AMU = Atomic Mass Unit. One mole of water has a mass of 18 grams. The scale of the mole was designed to have the same numerical measurement in grams as an atom in atomic mass units. 1 mol of water = 18 grams.
What is the molar mass of the following?
Ca(NO3)2, CuO, CH4 , C6H12O6
164.088 (g/ mole), 79.55 (g/ mole), 16.05 (g/ mole), and 180.18 (g/ mole) respectively.
What do we call atoms that have the same number of protons (identity) but different numbers of neutrons (mass)?
Atoms with the same number of protons but different overall masses are called isotopes.
How many neutrons does Chlorine-35 have? How many neutrons does Chlorine-37 have? How many protons do they have?
Chlorine 35 has 18 neutrons and 17 protons. Chlorine 37 has 20 neutrons and 17 protons.
Vertical columns on the periodic table are called _________ or ________. Horizontal rows on the periodic table are called __________. How can you tell which elements will have similar properties? Why do they have similar properties?
Vertical columns = groups or families. Horizontal rows = periods. Elements with similar properties have the same number of valence electrons. These similar elements are found in the same group.
Match the following descriptions with their groups on the periodic table.
a. Element Bob tends to steal an electron when bonding.
b. Element Betty explodes when I put it in water.
c. Element Snobby refuses to bond with anything.
Bob is a Halogen, Betty is an alkali metal, and Snobby is a noble gas.
What is an "energy level"? Light (photons) are involved whenever an electron changes energy levels. Light is absorbed when _____________________. Light is emitted when ________________.
The energy level of an atom is a measure of the relative amount of energy absorbed by electron waves. Energy is absorbed or released by electron waves in the form of photons or quanta (small packets of energy). Light is absorbed as electrons increase in energy. Light is emitted when electrons decrease in energy.
The bigger a WAVELENGTH is, the ______ energy it has. We say that wavelength and energy are _________ related.
less, inversely
The higher the FREQUENCY is, the ________ energy it has. We say that frequency and energy are _______ related.
more, directly
What do we call the little "packets" of energy that our universe is made out of? (The smallest measurable amount of energy that make everything else.)
Small measures of energy are described as quanta (photons).
What is a bright line emission spectrum? How can we use them to identify unknown elements?
When the light emitted by a specific element is passed through a prism, its emission spectra is observed. Since the electrons moving between energy levels are unique for each element, the spectra is different for every element and can be used to identify unknown elements.
If an electron makes a really BIG jump up in energy levels, it means that a (lot/little bit) of energy was needed. What color of light was probably absorbed? ___________ If an electron makes a really SMALL jump down in energy levels, it means that a (lot/little bit) of energy was released. What color of light will we see if we are standing nearby? ________
Lot, purple, little bit, red
Each element emits/absorbs only very specific colors of light. Why does this happen? How does this support the theory that electrons can only occur in allowed energy levels?
As electrons absorb light energy, electron waves expand out to higher energy orbitals. Each element has a different number of electrons, and each element's ground state of electrons is different, so every element will have its own unique electron movement between energy levels as energy is absorbed. With every jump in energy level, a specific frequency of light is absorbed, as electrons fall back to original energy levels the same frequency of light is released.
What do we call it when two nucleuses join together? What do we call it when one nucleus splits apart?
Fusion, the nuclei of elements smaller than iron may fuse to create more stable nuclei. Fission, the nuclei of elements larger than iron may divide to form more stable, smaller nuclei.
What are the three kinds of radioactive radiation. Say what they are made of, how much energy they have, and how we can stop them.
Alpha particles - released when nucleus is too big, same as a helium nucleus, high energy with high mass, can be stopped with paper.

Beta particles - released when there are too many neutrons in the nucleus to create a new proton, same as an electron, high energy low mass, can be stopped with metallic foils.

Gamma radiation - released anytime there is a change in the nucleus, high energy, no mass, pure photons, not fully stopped with thick concrete or thick lead.
What is a half-life?
Time needed for one half of a radioactive sample to decay.
Give two examples of how radiation is harmful.
Radiation strips atoms and molecules of electrons, changing chemical processes in the body.

High energy radiation can cause burns, lesions, and other harmful effects.
Give two examples of how radiation is helpful.
High energy radiation can be used to kill harmful bacteria on food or tools increasing the time it takes for food to spoil, and preparing sterile surgical tools.

Harmless radioisotopes can be added to the bloodstream and detected as they travel through the body to create detailed images of internal organs which is used to diagnose potential problems.
Which electrons are involved in bonding? What do we call these electrons? What is a quick way to find out how many of these electrons an atom has?
Outer level electrons are involved in bonding. We call these electrons, valence electrons. Valence electrons can be determined by the group number of the element on the periodic table.
What is a "family" on the periodic table? What else do we call it? Why are these elements so similar to each other?
Families are the groups or columns on the periodic table. Each member of a group has the same number of valence electrons and tend to have very similar bonding processes.
Which atoms form positive ions? (are happy to get rid of electrons) Why? How can you predict the charge the ion will have?
Metallic atoms readily release electrons to form positive ions. The effective strength of the nucleus is weaker than other elements in the same period. The charge of an ion is determined by how many electrons are lost or gained in order to have the outer electron shell filled.
Which atoms form negative ions? (are happy to gain extra electrons) Why? How can you predict the charge the ion will have?
Nonmetallic atoms form negative electrons. The effective strength of the nucleus is sufficient to attract the electrons needed to fill the outer electron shell. The charge is determined by how many electrons are needed to fill the outer shell.
What is a chemical bond? Name the three types of chemical bonds and describe them. Which bonds are the strongest?
Chemical bonds are the electrostatic attractions between particles.

Ionic bonds form as one particle loses electrons to become a positive ion, and bonds to another particle that has gained electrons to become a negative ion.

Covalent bonding involves overlapping electron orbitals to share electrons between two particles.

Metallic bonding involves delocalized electrons throughout a lattice to create a sea of electrons that contain metallic cations.

Bond strength increase as the charge and attractive forces involved increase. The strongest bonds have the strongest attractive forces.
What combinations of atoms tend to form ionic bonds? Where are they on the periodic table?
Nonmetals form ionic bonds with metals. Nonmetals are above the staircase, metals below.
What combinations of atoms tend to form covalent bonds? Where are they on the periodic table?
Nonmetals form covalent bonds with nonmetals. Nonmetals are found above the staircase.
What combinations of atoms tend to form metallic bonds? Where are they on the periodic table?
Metallic bonds are formed between metals. Metals are found below the staircase.
What is the difference between a physical property and a chemical property?
Physical properties describe a substance without changing its makeup or composition. Chemical properties describe a substance's characteristics that involve changes in makeup or composition.
Name these compounds:
1) CaO
2) MgCl2
3) Fe2O3
4) CO2
5) SO3
1) Calcium hydroxide
2) Magnesium Chloride
3) Iron (iii) oxide
4) Carbon dioxide
5) Sulfur trioxide
Write these formulas:
1) Sodium Oxide
2) Potassium Bromide
3) Copper (II) Oxide
4) Carbon Tetrachloride
5) Nitrogen Trioxide
1) Na2O
2) KBr
3) CuO
4) CCl4
5) NO3
There are only about 100 known elements in the universe, yet there are BILLIONS of different substances. How is this possible?
Every combination of substances is unique. For example, if we only use H and O, we could make many, many combinations: one H with one O, or two H with one O, etc.
H2O (water) and H2O2 (hydrogen peroxide) are both made of hydrogen and oxygen. Do they behave the same?
No, their bonding is different, composition is different, and properties are very different.
Draw Lewis Structures for water (H2O), methane(CH4), and ammonia (NH3). Predict their shapes based on your drawing.
Water is bent, methane is tetrahedral, and ammonia is trigonal pyramidal (draw these shapes).
What is polarity? State whether water (H2O), methane (CH4), and ammonia (NH3) will be polar and why.
Polarity occurs when the distribution of charge in a molecule is uneven resulting in a positive pole or side and a negative pole or side. Methane is balanced symmetrically so it will be nonpolar. Water is not balanced, one side has lone pair electrons and the other has hydrogen atoms, it will be polar. The ammonia is the same, one part has a lone pair, and the other side has hydrogen atoms, it will be polar.
Water is very unique because it has lots and lots of lone pairs on one molecule attracted to the hydrogen atoms of another molecule forming hydrogen bonds. What is a hydrogen bond? How does it compare to REAL bonds? How does it compare to other Intermolecular Forces?
It is where the polarity of molecules with nitrogen, oxygen, and fluorine bonded to hydrogen becomes very strong. This polarity results in the lone pair of one molecule attracting to the hydrogen of another molecule and forming a very strong attraction. Hydrogen bonds are not as strong as a true ionic or covalent bond. The attractions of hydrogen bonding is stronger than normal dipole attractions or dispersion attractions.
What happens during a chemical reaction? What is the difference between a physical change and a chemical change? How can you tell that a chemical change has happened?
Bonds of reactant compounds break and atoms rearrange to form new compounds. Physical changes result in no formation of new compounds. Chemical changes result in the formation of new substances. The formation of new compounds usually result in one or more of the following: Color change, formation of a gas, precipitate, a new odor, temperature change.
Do products have the same properties as the reactants they came from? Why or why not?
No. The bonding in the products is different. Electron configurations are different. New properties result.
The number (and identity) of _________ stays the same during a chemical reaction. The atoms are just _____________. This can be used to explain the law of ___________________.
Atoms, rearranged, conservation of mass.
Bob decomposes hydrogen peroxide in the lab according to the following reaction: 2 H2O2 → 2H2O + O2 He collects the water and the oxygen produced and weighs them. He started with 15 grams of hydrogen peroxide. At the end of the lab he has 8 grams of water and 7 grams of oxygen. Does this support the conservation of mass? Explain.
Yes, the mass at the beginning was 15 grams, The total mass of the products is still 15 grams (7+8). Mass was conserved.
What do the numbers in front of the chemicals tell us?
The coefficients relate the number of moles required to balance the reaction and produce products. The reaction must always be balanced in order to reflect the conservation of mass.
Equation: 3 NO2 + H2O → 2 HNO3 + NO
If I have 5 moles of water, how many moles of NO can I produce?
The ratio of water to NO in the reaction is 1 to 1. So 5 moles of water should produce 5 moles of NO.
If heat energy is going into the system, this is called ____________. If heat energy is lost from the system, this is called __________.
Enter = Endothermic ; Exit = Exothermic
What are five things that can be done to increase the rate of a reaction (speed it up). Say WHY each one helps. (Use the terms "frequency of collisions" and "energy of collisions" in your explanations.)
Increasing concentrations, stirring, surface area, and temperature allow for more frequent collisions which increases reaction rates.
Sketch a picture of NaCl (table salt) before and after being dissolved by water. Be sure to show which particles are attracted to each other and where.
The positively charged hydrogen on the water is attracted to the negative chloride ions. The negatively charged oxygen on the water is attracted to the positive sodium ions.
If you had 35 mL of a 3.0M HCl solution, how would you calculate the number of moles of HCl present?
The capital M indicates moles per liter. So we have 3 moles of HCl in every liter. 35 milliliters is equivalent to 0.035 liters, as a milliliter is one one thousandth of a liter. Multiplying 0.035 liters by 3 moles per liter will provide the number of moles of HCl present, a total of .105 moles of HCl.
Define the following words: Hydrogen Ion, Hydroxide Ion , Hydronium Ion, pH scale.
Hydrogen Ion - A hydrogen atom that has lost its electron, a proton. H+

Hydroxide Ion - A water molecule that has lost a hydrogen ion, OH-

Hydronium Ion - A water molecule that has gained an extra hydrogen ion, H3O+

On the pH scale, values between 0 and 7 are acidic. Values between 7 and 14 are basic. When pH equals 7, hydronium and hydroxide concentrations are equal and the solution is neutral. The scale spans from 0 to 14.
How are H3O+ and H+ ions related?
H+ ions present in water are usually attached to a water molecule resulting in H3O+ ions. If aqueous, H+ and H3O+ symbols both indicate dissolved hydrogen ions.
How are OH- and H+ ions related? What does "pH" stand for? What does "pOH" stand for?
When combined H+ ions and OH- ions form a water molecule. If a water molecule is dissociated into ions H+ and OH- result.

pH is "the negative log of H+ concentration" written mathematically as -log[H+].

pOH is "the negative log of OH- concentration" written mathematically as -log[OH-].

pH + pOH = 14
If a solution has too many hydrogen ions floating around, then it is _________. If a solution has perfectly balanced hydrogen ions and hydroxide ions, then it is __________. If a solution doesn't have enough hydrogen ions floating around, then it is __________.
Acidic, neutral, basic
Describe a titration. (What chemicals go where and why?) What do we use titrations for?
A titration is a controlled neutralization reaction used to determine chemical levels of solutions of unknown concentrations. A chemical of known concentration that can neutralize the unknown solution is placed in a burette and dispensed in a controlled fashion into the flask containing the unknown solution. An indicator chemical is added to the unknown chemical to indicate the point at which the chemical is neutralized. Titrations are used to determine the concentrations of solutions.
What is the concentration of a 50 mL solution HCL which is neutralized by 25 mL of a 0.5M solution of Ca(OH)2?
0.52 M is the concentration of the acid. (SHOW YOUR WORK AND CALCULATIONS for credit).

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