AP Biology Essential Chemistry
What is special about carbon that makes it the central atom in the chemistry of life?
-Forms varied and complex molecules -Branches in 4 directions rather than becoming an ion -Makes up living organisms (secondary to water though)
Why is organic chemistry so important in the study of biology?
-Most biological reactions are organic - Different organic molecules can be tested in reactions -Organic chemistry has let us synthesize and analyze various things (ex: petroleum)
Why are small changes in pH so important in biology?
-The changes can affect chemical reactions -Cells' chemical processes are very sensitive to H+ and OH- levels - pH levels in the environment determine where certain plant and animal species can live
1. What is the molarity of a solution formed by mixing 10.0 g of H2SO4 with enough water to make 0.100 L of solution? 2. To prepare 10.5 L of a 2.50 M solution of KOH, how many grams of potassium hydroxide must be used? 3. How many moles of LiBr must be added to .650 L of water to make a 2.0 M solution? 4. What is the molarity of the solution produced when 145 g of NaCl is dissolved in sufficient water to prepare 2.75 L of solution? 5. How many grams of KCl are needed to prepare 0.750 L of a 1.50 M solution? 6. What is the molarity of the solution produced when .594 mol of HCl is dissolved in 0.385 L of water? 7. To produce 3.00 L of a 1.90 M solution of sodium hydroxide, how many grams of NaOH must be dissolved? 8. If 8.77 g of KI are dissolved in enough water to make 4.75 L of solution, what is the molarity of the solution?
1. 1.02 2. 1470 3. 1.3 4. .902 5. 83.9 6. 1.54 7. 228 8. .0111
What is a buffer? Give an example on how they would work in a living organism.
A substance that minimizes pH changes by either accepting or donating H+ ions. An example is carbonic acid in blood; the equilibrium of its dissociation shifts to counter pH changes.
What defines an acid and a base?
Acids increase H+ concentration, bases decrease it
What is the difference between the terms atomic mass and atomic weight?
Atomic mass- total mass of an atom Atomic weight- average mass of all of the atoms of an elements (the isotopes of the type)
Contrast the terms atomic mass and atomic number.
Atomic number- number of protons Atomic mass- total mass of an atom (neutrons+protons)
What determines interactions between atoms? Why are valence electrons important?
Chemical behavior mostly depends on the number of electrons in the valence/outermost shell of an atom. They're important since the valence shell needs to be completed, affecting whether electrons are given away or gained.
Label the diagram below to demonstrate the dissociation of the water molecule and then relate this diagram to the term pH.
Currently neutral pH unless more acids or bases are added. Water is acting as both an acid and a base. If more H+ is added, the pH dips, and if it is taken, it increases.
Contrast the term element with compound.
Elements are substances that cannot be broken down. Compounds are made up of multiple elements and have different properties than the elements.
What is an isotope and what is "special" about radioactive isotopes?
Forms of an element with different numbers of neutrons (same number of protons though) and therefore with the same atomic number but different atomic masses. Radioactives are special since the nucleus decays and gives off energy and particles, allowing them to be used as tracers, daters (for relics), and diagnosers of disease.
Compare and contrast hydrogen bonds and van der Waals interactions.
Hydrogen- noncovalent attraction between a hydrogen and an electronegative atom van der Waals- weak attraction resulting in changing regions of positive and negative charge Same- intermolecular forces, generally weak Different- Hydrogen generally stronger, van der Waals have potential to be incredibly powerful, van der Waals uses nonpolar molecules, and hydrogen is a type of van der Waals
How do ionic bonds compare with covalent bonds?
Ionic- strong bonds between cations and anions involving the transfer of electrons Covalent- strong bonds in which electrons are shared (generally weaker than ionic bonds)
Why is water considered a polar molecule?
Its V-like shape and unequal sharing of electrons give the oxygen region a partial negative charge and the hydrogen regions partial positive charges; this inequality makes it polar
Label the diagram below and define the terms that you label
Nucleus- center of the atom with protons and neutrons Electrons- negatively charged particles around the nucleus Protons- positively charged particles Neutrons- neutrally charged particles
What is acid precipitation and why is it important to living organisms?
Rain, snow, or fog with a pH less than or equal to 5.6. Caused by burning fossil fuels, as released gasses turn cloud water acidic. Ruins environment by lowering ocean pH, removing carbonate from ocean (harms coral reefs), and seeping into and harming trees.
What is special about water and density?
Solid H2O is less dense that liquid water; as water goes from 4 degrees C to 0 degrees, the hydrogen bonds cannot be broken since the molecules are moving too slowly. The crystalline lattice structure forms. Ice is 10% less dense than water at 4 degrees C.
What is the difference between a structural and molecular formula?
Structural- a graphic representation of the types of bonds and the arrangements of the atoms Molecular- the numbers and types of atoms
Define a dynamic chemical equilibrium in terms of quantities of reactants and products. This is a critical concept!
The quantities of products and reactants are stabilized in a ratio; the reactions still occur, but the net concentrations don't change
Describe and contrast the three types of isomers. Draw a sketch of each a. Structural b. Geometric c. Enantiomers
a. -Differ in covalent partenrs - Same molecular formula -Differ in arrangement/location of double bonds b. -Differ in arrangement about a double bond - Same number and types of atoms and bonds -Different spacial arrangement -Creates various geometric structures through arrangements - Can occur when there is a restricted rotation in the molecule c. -Differs in spacial arrangement about an asymmetric carbon - Results in molecules that are mirror images
Define the following terms: a. Chemical bond b. Covalent bond c. Single bond d. Double bond e. Electronegativity f. Nonpolar covalent bond g. Polar covalent bond
a. Attractions between atoms that result from interactions in which valence electrons are shared or transferred; can also form due to opposite charges b. Bonds in which atoms share pairs of electrons c. Bonds in which a single pair of electrons is shared d. Bonds in which two pairs of electrons are shared e. Attraction of a particular atom for the electrons of a covalent bond f. A covalent bond between two atoms of equal electronegativity (electrons shared equally) g. A covalent bond between two atoms with different electronegativities (unequal sharing of electrons)
Know the symbols of the following elements and their charge: a. Carbon b. Hydrogen c. Oxygen d. Nitrogen e. Phosphorous f. Sulfur
a. C +/-4 b. H +1 c. O -2 d. N -3 e. P -3 f. S -2
Explain how these properties of water are related to the phenomena described in the statements below. More than one property may be used to explain a given phenomenon. a. During the winter, air temperatures in the northern United States can remain below 0°C for months; however, the fish and other animals living in the lakes survive. b. Many substances—for example, salt (NaCl) and sucrose—dissolve quickly in water. c. When you pour water into a 25-ml graduated cylinder, a meniscus forms at the top of the water column. d. Sweating and the evaporation of sweat from the body surface help reduce a human's body temperature. e. Water drops that fall on a surface tend to form rounded drops or beads. f. Water drops that fall on your car tend to bead or round up more after you polish (or wax) the car than before you polished it. g. If you touch the edge of a paper towel to a drop of colored water, the water will move up into (or be absorbed by) the towel.
a. High specific heat prevents sudden changes from hurting the fish. Ice's lower density means that when some of the lake freezes, it floats to the surface and acts as insulation for the rest of the lake. b. Water's polarity attracts the Na+ ions and Cl- ions, pulling NaCl apart (adheres to the two ions separately) c. Water adheres to the cylinder and coheres somewhat to itself, resulting in the curved shape. d. High specific heat means that a lot of heat is needed to change temperatures, so a lot of heat is needed for the water to evaporate. Therefore, when it does evaporate, the large amounts of kinetic energy it had to gather also leaves the body's surface. e. Water adheres to the surface and cohesion causes it to merge into a bead. f. Wax is hydrophobic, and using it leaves the surface less polar, weakening adhesion. Therefore, the cohesive forces are relatively stronger and the water beads up more. g. Cohesion causes the water to move up as a group and pull itself up, so to speak (one molecule goes up with multiple), while the water also adheres to the paper towel.
Know both the structural and molecular formula for the following compounds. a. Oxygen gas b. Carbon dioxide c. Glucose d. Phosphate e. Ammonia f. Water
a. O2 b. CO2 c. C6H12O6 d. PO4(3-) e. NH3 f. H2O
Be familiar with each of the following functional groups - know it's chemical compound and the functional properties a. Hydroxyl b. Carbonyl c. Carboxyl d. Amino e. Sulfhydryl f. Phosphate
a. Polar as a result of the electronegative oxygen atom. Attracts water molecules, helping dissolve organic compounds. b. Ketones and aldehydes: can be structural isomers with different properties. All sugar molecules have one carbonyl group. Make molecules water soluble. c. Has acidic properties (source of H+). Covalent bond between O ad H is so polar that hydrogen ions dissociate reversibly. Found in cells as carboxylate, a -1 ion. d. Nitrogen to two hydrogens. When compounded with carboxylic, becomes an amino acid. Acts as a base, picks up protons from acids. In cells, is a +1 cation. e. Sulfur bonded to hydrogen. Can stablize proteins when 2 react, forming a covalent bond and "cross mixing". Cross linking bonds actually control curliness or straightness of hair. f. Acidic. Can react with water and release energy. Phosphate with 3 single and 1 double bond to oxygens. Compounds it is attached to become anions. Key parts of energy molecules like ATP.
For each of the below listed properties of water - briefly define the property and then explain how water's polar nature and polar covalent bonds contribute to the water special property. a. Cohesion b. Adhesion c. Surface tension d. High specific heat e. Heat of vaporization f. Evaporative cooling
a. Property of molecules to stick together with mutual attraction. Water as a liquid is fragile, but cohesion binds H2O molecules to each other and holds them together as a body. b. Attraction between unalike molecules. Water's polarity lets it stick to various surfaces. c. Measure of how hard it is to stretch or break the surface of a liquid. Water has an unusually high surface tension, making it behave as if it were coated in an invisible film. d. Amount of heat that must be gained or lost for 1 gram of a substance to change its temperature by 1 degree C. In this case, since hydrogen bonds must change for the temperature to change (break or form to absorb or release heat respectively), polarity plays a part. Note that it allows water to stabilize its temperature and avoid drastic changes in it. e. Quantity of heat that must be absorbed for 1 g of a liquid to go to gaseous state. The polar hydrogen bonds make it relatively difficult to convert too much at once, as this is also a high requirement. f. As liquid evaporates, the surface of the liquid that it leaves behind is cool. Polarity requires a high specific heat, so when hydrogen bonds leave, a lot of kinetic energy leaves and it feels much cooler.
Define the following terms: a. Solute b. Solvent c. Aqueous solution d. Hydrophilic e. Hydrophobic f. Molarity
a. Substance dissolved in a solution b. Dissolving agent of a solution c. Solution with water as the solvent d. Substance with an affinity for water e. Substance that repels water (nonionic or nonpolar) f. Moles of solute per liter of solution, unit of concentration biologists most often use (for aqueous solutions)