Ch. 3 Concept check Test your understanding Same thing as Ch. 2, answers in black and my thoughts in red.

Concept Check 3.1 Question #1 Electronegativity is the attraction of an atom for the electrons of a covalent bond. Because oxygen is more electronegative than hydrogen, the oxygen atom in H2O pulls electrons toward itself, resulting in a partial negative charge on the on the oxygen atom and a partial positive charges on the hydrogen atoms. Atoms in neighboring water molecules with opposite partial charges are attracted to each other, forming a hydrogen bond.

Concept Check 3.1 Question #2 The hydrogen atoms of one molecule , with their partial positive charges, would repel the hydrogen atoms of the adjacent molecule.

Concept Check 3.1 Question #3 The covalent bonds of water molecules would not be polar, and water molecules would not form hydrogen bonds with each other. There would be weak cohesion, surface tension, adhesion, low boiling point, and temp. would change quickly.

Concept Check 3.2 Question #1 Hydrogen bonds hold neighboring water molecules together. This cohesion helps the chain of water molecules move upward against gravity in water-conducting cells as water evaporates from the leaves. Adhesion between water molecules and the walls of the water conducting cells also helps counter gravity.

Concept Check 3.2 Question #2 High humidity hampers cooling by suppressing the evaporation of sweat. Remember, when molecules move fast, they are “hot”. If the fast ones leave, the slow ones stay behind. The slow ones are the “cool” ones that you feel. If the air is saturated with water, the fast ones cannot leave. So you are stuck with the “hot” molecules.

Concept Check 3.2 Question #3 As water freezes, it expands because water molecules move farther apart in forming ice crystals. When there is water in a crevice of a boulder, expansion due to freezing may crack the boulder.

Concept Check 3.2 Question #4 A liter of blood would contain 7.8 x 1013 molecules of ghrelin (1.3 x 10-10 moles per liter x 6.02 x 1023 molecules per mole).

Concept Check 3.1 Question #5 The hydrophobic substance repels water, perhaps helping to keep the ends of the legs from becoming coated with water and breaking through the surface. If the legs were coated with a hydrophilic substance, water would be drawn up them, possibly making it more difficult for the water strider to walk on water.

Concept Check 3.3 Question #1 105 or 100,000 Every number you move on the pH scale is times 10, either ten times more or ten times less 1 number = x 10 = (10) 2 numbers = 10 x 10 = (100) 3 numbers = 10 x 10 x 10 = (1,000) 4 numbers = 10 x 10 x 10 x 10 = (10,000) 5 numbers = 10 x 10 x 10 x 10 x 10 = (100,000)

Concept Check 3.3 Question #2 [H+] = 0.01 M, which is 10-2 M, so pH = 2

Concept Check 3.3 Question #3 CH3COOH  CH3COO- + H+ CH3COOH is the acid (the H+ donor) and CH3COO- is the base (the H+ acceptor)

Concept Check 3.3 Question #4 The pH of the water should decrease from 7 to about 2 pH of water 10-7 but you are adding 10-2 with no buffer present in solution The pH of the acetic acid solution will decrease only a small amount, because the reaction shown for question 3 will shift to the left, with CH3COO- accepting the influx of H+ and becoming CH3COOH molecules We have a buffer at work Remember at equalibrium the arrows go both directions

Label a hydrogen bond and a polar covalent bond in this figure Label a hydrogen bond and a polar covalent bond in this figure. How many hydrogen bonds can each water molecule make? Each water molecule can make 4 hydrogen bonds with neighboring molecules

Describe how different types of solutes dissolve in water Describe how different types of solutes dissolve in water. Explain the difference between a solution and a colloid. Water molecules will form a hydration shell around the ions. Polar molecules dissolve as water molecules form hydrogen bonds with them and around them. Solutions are homogenous mixtures of solute and solvent. Colloids form when particles that are too large to dissolve remain suspended in a liquid.

Explain how increasing amounts of CO2 dissolving in the ocean leads to ocean acidification. How does this change in pH affect carbonate ion concentration and the rate of calcification. H2O will react with CO2 to form carbonic acid H2CO3 can become H+ and HCO3- That loose H+ is the problem It will combine with CO32- and tie it up There is less calcium carbonate for coral

Next part is…………… Ch. 3 Test your understanding

#1 D When water vaporizes or evaporates, the hydrogen bonds would be breaking, not forming. The release of water into the air helps to cool the body by releasing heat. The opposite would be a steam burn. Water goes from vapor to liquid and the heat is released, ON YOUR SKIN! Ouch! Also remember the speed of molecules and temp. if the fast ones (high temp) leave (evaporate) the slow ones are left behind (lower temp.)

#2 B Easy question

#3 C Which would not dissolve in water? Something that is not polar, so, there is no attraction.

#4 E The same number of molecules are needed for 1:1 ratios. Daltons and grams are by weight. Not all molecules weigh the same and volume is silly. Atoms in molecules can vary dramatically but molecules in a mole are 6.02 X 1023

#5 C Think negative logarithms -(-4) = 4 The questions is asking H+ ions and not OH- ions

#6 A [H+][OH-] = 10-14 Figures for both acid and base should add up to 10-14 [10-4] [10x] = 10-14 So, -4 + -10 = -14

#7 E

#8 D Figure out the molecular weight of molecule 2-C (12) = 24 4-H (1) = 4 2-O (16) = 32 24 + 4 + 32 = 60 daltons 60 g There are 60 grams of acetic acid in a 1M solution To fix solution, put 60 g in flask, fill with H2O till 1L We want a .1 M solution so we would use 6 grams But we want 10 L, not one L, so times it (6g) by 10 That gives you an answer of 60g

#9 All you have to do is draw an atom of K and an atom of Cl Put a hydration sphere around each If the atom is positive, all of the O in the water molecules will be facing it If the atom is negative, all of the H in the water molecule will be facing it

#10 Both global warming and ocean acidification are caused by increasing levels of CO2 in the atmosphere, the result of the burning of fossil fuels. Both have CO2 that will react with H2O to form carbonic acid. This is where the problem begins.

#11 Due to intermolecular hydrogen bonds, water has a high specific heat (the amount of heat required to increase the temperature of water, by 1 degree C). When water is heated, much of the heat is absorbed in breaking hydrogen bonds before the water molecules increase their motion and the temperature increases. Conversely, when water is cooled, many H bonds are formed, which releases a significant amount of heat. This release of heat can provide some protection against freezing of the plants leaves and protects cells from damage.

#12 We would like to know if life could exist on other planets where conditions are extreme. If we have organisms that can survive in super harsh environments on earth, then maybe there are organisms on other planets that could survive too.

#13 Design an experiment

#14 Inquiry

#15 What would you do?

#16 Essay