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72 Cards in this Set
- Front
- Back
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What is the biological medium on Earth
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Water.
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What percent of water are living cells?
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70%-95%.
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How much of earth is covered by water?
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3/4.
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What does water's unique behavior depend on?
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Its structure and the interaction of its molecules.
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What does the polarity of water molecules result in?
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Hydrogen bonding.
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What are water molecules shaped like?
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A V.
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Why does oxygen pull the electron pair closer to itself?
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Oxygen is more electronegative than hydrogen.
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In water molecules, what kind of charge do hydrogens acquire?
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A partial positive charge.
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What kind of molecule is water?
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It is a polar molecule.
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Why do water molecules attract each other?
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The slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of a nearby molecule.
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How many emergent properties of water are there?
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There are 4.
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What part of water do organisms depend on in particular?
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The cohesion of water molecules.
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What is cohesion?
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Hydrogen bonds holding the water molecules together.
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What do hydrogen bonds do frequently?
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They form, break, and reform frequently.
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What is adhesion?
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Water's tendency to cling to other substances that are polar or partially polar.
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What two things are responsible for the movement of water up the plant?
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Adhesion and cohesion.
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What two things are the result of the attractive forces of hydrogen?
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Capillary action and surface tension.
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What is surface tension?
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A measure of the difficulty on breaking or stretching the surface of a liquid.
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What is kinetic energy?
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The energy of motion.
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What is heat?
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A measure of the total quantity of kinetic energy due to molecular motion in a body of matter.
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What is an important consideration when talking about heat and why?
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Mass: The greater the mass, the greater the heat.
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How does water moderate air temperature?
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Absorbing heat from air that is warmer and releasing the stored heat to air that is cooler.
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What is temperature?
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A measurement of the average kinetic energy of a substance.
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What scale does science use to measure temperature?
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The Celsius scale.
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What is the "relative" specific heat of water?
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A high specific heat.
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What is 1 calorie?
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The energy required to raise 1g of water 1 degree celsius.
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What is one calorie equal to?
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1 calorie = 4.184 joules.
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What does the specific heat refer to?
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The amount of energy required to raise the temperature of 1 gram of a substance 1 degree celsius.
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What is the heat of vaporization?
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The amount of energy that must be absorbed by 1g of liquid water at 100 degrees celsius to change 1g of water vapor at 1 degree celsius.
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What must happen for water to evaporate?
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Hydrogen bonds must be broken, which requires energy.
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Why does evaporative cooling occur?
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The molecules leaving the liquid are those with higher kinetic energy. Molecules that remain have a lower kinetic energy (hence cooler).
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What does water do as it freezes?
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It expands.
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What does water do as it cools down to 4 degrees celsius?
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It contracts.
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At what temperature is water densest?
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4 degrees celsius.
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What is the heat of fusion of water?
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79.7 cal/g or 333.5 J/g.
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When water begins to freeze, what happens?
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The molecules do not have enough kinetic energy to break hydrogen bonds.
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What happens as the crystalline lattice forms in frozen water?
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Each water molecule forms a maximum of 4 hydrogen bonds.
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What does the expansion of water contribute to?
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The fitness of the environment for life.
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The expansion of water prevents deep bodies of water from doing what?
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Freezing solid from the bottom up.
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What happens because ice is less dense that liquid?
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It forms on the surface first.
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What happens as water freezes?
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It releases heat to the water below and insulates it.
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What is a solution?
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A homogeneous mixture of two substances.
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What is a dissolving agent called?
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A solvent.
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What is a solute?
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The substance that is dissolved.
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What is an aqueous solution?
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One in which water is the solvent.
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What happens in a solution?
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The solute is broken down to the ionic or molecular level.
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What happens if an ionic crystal is dissolved?
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Positive and negative ions go into the solution.
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What is the negative oxygen region of the polar water molecule attracted to?
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The positive ion.
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What is the positive hydrogen region of the polar water molecules attracted to?
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The negative ion.
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In a solution, what do the surrounding water molecules do?
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They shield the positive and negative ions from one another.
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What is a hydration shell?
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The water molecules surrounding ions in a solutions.
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What do hydrophilic substances do?
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They interact readily with water.
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What do hyrdophobic substances do?
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They repel water.
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What are hydrophobic substances not?
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They are not ionic or polar.
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What is a colloid?
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A stable suspension of fine, solid particles in a liquid.
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How many atoms or molecules are in one mole?
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6.02 x 10^23.
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What is 6.02 x 10^23 called?
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Avogadro's number.
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What is molarity?
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The number of moles of solute per liter of solution.
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What does water dissociate into?
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H+ and OH- ions.
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What does the dissociation of water lead to?
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Acidity and alkalinity.
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What is formed when a hydrogen ion becomes attached to a water molecule?
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A hydronium ion H3O+
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What are acids?
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Acids are proton (H+) donors.
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What are bases?
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Bases are proton acceptors.
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What do strong acids and bases do in water?
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They dissociate completely in water.
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What is used to measure the hydrogen ions (protons) in a solution?
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The pH scale.
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What are buffers?
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Combinations of H+ donors and H+ acceptors that form weak acids or bases.
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What do buffer solutions do?
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They resist changes in pH when acids or bases are added and minimize changes in concentrations of H+ and OH-.
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What are salts?
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Compounds in which the hydrogen atom of an acid is replaced by some other cation.
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How are salts formed?
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Reactions of acids with bases.
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What are electrolytes?
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Salts, acids, and bases that conduct electricity when in a solution.
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What is acid precipitation?
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Rain, snow, or fog with a pH below 5.6.
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What does acid precipitation result from?
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A reaction in the air between water vapor and sulfur oxides and nitrogen oxides produced by the combustion of fossil fuels.
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