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biology unit 3
| Question | Answer |
|---|---|
| In water molecules, where do the electrons spend most of their time? | near the oxygen |
| What type of molecule is water? | polar molecule, unevenly distributed charge |
| What type of bonds do water make because of its polarity? | hydrogen bonds |
| What are the four properties of water that makes it essential for life? | Cohesive behavior, ability to moderate temperature, expansion upon freezing, versatility as a solvent |
| What is cohesion | the ability to hold water molecules together via hydrogen bonds |
| What does cohesion result in? | high surface tension |
| What is adhesion? | attraction between different substances |
| What is kinetic energy? | the energy of motion |
| How does water moderate its temperature? | it absorbs large amounts of heat only with a slight change to its own temperature |
| What is thermal energy? | kinetic energy associated with random motion of atoms or molecules |
| what does temperature represent? | average kinetic energy of molecules in a body of matter |
| What is heat? | thermal energy transfer from one body of matter to another |
| What is a kilocalorie and how much is in one kcal? | food calories, 1,000 cal |
| What is a calorie? | the amount of heat required to raise the temperature of 1g of water by 1 degree. it is also the amount of heat released when 1g of water is cooled by 1 degree |
| what is a joule and how much is it? | unit of energy, 1j = .239 cal |
| What is specific heat? | the amount of energy that needs to be gained/lost for 1g of that substance to change by 1 degree C |
| what is the specific heat of water? | 1 cal/(g x c) |
| Why does water resist changing its temperature? | because of its high specific heat |
| What can waters high specific heat be traced to? | hydrogen bonding, heating is absorbed/released when bonds break/form |
| What does water's high specific heat minimize? | temperature to permit life |
| What is evaporation? | transformation of a liquid to gas |
| What is heat vaporation? | the heat of a liquid must absorb 1g to be converted to gas |
| what is evaporative cooling? | as liquid evaporates, its remaining surface cools |
| How do molecules of water evaporate? | water molecules with the greatest kinetic energy leave as death |
| Is water less dense as a solid or liquid? | solid |
| What is crystalline lattice? | water molecules at 0ylstac |
| How is ice less dense? | the hydrogen bonds are far enough apart to make it |
| When is water densest? | 4 C |
| What is a solution? | a liquid that is a completely homogenous mixture of substances |
| What is a solvent? | the dissolving agent of a solution |
| What is a solute? | the substance that is dissolved |
| What is an aqueous solution? | when water is a solvent |
| Why is water a versatile solvent? | polarity |
| What is a hydration shell? | When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules |
| What is a hydrophilic substance? | a substance that has an affinity for water |
| what is a hydrophobic substance? | a substance that does NOT have an affinity for water |
| Why are oil molecules hydrophobic? | they have non polar bonds |
| What is molecular mass? | sum of masses of all molecules in an atom |
| What are molecules measured in? | moles (mol) 6.02 x 10^23 = 1 mol |
| what is molarity? | number of mols of solute per liter of solution |
| A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other | true |
| The hydrogen atom leaves its electron behind and is transferred as | a proton, or hydrogen ion (H+) |
| The molecule that lost the proton in a hydrogen atom is now a | hydroxide ion ( OH-) |
| The molecule with the extra proton in a hydrogen atom is now a | hydronium ion (H3O+) though it is often represented as H+ |
| Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed | true |
| what is an acid? | a substance that increases H+ concentration of a solution |
| what is a base? | a substance that reduces H+ concentration of a solution |
| Strong acids and bases dissociate completely in water | true |
| Weak acids and bases reversibly release and accept back hydrogen ions, but can still shift the balance of H+ and OH- away from neutrality | true |
| In any aqueous solution at 25C degrees , the product of H+ and OH- is constant and can be written as | [H+][OH-] = 10^-14 |
| The pH of a solution is defined by the negative logarithm of H+ concentration, written as | pH= -log[H+] |
| For a neutral aqueous solution, [H+] is | 10^-7, so pH=-(-7) = 7 |
| Acidic solutions have pH values | less than 7 |
| Basic solutions have pH values | greater than 7 |
| What is a buffer? | substances that minimize the concentration of H+ and OH- in a solution |
Created by:
gigib0805
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