Chapter 3 Flashcards
Why is water polar?
Opposite ends of the molecule have opposite charges.
Define cohesion. How is cohesion beneficial to plants?
The hydrogen bonds collectively hold the substance together. It transports water and dissolved nutrients against gravity in plants. Roots to leaves
Define adhesion. How is adhesion beneficial to plants?
The clinging of one substance to another. The clinging of water to the walls of the cells counters the downward pull of water by gravity.
How does water help moderate temperature?
It can absorb or release a large quantity of heat with only a slight change in its own temperature.
Distinguish between heat and temperature.
Heat is the total kinetic energy due to the molecular motion in a body of matter. Temperature measure the intensity of heat due to the average kinetic energy of the molecules.
Define specific heat.
The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1º C. Water has a high specific heat of 1 cal/g /ºC
What is evaporation cooling?
The molecules with the greatest kinetic energy are the most likely to leave as a gas. Contributes to the stability of temperature in lakes and ponds.
Why does ice float? Why is that important for life?
The hydrogen bonds keep the molecules further apart in ice so that it is less dense than water. It actually expands as it freezes. This allows a stabilization of the temperature of the water below so it does not freeze.
Distinguish among solution, solute and solvent.
Solution is a completely homogeneous mixture of two or more substances. Solute is the substance that is dissolved and Solvent is the dissolving agent of the solution.
What is a hydration shell?
The sphere of water molecules around each dissolved ion.
Distinguish between hydrophilic and hydrophobic.
Hydrophilic is any substance that has an affinity for water. Can be ionic or polar.
Hydrophobic is a substance that has no affinity for water.Substances that are nonionic and nonpolar actually seem to repel water.
Describe the dissociation of water (what is formed).
The separation of a water molecule into a hydrogen ion and a hydroxide ion.
Distinguish between acids and bases (know pH, hydrogen concentration and hydroxide concentration).
H20=H+ +OH-
Water=Hydrogen Ion plus hydroxide ion
Acid- a substance that increases the hydrogen ion concentration of a substance
Base-a substance that reduces the ion concentration of a substance.
PH-the negative logarithm (base) of the hydrogen ion concentration
In any aqueous solution at 25ºC (room temp) the product of the [H+]=10^-7 and [OH-]=10^-7 (Neutral concentrations is product of =10^-14). If we add acid to a neutral solution so [H+] is10^-5 the other is [OH-]10^-9 It is a constant relationship to equal 10^-14
What is a buffer?
Substances that minimize changes in the concentrations of H+ and OH- in a solution.
