Exam 1 - Chapter 3 Flashcards
life sustaining properties of water
- cohesive and adhesive nature
- ability to moderate temperature
- expansion upon freezing
- versatility as a solvent
cohesive and adhesive nature
- cohesion=attraction between molecules of same type
- adhesion=attraction between different substances
- surface tension=measure of how hard it is to break surface of liquid
temperature moderation
water only liquid to be in three different states
temperature
measure of average molecular motion
specific heat
amount of heat required for 1g of a substance to change its temp by 1C
calories
amount of heat needed to raise 1g of water by 1C
high spcific heat of water
heat is absorbed to break bonds, heat is released when bonds form
heat of vaporaziation
quantity of heat a liquid must absorb for 1g to be converted to gas
evaporative cooling
as liquid evaporates its remaining surface cools
expansion on freezing
ice is less dense than liquid water, hydrogen bonds in ice are more ordered, molecules are farther apart, bonds are more stable, ice insulates water below
versatile solvent
- Solute is dissolved in a solvent >solution
- Solute – a dissolved substance
- Solvent – dissolving agent
- Solution – uniform mixture of solute completely dissolved in solvent
- Aqueous solution – solution where water is the solvent
- Chemical bonds do not form between molecules of solute and solvent
- Hydration shell forms around solute keeping it in solution
solute concentrations in aqueous solutions
- molarity (M) = moles/L
- 1 mole = 6.02 x 10^23 particles = molecular mass of substance (g) = formula weight (FW) in grams
- M = moles/L = (g/MW)/L = (g/FW)/L
pH and Buffers
- water dissociates into hydroxide ions (OH-) and hydrogen ions (H+)
- numeric definition of pH = -log [H+]
- pH scale is an inverse log ranging from pH 0-14
- [H+][OH-] = 1 x 10-14
