Chapter 2: Water! Flashcards
Why is water so important?
Its the medium of life! Water is also an excellent agent for getting substances into solution.
What type of molecule is water?
Water is a polar molecule due to the polar covalent bonds between oxygen and hydrogen.
What are hydrogen bonds (non-covalent bonds)?
strongest intermolecular bond; occurs between the partially positive hydrogen atoms of one water molecule and the partially negative oxygen atoms of adjacent water molecules
What do hydrogen bonds contribute to?
making liquid water cohesive and its really high surface tension
What are some properties of water?
cohesion, adhesion, surface tension, heat capacity, heat of vaporization, density, solvent
Cohesion
binding between like molecules
Adhesion
binding between unlike molecules
Surface Tension
a measure of how difficult it is to break the surface of a liquid
What is cohesion related to?
surface tension
Why is cohesion important in evaporation?
important in evaporation of water molecules all the way from the roots of plants, up to their leaves. Cohesion prevents gravity from weighing the water molecules back down.
Specific Heat
amount of energy needed to raise temperature of 1 gram of substance by 1ºC
Why does water have a high specific heat capacity?
Heat has to be absorbed to break hydrogen bonds, and heat is released when hydrogen bonds form
▪ This helps keep temperatures relativity steady (heat capacity)
Why does water have a high heat of vaporization?
- Hydrogen bonds between water molecules mean it takes a lot of heat to increase the temperature of water enough to boil (heat of vaporization)
How does high humidity hamper cooling?
by slowing the evaporation of sweat
What phase of water is most dense?
liquid phase
Why is ice less dense?
Hydrogen bonding!
- When water freezes, each molecule forms a stable hydrogen bond with its neighbors
▪ As ice crystals form, the molecules are less densely packed than in liquid water
▪ Because is less dense than water, it floats!
Solution
a liquid consisting of a uniform mixture of two or more substances
Why is water a versatile solvent?
its molecules are polar
Aqueous Solution
polar/charged solutes dissolve when water surround them
Hydrophilic Molecules
polar/charged molecules that can be dissolved by water
Hydrophobic Molecules
nonpolar molecules that are mostly or exclusively made up of nonpolar covalent bonds and do not dissolve in water
Ex: hydrocarbons
