Chemistry of Water Flashcards
What are water molecules made of
A central oxygen atom bonded by covalent bonds to two hydrogen atoms
Water is made of “polar molecules”, this means what?
A water molecule has one end with a slight negative charge and one end with a slight positive charge
What is hydrogen bonding responsible for
Many of waters unusual properties
Why does water dissolve many substances
“Like dissolves like”. Because water is a polar molecule, it dissolves compounds made of ions or polar molecules
What is an example of water dissolving many substances
Water provides a medium in which substances can undergo chemical reactions in living systems. Within living systems, water solutions (such as blood plasma) transport dissolved substances to where they are needed.
Why does water expand as it freezes
Ice is less dense than liquid water. As water freezes, the ice floats on the surface of the denser liquid water below.
What is an example of water expanding as it freezes
When the air temperature drops, a small amount of water freezes at the lakes surface. A solid cap of ice forms, which traps heat in the water below, preventing the water from freezing further and protecting aquatic organisms from freezing
Why does water take part in life’s chemical reactions
Nearly all of life’s chemical reactions occur in the watery solution that fills and bathes cells. In addition, water is either a reactant in or a product of many of life’s chemical reactions
What is an example of water taking part in life’s chemical reactions
In photosynthesis, plants use the sun’s energy to assemble food using carbon dioxide and water. Oxygen, which nearly all organisms require, is released
Why is water cohesive
Hydrogen bonds contribute to a property of water called ¨cohesion”: the tendency of water molecules to stick together. The water molecules at the surface of water hold together so strongly that they form a “skin” at the surface
What is an example of water being cohesive
Surface tension allows insects such as the water skimmer to literally walk on water
Why does water adhere to other substances
Water demonstrates “adhesion” : an attraction to the molecules of other substances. Adhesion provides an upward force on water and counteracts the pull of gravity.
What is an example of water adhering to other substances
Adhesion causes water molecules to stick to the inner surface of a glass tube or the water conducting vessels in a plant. When evaporation draws water out from a plant’s leaves, the remaining water in the stem is pulled up by adhesion and cohesion
What does hydrophilic mean
Describes substances made of POLAR molecules or ions, so they dissolve in water
What does hydrophobic mean
Describes substances made of NON-POLAR molecules, so they do not dissolve in water
What is an acid
A substance that increases Hydrogen ion (H+) concentration when added to water
What is a base
A substance that increases hydroxide ion (OH-) concentration when added to water
