A1.1 Water Flashcards
(30 cards)
Aqueous solution
Water with substances dissolved in it
“Primeval soup”
The aqueous solution that the first living cells originated from
Hydrogen Bonds
A weak bond between a hydrogen atom and a highly electronegative atom such as N, O, or F. Water molecules create hydrogen bonds with each other. The positive charge of a hydrogen atom of one water molecule attracts to the oxygen atom of another water molecule.
Intermolecular Force
An attraction between molecules such as the hydrogen bonds between water molecules.
Covalent Bond
When two atoms share a pair of electrons. Sometimes the electrons are more attracted to the nucleus of one atom, which can cause the atom to have a slight negative charge. Two hydrogen atoms each have a covalent bonds with an oxygen atom to form a water molecule.
Intramolecular Force
A bond between atoms within a molecule such as the covalent bonds between the hydrogen atoms and oxygen atom within a water molecule.
Review: What are the two types of bonds that form within and between water molecules?
Covalent bonds occur between hydrogen and oxygen atoms, where they share a pair of electrons.
Hydrogen bonds occur between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another.
Polarity
When a molecule has two opposite poles, one negative and one positive. Water molecules are polar because their hydrogen atoms are slightly positive while their oxygen atom is slightly negative.
δ− and δ+
Symbols that indicate the direction of polarity. δ+ means an atom is partially positive and δ− means an atom is partially negative. In water, oxygen atoms will be marked with a δ− symbol and hydrogen atoms with a δ+ symbol
Cohesion
One of the major molecular properties of water. Water molecules stick to each other because of their hydrogen bonds. This creates tension between the molecules which allows for water to be pulled up plant stems and also forms surface tension on top of water.
Surface tension
An effect of cohesion that makes the surface of the water a cohesive structure. To break through the surface, enough energy must be exerted to break the hydrogen bonds between water molecules. Water insects such as water striders can use the surface of the water as a habitat because of this.
Adhesion
One of the major molecular properties of water. Water molecules can stick to other substances if they are hydrophilic: with the ability to form intramolecular bonds with water molecules.
Capillary Action
The movement of water within spaces of a porous material as a result of adhesion, cohesion, and surface tension. Water is able to move up through dry soil by adhering to solid matter like dead matter, sand, silt, and clay.
Cellulose
The primary structural component of plant cell walls. They create hydrogen bonds with water molecules that allow they to remain saturated with water. This is an example of adhesion.
Solvent
One of the major molecular properties of water. A liquid in which something can be dissolved. Water is a solvent, which allows for nutrition transportation via blood and more.
Solute
A dissolved substance in a solution. For example the salt (NaCl) is a solute to water when they are combined.
Electrostatic Interactions
The attraction/repulsion of two opposite charges. Ions have both attractive and repulsive charges with water molecules, which can pull the ion apart to dissolve it.
Review: What are the major three molecular properties of water?
Cohesion, adhesion, and solvent properties
Review: Why is the polar property of water important?
It gives rise to the three major molecular properties of water: cohesion, adhesion, and solvency.
Hydrophobic substances
Molecules that cannot create intramolecular bonds with water. All non-polar molecules are hydrophobic. They aren’t repelled by water; the water molecules are simply more attracted to each other than non-polar substances. Hydrophobic substances can create barriers between water and hydrophilic substances as well; for example, wax on plant leaves and human skin prevent dehydration.
Insoluble
Unable to dissolve in a solution. Hydrophobic substances are insoluble to water.
Buoyancy
A physical property of water. Solids will float in air or water if their density it lower. Because water has a much higher density than air, organisms have to exert much less energy to stay afloat in their habitat.
Viscosity
The resistance of flow of a fluid or gas due to cohesion between molecules. Water has a much higher viscosity than air, so water organisms much overcome more resistance when moving through water.
Thermal Conductivity
The ability of a material to transfer heat. Water has a much higher thermal conductivity than air partially because of its higher density (think of liquids vs gases and the difference in the spacing between their atoms). This means aquatic organisms are more prone to hot or cold temperatures in the water.
