2.2: Water

Terms in this set (41)

Describe the structure of an atom.



Understanding: Water molecules are polar and hydrogen bonds form between them.
Atoms are composed of protons, neutrons and electrons. Protons have a positive charge, neutrons have no charge and electrons have a negative charge.

Protons and neutrons are found in the atomic nucleus. Electrons are found in a cloud surrounding the nucleus.
Contrast ion with atom.



Understanding: Water molecules are polar and hydrogen bonds form between them.
Atoms have no net charge because the have equal numbers of protons (+) and electrons (-). If an atom gains or loses an electron it will have a net charge and be called an ion.
Define anion.



Understanding: Water molecules are polar and hydrogen bonds form between them.
A negatively charged ion because it has gained electrons
Define cation.



Understanding: Water molecules are polar and hydrogen bonds form between them.
A positively charged ion because it has lost electrons.
Contrast covalent, ionic and hydrogen bonds.



Understanding: Water molecules are polar and hydrogen bonds form between them.
All bonding involves electrons or the charges that result from the giving/taking of electrons.

Covalent bond: electrons are shared between two atoms

Ionic bond: attraction between cation and anion (no sharing of electrons)

Hydrogen bond: an attraction (not a true bond) between two polar molecules.
Write the molecular formula for water.



Understanding: Water molecules are polar and hydrogen bonds form between them.
Water is H2O
Define "polar" in relation to chemical bonding.



Understanding: Water molecules are polar and hydrogen bonds form between them.
Polar means a molecule has regions of slight charge due to the unequal sharing of electrons in a polar covalent bond. One of the atoms has more of a tug on the electrons that another, making it slightly negatively charged.
Describe the cause and effect of the polar nature of water.



Understanding: Water molecules are polar and hydrogen bonds form between them.
In water, the oxygen has a greater "pull" on the shared electrons than the hydrogen atoms. As a result, there is unequal sharing of the electrons, with the electrons drawn closer to the oxygen.

As a result, the oxygen has a slightly negative charge and the hydrogens have a slightly positive charge.
Describe where and how water is able to form hydrogen bonds.​



Understanding: Water molecules are polar and hydrogen bonds form between them.
Water forms hydrogen bonds between the partial positive hydrogen of one water molecule and the partial negative oxygen of ANOTHER water molecule.

One water molecule is capable of forming up to four hydrogen bonds with other water molecules.
Define adhesion.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Water molecules bonding to non-water molecules through hydrogen bonding or attraction to an ionic charge.
Define cohesion.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Water molecules attaching to other water molecules through hydrogen bonding.
Outline an example of the cohesive property of water being of benefit to life.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Water cohesion allows for surface tension, allowing some insects to stay on the surface of the water.

Water cohesion creates a chain of water molecules that allows for the transport of water from the roots to the leaves of plants.

Water cohesion is responsible for the high heat capacity of water, maintaining a relatively stable internal temperature and external environment for living organisms.
Outline an example of the adhesive property of water being of benefit to life.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
Adhesion is needed for water to move from the roots to the leaves of plants. Water sticks to the sides of the xylem wall through adhesion.
Outline a benefit to life of water's high specific heat capacity.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
It takes a relatively large amount of heat energy to raise the temperature of water. This is a benefit because the temperature of large bodies of water remains relatively constant, protecting life from potentially lethal temperature fluctuations.
Outline a benefit to life of water's high latent heat of vaporization.



Understanding: Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water.
It takes a relatively high amount of heat energy to vaporize water (convert from liquid to gas) because hydrogen bonds must be broken.

As the water evaporates, the surface it leaves becomes cooler. This is called evaporative cooling and allows organisms to cool with sweating.
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