Question

1. list 5 ways that water helps to maintain homeostasis.
2. what property of water causes surface tension?
3. give an example that you observed of surface tension (think penny lab).
4. define cohesion in your own words. give an example.
5. define adhesion in your own words. give an example.
6. write the dissociation equation for water (when water breaks into hydrogen ions and hydroxide ions).
7. draw a ph scale. a. on the scale, label 1 - 14. b. label neutral. c. label the basic side and identify the direction that is increasingly basic. d. label the acidic side and identify the direction that is increasingly acidic. e. identify 2 strong acids and put them on the scale in the appropriate place. f. identify 2 strong bases and put them on the scale in the appropriate place.
8. describe a buffer using your own words. why are they important to all living things?

Explanation:

1. Water helps maintain homeostasis by regulating body temperature (through sweating and evaporation), transporting nutrients and waste (in blood and other body - fluids), participating in chemical reactions (as a solvent), lubricating joints and organs, and maintaining cell turgor pressure.
2. Hydrogen bonding between water molecules causes surface tension. Water molecules at the surface are more strongly attracted to each other than to the air above, creating a "skin - like" effect.
3. In the penny lab, you can observe surface tension when you slowly add water to the surface of a penny. The water forms a dome - like shape on top of the penny instead of immediately spilling over, due to surface tension.
4. Cohesion is the attraction between molecules of the same substance. An example is water droplets. Water molecules stick together to form droplets because of cohesion.
5. Adhesion is the attraction between molecules of different substances. An example is water climbing up the sides of a glass tube (capillary action), where water molecules are attracted to the glass molecules.
6. The dissociation equation for water is $H_2O

ightleftharpoons H^++OH^-$.
20.
a. The pH scale ranges from 1 - 14.
b. A pH of 7 is neutral.
c. The basic side of the pH scale is from 7 - 14, and the direction of increasing basicity is from 7 to 14.
d. The acidic side of the pH scale is from 1 - 7, and the direction of increasing acidity is from 7 to 1.
e. Examples of strong acids are hydrochloric acid (HCl) with a pH close to 1 and sulfuric acid ($H_2SO_4$) with a pH around 1 - 2. They would be placed on the lower end of the pH scale (1 - 2).
f. Examples of strong bases are sodium hydroxide (NaOH) with a pH around 13 - 14 and potassium hydroxide (KOH) with a pH around 13 - 14. They would be placed on the higher end of the pH scale (13 - 14).

1. A buffer is a solution that resists changes in pH when small amounts of an acid or a base are added to it. Buffers are important to all living things because they help maintain a stable internal pH environment. Many biochemical reactions in living organisms are very sensitive to changes in pH, and buffers ensure that the pH remains within a narrow range necessary for proper functioning.

Answer:

1. Regulating body temperature; transporting nutrients and waste; participating in chemical reactions; lubricating joints and organs; maintaining cell turgor pressure.
2. Hydrogen bonding between water molecules.
3. Water forming a dome - like shape on a penny.
4. Attraction between molecules of the same substance; water droplets.
5. Attraction between molecules of different substances; water climbing up the sides of a glass tube.
6. $H_2O

ightleftharpoons H^++OH^-$
20.
a. pH scale ranges 1 - 14.
b. pH = 7 is neutral.
c. Basic side: 7 - 14, increasing basicity from 7 to 14.
d. Acidic side: 1 - 7, increasing acidity from 7 to 1.
e. Hydrochloric acid (pH 1 - 2), sulfuric acid (pH 1 - 2).
f. Sodium hydroxide (pH 13 - 14), potassium hydroxide (pH 13 - 14).

1. A solution that resists pH changes; important for maintaining stable internal pH for biochemical reactions.