Question

hmh science dimensions biology. unit 2. lesson 1. pages 76 - 78

1. what characteristics of a water molecule make it unique?
2. how are hydrogen bonds similar to ionic bonds?
3. why is the ability to dissolve many substances important for a solvent that is found in living things?
4. how do hydrogen bonds affect the boiling temperature of water?
5. lemon juice has a high hydrogen ion concentration. where would you expect to find it on the ph scale?

Explanation:

1. A water molecule is unique due to its polarity (unequal sharing of electrons creating a positive and negative end), and its ability to form hydrogen - bonds. These properties give water high surface tension, cohesion, adhesion, and make it a good solvent.
2. Hydrogen bonds are similar to ionic bonds in that they both involve attractions between charged regions. In ionic bonds, it's between ions (charged atoms), while in hydrogen bonds, it's between a slightly positive hydrogen atom and a slightly negative atom (like oxygen, nitrogen or fluorine).
3. The ability to dissolve many substances is important for a solvent in living things because it allows for the transport of nutrients, waste removal, and chemical reactions to occur. Many biological molecules need to be dissolved to interact with each other.
4. Hydrogen bonds increase the boiling temperature of water. They are intermolecular forces that need to be broken for water to change from liquid to gas. The more hydrogen - bonds, the more energy (higher temperature) is required to break them and boil the water.
5. The pH scale ranges from 0 - 14, with lower numbers indicating higher hydrogen ion concentration. Since lemon juice has a high hydrogen ion concentration, it would be found on the lower end (around 2 - 3) of the pH scale.

Answer:

1. Polarity and hydrogen - bonding ability.
2. Both involve attractions between charged regions.
3. Enables nutrient transport, waste removal and chemical reactions.
4. Increase the boiling temperature.
5. Lower end of the pH scale (around 2 - 3).