Biology



Biology Name___________________

Notes – Section 2.2 Date___________Hour_____

Properties of Water

Structure of Water

The chemical formula for water is ___________. Water is made up of _____ hydrogen and _____ oxygen atoms bonded together. Each hydrogen atom is bonded to the oxygen atom by a covalent bond.

What is a covalent bond?

Water is a polar molecule. A polar molecule is a molecule that has a ______________charged part and a _________________ charged part. In water, oxygen pulls electrons more strongly therefore oxygen has a slight _______________ charge and each hydrogen has a slight ______________ charge.

Draw a water molecule showing the positive and negative poles.

Water is a special compound with unique properties that are crucial for life. Water molecules are attracted to each other. The slightly negative oxygen end of one water molecule is attracted to slightly positive hydrogen atoms on other water molecules. This is because opposite charges ____________. These weak attractions are called ______________ bonds.

Draw a few water molecules. Label the covalent bonds and the hydrogen bonds.

Water’s Life-Supporting Properties

Due to water’s polarity and the effects of hydrogen bonds, water has 5 unique properties. These 5 properties are:

1. Cohesion

2. Adhesion

3. High Heat Capacity

4. Density of Ice is Lower than the Density of Liquid Water

5. Ability to Dissolve Other Substances

Acids, Bases, and pH

While most of the time water is in the form of H2O, there is always a small percentage of water molecules that break down into _______________ (H+) and _________________ (OH-)

Write a chemical equation that shows the breakdown and the formation of water.

Draw three beakers. The first beaker should have more hydrogen ions than hydroxide ions. The second beaker should have equal amounts of hydrogen ions and hydroxide ions. The third beaker should have more hydroxide ions than hydrogen ions.

A solution that has more hydrogen ions than hydroxide ions is called an _____________. A solution that has more hydroxide ions than hydrogen ions is called a ______________. Solutions that have nearly equal amounts of hydrogen ions and hydroxide ions are referred to as ____________.

Label the 3 beakers above as either acidic, basic or neutral.

The ________ scale measures how acidic or basic a solution is. This scale ranges from ____(acidic) to ____(basic). A neutral solution has a pH of ______. Each pH unit represent a ten-fold change in the concentration. For example, a solution with a pH of 5 has _______ times as much hydrogen ions as a solution with a pH of 7.

Draw the pH scale below the 3 beakers. List some examples of common substances that fall under each pH range.

Molecules in cells are very sensitive to concentrations of H+ and OH- ions. A slight change in pH can be harmful to living organisms. To counterbalance the effects of these ions (which are formed when the body metabolizes), living organisms have ____________. Buffers are substances that cause a solution to resist a change in pH. Buffers act by accepting extra _______ ions when the pH is low and by giving up H+ ions when the pH is ______.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download