Properties of Water (BIO)

Flashcards covering chemical bonds, polarity, pH, and the four key properties of water.

How much of Earth's surface is covered by water, and what proportion of known lifeforms are made of water?

Water covers about three quarters of Earth's surface, and all known lifeforms are made mostly of water.

What are the specific percentages of water in various human body parts listed in the notes?

Lungs: 90%, Blood: 82%, Skin: 80%, Muscle: 75%, Brain: 10%, and Bones: 22%.

What is the pH of water, and how are solutions categorized on the pH scale?

Water has a pH of 7 and is neutral (not acidic or basic). Solutions with a pH below 7 are acidic, while solutions with a pH above 7 are basic (alkaline).

What is the chemical formula for water, and what bonds hold its individual atoms together?

The chemical formula for water is $H_2O$ (2 hydrogen, 1 oxygen). Hydrogen is connected to the oxygen atom by covalent bonds, where electrons are shared.

Why is a water molecule polar, and what slight charges do its atoms carry?

The sharing of electrons is not equal because the larger oxygen atom attracts electrons more strongly than the hydrogen atoms. As a result, oxygen has a slightly negative charge and hydrogen has a slightly positive charge.

How do hydrogen bonds form between water molecules, and how does their strength vary by state?

Hydrogen bonds connect water molecules to each other between slightly positive hydrogen atoms and slightly negative oxygen atoms. They are weak when liquid, and strong when solid and cold.

What are the four important properties of water enabled by hydrogen bonds?

1. Expansion upon freezing (ice floats)
2. Adhesive and cohesive behavior (stickiness)
3. Ability to moderate temperature
4. Versatility as a solvent

Why does ice float on top of liquid water instead of sinking to the bottom?

Water is less dense as a solid due to its hydrogen bonds, whereas most other substances become more dense as they freeze.

What is the difference between cohesion and adhesion?

Cohesion is the attraction between molecules of the same substance (water sticking to water). Adhesion is the attraction between molecules of a different substance (water sticking to other substances).

Why are insects able to walk on the surface of water?

Insects can walk on water because water has a high surface tension due to its cohesive behavior.

What is capillary action, and how does it help tall trees like giant sequoias?

Capillary action is the movement of water molecules through a narrow space resulting from cohesion, adhesion, and transpiration. It allows giant sequoias to transport water molecules from soil to leaves over 300 ft. above.

What does high heat capacity mean, and why does water have it?

High heat capacity means a substance can absorb a lot of heat before registering a change in temperature. Water's heat capacity is relatively high because of hydrogen bonding.

How does water's high heat capacity affect large bodies of water like lakes and oceans?

It gives water the ability to moderate temperature, enabling large bodies of water to not fluctuate in temperature quickly.

Why is water referred to as the "universal solvent"?

Water is called the universal solvent because it dissolves more substances than any other liquid, which it can do because it is polar.

What is the difference between a solute and a solvent, and which is which in saltwater?

A solute is the substance that is dissolved, while a solvent is the substance in which the solute dissolves. In saltwater, salt is the solute and water is the solvent.

Why can oil not be dissolved in water?

Oil cannot be dissolved in water because oil is nonpolar.