Chapter 3: Water and Life

Cohesion in water

Water molecules stick together due to hydrogen bonding.

Adhesion in water

Water molecules stick to other substances, such as plant cell walls.

Surface Tension

A measure of how difficult it is to break the surface of a liquid; water has high surface tension due to hydrogen bonds.

Heat vs. Temperature

Heat is the total kinetic energy of molecules in a substance, while temperature is the average kinetic energy of molecules.

Specific Heat of Water

Water has a high specific heat (1 cal/g/°C), meaning it resists temperature changes.

Heat of Vaporization

Water requires a lot of energy to change from liquid to gas, aiding in evaporative cooling.

Why does ice float?

Ice floats because it expands when frozen, making it less dense than liquid water.

Hydrophilic substances

Substances that dissolve in water, such as salt and sugar.

Hydrophobic substances

Substances that do not dissolve in water, such as oils and fats.

Avogadro’s Number

1 mole (mol) = 6.02 × 10²³ molecules.

Acid (in chemistry)

A substance that increases H⁺ concentration in a solution; acidic solutions have pH < 7.

Base (in chemistry)

A substance that reduces H⁺ concentration; basic solutions have pH > 7.

pH Scale

Measures H⁺ concentration, with lower pH indicating higher acidity.

Ocean Acidification

The process where CO₂ from fossil fuels dissolves in seawater, forming carbonic acid and lowering ocean pH.

Acidic Precipitation

Caused by sulfur dioxide and nitrogen oxides from burning fossil fuels, leading to acid rain with pH < 5.2.