AP Biology Chapter 3 Flashcards

Water's Polarity

• Water is a polar molecule because oxygen is more electronegative than hydrogen, causing unequal electron sharing.
• This polarity leads to a more negatively charged oxygen atom and positively charged hydrogen atoms.

Importance of Water's Polarity

• The properties of water, such as cohesion, temperature regulation, expansion upon freezing, and solvent versatility, derive from its polarity.
• These characteristics support life and ecological balance on Earth.

Key Properties of Water

• Cohesion: Attraction between water molecules, helping to hold them together.
• Adhesion: Attraction between water molecules and other substances.
• Capillary Action: Water's ability to rise or fall in narrow spaces due to adhesive forces.
• Surface Tension: Resistance to being stretched or broken, allowing some organisms to walk on water.

Energy Concepts Related to Water

• Kinetic Energy: The energy of motion, related to the movement of particles.
• Heat: Total kinetic energy resulting from molecular motion.
• Calorie: The amount of heat required to raise the temperature of one gram of water by one degree Celsius.
• Temperature: A measure of the average kinetic energy of particles in a substance.

Specific Heat

• Specific Heat of Water: 1 calorie per gram per degree Celsius, allowing it to absorb significant heat without a large temperature change.
• High specific heat regulates temperatures in large bodies of water, moderating climate and air temperatures.

Phase Changes and Cooling

• Evaporative Cooling: Cooling that occurs when molecules with higher kinetic energy (heat) evaporate, leaving cooler molecules behind.
• Heat of Vaporization: The amount of energy required to convert liquid to gas, contributing to the stability of temperatures in lakes and ponds.

Density and Water's Behavior

• Water is unique in that it expands upon freezing, forming a crystalline structure that is less dense than liquid water.
• The resulting ice floats, insulating the water below and protecting aquatic life during winter.

Solutions and Concentration

• Solution: A homogeneous mixture of two or more substances.
• Solvent: The substance that dissolves another (e.g., water).
• Solute: The substance that is dissolved in a solvent.

Ion Concentration

• Hydration Shell: A cluster of water molecules surrounding dissolved ions.
• Hydrogen Ion (H+): A positively charged ion formed when an acid donates a proton.
• Hydroxide Ion (OH-): A negatively charged ion present in basic solutions.
• Hydronium Ion (H3O+): Formed when water accepts a hydrogen ion.

Acids and Bases

• Acids: Substances that increase H+ concentration in solution.
• Bases: Substances that reduce H+ concentration in solution.
• Strong Acids/Bases: Fully ionize in water, releasing H+ or OH- completely.
• Weak Acids/Bases: Only partially ionize and establish an equilibrium with their molecules.

pH Scale

• The pH scale ranges from 1 to 14, measuring the concentration of H+ ions in a solution.
• Buffers are substances that stabilize pH by minimizing changes in H+/OH- concentration, crucial for maintaining physiological conditions.

Environmental Impact

• Acid precipitation arises from reactions of sulfur oxides and nitrogen oxides with atmospheric water, impacting ecosystems.

Dive into the essential concepts of water's polarity with these flashcards from Chapter 3 of Campbell's AP Biology. Understand how water's unique properties contribute to life on Earth, including its cohesion and temperature stabilization. Perfect for mastering key ideas in biology!