Water Properties & Movement Quiz

Water Molecules & Properties

• Water molecules are polar, with an uneven distribution of charges.
• Adhesion is water sticking to other surfaces, cohesion is water sticking to itself.
• Surface tension, due to cohesion, allows small insects to walk on water. Hydrogen bonds are responsible.
• Density is mass per unit volume (Density = Mass / Volume).
• To increase density, decrease volume. Increase by cooling, decrease by heating.
• Irregular objects' volume is found using Archimedes' principle (measuring displaced water).
• An object floats if its density is less than water's (1 g/cm³), sinks otherwise.

Diffusion & Osmosis

• Diffusion is the movement of molecules from high to low concentration until equilibrium.
• Osmosis is the diffusion of water across a partially permeable membrane from high to low water concentration.
• Partially permeable membranes allow specific molecules (e.g., water) through small holes, blocking others.
• In both diffusion and osmosis, concentration gradients are equalized. However, diffusion involves both solutes and solvent, while osmosis only involves solvent (water) movement.
• Osmosis moves water from low solute concentration to high solute concentration to balance solute concentration.
• Too much water swells cells (possibly bursting); too little water shrinks cells, hindering function.

Transpiration

• Transpiration is the process of water movement through plants and release into atmosphere. It helps plants cool and transports nutrients.
• Xylem cells transport water from roots to leaves; they are hollow and strong.
• Root hair cells absorb water and nutrients; their thin, extensive hairs maximize surface area.
• Stomata are small leaf openings letting gases in/out; guard cells regulate stomata, controlling water loss and gas exchange for photosynthesis.
• Light increases transpiration (more stomatal opening); high humidity slows it; moving air speeds it up (removes water vapor around the plant).

Air & Gas Behavior

• Gases fill their container.
• Pressure increases with more molecules or higher temperature.
• Temperature increases, gas speeds up and spreads out, increasing pressure (if volume is fixed).
• Gas molecules move quickly and randomly.
• Increased temperature = increased speed of gas molecules, increased pressure if constant volume.
• Decreased volume = increase in molecular collisions; increased pressure.

Photosynthesis & Respiration

• Photosynthesis: Carbon dioxide + water + light energy → glucose + oxygen
• Respiration: glucose + oxygen → carbon dioxide + water + energy
• Aerobic respiration occurs within the cell (not specified where).