States of Matter

Oil is hydrophobic, meaning it repels water and does not mix with it. This property is due to oil's nonpolar molecular structure, which cannot form hydrogen bonds with polar water molecules. This is why oil and water separate into distinct layers when mixed.

Cohesion is the property of water molecules sticking to each other through hydrogen bonding. This is different from adhesion (sticking to other surfaces). Cohesion gives water its high surface tension and allows for phenomena like water droplets forming spherical shapes and capillary action in plants.

Evaporation is the phase change where liquid water gains thermal energy and transforms into water vapor (gas). This process is primarily driven by solar energy heating surface waters like oceans, lakes, and rivers. Evaporation is a fundamental step in the water cycle that returns water to the atmosphere.

The human body is approximately 60% water by weight. This percentage varies slightly by age (infants are about 75% water), gender, and body composition (lean body mass has more water than fatty tissue), but 60% is the widely accepted average for adult humans. Water is essential for nearly all bodily functions.

Surface tension is the cohesive force between water molecules that causes them to minimize surface area, creating droplet shapes. On waxy (hydrophobic) surfaces, water cannot spread out due to weak adhesive forces, so surface tension dominates and forms beads. Capillary action would actually pull water into narrow spaces, which is the opposite of beading.

In an isentropic (constant entropy) expansion process, the pressure decreases as the volume increases. This is an adiabatic reversible process where no heat is exchanged with the surroundings.

Cabbage, like most leafy vegetables, consists primarily of water - approximately 90% by weight. This high water content is typical of vegetables in the brassica family and contributes to their low caloric density.

Pearls are primarily composed of calcium carbonate (aragonite). Vinegar contains acetic acid, which reacts with and dissolves calcium carbonate. This is why pearls should not be exposed to vinegar or other acidic substances.

Surface tension is the cohesive force that allows water to form droplets and stick to surfaces. This property enables water molecules to cling to most materials through adhesive forces. Viscosity is about fluid thickness, capillary action is about narrow tube movement, and specific heat relates to temperature change.

Water's effectiveness as a coolant comes from two key properties: very high specific heat capacity (absorbs large heat energy with small temperature rise) and poor thermal conductivity (heat doesn't quickly transfer back). This dual nature makes water ideal for cooling systems. Neither property alone would be as effective.

Capillary action is the property that allows liquids to flow in narrow spaces without external forces like gravity. In a wick, the liquid rises due to adhesive forces between the liquid and wick material overcoming cohesive forces within the liquid and gravity.

When hot liquid mixes with cold liquid, heat flows from the higher temperature region to the lower temperature region until thermal equilibrium is reached. This mixing process increases the overall entropy of the system because the energy becomes more dispersed and the system moves toward a more disordered state.

Water has strong hydrogen bonding due to its polar nature (oxygen is electronegative, creating partial charges), requiring more energy to break these bonds and boil. Methane is nonpolar with only weak London dispersion forces, explaining its much lower boiling point.