States of Matter

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.

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.

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.

Under standard atmospheric pressure (1 atm), the freezing point and melting point of water are the same: 0°C (32°F). This equilibrium temperature is where solid and liquid phases coexist. The terms 'freezing' and 'melting' describe opposite phase transitions but occur at the same temperature.

Pearls are primarily calcium carbonate (CaCO3) and will dissolve in vinegar due to its acetic acid content. The acid reacts with the calcium carbonate, causing the pearl to gradually break down. Water, petrol, and mercury do not have the chemical properties to dissolve pearls - vinegar is the only substance listed that causes this reaction.

Dry ice is solid carbon dioxide (CO2). When it sublimates (turns directly from solid to gas), it becomes carbon dioxide gas. This is why dry ice 'disappears' without leaving a liquid residue. Carbon monoxide is a different, toxic gas.