States of Matter

At 28°F and 32°F, water is frozen or at its freezing point. The coin dropped into glass A (28°F) would land on ice since water freezes at 32°F. Similarly, glass B at 32°F would contain ice or water at freezing temperature. Coins would not sink through ice, so neither would reach the bottom.

The human body is approximately 60-65% water, which is about two-thirds of total body mass. This water is distributed in cells (intracellular), blood, and extracellular fluids. Water content varies by tissue - blood is about 92% water, while bones are only about 22% water.

The human brain is approximately 75% water by weight, similar to the water content of many other organs. This high water content is essential for biochemical reactions, nutrient transport, and maintaining cellular structure. Options A (10%) is far too low, B (50%) underestimates, and D (90%) is slightly too high for brain tissue.

Water's polar nature creates strong hydrogen bonding between molecules. These intermolecular forces create high surface tension, allowing small insects to walk on water without breaking through. Polarity refers to the uneven charge distribution in the water molecule.

Ammonia (NH3) has the highest specific heat capacity among known substances at around 4.7 J/g-K. Water follows closely at 4.18 J/g-K. This is due to ammonia's strong hydrogen bonding and molecular structure, which requires significant energy to change temperature.

Water boils when its vapor pressure equals atmospheric (barometric) pressure. Higher atmospheric pressure raises the boiling point, while lower pressure (like at high altitudes) lowers it. This is why water boils at lower temperatures on mountains.

Heavy water is water where the hydrogen atoms are replaced by deuterium, a heavier isotope of hydrogen with one neutron. The chemical formula is D2O or deuterium oxide (²H₂O). Tritium oxide would be even heavier, while hydrogen peroxide (H₂O₂) is a different compound entirely.

Glass is highly stable and does not decompose; it can remain in the environment for thousands of years without breaking down, unlike organic materials.

On the moon's surface with near-vacuum conditions, water would rapidly evaporate (sublime) due to extremely low atmospheric pressure. The water wouldn't simply float (A), freeze immediately (B), or form slow droplets (C). Evaporation into the vacuum happens quickly.

When atoms of two or more different elements chemically combine, they form a compound. A compound has unique properties different from its constituent elements. Crystals are structured arrangements, particles is too general, and liquids describe a state of matter, not a product of chemical combination.

Pure water is a poor conductor of electricity. When NaCl (sodium chloride) is added, it dissociates into Na+ and Cl- ions, making the solution conductive. Options A (FCl) is not a standard compound, and carbon/chlorine don't produce the same ionic conduction effect.

Icebergs contain air bubbles trapped under high pressure during the formation of glacial ice. As the ice melts, these compressed air bubbles are released, creating a distinct 'fizzing' or 'popping' sound known as 'Bergie Seltzer'.

Water exists in liquid state at room temperature (typically 20-25°C or 68-77°F). This is because water's freezing point is 0°C and boiling point is 100°C at standard pressure. At room temperature, water is between these two phase transition points, so it remains liquid. The other options are incorrect because solids have fixed shapes, gases have no fixed volume, and plasma is an ionized high-energy state not found at room temperature.

Hygroscopic salts absorb moisture from the atmosphere without dissolving in it. Anhydrous salts are simply without water of crystallization, while hydrophilic refers to water-attracting substances more generally. Hydrophobic substances actually repel water.