States of Matter

Refrigerators produce cooling through the evaporation of a volatile liquid refrigerant. When the refrigerant evaporates in the evaporator coils, it absorbs heat from the refrigerator compartment, creating the cooling effect. This is based on the principle that evaporation requires latent heat.

The human body is approximately 60-65% water, which is about two-thirds. This water is distributed in cells, blood, and other bodily fluids.

Salt lowers the freezing point of water through freezing point depression, causing ice to melt at temperatures below 0°C. This colligative property depends on the number of solute particles, not their identity. Acids like H2SO4 and HCl would also lower freezing point but are corrosive and not used for de-icing.

The NRDC study in 1999 found that approximately one-third of bottled water brands tested contained contaminants including synthetic organic chemicals, bacteria, and arsenic at levels exceeding allowable limits. This highlighted that bottled water is not always safer than tap water.

Water is indeed reusable through Earth's natural hydrological cycle - it evaporates, condenses into clouds, falls as precipitation, and flows back to oceans. Through human technology, we can also treat and recycle wastewater for various uses, making water a renewable resource.

The human body is approximately 60% water by weight. 3/5 equals 60%, which is the accepted scientific average. Water is distributed in cells, blood, and tissues throughout the body.

Water does expand when it cools from 4°C to 0°C (ice is less dense than liquid water). All metals contract when cooled due to reduced thermal vibration of atoms. Option B is nonsense - 'electrocuted' is not a thermal process. Option D is false - gases expand when heated (Charles's Law).

According to Archimedes' principle, ice floats because it displaces a volume of water equal to its mass. When ice melts, it becomes exactly that amount of water, so the total volume remains unchanged and the water level stays the same. This is true regardless of the ice cube's shape or size, as long as it's floating.

At the critical pressure, a gas can condense into a liquid. The critical point represents the highest temperature and pressure at which a gas can be liquefied. Above this point, the gas and liquid phases become indistinguishable (supercritical fluid).

The correct answer is D because 'blood is thicker than water' is a well-known proverb meaning family bonds are stronger than other relationships. Mud, curd, and soup don't fit this traditional saying.

Water (H₂O) is a chemical compound made of hydrogen and oxygen atoms, not a chemical element. Elements contain only one type of atom (like oxygen or hydrogen alone), while compounds consist of two or more different elements chemically bonded.

The name hydrogen comes from the Greek words hydro meaning water and genes meaning forming or creator, literally translating to water-forming. This name was chosen because when hydrogen burns in air, it produces water as the product (2H2 + O2 → 2H2O). The other options are incorrect - hydrogen is a naturally occurring element, not artificial, has no connection to bringing light, and is actually one of the most abundant elements in the universe.

Under standard atmospheric pressure, the melting point of ice and freezing point of water both occur at 0°C (32°F). These are phase transition temperatures at which ice and liquid water coexist in equilibrium.

When the glass is whirled in a circular path, the flame points toward the center due to inertia. The more massive gases in the flame have greater inertia and resist the circular motion more than the lighter glass and air, causing them to lag inward relative to the center of rotation.

The brain is approximately 75-78% water by weight. While 80% is commonly cited in older sources, modern measurements place it closer to 75-78%. However, 80% is the best available approximation among these options.