In the water cycle, there are abiotic and biotic factors that contribute to the recycling of water. The process by which non-living things return water to the atmosphere is called evaporation. Plants, on the other hand, intake water through their roots and release the water as vapor through tiny openings on leaves called stomata. This process is called transpiration.

When water freezes, its density decreases (most substances do not exhibit this property). This means that ice will float on top of a lake, rather than sink to the bottom. Because the ice floats on top of a lake, it freezes from the top down rather than from the bottom up. The other answer choices are all properties of water, but they do not explain why lakes freeze from top down, and not from bottom up.

Hydrolysis is the reverse of a dehydration reaction; the bond between monomers is broken by the addition of a water molecule, with a hydrogen atom from water attaching to one monomer and the hydroxyl group attaching to the other.  

Water is unique in many ways. Much of its versatility is due to hydrogen bonding and polarity. The electronegativity of the oxygen atom creates a slightly positive charge on the hydrogen atoms—water is polar. Water can share hydrogen bonds and form them with itself. Because of this it has a high boiling point and high heat capacity. It is a good solvent because the oxygen can surround positively charged molecules and the slight positive charge on the hydrogen atoms can surround negative charges.

The cohesive nature of water stems from the fact it forms hydrogen bonds with itself. This allows water molecules to pull on lower molecules as they all travel up the xylem. The adhesive nature comes from the polarity of the molecule, which can be attracted to the walls of the xylem. 

Water actually has a high specific heat, higher than any other common substance. A high specific heat (defined as the amount of heat needed to raise one mass unit of substance by one unit of temperature, usually expressed in  or ) means that water can absorb a large amount of heat without changing temperature. This makes it important for organisms in things like thermoregulation (think prespiration).

Peroxisomes are responsible for detoxification. They contain many enzymes that breakdown lipids and amino acids. Additionally, they breakdown toxins like alcohol in the cells of the liver. 

Organic compounds are defined as solids, liquids, or gases whose molecular structure includes carbon. Inorganic compounds, in contrast, do not contain carbon. Organic compounds might contain other elements, like hydrogen and oxygen, but not all compounds need these other elements to be considered organic.

Living organisms are primarily made up of organic molecules, which contain carbon. The six most prevalent elements in living organisms are carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur, in that order.

Carbon and hydrogen are found in the basic monomer structure of all biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids). Nitrogen is found in amino acids, which form proteins, and the nitrogenous bases in nucleic acids (DNA and RNA). Oxygen is found in all biological macromolecules. Phosphorous is found in nucleic acids and lipids, such as phospholipids in the cell membrane. Sulfur is found in cysteine, a specific amino acid.

Since carbon is in group IV of the periodic table, we know that it has four valence electrons. Most elements (with the exceptions of hydrogen and helium) are most stable when they have filled their valence shell with eight electrons. For carbon to fill its valence shell, it needs to make four covalent bonds. Remember that carbon is not very electronegative and only very rarely (if ever) forms ionic bonds. This means that carbon will not donate, nor accept electrons; rather it will share them with other atoms to form molecules.

Carbon has four electrons in its valence shell which means it needs four more to have a stable octet. This means that the maximum number of bonds it can form is four when each bond only contributes one electron to the relationship.