Khan Academy-Structure of Water and Hydrogen Bonding

Which of the following describes the most likely way in which two water molecules will interact?

A hydrogen bond will form between the hydrogen atom of one water molecule and the oxygen atom of the other water molecule. Because water molecules are polar, a hydrogen bond will form between the partially positive hydrogen end of one water molecule and the partially negative oxygen atom of the other water molecule.

Which of the following observations could be best explained by water's high surface tension?

A leaf floats on the surface of a puddle. Water molecules on the surface of the puddle form hydrogen bonds with one another, allowing them to resist the external force of the leaf.

Which of the following shows the most likely way that two water molecules will bond with each other?

Because water molecules are polar, a hydrogen bond will form between the partially positive hydrogen end of one water molecule and the partially negative oxygen of the other water molecule.

Given the structure of water, H2O, which of the following must be true?

Each water molecule can form four hydrogen bonds. Each water molecule can form up to four hydrogen bonds - two from the central oxygen atom and one each for the two hydrogen atoms.

Which of the following properties allows water to have a high boiling point?

It can form hydrogen bonds. Hydrogen bonds pull water molecules closer to each other, creating a dense liquid that cannot easily change from a liquid phase to a gas phase.

Which of the following best explains the ideal structure of the dish soap molecule?

The dish soap molecule must be non-polar at one and to dissolve grease, and polar at the other end so it can dissolve in water. The stains are formed by lipids which are non-polar, and can only be dissolved in nonpolar solvents. Water is a polar solvent, so non-polar molecules do not dissolve well in water. Therefore, the dish soap must have one nonpolar end and to dissolve the greasy, and one polar end in that is soluble in the dish soap water.

Which of the following best explains why coastal cities like San Diego often have a smaller air temperature range than inland cities?

The high heat capacity of water allows the ocean to moderate the temperature of nearby air and land. Water has a higher specific heat capacity than air or land due to hydrogen bonding. Because the temperature of the ocean is slow to change, the air temperature near the ocean is also slow to change. Therefore, cities on the coast often have more moderate air temperatures than inland cities.

Which of the following statements explains why the ice floats on the surface of the pond?

The increased number of hydrogen bonds water causes the water molecules in ice to be further apart. Because of this increase space between water molecules in ice, water is less dense as a solid then as a liquid

Which of the following best describes water's ability to dissolve certain substances such as glucose, but remain separate from other substances such as oils?

Water molecules are polar, consisting of two partially positive hydrogen atoms, and one partially negative oxygen atom. Water's polarity allows it to attract and interact with other polar molecules like glucose. However, oils are nonpolar and cannot attract water to form a solution.

Which statement best describes why water is an effective solvent?

Water's polarity allows it to dissolve ionic and polar compounds. Water is a polar molecule. The partially positive and partially negative ends of water interact with polar molecules and ions, helping disperse the molecules and ions in the solution.

Which of the following gives water it's cohesive properties?

Waters polarity makes it attracted to other charged molecules. each water molecule has a partially positive end and a partially negative end, allowing hydrogen bonding to occur between water molecules