Question

small insects can walk across the surface of calm water. their feet push the surface of the water down slightly, somewhat like a person walking across a trampoline, but they do not break the surface. what is the best explanation for why this happens? the insects feet are non - polar, so they are repelled by the polar water molecules and are pushed away from the waters surface the insects actually use their wings to hover slightly above the waters surface and they only skim it with their feet the insects are light enough so that they do not break the hydrogen bonds holding the water molecules together the insects are small enough to see the individual water molecules, so they are able to step carefully from one molecule to the next

Explanation:

The phenomenon of small insects walking on water is due to surface tension. Surface tension is caused by hydrogen bonds between water molecules. When insects' feet push the water surface slightly, the cohesive forces (hydrogen bonds) of water molecules can support the insects' weight as long as it is not too heavy.

• The first option about non - polar feet being repelled is incorrect. Water's surface tension is mainly due to hydrogen bonding (a polar interaction), not simple repulsion based on polarity of insect feet.
• The second option about using wings to hover is not in line with the common observation of insects like water striders that actually use their legs and the surface tension, not continuous wing - hovering for walking on water.
• The fourth option about seeing individual water molecules is wrong. Molecules are too small to be seen with the naked eye (or in the context of insect vision in this way), and the key is the collective effect of hydrogen bonds (surface tension), not stepping on individual molecules.

Answer:

The insects are light enough so that they do not break the hydrogen bonds holding the water molecules together.