Question

1. how does a crack in the sidewalk form?

Explanation:

When water seeps into small gaps in the sidewalk, it freezes in cold temperatures. Since water expands when it freezes, this expansion exerts pressure on the surrounding concrete. Over time, repeated cycles of freezing (expansion) and thawing (contraction) cause the concrete to crack. Additionally, soil movement beneath the sidewalk (due to factors like soil erosion, root growth from nearby plants, or uneven settling of the ground) can also put stress on the concrete slab, leading to cracks.

Answer:

A crack in the sidewalk forms mainly due to the expansion of water when it freezes (if water seeps into gaps and undergoes freeze - thaw cycles) and soil movement (such as erosion, root growth, or uneven ground settling) beneath the concrete slab.