For example, water actually expands when it freezes, becoming less dense.

Also, during evening games, as the sun sets, the surrounding air cools quickly due to the ocean climate, becoming more dense.

By midday the Waste was behind him and the forest had become increasingly dense and the ground uneven.

When he awoke, he did so because the darkness about him had become less dense.

Now it is becoming increasingly dense and expensive.

The warmer air near the surface expands, becoming less dense than the surrounding air mass.

This is expected if the disks are becoming more flat and dense over time.

When they branched off, we would again plunge into the woods which had steadily become more dense.

He couldn't even see her at first, the shadow around the mantelpiece had become so dense.

The crowd in the market-place had become very dense, and still people came running out of the side streets.