Fresh water freezes at 0 c. water expands when it freezes. On cold nights, ice may form in pipes, pushing against them and causing them to burst. Water I lighter as a solid than as a liqid. This is why ice floats and why it forms on top of a lake instead of at the bottom. It ice were heavier than water, it would sink to the bottom of a lake and freeze upwards to the top. Plant and animal life in the lake would dis as a result.