Ask A Scientist© Chemistry Archive

name         lilac
status       student
age          13

Question -   Why does metal expand?
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Dear Lilac,

Metal usually expands when heated because the atoms of
the metal start to move faster when they have more energy.
It's sort of like handing a piece of chocolate to a
5 year old; after they eat the chocolate, he or she starts
running around and bouncing off the walls, right?
The chocolate gives him/her more energy, so he/she moves
around more and explores more space. Same with the metal atoms;
when you heat the metal you give energy to the atoms and
they move around more as a result.

best wishes,
prof. topper
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Most materials expand when heated.  This is because, as you heat the
material, the atoms gain energy and move around more.  When they move
they push their neighbors away, thus expanding the space they 'occupy'.

Greg Bradburn
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