How hot is hot?
Which is hottest—ice cream, a glass of cool water, or a steaming-hot
cup of chocolate? Of course, the chocolate is hottest. But it wouldn’t
be quite right to say that the ice cream and the water aren’t hot at
all. Each one has some heat.
All things have heat—even very cold things. But some things have more
heat than others. So when we use words like hot and cold, we aren’t
really talking about two different ideas. We are simply telling how much
heat something has.
The molecules in the hot chocolate are moving very fast—they have a
lot of energy.
When you swallow those fast-moving molecules, they give you some of
their heat energy—they make you feel warm.
And the molecules in the cold ice cream are moving very slowly—but
they are moving! They have a small amount of heat energy. Because your
body has much more heat energy than the ice cream does, ice cream
can’t warm you up. Instead, it takes away heat energy—it makes you
feel cool.
The molecules in cool water move faster than the molecules in ice cream,
but they don’t move as fast as the molecules in hot chocolate. So,
compared to the molecules in ice cream, they are hot—and compared to
the molecules in chocolate, they are cold.
