از لینک زیر دانلود بفرمایید
Heat is more than a physical concept – it is a feeling. Heat is
taught to us at a very young age as a danger to be avoided. Yet,
have you ever stopped and thought about what heat really is?
How does it move? What are some of the ways we can move it?
Heat, commonly described in degrees of temperature, such
as Fahrenheit (°F) or Celsius (°C), describes the random motion
or “vibration” of molecules. When a substance becomes hotter,
its molecules move faster. How fast these molecules move
determines whether the substance is a solid, a liquid, or a gas.
In a solid, molecules are locked together in position. In a liquid,
molecules move and share a loose relationship with each other.
Molecules in a gas, share no relationship with each other because
they move very fast