Materials and Heat

KEY IDEAS

  • Heating can cause solid materials to melt or become softer
  • Heating can change liquids into gases
  • Cooling can change gases into liquids and liquids into solids
  • Different materials change state at different temperatures

EXAMPLE QUESTIONS

  • What solid materials have you seen change when they were heated?
  • What liquid materials have you seen change when they were cooled?
  • Do you think that all materials can be made to melt with heat?

HEATING AND COOLING CAN CHANGE MATERIALS

  • Heating and cooling affects materials, sometimes causing them to change states.
  • It can also affect their properties (for example, the electrical conductivity of metals).

MATERIALS CAN CHANGE AT DIFFERENT TEMPERATURES

  • Some materials change with just slight heating or cooling.
  • Water normally changes into ice at 0°C and into steam at 100°C.
  • Other materials change only in extreme hot or cold. (Steel melts at about 1500°C).

HEATING CAN CAUSE SOLID MATERIALS TO MELT OR BECOME SOFTER

  • Solid materials can change into liquids when heated.
  • Butter changes into a liquid with only a small rise in temperature, for example.
  • As some solids become heated, they become more pliable and can change shape more easily.
  • Examples of these changes are steel and glass, both of which become more bendable when heated to their melting temperatures.

HEATING CAN CHANGE LIQUIDS INTO GASES

  • Liquids change into gases when heated, but different liquids change at different temperatures.

COOLING CAN CHANGE GASES INTO LIQUIDS AND LIQUIDS INTO SOLIDS

  • Cooling has the opposite effedt on materials to that of heating.
  • With cooling, gases can change into liquids and liquids into solids.