sentences: if a thermal conductor is exposed to a source of heat then that conductor may become hot
docs: heat is energy. heat is what_makes_hot. furnace is heat_source. heat_sink is conductor. warmth is hotness. copper is good_conductor_of_heat. thermals is rising_currents_of_warm_air. radiators_and_fires is both_sources_of_heat. temperature is measure_of_thermal_energy.