How then can a solid be changed to a liquid?
By applying heat to a solid, it may be changed to a liquid.
What is meant by liquefaction?
Liquefaction is the changing of a solid to a liquid, by heat.
How may tallow be melted?
By heating the tallow, it may be melted.
Will the tallow become hard again when cold?
It will be hard again when cold.
Can lead and other metals be melted?
They can be melted or changed to a liquid state by heat.