Add heat.
That's the amount of heat you have to add to the solid form at the melting temperature in order to melt it to the liquid form at the same temperature. Looking at it the other way: It's the amount of heat you have to remove from the liquid at the freezing temperature in order to freeze it solid at the same temperature.
Most plastics are actually liquids .... they are just very viscous. The glass in your window is also a liquid. A solid has a defined crystal structure. Things like asphalt, plastic, and glass don't have a crystal structure and are therefore liquids. Really think, viscous liquids. As you heat them, they become softer and softer as opposed to melting and changing to a liquid all at once.
First you can not add a cold temperature to anything. Ask your teacher to explain what heat is an what temperature is, because you clearly do not understand this. When a liquid BOILS - it turns into gas. When a liquid FREEZES - it turn into a solid.
So that all the liquid isn't immediately pulled through the filter. To wash the solid, you want the solid to interact with the liquid, to stir it, to make sure that any soluble impurities have a chance to be dissolved and removed. If you leave the aspirator on while washing, the interaction time of the solid and the washing solvent will be reduced. Add liquid, stir, and then turn the aspirator back on to remove the impurity-containing solvent.
If the matter is in a liquid state, add heat to turn liquid to vapor. Remove heat to form a solid. If it is in the form of a vapor, remove heat to form a liquid, and remove more heat to form a solid. If it is in the form of a solid, add heat to turn it into a liquid. Add more heat to turn into a vapor.
It is called sublimation when you turn a solid into a gas. When you turn a gas into a solid it is called deposition.
Add heat.
It depends on the solid. Stone would probably become molten lava. Metals would become liquid and could by poured into moulds. Solid ice would turn into water.
That's the amount of heat you have to add to the solid form at the melting temperature in order to melt it to the liquid form at the same temperature. Looking at it the other way: It's the amount of heat you have to remove from the liquid at the freezing temperature in order to freeze it solid at the same temperature.
You add heat :)
latent heat of fusion.
To change the state of matter, you need to add or remove energy. For example, to change a solid to a liquid, heat is added to increase the temperature until it reaches the melting point. Likewise, to change a liquid to a gas, heat is added to increase the temperature until it reaches the boiling point.
For example, to melt ice, you need to add heat energy. To freeze liquid water (to turn it back into ice), you have to remove heat energy.
If a solid is subjected to heat, it will expand. On reaching its melting point, the solid will become liquid. At boiling point it will convert in to gaseous form. These are the three states of a matter.
First of all you cannot add cold. You can remove heat. In the first instance gas minus heat is cold gas. Then, depending on the substance, you can have mainly liquid or solid.
To change one state of matter to another, you need to either add or remove heat energy. For example, to change a solid to a liquid, you would need to add heat energy to melt the solid. Similarly, to change a liquid to a gas, you would need to add heat energy to evaporate the liquid.