Subject knowledge: How is melting and dissolving different?
Earlier this week we discussed how some children find it difficult to distinguish between the terms melting and dissolving.
A simple distinction is that dissolving requires a solvent, (liquid that a solid is able to dissolve in), whereas melting requires heating.
Dissolving involves a solid and a solvent. For example sugar is a soluble material or solute and water is the solvent that the sugar dissolves in. Many other solids dissolve in different liquids. When dissolving takes place a solid mixes with a liquid to become a solution of solid and liquid.
Melting involves a change of state of a material and requires heating for this to happen. For sugar to melt it needs to be heated until it becomes a liquid, as happens when you make toffee. In some situations both dissolving and melting may take place.
We have provided some examples of dissolving and melting here:
A. Nail varnish and remover
B. Ice in juice on a warm day
C. Vitamin C tablets in water
D. A boiled sweet in your mouth
E. Chocolate in a child’s pocket
F. Milk shake powder in milk
G. Jelly cubes in hot water
Sort the examples into whether they involve dissolving or melting. In the comments below, select one of the above that you found trickiest to decide, and explain why you chose it as either dissolving or melting.
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