I always think the concept of mass versus weight is a difficult one, especially as we generally use the terms interchangeably in our every day language.
Mass is the amount of matter in an object, and weight is the force of gravity acting on it. So, Dancing Toes’ mass will be the same whether she is standing on earth or the moon, or Mars, but her weight will be different.
To demonstrate mass, we measured out ingredients on a balance scale, in grams.
To demonstrate weight, we hung an assortment of items on a spring balance (used by the boys for IGCSE physics) and recorded how far they made the spring stretch. ie the effect of gravity on them. Weight is measured Newtons (after Isaac Newton).
It gets more complicated by IGCSE level and it was often the boys explaining to me, but I can just about manage an explanation at this stage!
Mothering through the seasons 
I am impressed. Your knowledge knows no bounds Molly. The girls will be teaching me next!
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