My daughter came home from school one day with an assignment to conduct a melting experiment at home. She was to observe how a change of state between solid and liquid is caused by adding or removing heat. So we set out to test and understand the chemistry behind some common melting experiences in the home. The children have loved being a part of this and even my pretoddler had a fair go getting herself wet and dirty with her ice experiment!
We begun our first experiment with melting chocolate. We used dark chocolate and melt them in 3 different locations – our mouth, the hot sun and over the hot griddle.
The ones in the kids’ mouths melted far too quickly before I could even ask any scientific questions, the one left in the cool shade took a few hours to barely melt but attracted a host of ants, and the one over the hot griddle melted quickly just under a minute.
We also tested how butter melted from its solid state over the fire on the hot pan. We used the same pan to provide heat to melt peanut butter, cheese and marshmallows. The children learn that all of these substances experience a change of state that was brought about by a change of temperature. They learn that substances have different, and specific melting points, from where they pass from their solid to the liquid state.
We observed how candle melts into liquid wax when lit.
We had an ‘aha’ learning moment observing how ice melt. I freeze large chunks of ice in different size containers and took them out into some large trays at room temperature. We then sprinkled some salt over the ice and dropped different food colouring to observe what happens.
As we observe, we understand that salt melt the ice and keeps it from refreezing. This works because salt lowers the freezing point of water, an effect which is termed ‘ freezing point of depression’. Adding salt to water introduces dissolved foreign particles into the water which then lower the freezing point of water as more particles are added until the point where the salt stops dissolving. Refer to this link here for full explanation and on how heat works here.
The kids truly loved the part where we then took some bread and toasted them over their melted substances – the butter, the chocolate, the peanut butter, the cheese…and tada…these end in their mouths!