Melting and freezing are REVERSIBLE changes. This means that if we undo the change, we can get-back the materials we started with. A good example of this is ICE and WATER.
Remember that in Science, MATERIAL means any solid, liquid or gas that you can detect using your senses! Non-reversible changes result in a NEW and DIFFERENT material.
Birthday cake is a good example of a NEW MATERIAL. We mix together eggs, butter, flour and sugar, add heat and enjoy! BUT... we cannot reverse the changes. 'Cake' cannot be changed back into the ingredients we started with. (We would'nt want to anyway!)
Many non-reversible changes are caused by HEATING.
Gita and Jasa are carrying-out some science investigations. They are checking their understanding of REVERSIBLE reactions.
Gita takes an ice lolly out of the freezer and leaves it on the kitchen table. Which change takes place?
In separate beakers, Gita mixes salt, sugar and coffee granules with water. They make clear liquids.
Help Gita choose the science word which describes this change...
Gita and Jasa look in their fridge. They know that butter and yoghurt are made from milk.
When milk is turned into new foods, we can describe the reaction as...
The students know that heating some solids results in non-reversible reactions. Which THREE of these are made by non-reversible reactions?
Gita thinks that they should extend their investigations to other materials around them.
They decide to have a bar-be-que. Yipee!
Mum has built a bar-be-que in the garden using bricks and concrete.
Bricks and concrete are examples of materials resulting from..?
Jasa puts the charcoal on the bar-be-que.
Charcoal is a material made by a non-reversible reaction. Which material is irreversibly changed to produce charcoal?
Jasa and Gita enjoy eating the food cooked on their bar-be-que.
They think about what they have learnt. Can you help them remember the FOUR non-reversible ways of changing materials from this list?