Is a volcano exploding a chemical or physical change?

Answer 1

This answer is complex. The short answer is both.

In general, if you go from a liquid to solid state without a change in the chemistry of the compound you are merely changing physical state, not chemical. This is most easily observed with making ice cubes. Water freezes but it stays water and when you put the cubes in a glass of water you still have water when it melts. So the major change when lava hardens is a physical change.

Lava however is not a uniform chemical compound like water. You can see this as lava hardens that it forms crystals in the rock. These crystals are also a physical change as compounds that are similar to one another fall out of solution and crystallize as the liquid rock cools, much the same way rock candy forms from a cooling solution of sugar and water. With rock candy this is still a physical process because you can reheat the rock candy in the water and it becomes a solution again.

The complex part of the answer is that with lava gases are often given off, some of which are as a result of chemical reactions during the cooling process. When you remelt the same rock, the chemical solution you get is not exactly the same as what you started with. So some chemical changes are occurring during the overall physical change.

For example, heat and cool Baking Chocolate over and over. Soon you get something you are not sure you really want to eat. This is because the chemical changes happening in each cycle are small enough to miss during one melt/cool cycle but repeating this process makes what is happening chemically more obvious.

Answer 2

It's a physical change - more intermolecular bonds (bonds between different molecules) are formed due to the cooling of the matter, and the state of matter changes from liquid to solid. The chemical makeup of the lava does not change.

Answer 3

Yes, because you can see that it changes!

Answer 4

it is achemical

Answer 5

Chemical