Classify each of the following as chemical and physical change
Paper burns
Food digest
ice melts
silver tarnish
glass breaks
baking bread
water evaporates
dead leaves decaying
Physical Change
Chemical Change
Imagine that you break a a glass cup. Has a new substance been formed?
Yes
No
Breaking a glass cup is a ......
physical change
chemical change
Is NaCl (table salt) dissolving in water a physical or a chemical change?
Physical change because a new substance was created
Chemical change because a new substance was created
Physical change because a new substance was not created
Chemical change just 'cause
You may have been told that a chemical change is something you can't undo, but a physical change is something you can undo. That isn't really true, but it is a decent rule of thumb. The better definition is:
it is a chemical change if the molecules are changed
it is a chemical change if you saw bubbles
it is a chemical change if the color changed
it is a chemical change if something changed phase or dissolved.