What are the definitions of a physical and chemical change?
Answer: A physical change happens when the properties of a material change but the
substances remain the same. In other words, it means that a physical change occurs if
the original material undergoes, and if and only if the substances can be reverted to its
normal form it is a physical change.
Creating a huge building with Lego blocks is an example of physical change. This is a
physical change, when creating building with blocks, the shape changes, but the identity
does not change.
Freezing water is a physical change, because when you freeze water, the shape changes,
but the substance water does not change. Now, the molecular movement is stationary, and
the molecules are packed together.
Sharpening a pencil is a physical change, because while sharpening the pencil you are not
changing the substances that make up the pencil. The molecules are escaping into the
Cutting a string is a physical change, because while cutting a string, you are changing the
shape but the string that is left is still string. The molecules move apart.
Boiling water is also a physical change. The molecules move apart because of heat.