A physical change alters a material's physical properties but not its chemical composition. Specifically, a physical change is one where the original material can be restored to its initial form through processes like melting, freezing, or reshaping. Examples of physical changes include creating a building with Lego blocks, freezing water, sharpening a pencil, cutting a string, and boiling water. In each case, the material's form changes but its chemical makeup remains the same.

1. 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.
Before
After
5 changes:

2. 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.
Before:
After:
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.
Before:

3. 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
atmosphere.
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.

4. Boiling water is also a physical change. The molecules move apart because of heat.

5. Sources:
http://www.baristanet.com/Legos% 203039.jpg
http://waynehodgins.typepad.com/ontarget/WindowsLiveWriter/Lego%20city_1.jpg
http://fireflyforest.net/firefly/2005/11/09/water/
http://www.freedigitalphotos.net/image/s_glass_of_water.jpg
http://www.seattlerobotics.org/encoder/200601/article1/Liquid%20plastic%20tut%201%20
b.JPG
http://www1.istockphoto.com/file_thumbview_approve/1457080/2/istockphoto_1457080_
how_long_is_a_piece_of_string.jpg