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

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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.

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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.

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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.

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

Sources: http://www.baristanet.com/Legos%203039.jpghttp://waynehodgins.typepad.com/ontarget/WindowsLiveWriter/Lego%20city_1.jpghttp://fireflyforest.net/firefly/2005/11/09/water/http://www.freedigitalphotos.net/image/s_glass_of_water.jpghttp://www.seattlerobotics.org/encoder/200601/article1/Liquid%20plastic%20tut%201%20b.JPGhttp://www1.istockphoto.com/file_thumbview_approve/1457080/2/istockphoto_1457080_how_long_is_a_piece_of_string.jpg