Chemical & Physical Changes

Physical and Chemical Changes

Hey people, so last class we did many experiments on physical and chemical changes and you guys got to see how matter of different substances can change when it’s influenced by other substances. You guys already know the basics of physical and chemical changes but if you don’t…I hope this blog will help you! J

Physical Changes:

Physical changes are changes that DO NOT result in the production of new substances. Physical changes affect size, shape, or state but it does not alter its composition. For example, if you melt a block of ice, you would still have water at the end of the change but the state changes, therefore, it is a physical change. You can change that water back into its solid form, by freezing it. Another good example would be bending a piece of copper wire. You can change the form or shape of the wire, however in the end it is still composed of the same material. Other common examples of physical changes are; melting, freezing, condensing, breaking, cutting and bending.

Chemical Changes:

Chemical changes are changes that result in a NEW production of another substance. Chemical changes undergo chemical reactions where substances react with each other to form new substances. You can notice the chemical change if the substance changes colour, or when two substances mix together. Dissolving and heavily reactive materials are also chemical changes. Bonds are broken and formed between different atoms. For instance when you burn a piece of wood, the burning will create carbon gas. When hydrogen is burned with oxygen, water is formed and heat will also be released.  When you light a Bunsen burner, it will produce water and carbon dioxide.  Some common examples of chemical changes are; burning, decomposition, photosynthesis and etc. Bottom line is, in the end, its original composition is altered into a new substance.

  

How can you tell physical and chemical changes apart?

Well first, chemical changes makes a new substance that wasn’t there before. There may be clues that a chemical reaction took place, for example light is emitted, heat is produced, colour changes, gas is produced, temperature changes and odor is produced. Second, the starting and ending of substances of physical changes are the same, even though they may look different.

Here is a little song that can hopefully help you understand chemical and physical change better!
(Entry by Melody Lu)