Errah is a bookwormy and logophilic writer and science & technology teacher. He often writes about scientific ideas, theories, and research.
Physical vs. Chemical Change
Let's begin our discussion with a simple experiment. Get a paper and describe its color, odor, size, and shape. Usually, paper is a thin, flat, rectangular, white material. Since it is made up of wood pulp, its odor is woody.
Now fold or cut the paper using scissors. What happened to the physical appearance of the paper after doing it? Does its color change? How about its odor? What happened to its size and shape?
After doing this, the shape and size of the paper have changed, but not its color, texture, and odor. The color, texture, and odor of the paper remain the same because its composition stays the same. It is still paper. It is just folded or cut.
Get a candle, light it, and then burn the paper with it. What happened to the paper? Does its color change? What color is the paper now? Now, smell the burned paper, does its smell changed or stay the same? Do you think it is still a paper? After burning, the color of the paper turns gray or black and its smell becomes unpleasant. This occurs because when the paper is burned, it no longer remains paper but transforms into a new substance known as ash.
From folding to burning, the paper undergoes two types of changes: physical and chemical changes. Let's take a look at what physical and chemical changes are to understand them in more detail.
What Is Physical Change?
Physical change is a change of matter without affecting the composition or the identity of a substance. The substance only changes size, shape, form, state, quantity, or mixed with other substances, but no new substance is formed and its composition stays the same. Like when you fold or cut the paper, it does not form a new substance. Its size and shape changed, but the chemical composition will remain the same. It is still a paper.
Another example of physical change is carving wood to create a sculpture. When you carve wood, whether you shape it into a human, an animal, or any other object, the composition of the wood remains the same. You simply change its shape to resemble another object, but the finished product is still made up of wood.
Another example of physical change is the transformation of the state of matter, such as from liquid to solid. At low temperatures, for example, water (liquid) freezes into ice (solid). When water freezes, its composition remains unchanged. What happens to the ice when it melts? Is it transformed into a new substance? No, it's still water?
When heated, water evaporates and turns into water vapor (gas). Water vapor cools and condenses as it rises high into the sky, forming clouds. When the clouds become too heavy for the air to support, they fall back to Earth as rain. So what is the composition of rain now? Isn't it water?
Mixing two or more substances is another kind of physical change, as long as they do not form a new substance. For example, mixing or dissolving the sugar in water. When you do this, it does not become a new thing. In fact, you can separate these substances using evaporation. When the mixture is heated, the water evaporates and wafts in the air, and you will see that the substance leaves in the container is still sugar.
What Is Chemical Change?
Chemical change, on the other hand, produces new substances that have different chemical structures, hence different chemical formulas and properties. A good example of chemical modification is the production of salt. Salt (NaCl) is made up of one atom of chlorine and one atom of sodium. Chlorine is a toxic gas, whereas sodium is a metal. When these two substances are combined, they produce a new substance which is salt. The new product, salt, has very different physical and chemical properties compared to chlorine and sodium. Salt is neither a poisonous gas nor metal. We can eat the salt without being harmed. It is not a gas but solid. It is brittle and can dissolve in water, unlike metals.
Another example of chemical change is the digestion of food such as bread. The bread is composed of starch, which is rich in carbohydrates. Once we eat it, it is stored in our stomach. The stomach secretes acid to digest the bread. The bread or starch liquefies in our stomach and is converted into a new substance which is carbohydrates. Digestion always produces many new substances. Later, the carbohydrates will be absorbed by the small intestine, and then the carbohydrates will be transported into our body and convert into energy. The unused carbohydrates will be stored in our bodies as fats. The other material that did not adsorb by our body becomes fecal matter which is another product of digestion. Other than bread, any food that is digested in our stomach becomes new substances.
Paper burning is another example of a chemical change. While the paper burns, the oxygen in the air combines with its constituents, such as cellulose, to form three new substances: smoke (carbon monoxide; CO), water vapor, and ash. Can you tell the difference between paper and the other three substances?
Signs of a Chemical Change
If something is undergoing a chemical change, you will notice the following signs:
1. Evolution of heat and light. As in the combustion of gasoline, it produces fire. Combining chlorine and sodium to form salt also releases heat and light.
2. Release of a gas. As in the burning paper, it releases smoke and water vapor.
3. A substance is precipitated from a solution. As in combining milk and vinegar, it forms curdling.
4. Production of electrical, sound, and mechanical energy. As in the reaction of water and sodium, it explodes.
5. The color and smell of a substance change. As for burning paper, the paper's color turns from white to black.
Another 30 more examples of chemical and physical change are listed in the table below.
30 Examples of Physical and Chemical Changes
|Physical Change||Chemical Change|
1. Making salt from seawater
1. Moldy bread
2. Shattered glass
2. Burning wood
3. Tearing a newspaper
3. Cooking food
4. Cutting meat, fruits, and vegetables
5. Pounding a garlic
5. Decaying dead matter
6. Hair cutting
7. Sharpening a pencil
7. Making wine from grapes
8. Sublimation of mothball
8. Making glass from sand
9. Dissolving salt in water
9. Making cheese from milk
10. Dew on grass
10. Rusting Iron
11. Blending foods
11. Explosion of fireworks
12. Bursting a balloon
12. Combustion of gasoline
13. Water vapor freezes to snow
13. Lighting a match
14. Disintegration of chalk while you use on the blackboard
14. A firefly giving off light
15. Folding a paper to make an origami
16. Trimming your fingernails
16. Tarnishing of silver
17. Mowing the lawn
17. Acid rain corrodes a statue
18. Cracking an egg
18. A banana ripens
19. Slicing a pizza
19. Exploding TNT
20. Grinding the black pepper
20. An igneous rocks turns into metamorphic rock
21. Soil Erosion
21. Developing of a photographic film
22. Folding the garments
22. Aerobic and anaerobic respiration
23. Bending a copper wire
23. The reaction of vinegar with baking soda
24. Knotting a rope
24. Charging of battery
25. Digging the soil for planting
25. Fertilizing a lawn
26. Molding clay
26. Growing of plants and animals
27. Solving a Rubik's cube
27. Formation of vinegar from coconut water
28. Formation of sawdust
28. Burning incense stick
29. Crushing a can
29. A metal melts in strong acid
30. Mixing stone and nails
30. Formation of oil from the palm tree.
- Chemical and Physical Changes of Matter — Science Notes
- Chemical Change vs. Physical Change - Chemistry LibreTexts
- Difference Between Physical Change and Chemical Change (with Comparison Chart) - Key Differences
- Examples of Chemical Changes in Everyday Life — Your Dictionary
- Everyday Examples of Physical Changes — Your Dictionary
- Examples of Physical Changes and Chemical Changes — Thoughtco
- Examples of Physical Changes — Thoughtco
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2021 Errah Caunca
Peggy Woods from Houston, Texas on October 13, 2021:
Your photos and written subject matter would make an excellent teaching aid for children or adults learning these concepts of physical verses chemical changes.
Errah Caunca (author) on October 13, 2021:
Thank you for your lovely comments. I so appreciate you taking the time to share your thoughts.
fran rooks from Toledo, Ohio on October 10, 2021:
Eric what an exceptional concise article. I learned a lot from your submission. Thank you for sharing.
Pamela Oglesby from Sunny Florida on October 09, 2021:
This is a very well-explained article on physical and chemical change, Eric. I felt like I was back in school, but I truly enjoyed reading the article. Thank you explained these changes so well.
Umesh Chandra Bhatt from Kharghar, Navi Mumbai, India on October 09, 2021:
Very nice article, well explained.