gasoline burning (water vapor and carbon dioxide form)
iron rusting (iron oxide forms)
bread rising (yeast converts carbohydrates into carbon dioxide gas)
eggs cooking (fluid protein molecules uncoil and crosslink to form a network)
suntanning (vitamin D and melanin is produced)
milk souring (sour-tasting lactic acid is produced)
Physical change rearranges molecules however does not affect their inner structures. Some physical change are:
whipping egg whites (air is pressured into the liquid, but no new substance is made)
magnetizing a compass needle (there is realignment of groups of iron atoms, however no real change in the iron atoms themselves).
A chemical change generates a fresh substance, although a physical change will not. A material may change forms or shapes while going through a physical change, however no chemical reactions take place and no new compounds are created.
Examples of Physical Changes
melting an ice cube
crumpling a sheet of paper
breaking a bottle
casting silver in a mold
Examples of Chemical Changes
dissolving salt in water
mixing acid and base
In some instances, it may be difficult to tell whether a physical or chemical change happened. For example, whenever you dissolve sugar in water, a physical change takes place. The form of the sugar changes, but it stays the same chemically. However, whenever you dissolve salt in water the salt dissociates into its ions therefore a chemical change occurs.
The changes could be of two kinds, chemical changes and physical changes.
Physical changes are changes within the physical properties of substances for example size, shape, colour and state of substances. No new substances are created in these changes.
Melting of ice, folding of paper and boiling of water are a few of the examples of physical change.
Physical changes could be reversible.
A change where a number of new substances are created is referred to as a chemical change. A chemical change is also known as a chemical reaction. All new substances are created as a result of chemical changes.
Cooking of food, burning of paper and rusting of iron articles are a few of the examples of chemical change.
Chemical changes are always irreversible
Here is the List of Chemical and Physical Changes:
baking a cake,
smelling different types of food
Burning firewood is also considered chemical changes.
melting an ice cube,
crushing a can,
mixing sand and water,
breaking a glass
mixing red and green marbles.
Rusting is actually a chemical change that impacts iron articles and gradually destroys them.
The procedure of rusting is symbolized by the following equation:
Iron (Fe) + Oxygen (O2 from the air) + water (H2O) ——-> Rust (iron oxide Fe2O3)
For rusting, the existence of both water (or water vapour) and oxygen is important.
Methods of Avoiding Rusting:
The operation of depositing a layer of zinc upon iron is known as galvanisation.
Crystallisation:Crystallisation is a physical change where large crystals of genuine substances are created from their solutions.