Possible and irreversible are two different things reversible are things that you can DO and UNDO. Irreversible now things you can do but CANNOT undo. EXAMPLE : IRREVERSIBLE Egg you try it but can't unfry the egg EXAMPLE 2 : REVERSIBLE Ice when it melt it becomes liquid but when it freeze again it's becomes ice.
Answers
Answer:
Physical changes involve states of matter and energy. No new substance is created during a physical change, although the matter takes a different form. The size, shape, and color of matter may change. Physical changes occur when substances are mixed but don't chemically react.
How to Identify a Physical Change
One way to identify a physical change is that such a change may be reversible, especially a phase change. For example, if you freeze water into an ice cube, you can melt it into the water again. Ask yourself:
Is the change reversible? Not all physical changes are easy to reverse.
Was there a color change (with exceptions), bubble formation, or formation of a precipitate? These are all signs of a chemical change, not a physical change.
Is the chemical identity of the end product the same as it was before the change? If the answer is yes, it's a physical change. If the answer is no, it's a chemical change.
Examples of Physical Changes
Remember, the appearance of matter changes in a physical change, but its chemical identity remains the same.
Crushing a can
Melting an ice cube
Boiling water
Mixing sand and water
Breaking a glass
Dissolving sugar and water
Shredding paper
Chopping wood
Mixing red and green marbles
Sublimation of dry ice
Crumpling a paper bag
Melting solid sulfur into liquid sulfur. This is an interesting example since the state change does cause a color change, even though the chemical composition is the same before and after the change. Several nonmetals, such as oxygen and radon, change color as they change phase.
Chopping an apple
Mixing salt and sand
Filling a candy bowl with different candies
Vaporizing liquid nitrogen
Mixing flour, salt, and sugar
Mixing water and oil
Indications of a Chemical Change
Sometimes the easiest way to identify a physical change is to rule out the possibility of a chemical change. There may be several indications that a chemical reaction has occurred. Note: It's possible for a substance to change color or temperature during a physical change.
Evolving bubbles or releasing gas
Absorbing or releasing heat
Changing color
Releasing an odor
Inability to reverse the change
Precipitation of a solid from a liquid solution
Formation of a new chemical species. This is the best and surest indicator. A change in the chemical properties of the sample may indicate a chemical change (e.g., flammability, oxidation state).
Explanation: