The melted ice cube may be refrozen, so melting is a reversible physical change. Physical changes can further be classified as reversible or irreversible. When liquid water (H 2O) freezes into a solid state (ice), it appears changed However, this change is only physical as the composition of the constituent molecules is the same: 11.19% hydrogen and 88.81% oxygen by mass. Figure 2.8.2: Ice Melting is a physical change. Again, this is an example of a physical change. What was paper before you started tearing is still paper when you are done. Similarly, if you have a piece of paper, you don't change it into something other than a piece of paper by ripping it up. This would be an example of a physical change. When you have a jar containing a mixture of pennies and nickels and you sort the mixture so that you have one pile of pennies and another pile of nickels, you have not altered the identity of the pennies or the nickels-you've merely separated them into two groups. We still have each water molecule containing two hydrogen atoms and one oxygen atom covalently bonded. But even though the physical properties have changed, the molecules are exactly the same as before. When we heat the liquid water, it changes to water vapor. A physical change is a change to a sample of matter in which some properties of the material change, but the identity of the matter does not. Melting is an example of a physical change. However, its composition does not change.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |