You are watching: Is boiling a chemical or physical change
Change is happening all around us all of the time. Just as ubraintv-jp.comists have classified elements and compounds, they have also classified types of changes. Changes are either classified as physical or ubraintv-jp.comical changes. ubraintv-jp.comists learn a lot about the nature of matter by studying the changes that matter can undergo. ubraintv-jp.comists make a distinction between two different types of changes that they study - physical changes and ubraintv-jp.comical changes.
Physical changes are changes in which no bonds are broken or formed. This means that the same types of compounds or elements that were there at the beginning of the change are there at the end of the change. Because the ending materials are the same as the beginning materials, the properties (such as color, boiling point, etc) will also be the same. Physical changes involve moving molecules around, but not changing them. Some types of physical changes include:Changes of state (changes from a solid to a liquid or a gas and vice versa) Separation of a mixture Physical deformation (cutting, denting, stretching) Making solutions (special kinds of mixtures)
As an ice cube melts, its shape changes as it acquires the ability to flow. However, its composition does not change. Melting is an example of a physical change. 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. When we heat the liquid water, it changes to water vapor. But even though the physical properties have changed, the molecules are exactly the same as before. We still have each water molecule containing two hydrogen atoms and one oxygen atom covalently bonded. 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 either the pennies or the nickels - you"ve merely separated them into two groups. This would be an example of a physical change. 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. What was paper before you started tearing is still paper when you"re done. Again, this is an example of a physical change.
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We can"t actually see molecules breaking and forming bonds, although that"s what defines ubraintv-jp.comical changes. We have to make other observations to indicate that a ubraintv-jp.comical change has happened. Some of the evidence for ubraintv-jp.comical change will involve the energy changes that occur in ubraintv-jp.comical changes, but some evidence involves the fact that new substances with different properties are formed in a ubraintv-jp.comical change.
Observations that help to indicate ubraintv-jp.comical change include:Temperature changes (either the temperature increases or decreases) Light is given off Unexpected color changes (a substance with a different color is made, rather than just mixing the original colors together) Bubbles are formed (but the substance is not boiling - you made a substance that is a gas at the temperature of the beginning materials, instead of a liquid) Different smell or taste (do not taste your ubraintv-jp.comistry experiments, though!) A solid forms if two clear liquids are mixed (look for floaties - technically called a precipitate)