about physical change
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Physical change is a concept introduced to contrast with the concept of chemical change. A physical change is any change not involving a change in the substance's chemical identity. Matter undergoes chemical change when the composition of the substances changes: one or more substances combine or break up (as in a relationship) to form new substances. Physical changes occur when objects undergo a change that does not change their chemical nature. A physical change involves a change in physical properties. Physical properties can be observed without changing the composition of matter. Examples of physical properties include: texture, shape, size, color, volume, mass, weight, and density.
An example of a physical change occurs when making a baseball bat. Wood is carefully crafted into a shape which will allow a batter to best apply force on the ball. Even though the wood has changed shape and therefore physical properties, the chemical nature of the wood has not been altered. The bat and the original piece of wood are still the same chemical substance.
Changes are sometimes hard to categorize strictly as physical or as chemical. Dissolving a salt in water involves the breaking of chemical bonds, yet is often described as a physical change. Some teachers hold that a chemical change is a rearrangement of atoms, but many physical changes also involve the rearrangement of atoms. Many chemical changes are irreversible, and many physical changes are reversible, but reversibility is not a certain criterion for classification. Although chemical changes are often recognized by an indication such as odor, color change, production of a precipitate, or production of a gas, every one of these indicators can result from physical change.
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Answers:Concentration doesnt change
Answers:The first is chemical, the second is physical. A chemical change occurs when two or more compounds or elements make a new substance. In the case of mixing salt and sand and water, you can still separate them from the water (though it may be a bit hard.) Like, when water turns to ice or becomes water vapor it is a physical change. A chemical change is when paper burns, or when ammonia and bleach mix to create chlorine gas.
Answers:http://chemistry.about.com/od/lecturenotesl3/a/chemphyschanges.htm Physical changes are changes of state- no new substances Chemical changes are basically everything else. For the iodine, I would just be careful since it's already tinted. If the solution turned into the same colour as the iodine, then it's probably just a physical change, no chemical changes observed. pH would indicated a chemical change.
Answers:1.property physical 2.property physical 3.change (oxidation) chemical 4. Chemical change not as certain about this second set 1. Chemical 2. physical 3. chemical change (bonds in pair up) 4.chemical (carbon forms) 5. physical 6. physical