1.) suppose a teaspoon of magnesium filings ans a teaspoon of powdered sulfur are placed together in a metal beaker. would this constitute a mixture or a pure substance? suppose the magnesium filings and sulfur are heated so they react with each other, forming magnesium sulfide. would this still be a "mixture"? why or why not?
2.) during a very cold winter, the temperature may remain below freezing for extended peroids.however, fallen snow can still disappear, even though it cannot melt.this is possible because a solid can vaporize directly,without passing through the liquid state. is this process(sublimation0 a physical or a chemical change?
chemistry..easy
2009-08-29 8:13 pm
回答 (2)
2009-09-01 5:14 am
✔ 最佳答案
1)It is not a "pure substance"(compound) cause the Mg and S and be separated physically(e.g magnet), so it is a mixture. When it is heated, Mg and S combined chemically, new substance is produced. A tea spoon of Mg and A tea spoon of S may not be in suitable proportion for them to react with each other completely. Thus, some Mg or S may left in the beaker. Therefore, it can be either a pure compound of Mg and S or a mixture of MgS and Mg or S.2)physical change, since there are no new substance produced during the process
參考: Me
2009-08-29 9:56 pm
1) This would constitute a mixture because it consist of two kind of substances. After being heated, there is only one substance in the beaker, magnesium sulfide, so this is not mixture anymore.
2)This process, sublimation, is a physical change because it does not form any new substances and only involves the change of state of water from solid to gas.
2)This process, sublimation, is a physical change because it does not form any new substances and only involves the change of state of water from solid to gas.
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