Physical and Chemical Changes

Topics: Significant figures, Flame, Chemistry Pages: 3 (887 words) Published: March 19, 2013
Physical and Chemical Changes
Say you are presented with two beakers, beaker A and beaker B, each containing a white, powdery compound. * a. From your initial observations, you suspect that the two beakers contain the same compound. Describe, in general terms, some experiments in a laboratory that you could do to help prove or disprove that the beakers contain the same compound. You may try some of the followings:

* Dissolving in water
* Dissolving in different chemical solution
* Heating both substance to see if they come out with different results * Doing the flame test for both solution to see if they can come out with different results * etc
* b. Would it be easier to prove that the compounds are the same or to prove that they different? Explain your reasoning. It is easier to prove that they are different because it is suffice to find just one experiment that their results do not match each other. In contrast, if there are many experiments that their results match each other, you can not even make a conclusion. Why? Because it is not guaranteed that you can not find a different experiment that their result fail to match each other. * c. Which of the experiments that you listed above are the most convincing in determining whether the compounds are the same? Justify your answer. Maybes the flame test because different substance may yield different flame colors while doing flame test. For example, sodium may yield yellow flame color but potassium yields purple flame color while burning. * d. A friend states that the best experiment for determining whether the compounds are the same is to see if they both dissolve in water. He proceeds to take 10.0 g of each compound and places them in separate beakers, each containing 100 mL of water. Both compounds completely dissolve. He then states, “Since the same amount of both substances dissolved in the same volume of water, they must both have the same chemical...
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