posted by AHS on .
Which method increases the surface of a solid, allowing it to dissolve faster?
A)changing the state of the solid
B)adding gas to the solid
C)heating the solid
D)reducing the size of the solid
I think the answer is C but i am not completely sure. If you can answer with an explanation, that would be a big help(:
I think I answered this earlier when you had some typos. I think the answer is D.
Think about some examples. A related example is melting ice. Which melts faster, one large piece of ice or hit the large piece with a hammer to make small pieces. The small pieces melt faster because the surface area of the large piece has been increased. Now think of a large piece of rock salt, say the size of a teaspoon. Which will dissolve faster in water, the large piece of rock salt or (now grind it up into tiny pieces) the many small pieces. The many small pieces will dissolve faster because the surface area has been increased by a large amount. With some caveats you can make a case for some of the others.
Heating the solid (C) will make it hotter and if it is in the solvent it probably will dissolve faster; however, heating the solid does not increase the surface area. The reason it dissolves faster is that most (but not all) substances are more soluble in hot water than cold water. Adding a gas (B) doesn't make sense to me. I don't see how that increases the surface area. If we change the state (A) (for example, melt NaCl so it is a liquid by heating it to about 1000 C) might make it dissolve faster; however, the surface area isn't increased that much. In addition, A is so general (changing the state could mean changing it from a gas to a solid) that I don't see that as a viable choice. Here is a site that discusses the mathematical formulas for surface areas of various solids. Scroll down to the "In Chemistry" part and note the example of the iron powder versus a block or iron.