Which is a chemical change? a. water boiling b. wood burning c. glass breaking d. ice melting e. molding iron

A chemical change alters the chemical makeup of a substance. So, wood burning would be a chemical change. The others just alter the physical makeup of the substance.

The answer would be "wood burning" or option B. Chemical change is when a element get's turned into another element. Many people mistaken chemical change, and physical change but psychical change would be this: if you cut a piece of wood in half that would be a physical change because it's still wood but it's smaller. But if you burn wood into ash it would be a chemical change that's because it's no longer wood it's ash.

Also, it wouldn't be option A because that's still water but in gas for which is water vapor which is a physical change. It's also not option C because glass being broken is also a physical change it's still glass but it's smaller. It's also not option D because it's also a physical change, it's still water but in a different form. It wouldn't be option E because it's a physical change it's being molded into liquid iron which means it's still iron but in a different form. Basically all of the other options are examples of a physical change.

Hope this helps!

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"