Chemistry - Reaction Help.

[MacWorld]

Im only 14 so i kinda find this hard. Can anyone help me with the following.

I am meant to find experiments where after a reaction has taken place there is either a weight increase or decrease. e.g When Magnesium is heated and oxygen let in magnesium oxide is formed. This weighs more than magnesium. Therefore there is weight increse. When Copper Sulphate and Zinc cause a reaction after being heated there is no weight increse.

Can anyone help me with a experiment where the weight decreases after a reaction takes place.

 

[Sureshot]

Look at Hydrogen Fusion into Helium. That's how the sun works, and it's the drastic decrease in weight that produces the intense heat and power needed to keep a stable solar system running.

http://www.nineplanets.org/sol.html

iirc, if you take the two hydrogen atoms as 100%, the helium atom they form will be 70% of the hydrogen atoms combined mass.

 

[Harrypotter_fan]

The example is good but I don't think he wants nuclear reactions sureshot. In the experiment MW explained, the increased weight was due to oxygen.

 

[Cricketman]

Mass is always conserved. You may have to change the number of moles of the substance to 'equalize' on either side. Like if you have 12 grams of something on the right hand side, change the number of moles of the new substance on the left hand side to make it equal 12 grams as well.

Kind of confusing but I hope you understand.

 

[Kshitiz_Indian]

Yeah Rohit is right. What you said in the first post wasn't exactly right. You used 10 grams of Magnesium which formed around 40gms of MgO maybe(example). But the additional 30 grams were due to Oxygen being involved in the reaction and not really weight increase / decrease in nature. Mass is conserved.

Sureshot is also right. Fusion reaction gives instant heat as mass converts into energy. Quite advanced stuff though...

 

[Sureshot]

Would impress the teacher though...[/teacherspet]

 

[MacWorld]

Thanks guys for the help so far. Hmmm sucking up to the teacher might work lol