Where's the Evidence

Guiding Question: What are signs that a chemical reaction has occured?

Hypothesis:

 I think that some signs of chemical change are color change, bubbling, overflowing, combustion. I think that most of the reactions will be either bubbling or color change. I think that all of the reactions will be easily spotted and there won’t be any reactions that will not be visible.

Materials:

1) Na2Co3- Sodium Carbonate
2)CaCl2- Calcium Chloride
3)HCl- Hydrochloric Acid
4)CuSO4- Copper Sulfate(acid)
5) Aluminium Foil
6)Zinc Pieces
7)Baking Soda
8)Vinegar
9)Magnesium Tablets
10)Spatula
11)Graduate Cylinders
12)Stirrer
13)Candle
14)Goggles
15)Beakers
16)Starch
17)Iodine

Analysis Table:

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Reaction	Observations Before Reaction	Predictions	Observations During Reaction	Observations After Reaction
Baking Soda + Vinegar	Vinegar is clear in the tube, the baking soda is white powder	It will bubble up and overflow	The liquid is bubbling up and the baking soda dissolved in the vinegar creating a fizz	The liquid is much less in volume and the baking soda is gone
Sugar + Heat	The sugar is grainy and hard, clear white	It will melt and become black	The sugar on top is bubbling while the sugar underneath is melting and becoming brown	The sugar became a brown liquid and the aluminum blackened.
Iodine + Starch	The Iodine is a dark purple though it is recognizably purple	It will change color	It is slowly becoming darker and darker	The Iodine is pitch black and very different from when it started.
Copper Sulfate + Aluminum Foil	Copper Sulfate is light blue and aluminum ball is shiny and gray	It will dissolve	It is becoming red and the copper sulfate is losing color	The Aluminum foil is dark red as if it rusted out and the copper sulfate has lost its color.
Zinc piece + HCl	The liquid is clear with the zinc piece normal	The zinc will dissolve	The zinc has bubbles coming out	The zinc seems the same and the HCl is a very whiteish blue
Copper Sulfate + Sodium Carbonate	Everything is normal	It will change color	It bubbles up	Its color has changed

Analysis of your results. 

How do the results of each reaction compare with your prediction? 

My predictions were all more or less correct except for a few. For the Zinc and HCl I predicted that the Zinc would dissolve. At the end the zinc was still there which meant my prediction was wrong, I also didn’t predict any color change. My prediction for copper sulfate and aluminum foil was also w bit off. I thought that the aluminum would dissolve but instead it just turned reddish, and the Copper Sulfate lost all its color.

How did you know when each reaction was over?  What was the evidence of a chemical reaction in all results?

From my observations I noticed that usually the way that you can see if a chemical reaction is over is quite obvious. For example, the baking soda and vinegar had a very noticeable reaction which was that the combination bubbled up and overflowed. It was easy to see that when it stopped bubbling and the foam receded that the chemical reaction was over. Another example is the zinc piece and HCl, which was also a noticeable reaction. When the reaction was happening the zinc had bubbles coming from it and the HCl was turning white-ish. When it eventually stopped and the zinc piece was normal I could tell that the reaction was over. I think that the evidence of a chemical reaction being over in all cases was that at the end everything had noticeably changed, be it color change, loss of liquid due to overflowing, but all of them had some sort of change you could see.

  Were there any endothermic or exothermic reactions?

Throughout the lab there were a few exothermic but no endothermic reactions. An endothermic reaction is when something’s temperature drastically drops down, there were none of these.

  Were the products always the same as what you started with?  How do you know?  

None of the end products were the same as what they started as because all of them had a chemical reaction happen. When a chemical reaction happens it means that chemical change has occurred resulting in something different than in the beginning. A chemical change, by definition, is when molecules change and cannot go back to their former state. This is how I know that none of the products stayed the same.

Conclusion:

The guiding question asked how to know when chemical change has occurred and I thing that this lab showed most ways to known when chemical change occurred. I think that my hypothesis was correct because I did see a lot of color change and bubbling though not much combustion. Some of the chemical changes were a lot harder to see than other ones, for example the copper sulfate and aluminum foil took a while to have effect but the baking soda and vinegar was nearly instant. My hypothesis stated what happened to most of the chemical reactions although one thing I think I missed in my hypothesis was dissolving. The zinc piece in the hydrochloric acid seemed to dissolve when put in it which I did not predict. It was the same thing with the baking soda and vinegar, and the starch and Iodine

Further Analysis:

I think that this was a goof lab and I dont know if I would make any changes to the procedure. I did have a few questions during the lab and probably the one I wondered most is that when we did baking soda and vinegar and put in a lot of vinegar and baking soda, the reaction was the same as if we put less. This was quite strange to me and I hope to find out why in our next lab.