Physics,chemistry and biology demonstrations


SCIENCE DEMONSTRATIONS 


CHEMISTRY - VITAMIN C CLOCK REACTION







Vitamin C Clock Reaction

 Two colorless liquids are mixed together and after a few moments the mixture turns a dark blue color. There are actually a couple of simple chemical reactions going on at the same time to make this “clock reaction” occur. This version of the classic “VITAMIN C clock reaction” uses safe household chemicals available easily at home.
AIM: To study the VITAMIN C clock reaction

Materials required:

·         distilled water (tap water will work OK as well)
·         a couple of plastic cups
·         1000 mg vitamin C tablets
·         tincture of iodine (2%)
·         hydrogen peroxide (3%)
·         liquid laundry starch

PROCEDURE

1.      Make a vitamin C solution by crushing a 1000 mg vitamin C tablet and dissolving it in 2 oz of water. Label this as “vitamin C stock solution”.
2.      Combine 1 tsp of the vitamin C stock solution with 1 tsp of iodine and 2 oz of water. Label this “solution A”.
3.      Prepare “solution B” by adding 2 oz of water to 3 tsp of hydrogen peroxide and 1/2 tsp of liquid starch solution.
4.      Pour solution A into solution B, and pour the resulting solution back into the empty cup to mix them thoroughly. Keep pouring the liquid back and forth between the cups.

RESULT: The iodine which is colorless in vitamin C solution becomes blue black when mixed with solution of starch and hydrogen peroxide.
Explanation: There are two forms of iodine:
Element form (Iodine): I2 + starch -------> blue
Ion form (Iodide): I- + starch --------> colorless
There are two reactions taking place simultaneously in the solution:
#1. 2I- + H2O2 ---(slow)-------> I2 + H2O
#2. I2 + Vitamin C ----(fast)----> I (colorless)
In Reaction # 1 iodide ions react with hydrogen peroxide to produce iodine element which is blue in the presence of starch
In Reaction # 2 The Vitamin C is immediately reacting with any iodine formed in reaction # 1. The net result, at least for part of the time is that the solution remains colorless with excess of iodide ions being present.
Now after a short time as the reactions keep proceeding in this fashion, the Vitamin C gets gradually used up. The Vitamin C creates a clock reaction (1 - 2 minutes) and once it is used up, the solution turns blue, because now the iodine element and starch are present.





PHYSICS EXPERIMENT 



 SPOON OR BELL EXPERIMENT



Aim: To prove vibrating spoon can sound like a bell.

Apparatus required: Spoon ,fork ,wooden ladle

Procedure:  
---> Tie a spoon in the middle of the string            
----> And hold the ends of the string with the index fingers and                       bring it close to ears.             
---> Ask your friend to hit gently the spoon with another spoon.
This step can be repeated using fork, other shaped spoons,or by decreasing the length of string etc.

Observation:             
If we listen carefully, we hear the sound which resembles like a bell lasting for a while.

Conclusion:   

Sound is produced by Vibrating Bodies. Sound travels faster in solid medium.
















 BIOLOGY EXPERIMENT 



 EFFECT OF BROMELAIN ON GELATIN


Pineapple Enzyme Many people love gelatin-based desserts. Many of us love pineapples too. Should you put them together? As many a gelatin-loving cook has discovered, certain fruits can change gelatin’s ability to set. In this experiment, we can discover what happens when gelatin meets pineapple.

AIM: To study effect of Bromelain (enzyme present in pineapple) on setting of gelatin

MATERIALS REQUIRED: Fresh pineapple, boiled pineapple, frozen pineapple, measuring cup Kettle Water Spoon Two quarters, 3 containers of gelatin

PROCEDURE:
1. Mix the gelatin powder with warm or hot water according to the package's instructions. 2. Pour an equal amount of gelatin into each of three bowls.
3. Add ten small chunks of fresh pineapple to one bowl, in another put boiled one and in last one put frozen pineapple chunks.
 4. Put all the bowls of gelatin in the refrigerator to set, and wait for several hours.


RESULTS: The gelatin with the fresh and frozen pineapple in it gets very watery, while the gelatin in the other bowl with boiled pine apple gets firm. A quarter will sink into the liquid in the pineapple gelatin, but it will sit on top of the gelatin in the plain gelatin bowl.
CONCLUSION: Pineapples contain the protein-digesting enzyme called bromelain. Bromelain is also used as a meat tenderizer; Gelatin is made out of animal proteins, particularly collagen. When you add water to the gelatin, long chains of protein form, making invisible protein “spaghetti”. Water gets trapped in the middle of these long chains, turning what should be a liquid into a semi-solid. Since pineapple bromelain digests proteins, when the pineapple meets the gelatin, it begins to eat away at it. The long protein chains collapse, making everything watery again. The bowl with boiled pineapple sets as normal as bromelain enzyme is heat sensitive and heating inactivates this enzyme.



















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