Question

Which of these is an example of a chemical reaction?

cooking eggs
boiling water
cutting vegetables
melting chocolate

Answer 1

@jazzyspazzy

Answer 2

Which one do you feel like is the right answer?

Answer 3

@Samara8954

Answer 4

Almost all of them appear to be physical changes, but cooking food (not melting or cutting) is a chemical change.

Answer 5

^ it is right. but i m just mentioning the explanation for each option. Hope it helps.
Cooking food:
It's a chemical change. the egg white or albumen becomes denatured and you cannot reverse cooking an egg. physical would be like making kool-aid. you mix it up, but you are still able to separate the components of the mixture.
Boiling water:
Boiling water is a physical change. ALL changes of state are physical changes. In a physical change no new substance is formed. Whether it's a solid (ice) liquid (water) or a gas it's the same substance. Also, when the water boils it changes to steam(gas), cool down the gas (condensation) and it changes back to water.
Cutting vegetables:
When you cut vegetables you make a change in their physical shape. There is no chemical change involved here. The chemicals which constituted the vegetables before you cut them remain the same as after you cut them. If a change is permanent it does not mean that it is a chemical change. You can take a sheet of aluminum foil,
cut it, wrap it around a sandwich, crush it into a ball, or do anything, but the aluminum remains the same. There is no chemical change. To make a chemical change in the vegetables you can cook them, or add chemicals that the vegetables would react to,
that would be a chemical change.
Melting chocolate:
it is a physical change. Anything that does not change the identity of the substance is a physical change.

Answer 6

boiling water

Answer 7

The answer would be A.
Chemical reaction is a phenomenon that takes place , altering the molecular arrangement or identity of the substance from initially.

Answer 8

I agree with everyone saying that denaturing proteins in an egg is a chemical change, but it is now reversible.

http://www.natureworldnews.com/articles/12242/20150126/unboiling-egg-make-treating-cancer-cheaper.htm
http://onlinelibrary.wiley.com/doi/10.1002/cbic.201402427/abstract

Answer 9

So it's no longer a chemical change to cook eggs? @aaronq

Answer 10

It is a chemical change.

Answer 11

You can take the example of boiling. The liquid transparent white part of the egg changes the colour to white. Other than that, the new formed structured is harder and is no longer as viscous as it was when liquid.

Answer 12

I mean, there are many reversible chemical reactions and were told in school that denaturing an egg is a non-reversible chemical process, but in light of this finding, it can now be considered as reversible.

My personal view (even prior to this) is that it depends on the temperature.
If the temperature is high enough to break bonds it's a chemical change, but if it's not it can't be considered a chemical change, because you're not breaking any covalent bonds but merely moving around amino acids apart so far from their original position that they overall structure is "impossible" to re-obtain. Most often this causes them to lose their soluble, "globular" shape and they precipitate out of solution.

It's hard to justify clearly what category protein denaturation falls under because you could make good arguments for both sides.

Answer 13

Cooking an egg