My nephew loves asking me science things, mostly because I always find a fun analogy to explain. Today I was explaining from where comes the gas of soda and I bumped with the concept of chemical equilibrium and he asked about that. Now I’m trying to find a creative analogy to explain chemical equilibrium to him the next time we meet.
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In every chemical reaction you have reactants and products. The system is in equilibrium when the reaction is no longer happening, i.e. when you run out of at least one of the necessary reactants.
Chemical equilibrium happens when there’s no *net* change in a chemical reaction. Certain reactions like to happen, and they produce the products. When it’s the reaction you want to happen, this is called the “forwards” direction. Reactions, especially simple ones, will also happen in the reverse direction. At a certain ratio, the forwards reaction happens at the same rate as the reverse reaction. This is equilibrium.
A good example is dissolving a bunch of salt in water. The salt dissolving is the forwards direction. The salt falling out of solution is the backwards reaction. Which individual salt atoms are dissolved at any given time changes, but once at equilibrium, the solution will have a constant amount of salt dissolved and a constant amount sitting on the bottom
A non-chemical analogy might be like when you put a kitten and a puppy who don’t know each other in the same room. At first, there will likely be some kind of reaction, but eventually they may learn to co-exist and ignore each other completely. Or if you expose a pet to a toy too much, they may get bored of it and stop responding.
At chemical equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction. Take
H2O <-> H+ + OH-. In this case, there is a point at which water will be breaking down at a rate equal to its formation rate.
If it was me I’d buy some cheap food coloring and make 8oz of blue water and 8oz of yellow water. Tell the kid some spiel along the lines of you have chemical A(blue) and chemical B(yellow). Pour them together in a clear vessel. As they mix that’s the chemical reaction. As they turn into green that’s equilibrium. Just a thought of the top of my head.
Oh plus throw in a “blue isn’t happy alone and neither is yellow… but together they make green and everyone is happy” type analogy.
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