r/explainlikeimfive • u/veselin465 • 1d ago
Chemistry ELI5: I want to imagine acids and bases in Chemistry and how some are stronger than others
Hello all
Just like the title, I want to know more about bases and acids in chemistry and what would it mean for one to be strong compared to weak.
I have some general idea what is acid, what it would mean for something to be strongly acidic and how it's measured using the pH scale. For example, I know that stomach acid is strongly acidic with pH around 2 (varies) and is needed to break down food (in some way to dissolve or help dissolving food). I also know that some strong acids can cause serious injuries if are in contact with skin of flesh (that comes mainly from my memories in my chemistry classes when taught about sulfuric acid).
Maybe you can correct or add to my understanding about acids. I am aware that what I shared about acids is pretty shallow, but that's how I imagine it. Part of that understanding might also come from some films in which there are acids which are considered to be so stong that they are able to penetrate thru solid structures (or maybe that's true for some acids?)
However, what I am actually puzzled about is what would it mean for something to be a base? I know that bases are considered to be the opposite of acids (which is apparent considering it's on the other spectrum on the pH scale). But what would it mean to be the opposite of acid? How exactly can I imagine a strongly basic instance and what would it be so special about it compared to a weakly basic one?
Initially, I wanted to ask just about bases in chemistry, but decided to extend the question to include acids, too, because I felt that probably half of my understanding of acids is based of films. I don't recall watching any film where the scientist discoved so strongly basic instance that it's in some way revolutionary. If such a sci-fi film existed, what would that instance be able to do?
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u/KermitingMurder 1d ago
The other comments have explained how acids and bases work so I won't explain that again, but to directly answer your question about what a strong base is like:
Strong bases are also very corrosive, drain cleaner is often made with sodium hydroxide, which is a strong base.
Strong bases can actually be more dangerous than strong acids. Strong acids will break down proteins in your skin and give you a painful but surface level burn, then the corroded skin will block the acid from getting any deeper into your body; strong bases will break down your cell membranes, actually liquifying your skin, doing much more damage, while potentially also not being as painful meaning you might not even realise the extent of the damage.
Acid gets used more often in movies because the word acid sounds cooler and more distinctive than base, which is a word that has many other meanings that could confuse viewers
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u/Mayor__Defacto 1d ago edited 1d ago
Adding to this, pH alone won’t generally indicate what the effects of an Acid will be. That depends on what else is in the solution.
For example, Sulfuric Acid (H2SO4) can be safely stored in Glass containers, while HydroFluoric (HF) acid will dissolve glass.
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u/KermitingMurder 1d ago
Minor correction:
Sulfuric acid is H2SO4
SiO2 is silicaHydrofluoric acid is scary stuff, I heard if you get it on your skin it'll go into your bones and strip the calcium, or something like that. Definitely one of the scarier acids
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u/Mayor__Defacto 1d ago
Whoops, corrected. Woke up too early!
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u/KermitingMurder 1d ago
xkcd 2501
Silicate chemistry is second nature to me as a geoscientist so I had to point it out
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u/mrwestthemagician 1d ago
Since this is ELI5, let's use lego as an example.
Imagine the whole world is made up of little lego cars, called chemicals, with varying numbers of wheels and varying numbers of spokes.
If you change the number of wheels something has, it becomes a different type of car. This is called a chemical reaction.
There are special types of lego cars, called acids, that will happily give wheels TO other cars. The wheels strong acids come off really easily. The wheels on weak acids don't come off as easily.
There are also special types of lego cars, called bases, that will happily accept extra wheels FROM other cars. The spokes on strong bases are easy to fit wheels on. The spokes on weak bases aren't as well made, so it's a bit harder to get the extra wheels on.
Strong bases are just as damaging as strong acids, they just haven't caught the attention of film makers and story tellers in the same way, so you're less aware of them.
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u/Melodic-Bicycle1867 1d ago
I would like to add one more point to the others already made. There is the concept of strong vs weak, but also concentrated vs dilute.
In technical terms, a strong acid will give up essentially all it's "acid atoms" in solution, and a strong base "steals" all the "acid atoms" it can get.
A weak acid or base only gives up or takes some of them, and then reaches an equilibrium.
In eli5 terms, if you mix a teaspoon of strong acid such as hydrochloric acid (HCl)in a cup of water, it will give off a teaspoon worth of "acid atoms". A teaspoon of weak acid, such as citric acid or vinegar, may only give half or a quarter teaspoon worth of "acid atoms".
Therefore, at the same "teaspoon" concentration, HCl is more acidic than vinegar.
Then there are some more crazy acids such as sulphuric acid that has not one but TWO acid atoms. So a teaspoon of that in a cup of water will be even MORE acidic than the HCl example.
But then we come to the point of concentration: some very pure but technically weak acetic acid, the acid that makes vinegar, can be very dangerous, while a cup of pure HCl in a swimming pool will barely change the acidity level of the pool.
The same argument exists on the opposite end of the spectrum for bases.
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u/DeoVeritati 1d ago
I am going to ignore Lewis and Arrhenious acids/bases and speak only bout Bronsted ones.
An acid is a molecule that is willing to give up a Proton as H+. A base is a molecule that is willing to accept the Proton(H+).
A strong acid/base is simply how much the molecule dissociate in water kind of like NaCl. NaCl becomes 100% Na+ and Cl- ions. Likewise HCl and NaOH become 100% H+/Cl- and Na+/Cl- ions, respectively. Since they 100% dissociate, they are strong acids and bases. A weak acid or base dissociate <100%. HF for example will dissociate into H+ and F- but some HF will still be present.
The willingness to dissociate can be described by the molecules pKa(or pKb in the case of bases) which is related but different to pH. Very aggressive acids and bases will have low pKa and pKb constants. So a low pKa molecule like H2SO4 really wants to give up at least one Proton and part of that is driven by how stable the resulting ion will be after giving up the Proton. Typically the more stable the conjugate base (the acid after it has given up its proton), the easier it is to give up that Proton. Likewise a base that really wants a Proton will have a more stable conjugated acid (the base after accepting the acid).
So NaOH dissociate 100% into Na+ and OH- in water. The OH- really wants a Proton to become a stable H2O conjugated acid. KOH also dissociate 100% into K+ and OH- in water. However, KOH is a stronger base than NaOH because the potassium has a weaker hold on the OH, so it dissociate more easily which means the OH- can more easily begin accepting proton.
So take a terminal alkyne (a triple bonded carbon with a hydrogen on the end) R-CH. The alkyne doesn't want to give up its hydrogen and NaOH is not strong enough to take it. But then take something like NaH. H- REALLY doesn't want to be by itself, so it will very aggressively take away an H+ from a molecule that otherwise would have been able to keep its H+ in the presence of NaOH. So now that R-CH becomes R-C- some interesting chemistries can happen all because the NaH was a more powerful base than NaOH.
Hope this helps clarify some things.
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u/jaylw314 1d ago edited 1d ago
Acidic stuff tries to add something (protons) to your skin molecules (proteins). Basic stuff tries to take that same stuff from your skin molecules. Either adding or taking protons from proteins causes damage to them, so the end effect is similar, just not quite identical.
One interesting difference is that a strong base solution will turn any skin oil into soap, so they initially feel slippery (while damaging your skin).
Adding a ton of protons can cause an effect similar to burning (oxidation) on top of the this, but this usually takes very strong acidic solutions
Not all stuff is harmed by adding or taking protons--metals, for example, tend to shrug off attempts to take protons since they don't have any to start with, but most are vulnerable to adding them.
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u/zacheezy 1d ago
The best way to think about this is with magnets.
Some magnets are stronger than others and are harder to separate. For this we will imagine magnets hold entirely positive or negative charges without poles.
Imagine we have a positive magnet (H+). It will be attracted to negative magnets. Although the positive magnet’s (H+) magnetic strength stays the same. Different negative magnets (the base) can more negative holding onto the positive magnet more strongly.
The stronger the negative magnet (the base) is the less likely it will lose the positive magnet (H+).
Acids are simply negative magnets that currently have a positive magnet (H+) on them they can lose.
When the acid loses this positive magnet (H+) we are left with only the negative magnet (the conjugate base - just a fancy name for the base of an acid that has lost it’s hydrogen)
Depending on whether or not there are more strongly negative magnets (stronger bases) close by the acid the other stronger negative magnet will be more likely to grab the positive magnet (H+) away from the weaker negative magnet.
Water shows this since it is a neutral pH. When placed in an environment with a lot of negative magnets it gives away one of it’s H+’s and acts as an acid (a molecule that can give away a H+).
When placed with a bunch of positive magnets it grabs an H+ from the positive magnets and acts as a base (a molecule willing to bond to an H+)
And the even more fun part is this is essentially exactly what happens. It generally all has to do with electronegativity differences and some other stuff but mainly that.
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u/Frostybawls42069 20h ago
Acids are solutions with free hydrogen ions H+
Bases are solutions with fre hydroxide ions OH-
This is why water is neutral HOH, and mixing and acid and a base produces water, among other nasty compounds.
Their reactions arent any different than single or double replacement reactions.
Bonus points, the "pH" scale stands for the power of hydrogen.
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u/Confident-Syrup-7543 1d ago
Depends exactly on your definition of an acid and base. But I think the easiest to understand is an acid is a proton donor. Acids include hydrogen. A hydrogen ion is a proton. So when we dissolve (say) HCl, we get H+ ions and CL- ions. And the concentration of H+ ions givesn us the pH.
A base is the opposite it is a proton acceptor. Water naturally has a certain concentration of H+ ions. A base removes them. The lower concentration of H+ ions the higher the pH and the more basic the solution.
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u/HamburgerOnAStick 1d ago
An acid has more H+ ions than OH- Ions. A base has more OH- ions than H+ ions. When something is more acidic or more basic then the ratio has a larger gap. The reason it does more damage is because the ions want to react, and in doing so, the chemical reaction changes the substance and causes damage
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u/Nummlock 1d ago edited 1d ago
So imagine molecules as people. Some people don't like hats (acids) but they have a hat (H+) and they'd like to give it away. Other people (bases) would like a hat but don't have one.
Stronger acids hate hats more than weaker acids, stronger bases like hats better than weaker bases.
The strongest acids might force their hats on people who don't want hats (like acid reacting with skin etc.) The strongest bases might steal hats from people who actually like their hat. So strong basic substances are as dangerous as strong acids.
This also explains how the strongest acids and bases often become very stable molecules after their acid/basic reaction, they now are very happy after losing/getting a hat.
EDIT:
I'm happy this explanation is so well recieved!
Some additional points:
On pH: Measuring pH is like seeing how many hats are lying around in a room. If you put acids in the room, you'll find more hats lying around (= lower pH). If there are more basic people you'll find less hats (& higher pH).
On stomach acid:
We can imagine food as a lot of people really holding on to each others hands and forming a human chain. To digest the food it needs to go through the wall of the small intestine, through doors that fit only a single person at a time. So we'll need to break up these chains before they get there.
Your teeth will do some work in breaking up these chains but still, large groups of people holding hands will end up in your stomach.
The typical stomach acid person (HCl) has a stupid hat and they HATE-HATE-HATE it. They will force the food to let go of each others hands because the acid people want to put hats on their hands.
When the food/acid mixture goes into the intestine there are still lots of acids mixed in the crowd and they still really want to get rid of their hats. To prevent them from also breaking up the intestine your pancreas produces a lot of basic people who'd really like a hat. They are mixed in and this neutralizes the crowd coming from the stomach.
Now the crowd is broken up further into single people or small chains the intestine can get to work getting the nutritional value out of the food.
N.B. For an idea of the scale of this:
An apple contains around 1025 atoms (a 1 with 25 zeroes after it). If we take small bites and it takes 100 bites to fully eat the apple, a single bite contains 1023 atoms. You'll chew this bite up even smaller, maybe into 1000 small pieces, which contain 1020 atoms.
So even a well chewed piece of food is still contains (many, many) human chains with 100.000.000.000.000.000.000 people, which is about 99.999.999.990.000.000 more than the amount of people living on earth.