Fun With Acid!




I'll show you something neat you can do with some easy to obtain acid.

Step 1: Supplies

You'll need the following:

- Muriatic acid (hydrochloric acid)
You can find this at your local hardware or paint store.

- Small glass

- Some shiny pennies
Only pennies from 1982 and newer will work.

Step 2: Grind Away

File away some of the copper on the side of the penny you don't want to keep.

In doing so, you'll expose the zinc inside.

Step 3: Now for the Bubbly! (and an Explanation)

Put the penny in the glass with the exposed zinc facing up.

Next, pour in just enough acid to cover the top of the penny.

Leave it for several hours or overnight.

So what's going on in the glass?

The composition of U.S. pennies changed in 1982.

Before 1982 (for about 20 years), pennies were an alloy of about 94% copper and 6% zinc.

The increasing cost of copper made this impractical. Therefore, some 1982 pennies and all
pennies produced after that time have a pure copper shell with a zinc interior.

The new pennies contain only about 2.4% copper and weigh 2.5 grams as opposed to the 3.1-gram weight of the older type.

Zinc is a more active metal than copper. In this experiment, we see that zinc will react
with acid to produce hydrogen gas:

Zn(s) + 2 HCl(aq) => ZnCl 2(aq) + H 2(g)

The hydrogen gas generated by the reaction will bubble up because it is less dense
than the penny and the acid solution.

However, towards the end of the reaction some bubbles of hydrogen may adhere to the copper or be trapped inside the shell. If this occurs, the combination of copper and hydrogen gas may be less dense than the acid solution and what is left of the penny may float!

Step 4: The Next Morning...

After the acid has finished reacting with the zinc, you will be left with a thin copper foil and a copper shell of a penny only one thousandth of an inch thick!

The shell will be very fragile, so use tweezers or a cotton swab to pull it out of the acid.

You can rinse the shell in the sink with some tap water.

NEVER, NEVER pour water into acid. Dispose of the acid by pouring it in the sink and then rinsing it down with water.

You can also neutralize the acid with some baking soda.

Step 5: Clean It and You're Done!

Now carefully clean the inside of the shell with a cotton swab. Be sure to place it on a flat surface so you don't bend it.

Now you're done!

You can use the penny shell to hide a dime in for an oldie but goodie magic trick.

More information can be found in these fine books on

Experiments That Explore Acid by M.Gutnik

365 Simple Science Experiments with Everyday Materials

Classic Chemistry Experiments by Hutchings



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    59 Discussions

    The reason to add acid to water is that many acids boil at low(ish) temperatures and heat up when combined with water. If you add acid to the water, you end up diluting the acid out very quickly, raising its boiling temperature closer to that of the water. Hot water with a little bit of acid in it is no big deal. If you add water to acid, the first few drops of water mix up and create heat in a very concentrated acid mixture. This can boil or fume or worse. Hot acid with a little bit of water in it is a problem.

    laci37The Real Elliot

    Reply 10 years ago on Introduction

    HCl(hydrogen-chloride) is not a liquid, it's a gas, hidrochloric acid can be mixed safely with water since it's the solution of HCl, but do not try this with sulfuric acid, because the water boils because of the exothermal reaction and the acid can go out of the container. If you want thin sulfuric acid you need to mix aysmall amount (few drops) of sulfuric acid with much water, because the water absorbs the heat of the reaction.


    Reply 3 years ago on Introduction

    Certainly, adding hydrochloric acid to water is far less dramatic. Still I notice a significant rise in temperature by adding 30+% into water. If that water is already 90 Celsius then you could get a POOF of HCl vapors in your face from the exothermic dilution.


    Adding water to HCl is an exothermic reaction. If you add water to the acid there's a chance that it will splash up and get you on the skin or in your eyes. You always slowly add the acid to water. Not water into acid.


    Reply 11 years ago on Introduction

    Yes, you're right. Concentrated sulphuric is quite exothermic, you need a bit of stirring even if you are doing it in the right way L (Hydrogen-bonding)


    11 years ago on Introduction

    When i readed : Fun With Acid! , i was really hoping it would be an instructable about our good friend , Lycergic Acid Diethylamide :p Nice Instructable anyhow

    11 replies

    Reply 10 years ago on Introduction

    lysergic acid diethylamide also known as LSD, is among many hallucinagens. LSD was created by albert hoffman. look it up on wikipedia, it'll tell you all about it.


    Reply 8 years ago on Introduction

    I've seen things! I've seen them with my eyes! I've seen things, they're often in disguise!


    8 years ago on Introduction

    does it wok with old muratic acid because ive had some in my garage for about 3 years and also how can you trick someone if the dime dosent have the other side of the penny


    11 years ago on Introduction

    "Don't breath the fumes" No problem breathing the fumes - they're competely non-toxic. They do, however, go bang - It's hydrogen. Leave an inverted tub over the penny to collect the bubbles, you can celebrate getting your (quite excellent) penny shell by lighting the hydrogen!