Monday, April 4, 2016

// // Leave a Comment

Sedimentary Rocks Experiment: Fizzing Rocks!

Nope, there is no baking soda or vinegar here!  These are real rocks reacting with acid and fizzing!

I'm teaching a Geology Rocks! class for kids in kindergarten through second grade in our homeschool group, and I thought I'd share the experiment I brought for them on our Sedimentary Rocks day.

This sedimentary rocks experiment is appropriate for any age, preschool through high school!  I've even seen adults get excited about it!

It's super cool because it has implications for real life!

And because it fizzes. Fizzing is always cool!

Anyways, you will need these

Simple Supplies:

* limestone
* 10% hydrochloric acid

The easiest place to get limestone is just outside, but you can also buy it at a hardware store where they sell paving stones.  It's usually in the $1-$5 per stone range.

You can get hydrochloric acid at the same hardware store (also called muriatic acid or concrete cleaner).  Here is an amazon affiliate link for hydrochloric acid:

To use the hydrochloric acid, you'll want to dilute it down to the 5%-10% range. Always use safety precautions like safety goggles and working near running water.  One simple way to dilute the hydrochloric acid (with the 32% HCl pictured above) is to put 3.5 teaspoons water in a safe container and add 1 teaspoon hydrochloric acid.  Always remember to add the acid to the water; do NOT add water to acid. You can place it in a dropper bottle or use a pipette for the experiment.  Obviously the bottle pictured above will last for a long time, so be sure to store it safely out of the reach of children and pets!

Easy How To:

1- Gather around a piece of limestone.  Make sure everyone has safety goggles on.

2- Carefully pour a TINY amount of hydrochloric acid on the limestone, and watch it react!!

What's Going On:

Most limestone is a sedimentary rock made by crushed and cemented bits of shells and other rock fragments full of calcite.  Calcite is a naturally occurring mineral with a high pH.  It reacts with hydrochloric acid (which has a low pH), and creates carbon dioxide (which bubbles up and looks cool)!  For my science loving friends, the reaction is summarized by this equation:

CaCO3 + 2HCl à CO2 + Ca++ + 2Cl-

Here's a short video so you know exactly what to expect (click on the link)!

Discussion Topics:

* The great pyramids of Egypt have a lot of limestone in them.  How could they be affected by acid rain?
* How could you use hydrochloric acid to identify rocks?

Amazon Affiliate Links:

I may share at any of these parties!

Never miss another post again!  Sign up for our weekly updates newsletter and get links to all our posts once a week in your inbox!  Sign up here!!