Soil Chemistry Experiment - Soil Science

Chemistry experiments with soil are loads of fun, and can be expanded into lots of different areas of chemistry! This particular experiment focuses on pH and is perfect for a DIY Summer Camp project because it helps you learn about the area YOU live in!

pH is a scale that chemists use to measure how much acid is in a solution. It is logarithmic, meaning that a solution with a pH of 5 is ten times more acidic than a solution with a pH of 6 and 100 times more acidic than a solution with a pH of 7.*

Some plants grow best in an acidic soil (with a pH under 7) and some plants grow best in a basic or alkaline soil (with a pH over 7). 7 is considered neutral--neither acidic nor basic.

What do you think the soil in your area is? Do you think it is the same all around your yard? Write down some hypotheses, and then find out!

Simple Supplies:
* Distilled water (available at grocery stores)
* litmus paper strips (available on Amazon or science sites)
* soil from your yard

Once you collect your soil, place some in a bowl or cup and add a little distilled water. 

You want to use distilled water because it will have a pH of 7, so it will not change your results significantly.

Stir the water and the soil together so that the acid (or basic) ions are floating throughout the solution. Then dip the litmus paper into the solution. The litmus paper should come with a "key" showing you what pH each color indicates.

As you can see, our soil is weakly acidic!

You can also try adding baking soda or vinegar to the cup to see if your soil solution reacts with either of them. Ours had a weak reaction with the baking soda...I circled some of the bubbles so you can see them in the picture below:

Finally, it's a lot of fun if you can gather different types of soils so you can see different pH levels. Soil or sand from a beach, under pine trees, in a forest, and in a garden might all have different pH levels.

One particularly fun plant that is affected by pH is a hydrangea. If it is in very acidic soil (less than 5.5), the hydrangea will grow blue flowers, but if it is in more neutral or basic soil (over 6.5), the hydrangea flowers will be pink! If it is in the middle (between 5.5 and 6.5), the flowers will be purple!

A fun follow-up project is to research what plants prefer acidic soil and what plants prefer basic soil! You can also test the pH of fertilizers and soil additives!

Are you planning a DIY Summer Camp? If so, check out these awesome ideas! There is a whole week just for chemistry!!

* Note: High school students may understand that you can calculate a solution's pH by taking the (-)log of the concentration of hydronium ions in the solution, but that level of math is not necessary for this experiment, and is not something most middle school/upper elementary students are ready for.

And if you're looking for more homeschool unit studies, be sure to check out our growing collection here!

Happy Educating,
Carla & the kids who don't sit still!