Science Buddies: "Ask an Expert"

Hi! I'm considering conducting the experiment I found on this website entitled "How Does Soil Affect the pH of Water?" (https://www.sciencebuddies.org/science- ... ml#summary)

Can someone tell me if the pH of pure water will actually change during this experiment? I'm afraid of my experiment failing, and I won't have time to do something else if it does fail.

I could also use an explanation as to why this is important in the "grand scheme of things". I need a reason why my experiment matters.

Thanks so much!

Hi,

The key to success in this project is collecting soils from different areas. The project instructions tell you:

Look for soils with different colors and textures.
Look for differences in the kinds of plants growing in a place. Different plants prefer different kinds of soils, so plant populations can be a clue to differences in soil type.
Try sampling different environments, such as a floodplain, beach, man-made garden, forest, or desert.

The effect of soil pH is on plant growth and not on water. Water just carries the ions and nutrients to plants. It is important to learn that soils come from different sources--erosion of rocks, decomposition of plant material, etc.--and that this affects what we call the pH of the soil. It is actually the pH of water that comes in contact with the soil, but the soil is the source of the ions that cause the pH to be a certain value.

Does this answer your question? If not, post again and I will try to clarify what i mean.

Sybee

Hi,

I agree with Sybeel that the pH of the soil will be different. In order to be accurate, or work at their best, pH testers need to measure a wet soil (called a soil slurry). For example, the manual of this soil pH tester (http://www.edaphic.com.au/products/soils/soil-ph-meter/) has an excellent description of why pH of soil is important, how it can affect different plants, and the ideal conditions to test soil pH.

I am not sure where you are located, but if you can sample soil from beneath pine trees then these tend to be more on the acidic side. A healthy garden soil may be closer to neutral.