Experimental Design

Materials

– 4 glass jars

– 2 samples of each: granite, sandstone, shale, and limestone

– Stopwatch

– Piece of paper and pencil

– Hammer

– camera

– Triple-beam balance (food scale)

– Goggles

– Diluted acid (lemon juice)

– pH strips

– Tarp (optional)

– Latex gloves

– Diluted acid

Procedure

  1. Gather materials listed.
  2. Organize samples of rocks into two groups: chemical and mechanical. Each group will have one sample of each type of rock.
  3. Weigh each sample of rock on a triple beam balance (scale) and record the data on a piece of paper.
  4. Place one sample of each rock from the chemical group in the glass jars.
  5. Put on latex gloves, goggles and if it applies, tie long hair back.
  6. Measure out enough acid to cover each rock individually. Slowly pour the acid on top of each rock sample so it is fully submerged in the jars
  7. Repeat daily, but add just enough acid so the pH level is the same as in the beginning..
  8. Set out the mechanical group of samples on a tarp or concrete. (areas like sidewalk or driveway.)
  9. Take the hammer and hit each sample of rock on the tarp or concrete with mild to medium force once. Then drop each rock from a height of 15.4 centimeters and sand each rock with sandpaper for 1 minute.
  10. Weigh the mechanical set of samples every day after weathering occurs.
  11. Repeat steps daily and take pictures of each sample for two weeks while adjusting the pH levels of the diluted acid.
  12. After all trials are completed for both chemical and mechanical weathering, weigh the rocks again and compare the results with the control.

Variables

Independent variable: chemical weathering (changing pH level of acid), mechanical weathering (hitting rock with hammer)

Dependent variable: how fast each weathered (limestone vs. others)

Constants: type of acid, size of hammerhead, amount of time, amount of times rock is hit with hammer, direct or indirect sunlight, type of jar, force used to hit rock with hammer, person with hammer, amount of acid

Controls: untouched samples of sandstone, granite, shale, limestone

Hypothesis: If limestone is chemically and mechanically weathered, then it will weather faster than granite, sandstone, and shale because it is more susceptible to weathering than the other rocks.