The protection afforded by calcium oxalate against acid rain
The materials required for the science fair project:
- 3 pieces of marble tiles, each weighing 100 grams
- 1 bottle of oxalic acid
- 1 bottle of commercial marble sealant
- 3 beakers
- 1200 milliliters of vinegar
- 1 measuring cylinder
- 1 piece of cloth
- 1 sheet of sandpaper
- 1 digital weighing scale
1. For this science fair project, the independent variable is the type of coating on the marble tile – one tile will not have any coating, one will be coated with an industrial sealant, and the last, with calcium oxalate. The dependent variable is the weight of the marble tiles in acid solution over time, and will be measured using a digital weighing scale. The constants (control variables) are the acidity of the vinegar solution, the amount of vinegar used, the initial weight of the marble tile and the length of time the science fair project is conducted for.
2. Clean all 3 marble tiles. Using the digital weighing scale, ensure that they weigh exactly 100g each. If a tile weighs more than 100g, reduce its weight by sanding it down with the sandpaper. Record the starting weight of the sample tiles in a table, as shown below.
3. Prepare the tiles for the science fair project. Place the first tile in a beaker labeled ‘No protection’. Polish the second tile with the commercial marble sealant according to the instructions on the packaging, and place it in a beaker labeled ‘Sealant’. Coat the third tile with oxalic acid, and place it in a beaker labeled ‘Calcium oxalate’.
4. The next day, measure 1200ml of vinegar with the measuring cylinder and pour 400ml into each of the 3 beakers. The vinegar solution will be used to simulate acid rain.
5. At the end of the day, remove and wipe the tiles down lightly, and record their weights in the table, under ‘Day 1’.
6. Repeat step 5 every day for the next 4 days, recording the new weights of the tiles in the table.
Warning - An adult is required for the purposes of handling oxalic acid and gloves should be worn at all times. Oxalic acid can be absorbed through the skin and it will react with calcium in the bloodstream, forming kidney stones.