The Effect of Environmental Factors on Wood Decay
The materials required for this science fair project:
- 20 oak wood planks (proposed size 50mm x 25mm x 500mm)
- 16 bricks
- 20 weights, each of 0.5 kg
- Tap water
- 1 pail of rain water (the water should be collected in an open field, away from trees, roof edges and other obstructing objects)
- 1 bottle of vinegar
- 1000 grams of salt
- 4 pails (minimum 500mm in height)
- 1 rope, of about 2 meters’ length
- pH paper
- 1 black marker pen
1. For this science fair project, the independent variable is the environment in which the pieces of wood are kept for 2 weeks – whether in rain water, acid water, salt water or wet soil. The dependent variable is the average strength of the wood after 2 weeks. This is determined by applying weight to the planks and noting the breaking point of the wood. The constants (control variables) are the size of the wooden planks used, the length of time they are exposed to the environment, and the type of wood used.
2. The experiment is begun by inspecting the dimensions of the wooden planks and ensuring that all 20 are of the same size. The 20 planks are divided into 5 groups of 4 planks each. All the planks in each group are labeled with the group’s letter – either A, B, C, D or E.
3. The 4 pails are marked as either B, C, D or E. The pails are prepared as follows:
a. Pail B is filled with rain water. The 4 planks labeled B are placed inside it.
b. Pail C is filled with a mixture of water and vinegar, using an appropriate concentration of vinegar such that pH 4.5 is obtained. This is used to simulate acid rain. The 4 planks labeled C are placed inside it.
c. Pail D is filled with water and salt. 40g of salt is added to every liter of tap water. This is to simulate sea water. The 4 planks labeled D are placed inside it.
d. Pail E is filled with soil. Water is added to the soil daily to keep it wet. The 4 planks labeled E are placed inside it.
4. The planks labeled A are not placed in any pail. They are left in a dry place and protected from accidental exposure to moisture.
5. The wooden planks are left in the respective environments mentioned above for 2 weeks. After that they are taken out of the pails and left to dry for 3 days.
6. The strength of the wooden planks is tested using the set-up shown in Figure 1 below. 2 stacks of 8 bricks each are placed some distance apart, and the piece of wood to be tested is placed across the stacks of bricks. The weights are hung from the center of the plank, as shown. More weights are added, 0.5kg at a time, until the plank breaks. The average weight that caused the plank to break in each group is calculated and recorded in the table given below.
Basic safety requirements