Bio culminating lab Essay

Submitted By Kimberly-Tran
Words: 1733
Pages: 7

Investigating the effect of water temperature on the rate of photosynthesis as measured by the amount of floating spinach leaf discs over 15 minutes.

Research Question:

How does different water temperature affect the rate of photosynthesis as measured by the amount of floating spinach leaf discs over 15 minutes?


The goal of this inquiry is to investigate the effect of different kind of water temperature on the rate of photosynthesis in spinach leaves by measuring the number of leaf discs that rise over 15 minute time period. During the investigation, the spinach leaves will be vacuum treated with a 1% or 1g of sodium bicarbonate which is baking soda solution using a syringe. We had 30 spinach leaf discs in total so 1/3 of the leaf discs which is 10 leaf discs will be placed under hot water temperature which was 60°C, 10 leaf discs under room temperature water which was 21.3°C and lastly 10 leaf discs placed under cold water temperature (9.5°C).

Photosynthesis is a series of chemical reactions. Heat speeds up chemical reactions by adding kinetic energy to the reactants. Reactants with high kinetic energy move around and bump into one another more often than reactants with low kinetic energy. Collisions between reactants initiate possible chemical reactions. More kinetic energy leads to more collisions between the reactants in photosynthesis causing the increase in the rate of photosynthesis. Therefore, it is predicted that if the temperature is high, the rate of photosynthesis will be faster which will cause the more leaf discs to rise at faster amount of time. The lower temperature will have slow rate of photosynthesis which will cause the leaf discs rise at slower amount of time.

Independent Variable:

Temperature is the independent variable in this experiment. The presence of the temperature will allow the photosynthesis to occur, whereas the different temperature will have different effects on the rate of photosynthesis. For that reason, it is predicted that the higher temperature will have higher rate photosynthesis whereas lower temperature will have lower rate of photosynthesis. Eventually as a predicted result, the higher temperature will cause the spinach leaf discs to rise faster however, the lower temperature to rise at slower time.

Dependent Variable:

The dependent variable is the number of leaf discs floating after 15 minutes of being exposed to the light source. The leaf discs in higher temperature solution will undergo photosynthesis at a faster rate which will allow the leaf discs to rise faster. The lower temperature will undergo photosynthesis slower, therefore resulting in the small amount of leaf discs to rise while the rest of the discs still sunk.

Controlled Variables:

Controlled variables include the time, size of the discs, amount of sodium bicarbonate and the light exposure. The surface area of the leaves photosynthesizing will be controlled by using the same straw to punch out discs of exact same size. All of the leaf discs will be exposed to same light in their specified temperatures for the same amount of time of 15 minutes. All leaf discs will be vacuum treated with same amount of 1 % sodium bicarbonate (baking soda) solution in each beaker with 100mL of water.

Extraneous Variable:

The heat from the light bulb to the solution would alter the rate of the photosynthesis, but this variable was not controlled. The light source would increase the temperature of the treatment exposed to the light, but not the absence of light treatment, which would alter the rate of photosynthesis.


3 Beakers
1 Thermometer
3 Retort stand
3 light bulb
3x1% of Sodium Bicarbonate (1.0g)
1 Syringe
3x1 drop of Liquid Dish soap
1 Hot water bath
1 Cold water bath
1 Room temperature water bath
1 Electronic weigh scale
1 Plastic straw
3x100mL of water
2 Spinach leaves
1 Glass rod


1. Get 3 beakers and put 1% or 1g of sodium bicarbonate in each…