Science Buddies: "Ask an Expert"

I want to help my son understand the effect of temperature on plant growth. I want him to try different temperatures, different kinds of soils with different temperatures and also different amount of sunlight with different temperatures of water.
My son is in 2nd grade. And we have lot of time of the project. SO, I am thinking this will be appropriate for him.

I want to know if I am combining too many variables or is it ok? Please need advice.

Hi,

Generally, for younger students, we suggest that they stick with one variable (say, air temperature or soil temperature). The reason for this is that since you need approximately 6-10 samples of each 'level' of each variable, projects with multiple variables can soon get out of control or do not test any single variable well. For example, if you picked, say, 4 air temperatures, 4 soil temperatures, 4 water temperatures, and 4 kinds of soil, in order to test all of the different combinations, you would have 4*4*4*4=256 combinations! My advice is to start with just one variable with everything else held constant, see what it does, and then, if you have time, investigate another variable. If you really want to look at multiple variables, I suggest no more than two.

Good luck, and good for you for being on the ball and starting the process so early!

Thank you very much for the reply. Do you think this is appropriate for the 2nd grade. And usually does these kind of projects have potential to win prize. I know its not for prize but just wanted to boost the confidence of my child.

Trying to control the temperature may be difficult even with a parent helping. Controlling the amount of sunlight could be done by using a tarp strategically placed over the plants although you would have to time it out for a whole day. In the end this would be easier than moving the plants into the sun or out of the sun throughout the day especially if you are not at home all day. Using different soils may be the easiest but it's a matter of where do you get your soils from? If you could get soil samples from different states and/or different regions of the country that would be great. If it was my son, I would experiment with different watering amounts or schedules. For instance, you could water all the plants at the same time each day but each plant gets a different amount. The hopeful result would be one end of the spectrum would be dry and dead while the other end of the spectrum may be over-saturated and dieing while the middle of the spectrum would be perfect.

Miss Lizzy
3rd Grade Science Teacher