Science Buddies: "Ask an Expert"

Do you know a way of simulating a "hot sunny day" for a science project?

NiceGirl761,

If you are looking to simulate the heat energy transfered onto a certain area, I'd use heat lamp(s). These can be obtained easily from most hardware stores. Place it/them far enough away to heat your test subject up to the desired "hot day" temperature. This can be measured by placing a thermometer near or next to the test subject. You could test several temperatures, like a nice warm, but not overly hot day ~ 26 deg C, A very hot day ~ 32 deg C, and the record high for your area (in my area that was 38 deg C).

It would be helpful if you provided more detail about your experiment so we can provide more accurate advice. If you are looking to be more elaborate than that, let us know.

Well I was going to test plastic in a liquid and see how toxins leaching from plastic increase. The heat source is to mimic a "hot summer day" at 95 degrees F.

NiceGirl761,

This sounds like a very interesting experiment. A bit of a twist on the effects on a test subject by leaving it out in the sun. In this case, I would say what you are looking to simulate is the ambient temperature (the temperature of the air/environment around the test subject). This can be done in an oven set to your desired temperature, in your case 95 deg F for what ever amount of time your experiment calls for. If you have access to an oven with a digital thermometer then it should be able to maintain the desired temperature automatically. Otherwise, i'd get a digital oven thermometer so you can obtain an accurate reading of the temperature of the ambient air around your test article (you may want to do this anyway, just to be the most accurate). The heat lamp technique will also work, but will tend to be more directional. For example, your test item will be warmer on the side facing the heat lamp and cooler on the "far" side. To even out the temperature on all sides, you'd need multiple lamps.

If I may ask, what are your dependant, independant, and control variables?

Dependent-Concentrations of toxins
Independent-Plastic type

Different beverages are being tested.

NiceGirl761,

Ok. In this case, one of your control variables is temperature so picking a single temp of 95 deg F is valid. Be sure you test all your plastic samples under the same environment conditions (i.e. temp, size of bottle/plastic sample, amount of fluid/beverage, type of fluid/beverage, exposure time, etc...)

As such, i'm not sure what aspect you are testing with respect to the amount of toxic leaching by varying the beverage type. In order to ensure you change only one variable at a time, you will have to run a test with each plastic along with each beverage type to get a full set of objective data. Per the scientific method, if you change the plastic AND beverage between experiments then you have changed 2 parameters. So if you detect an increase in toxic levels, you cannot say which change caused the increase, leaving any conclusion you draw suspect. The number of experiments (E) required will be the number of plastics (P) times the number of beverages (b): E = P x b . For example: you have 4 plastic samples: A, B, C, D; and you have 3 beverage types: 1, 2, 3. You will have (4 x 3 = 12), to have test runs comprising all possible combinations, i.e. A1, A2, A3, B1, B2, B3, C1, C2, C3, D1, D2, D3. Then, if you repeat the experiments to verify your results (as you should) then you have to multiply by the number of times you duplicate the experiment...so if you run it 3 times, you will have to perform the experiment 36 times.

Now, all this is worth it if you think the amount of leaching will be different for different liquids as well different plastics, but if your question is really only the leaching properties of the different plastics under a heat source, I think you could get away with picking one baseline liquid for all plastic samples as a control variable, thereby giving you a requirement, in my example, for only 12 experiments, (4 x 1) x 3 = 12. I would use distilled water for this baseline. It will be free of additional contaminents that you must account for and easily tested for an increase in various parameters, like pH levels, toxic compounds, etc... Actually, if reactivity of different liquids is your objective (as is suggested in your post), then you might consider using distilled water as one of your liquids anyway, as a control.

Again, just some suggestions of things to think about as you design your experiment, since I don't know what all your experiment objectives are.