Struggling to help my 5th grader understand the Liquid Density of Lamp Oil

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beepatient321
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Struggling to help my 5th grader understand the Liquid Density of Lamp Oil

Post by beepatient321 »

My daughter has just done the Seven-Layer Density Column Science Fair experiment found here https://www.stevespanglerscience.com/la ... ty-column/

We are tracking that Lamp oil (refined kerosene) has an .81 density measurement and Rubbing Alcohol has a 0.79 density measurement.
Although the numbers are showing that the Alcohol is lighter than the Lamp Oil we are finding that the Lamp Oil floats on top of the Rubbing Alcohol, and we don’t understand why.

I was able to find this “explanation” within the narrative of the experiment.

"You’ll notice that according to the number, rubbing alcohol should float on top of the lamp oil; however, we know from our density of liquids experiment that the lamp oil is the top layer. Chemically speaking, lamp oil is nothing more than refined kerosene with coloring and fragrance added. "

This is where I am stumped…what does this explain exactly? I’m trying to understand how lamp oil is the top layer with a higher density measurement than the alcohol.

I can't get it! Please help...

Thank You :-)
audreyln
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Re: Struggling to help my 5th grader understand the Liquid Density of Lamp Oil

Post by audreyln »

Hello,

This sounds like a fun project! I agree that the "explanation" below is not really an explanation of what you're observing. The densities listed in the table of rubbing alcohol (0.79 g/ml) and lamp oil (0.81 g/ml) are very close together. The website does mention that densities may vary from brand to brand. It could be that the brand of lamp oil you purchased actually has a density of 0.78 and is therefore lighter than the rubbing alcohol. Lamp oil is distilled from crude oil and based on the type of crude oil used, the manufacturer's equipment, and what other products the manufacturer was making (jet fuel, diesel fuel, gasoline) the density of the lamp oil may change.

To investigate this further you could try different brands of lamp oil or you could calculate the density of the lamp oil and rubbing alcohol you have at home. You would need a sensitive scale to do this. Look for a digital kitchen or jewelry scale with 0.01g accuracy ($10-20 online). Here are some instructions for calculating the density of a liquid:
https://sciencing.com/gallons-kilograms ... 95429.html
https://spark.iop.org/measuring-density-liquids (more complex with multiple measurements)

Let us know what you find out!

Good luck,

Audrey
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