How to Explain the Best Method to Calculate Density for Chemistry Lab

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Sometimes explaining the best method for calculating density in chemistry is more difficult than the actual calculation itself. Explain the best method to calculate density in chemistry with help from an expert in the field of chemistry in this free video clip.

Part of the Video Series: Chemistry Lessons
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Hi, I'm Professor Don Mueller, although I'm perhaps better known as Doctor Bones. I'm involved with Science and health education. Science, you'll never know what you'll find inside. So, today, we're going to be doing some Science. Calculating density, um, let's take a look, calculating density. Density is mass divided by volume. You can calculate densities for solids, liquids and gases. And if we turn this over, we can see that there's another density related item called specific gravity. Specific gravity is unit-less because we have the density of a substance divided by the density of water. O.k., so, it's based on the density of water, the units cancel. Alright, what about density? We've got mass divided by volume. In a typical chemistry or physics lab, you would take masses of these small items. We've got a cylinder, we've got a cube, we've got a parallelepiped, if you will. And we would take their masses , where they balance like, the old triple balance. Or, you could get more sophisticated massing devices and then, you'd measure the volumes. Now, you can measure volumes by measuring the distances of these objects. Again, since they're so small, let's find something much larger. We've got our cube, we've got our parallelepiped, we've got our cylinder. I've got a sphere, I've got a cone. And you can use the simple geometric formulas to calculate volumes for these items. Four-thirds, Pie-R-cubed, right, we've got side-cubed, for the cube. We've got the length times width times height, for the parallelepiped. We've got the circumference of the circle, in this case, the area of the circle. So, area, Pie-R-squared times the height or the volume of the cylinder. And you'd use simple measuring devices. You'd take your ruler, you could take a caliper to measure different size distances as well. That would be obviously better for the smaller items, but you could still do the same thing. Here, we just simply use a ruler. Other ways to measure volume for unusual shaped objects, would be to have a volume of water. This case, you'd probably wouldn't want to use your kitchen measuring cup. You'd have something like volumetric flask, you'd have a graduated cylinder, maybe even the Erlenmeyer flask, not as accurate. The volumetric flask is more accurate for measuring liquid densities, alright. So, if you have a liquid that you want to enter, and have a certain volume, or you could simply use the pipette to measure the volume of the liquid. So, again, solids, liquids and gases, all, you can find all of these things, all of their densities through the simple relationships. Gas densities through the ideal gas equation. So, again, mass, volume, density. I've got my friend, Skelly, Skeleton here, he'd like to introduce you to our websites. Skelly, take it away. Hey, Doctor Bones, how are you? You can find out more about us at DrBonesShow.com and BrainBuildingshows.com, see you there. See you there.

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