What Is the Equation Used to Calculate Density?
By the cease of this lesson, you lot will exist able to:
- calculate a unmarried variable (density, mass or book) from the density equation
- calculate specific gravity of an object, and
- determine whether an object will float or sink given its density and the density of its surroundings.
How practice I Summate Density?
Density and specific gravity in the geosciences
An introduction to density
Density is the mass of an object divided past its volume.
Density ofttimes has units of grams per cubic centimeter (g/cm3). Remember, grams is a mass and cubic centimeters is a book (the same volume as i milliliter).
A box with more particles in it will be more than dense than the aforementioned box with fewer particles
Density is a fundamental concept in the sciences; y'all will come across it throughout your studies. Information technology is used quite often in identifying rocks and minerals since the density of substances rarely changes significantly. For example, gilt will always accept a density of 19.3 thousand/cm3; if a mineral has a density other than that, it isn't gold.
Y'all probably have an intuitive feeling for density in the materials you use oft. For example, sponges are depression in density; they take a low mass per unit of measurement volume. You are not surprised when a big sponge is piece of cake to lift. In contrast, atomic number 26 is dense. If you option up an iron skillet, you lot expect it to be heavy.
Students, and fifty-fifty teachers, often confuse mass and density. The words heavy and light on their own refer to mass, and not density. A very large sponge may weigh a lot (have a loftier mass), just its density is low because it still weighs very little per unit of book. For density, y'all also need to consider the size, or volume, of the object.
How practice I determine density?
A concrete cube will weigh more a cube of air the same size because it is denser
Density is not something that is direct measured. Typically if yous want to know the density of something you will weigh it and then measure its book.
Another tricky thing most density is that yous tin can't add together densities. If I have a rock that is made up of 2 minerals, one with a density of 2.8 g/cm3, and one with a density of iii.5 g/cm3, the rock volition have a density between iii.5 and 2.eight k/cmiii, not a density of 6.3 chiliad/cm3. This is because both the mass and the volume of the two minerals will be added, and then when they are divided to get the density the result will be between the ii.
Typical densities for gasses are on the lodge of thousandths of grams per cubic centimeter. Liquids often have densities of about ane.0 g/cm3, and indeed, fresh water has a density of 1.0 g/cm3. Rocks often have a density effectually iii g/cm3, and metals often have densities above half-dozen or 7 1000/cm3.
How do I calculate specific gravity?
To summate the specific gravity (SG) of an object, you compare the object's density to the density of water:
Because the density of water in g/cm3 is 1.0, the SG of an object is will be almost the same as its density in g/cm3. Withal, specific gravity is a unitless number, and is the aforementioned in the metric organisation or any other measurement system. It is very useful when comparing the density of two objects. Since specific gravity is unitless, it doesn't thing whether the density was measured in m/cm3 or in another units (like lbs/ft3).
Why should I calculate density or specific gravity?
Densities are critical for many uses. One of the most critical is that the density of a substance will determine if information technology will float on another. Less dense substances will float on (or rising through) more dense substances. Here are some examples of how this explains everyday occurrences:
- Accept y'all wondered why hot air balloons rise? When the air is heated, it becomes less dense until the airship's total density is less than that of the atmosphere; A hot air balloon is literally floating on the denser, colder air.
- Take yous always noticed in a lake or the bounding main that water is warmer at the surface and colder at the lesser? This is considering the warmer h2o is slightly less dumbo and, as a result floats on the denser, colder water
- Do y'all know why volcanoes erupt?
The main reason that magma rises to the surface to erupt at volcanoes is considering information technology is less dumbo than the rocks that environment it.
This huge gunkhole weighs a lot, just it its density must be less than i.0 g/cm3 because it is floating.
A ship floating on water is a keen illustration of the divergence between mass and density. A ship must have a density of less than i.0 chiliad/cmiii(the density of water), or it will sink. Ships have a large mass, considering they are made of steel, simply because they accept a large volume, their density is less than ane.0 g/cmthree. If enough mass is added to them such that their density goes higher up i.0 chiliad/cm3, they will sink.
To try some practice issues, go to the sample problem page!
Where is density used in the geosciences?
Galena, a lead ore, is ane of the densest mutual minerals
- Isostasy - determining how high continents volition sit down on the mantle
- Plate tectonics - mechanisms that drive plate tectonics
- Minerals - determining the name of a mineral through its density
- Rocks - determining the proper name and composition of a rock by its density
- The hypsometric bend - examining the causes of peak variation on Earth
- Oceanography - some ocean currents and ocean apportionment is controlled by density
Side by side Steps
More help with Density
Edinformatics on-line lab on mass, volume and density is put together by NYU. It allows you to look at pictures of measurements and to enter data.
Hyperphysics, at the Georgia Country has a folio most density and a density converter. This includes several related pages including instructions of measuring density using the Archimedes principle.
Wikipedia's specific gravity page has an caption of what specific gravity is and how it is used and even discusses its utilise in the geosciences and mineralogy. Nonetheless, the content of Wikipedia articles may modify and and so you may want to be cautious.
Wikipedia's Density page has a general discussion of density and its history, adding, and units. Even so, the content of Wikipedia articles may modify so y'all may desire to exist cautious.
This page was written and compiled by Dr. Eric M. Baer, Geology Program, Highline Community Higher, and Dr. Jennifer M. Wenner, Geology Department, University of Wisconsin Oshkosh
Source: https://serc.carleton.edu/mathyouneed/density/index.html
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