What is the Density of copper?

Letter 10854

Q. What is the Density of Copper?

United States Mint image

I am trying to accomplish a school project. Part of it is to identify the actual density of copper and I do not know the answer. Thank you. Very appreciated if answered.

Andrea H [last names of students are deleted]
- Cudahy, Wisconsin

Coach's notes: Skip ahead to the big red answer if you know what "density" means. But if you're confused because you know that a pound of gold weighs the same as a pound of feathers, but still feel that "gold is heavier than feathers", let's think it through :-)

Yes, a pound of gold weighs the same as a pound of feathers, but a pound of gold is a small thing, something you could put in a pretty little pocket -- but you'd need a big pillowcase for a pound of feathers. So when we say that gold is heavier than feathers, what we really mean is that it is denser than feathers, that is, that a given volume of gold will be heavier than the same volume of feathers.

The "density" of a material is a measure of how much it weighs for a given volume. If you had a cardboard box that was one foot wide and one foot long and one foot high, its volume would be one cubic foot. If it was full of the finest and lightest packed goose down (the fluffiest feather-like stuffing), it would weigh only about 3 ounces; that is, the density of goose down is about 3 ounces per cubic foot. If the box had a block of gold in it, it would weigh 1,200 pounds (and be worth about twenty million dollars!).

So density is written as a weight per volume, like: so many pounds per cubic foot, or so many ounces per cubic inch, or so many grams per cubic centimeter.

A. The density of copper is 8.92 gm/cm³

Measure the weight of copper piece and measure dimensions. Divide weight by volume. Compare with above number. If the copper is not dense or pure, or your measurements are not accurate, you will get a slightly different number.

If the object is complex shape, you have to use "EUREKA!!!" method. Use distilled water. 1 cu.cm water weighs 1 gram. You have to dip the copper in water in a beaker and find very accurately how much increase in volume has occurred.

Mandar Sunthankar
- Fort Collins, CO

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Sometimes it is not possible to measure exact dimensions, say for instance if you only have a blob of material. What you can do is weigh this material, and find out how much mass it has. Then place the material in water (or your favorite liquid ;) ) and see how much liquid is displaced. You now know how much volume the material takes up and voila! rho = mass/volume. =)

Vincent Mamo
- Daytona Beach, Florida

Learn more:

What is My Weight in Pennies?
A Penny's Worth of Copper, A Nickel's Worth of Nickel
Density of Zinc & Copper

The chemical symbol for copper is Cu.

A cooper makes wooden casks held together with bands of steel, not copper.

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Wow thanks guys I need it for a lab writeup and you guys saved my skin without me even having to ask! tyvmlots

John H
- Richmond, Virginia

^-- Browse ebay for Cool Coins . . .

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thanks for that info! I was on an online scavenger hunt and thanks to you, I won. Donka!

Sumone E
school - Kennebunk, Maine

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You're welcome, folks. Glad you won, Sumone!

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

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Still confused. I have the same question in a lab. If all I have is the question and no material to weigh or measure, how do I still figure this one out?

Liza K
- Rockwall, Texas

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It isn't clear what's confusing you, Liza. You have the density of copper on this page, and you should double-check it in a published book at the library.

If you still don't quite understand what is meant by density, recognize that a gallon of milk (which is a particular volume of milk) weighs the same every time you buy one. A half gallon of milk weighs half as much. If you multiply the volume times the density you get the weight. Or, if you divide the weight by the volume you get the density. Styrofoam & wood float because their density is less than the density of water; coins & bricks sink because their density is greater than the density of water. Ice cubes just barely float because their density is just barely less than the density of water. When you look it up you will find that one cubic centimeter of copper weighs 8.92 grams, that is, its density is 8.92 grams / cubic centimeter. A cubic centimeter is about the size of a small dice cube. How much will two cubic centimeters weigh, that is, two small dice cubes of copper?

Ted Mooney
finishing.com
Brick, New Jersey

Read this to your kid brother or sister, to learn by teaching . . .

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Wow, this is a pretty interesting site. I guess there are forums for everything now, just didn't know that members of the finishing industry used smileys "=)". Thanks for the info, needed the density of copper for a lab in Chem. MR (mathematically riggorus^{-2 sp :-)})(rigorus^{-2 sp :-)}? sorry 'bout the spelling). We found the density of pennies before 1982 and after, because before 1982 pennies contained a higher percentage of copper than after due to inflation of the value of copper becoming so that a penny was worth more than a cent in materials. Why am I telling you all this? You probably already know this. Anyway, thanks. Appreciate it.

Charles, Junior at Lebanon High School

Charles D
Lebanon High School o_O - Lebanon, New Hampshire

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Thanks, Charles. Although some readers knew when & why we switched from solid copper pennies to copper plated zinc cores, others don't, so your info will be helpful.

I just saw on google that yesterday was the 25th anniversary of the ASCII smiley :-)

Ted Mooney
finishing.com
Brick, New Jersey

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I'm doing a school project about copper and I have no clue what these are -- what are the physical description of copper? what is the abundance of copper? what are the regions of major deposits of copper? what are the dangers and cautions to be used when handling copper? I need this before 10/18. Thanks for your help. I have posted this question because I'm doing a school project. I will be very glad if you answered me. I'm doing this project but I have no clue. I hope somebody answers me before 10/18.

Sumaiya M.
student - Richmond, Virginia

The fun way to learn is "hands on". Get yourself a precision scale . . .

Hello, Sumaiya. Please ask your librarian to help you find an age-appropriate book about copper. We'll be happy to help if you get stuck on some particular question, but teachers tell us that when students post their homework assignments we should always just tell them to do their own homework :-)

Regards,

Ted Mooney
finishing.com
Brick, New Jersey

March 15, 2008

I'm a little late for this discussion, but let me throw in my 2 cents. In 1982, the U.S. Mint changed the composition of pennies from 95% copper 5% zinc to basically no copper. So, some 1982 pennies are 95% copper and others have no copper. The quick way to tell the difference is weight. 95% copper pennies weigh about 3.11 grams; the non-copper pennies weigh about 2.5 grams. Currently, pennies (that contain no copper) being minted by Uncle Sam cost about 2 cents to make; yes, you read that correctly. Pre-1982 pennies, and some 1982 pennies, actually contain about 3 cents worth of copper. Copper is trading for about $3.84 a pound. And, that would be a troy pound. Precious metals are traded in troy weight; roughly 31.1 grams equals a troy ounce - not to be confused with dry weight.

Since I'm over 50, I remember when the amount of silver in pre-1965 dimes, quarters, half dollars, and dollar coins was worth more than their face value. So, when all the silver coins were worth more than their face value (the silver content cost more than their face value) people started hoarding them for their silver value. The hoarding caught the Mint off guard, and there was a shortage of coins until the Mint could crank out the silver clad coins. I remember stores handing out candy or coupons for change until the Mint could get new coins into circulation.

If you're thinking about hoarding pennies, you'll need an awful lot of pennies to make it worth the trouble.

This is one of those real-life applications of math, chemistry, economics, commodities, and some law.

Peter G. Heckler, J.D.
- Houston, Texas

March 29, 2008

lol you guys just saved my butt! i had a huge report to write and believe it or not, it is hard to find a simple answer to this question, thank you!!

Brittany M
- Prescott, Arizona

More fun with science . . .

July 8, 2008

Okay, so here is a slight twist on the discussion of Copper density: does it change as you permanently deform it? This question has very real-world applications.
Example: I have a cylinder of pure Cu with an outside diameter = 1.00 in, wall thickness 0.05 in and length = 1.00 in. I want to expand that cylinder so that the outside diameter is now equal to 1.02 in. What I want to know is what the inside diameter (ID) would be after I expand it.

Some background: I have seen two schools of thought on this. The first is to simply say the final ID is equal to the original ID plus the amount you expanded. However, for this to be true, the density of Cu after you expanded it (deformed it) would have to decrease. The second is to assume constant density and thus constant volume. Your calculated ID is different than the first school of thought. I do have an experiment planned, but I would like to know the science behind it. My gut tells me the density is constant, but I don't know how the increased dislocation density affects the microstructure.

Dave Osborn
Researcher - Zeeland, Michigan

July 10, 2008

Hi, Dave. I think that first school is going to have its accreditation revoked! But in its defense, I don't think that they were advancing a theory that metals get denser when you deform them; just offering a simple approximation which is very accurate for thin wall cylinders, but not accurate when used for thick walled cylinders.

Your cylinder is not quite that thin walled, so whereas that formula claims that to get the OD from 1.00 to 1.02 you would have to expand the ID from 0.90 to 0.92, you really need to expand it to 0.92217 (still off by only a couple of parts in a thousand though)

Regards,

Ted Mooney
finishing.com
Brick, New Jersey

September 3, 2008

wow, a lot of people are doing the same lab report. I'm also doing the penny lab report and have to find the density of copper in a penny.

David B
- Brownsville, Tennessee

September 10, 2008

Shhh, don't tell David B's teacher that pennies have been made of zinc (with a very thin copper coating) since 1983, so you can't find the density of copper this way :-)

Ted Mooney
finishing.com
Brick, New Jersey

September 10, 2008

Man this is crazy. It seems that every Chemistry class is doing this. Thanks for the info.

Brady S
- Poway, California

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