How can I tell the difference between a zinc and copper penny?

I just started a collection of circulated pennies and I have 8 slots available for the 1982 penny in my H.E. Harris folder.
I know that the main difference between the copper and zinc pennies is that the copper penny weighs more. The problem is that I don't have a scale to weight them on. Someone suggested I hold the penny on the tip of my finger and tap it with another penny and hear the difference they make. Does this really work? if so, what sound difference am I going to hear? Also, can someone tell me if these are large/small dates. I believe these are large date, but I'm not really good at telling them apart.

Here are the 1982 pennies I have:

I think the zinc pennies are in the first picture and the copper in the second. Thanks for the help!

 

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On the large date, the two circles of the 8 are the same size. On the small date, the upper circle of the 8 is visibly smaller than the bottom circle. Also on the large date, the bottom stroke of the 2 is thicker than on the small date. If you google it, you'll probably find large pictures of the two different dates for comparison.

A couple of years ago, a friend asked me to sort some 1982 into large/small date, copper/zinc. I thought he meant a few or a roll. It was 20 or 30 rolls. At first, I weighed them to sort between copper/zinc, but after awhile, the zinc seemed to have a different "look" to them than the copper ones, so I never learned any other tricks to telling them apart.

I'm not good with looking at pictures, but the 1st, 3rd and 4th look like large date. The 2nd is angled a bit and I'm not sure.

 

Just build a simple balance from a tongue depressor: http://www.lincolncentresource.com/smalldates/1982.html . On such a device, I found copper pennies are almost exactly a full diameter inboard of a zinc to balance the opposite side. Just use a 1981 and a 1983 to calibrate!

 

or a playing card, or a ruler, or a bit of cardboard cut from, say, a case of pop....
Do it up MacGuyver!

 

So I made a balance by balancing a ruler on a bottle of water that I laid on its side and taped to the table. I first balanced it by using 2 2001 pennies on each side. Then I carefully removed one side and added each of the 1982 one at a time.

The results were what I got from the sound test I made earlier. Both the pennies in my first picture were indeed zinc and the other two were copper. Thanks a lot guys. Now I just need to check for small and large dates.