00:01
Hello students.
00:02
In this question we are said that during the historical times, pennies were made, we had coins and they had a very different composition as compared to the coins that are made today.
00:12
Earlier the coins used to be made of pure copper and now the pennies or the coins, they are made of a mixture of zinc and copper.
00:22
The composition of zinc being 97 .5 % zinc and 2 .5 % copper so it has significantly reduced in proportion the copper content in the in the coins and it is mostly made up of zinc right now so in the question it is asked that if we are provided with two coins how do you determine which of the coin is made up of pure copper and which is mostly made up of zinc so how do you differentiate so we basically have to find out the differences in the properties of copper and zinc as a whole so there are various different ways of understanding this the very first way is to test the sound is to test the sound of the coin sound of the coin so in this what we do is that we have a smooth granite surface so we can write here we have a smooth granite surface and we are dropping a smooth granite surface and we are dropping a two pennies or two coins from the same height let us assume that this is coin a and coin b so if coin b on hitting the smooth granite surface makes a high pitched tone it makes a high pitched tone which mostly sounds melodious then we can see that this kind of coin is made of of pure copper whereas if the coin is the coin is made of pure copper whereas if the coin in this case coin b is made up of mostly of zinc and a little proportion of copper on hitting the granite surface it will have a flat tone so the pure copper coin would have a high pitch tone whereas the one which is mostly made up of zinc will have a flatter tone so by testing the sound or by listening to the sound that the coin makes on hitting the granite surface we can determine which of the coin is pitch the second second way of differentiating between both of them is to scratch the surface.
02:39
It's to scratch the surface and get the base layer.
02:48
Scratch the surface and get the base layer.
02:55
So what that means is that if you have a coin, let us assume that this is coin a and this is made up of pure copper, then if we keep on scratching the surface of this coin, if you just keep on scratching the surface of this coin, if you just keep on a coin, scratching away and taking out elements out of this coin just taking out bit by bits by the time we reach the core of the coin the core of the coin would be somewhat golden brownish in color golden brownish in color this is because it is made up of pure copper and copper is golden brownish in color in its natural element so we can say that if we keep on scratching the surface if we get to the core and if the core is golden brownish in color the coin is made up of pure copper similarly if the coin is made up of a mixture of zinc and copper and we keep on scratching away the elements of the coin we will reach the core and the core will be silver in colour it would be it would be dominantly silver in colour this is because zinc is this is because zinc is silver in its natural element so this is another method of differentiating between the coins that is provided to us the third way is to test the melting point of both the coins.
04:15
So if we test the melting point, melting point using bunsen burner.
04:30
So let us assume that we have a bunsen burner here.
04:37
And again, we have the same setup here.
04:41
And this is coin a and this is coin b.
04:45
So upon igniting the benson burner, if if coin a starts melting, then we can see that this type of coin is made up of a mixture of zinc and copper.
04:59
This is because zinc, we are considering the melting point of zinc when we are talking about zinc and copper coin...