Calcium Carbonate – Disintegrating Quicklime


[MUSIC PLAYING] Earth. Billions of years ago, it was
just a hot jumble of elements, which over time have solidified
into the very rocks that we stand on. Right? OK. These rocks have come from
a quarry in Portland, and they’re made of limestone,
which is a type of calcium carbonate. Masons would use these blocks
pretty much as they are in the construction industry. These rocks have been formed
over millions of years from shells like this. So these have just collected at
the bottom of the ocean and been compressed, and we can
actually even see some of the shells in this rock here. Because the shell and the rock
are made of the same chemical substance, calcium carbonate,
they have the same chemical properties. So here we have some
hydrochloric acid. And the bubbles that you see
instantly formed in here, this is carbon dioxide gas. There’s another way we can drive
out the carbon dioxide, and that’s simply
by heating it. So this block now has been
in the oven for 24 hours. It was allowed to
cool overnight. And well it looks pretty much
just the same as it did before, but actually, it’s
completely different. its chemical structure
has now changed. Before, we hand calcium
carbonate, and heating it up drives out the carbon dioxide
and leaves us with calcium oxide, or quicklime. Because we’ve driven out all
of the carbon dioxide from this rock, it’s actually lost
quite a lot of its weight. But it’s also changed in
structure, and we’re now going to see why it is that you won’t
find any buildings made out of calcium oxide. The change that takes place when
limestone is converted into quicklime, or calcium
oxide, has been known for many hundreds of years. Here, in this book from 1526,
we see the process. We see a chap with a furnace in
the background and boulders of limestone and he’s pouring
water on this. Quicklime literally means,
living lime. And we can see this as the water
instantly vaporises. It’s turning into steam in this
very violent reaction. It’s combining with the
quicklime, we can see it crumbling away, blistering. Bits of it are flying off,
popping in all directions, generating a lot of heat,
which we can see as the steam here. During this process, called
slaking, the calcium oxide reacts with the water to form
calcium hydroxide, and this is a key component of cement. This has been used since
Roman times and it’s still used today. [MUSIC PLAYING]

26 thoughts on “Calcium Carbonate – Disintegrating Quicklime”

  1. The reverse of this would be suspended fine calcium hydroxide particles in water & is called milk of lime. The solution is called limewater and is a medium strength base that reacts with acids and attacks many metals. Limewater turns milky in the presence of carbon dioxide due to formation of calcium carbonate, a process called carbonation (blowing exhaled air through limewater for example).

  2. Well, I mean, be fair– CaCO3 is only 20% metal, but then it came up to 50% with the formation of CaO. I guess it does become less metal again when they made Ca(OH)2–back down to 20%–, but overall, this video's pretty metal.

  3. I've used cement, mortar, concrete most of my life and am very grateful for this video. Thank you!!

  4. Could i do the same water+quicklime reaction with sea shells?
    Or is the composition not pure enough or something.

  5. I'm not left with a very good understanding of why the last reaction is important or why people hundreds of years ago would have done it. I know it's "part of cement," but you spent all that time and money getting and messing around with these blocks, and in the end I haven't seen you do anything particularly USEFUL with them. It would have been much more interesting to see you make some actual cement.

  6. So how then is limestone used as a building material???… say there is a heatwave, or said building is in a dessert… will the limestone turn into calcium oxide (and thus fizz out when it rains?)

  7. Thanks for the video! I have done this myself. It is an amazing reaction to witness first hand. Making concrete from it however proved to be somewhat of a failure. I did manage to glue some small bricks together though. The mortar was extremely soft and crumbled as soon as I applied pressure to it. My next search will be what ingredients are added to make Portland cement.

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