Unit 1: Chapter 2 - Rocks And Building materials Flashcards
Reaction of Carbonates
What happens when CO2 mixes with Ca(OH)2?
What are the products when carbonates mix with acids?
Do the metals of the same group behave the same way as calcium?
When acid reacts with CaCO3, carbonation occurs, which produces CO2.
This can be tested by using limewater (Calcium hydroxide) and mixing it with CO2.
This happens because Ca(OH)2 is alkaline and carbon dioxide is weakly acidic (Neutralisation)
The precipitate of calcium carbonate makes limewater turn cloudy, because light can’t pas through the solution completely.
Carbonates react with acid to give salt, water and CO2.
CaCO3 + 2HCl -> CaCl2 + H2O + CO2
Other metals of the same group behave in the same way as Calcium.
The Limestone Reaction Cycle
What is the Limestone Cycle?
What is the reaction process called when an acid an alkali reacts together?
How is this useful?
When we HEAT CaCO3, we produce CaO.
When we add some WATER to CaO, we produce Ca(OH)2
When we add MORE WATER and filter, we produce Calcium Hydroxide solution.
Adding CO2 to calcium hydroxide solution will form CaCO3.
NEUTRALISATION
Acid + Alkali -> Neutralisation
Products = salt + water
Neutralisation occurs in agriculture and industries that release waste gases.
Cement and Concrete
How do you make Lime Mortar and modern motar?
How can you make concrete?
Advantages?
CEMENT VS LIME MORTAR
LIME MORTAR
Ca(OH)2 + Sand + Water -> Lime Mortar
(Cement replaces Ca(OH)2 to make modern mortar)
Lime mortar is very strong but sets very slowly. It will not set in conditions where water prevents it reacting with CO2. It absorbs CO2 to set.
CEMENT
Cement can formed by heating powdered CLAY and LIMESTONE in a kiln. When mixed with water, it sets in a few days.
CONCRETE
Aggregate + Cement + Water + Sand
-> Concrete
+ Very strong
+ Good at resisting forces
+ Can be reinforced with steel bars
Limestone Issues
Economical issues? (+ advantages)
Social issues? (+ advantages)
Environmental advantages?
Environmental issues+ advantages?
-Destroys habitats of animals
+Can restore quarry after used.
Social issues + advantages?
- Dust may settle on crops and animals of farmers
- Noise pollution
- Lorries carry dust and go through villages
- Traffic may cause accidents
+Creates jobs
Economical advantages
+Creates jobs
+Multiplier effect
Limestone and its Uses
What are limestone uses?
What happens when we heat limestone?
How and what does the industry use to heat limestone?
Limestone is CaCO3, which is a rock.
Some types of limestone were made by the remains of tiny animals and plants that lived in the sea millions of years ago.
Limestone had many uses such as building material.
For e.g. Powdered limestone can be heated with powdered clay to make cement.
Cement + water + sand + crushed rock makes a slow reaction. This then forms a hard rock called concrete.
HEATING LIMESTONE
CaCO3 -> CaO + CO2
Calcium carbonate -> calcium oxide +
Carbon dioxide
This is called THERMAL DECOMPOSITION. (The breaking down of a chemical by heat.)
A ROTARY LIME KILN
To make CaO, we use a lime kiln.
When crushed limstone is placed in the kiln, a hot supply of air heats it on the other end of the kiln. This produces waste gases, such as CO2 that leaves at the top. The CaO leaves at the bottom.
The limestone kiln is rotated to make sure the hot air mixes thoroughly with the limestone so it decomposes completely.
