What is limestone formed from?
How is limestone gotten?
It is quarried out of the ground
Uses of limestone?
- Building blocks
- Powdered limestone is heated in a kilm with powdered clay to make cement
- Cement can be mixed with sand and water to make mortar. Mortar is used to stick bricks together (you can also add calcium hydroxide to mortar)
- You can mix cement with sand and aggregate (water and gravel) to make concrete
What is limestone mainly made of?
What happens to limestone when it's heated?
It thermally decomposes to make calcium oxide and carbon dioxide
Calcium carbonate → Calcium Oxide + Carbon Dioxide
What is thermal decomposition?
When one substance chemically changes into at least 2 new substances when it's heated
When carbonates are heated what do they produce?
An oxide of their metal (eg magnesium oxide) and carbon dioxide
→ They decompose in the same way
Which carbonates decompose in the same way?
Magnesium, copper, zinc and sodium
What does calcium carbonate produce when reacted with acid?
It makes calcium salt, carbon dioxide and water
Calcium Carbonate + Sulfuric Acid → Calcium Sulfae + Carbon Dioxide + Water
What does the type of salt produced when a carbonate reacts with an acid depend on?
It depends on the type of acid
→ Eg a reaction with hydrochloric acid would make a chloride
What does calcium oxide react with water to produce?
Good things about limestone?
- It provides things people want - like houses and roads, chemicals used in making dyes, paints and medicines also come from medicine
- Limestone products are used to neutralise acidic soil. Acidity in lakes and rivers caused by acid rain is also neutralised by limestone products
- Limestone is also used in power station chimneys to neutralise sulfur dioxide, which is a cause of acid rain
- The quarry and associated buisinesses provide jobs for people and bring more money into the local economy. This can lead to local improvements in transport, roads, recreation facilities and health
- Once quarrying is complete, landscaping and restoration of the area is normally required as part of the planning permission
What can be used to neutralise acidic soil in fields?
Calcium hydroxide: It is an alkali, and is therefore used to neutralise acidic soil in fields
→ Calcium hydroxide works much faster than powdered limestone
What can calcium hydroxide be used for?
In a test for carbon dioxide
→ If you make a soultion of calcium hydroxide in water (called limewater) and bubble gas through it, the solution will turn cloudy if there's carbon dioxide in the gas
The cloudyness is caused by the formation of caclium carbonate
Also to neutralise acidic soil
Problems with quarrying limestone?
- It makes an hole which is eye sore, which permanently changes the landscape
- Quarrying processes, like using explosives makes pollution by making dust and noise in quiet, senic areas
- Quarrying destroys habitats of animals and birds
- Noise and pollution comes from transporting the limestone
- Waste materials produce unsightly tips
Problems with making stuff from limestone?
- Cement factories make a lot of dust, which causes breathing problems for some people
- Energy is needed to produce cement and quicklime
→ The energy is likely to come from burning fossil fuels; which causes pollution
Advantages and disadvantages of limestone products?
- Limestone is widely avaliable and cheaper than granite or marble - it is a fairly easy rock to cut
- Some limestone is more hardwearing than marble, but it still looks attractive
- Concrete can be poured into moulds to make blocks or panels that can be joined together. It is a very quick and cheap way of constructing buildings BUT it is a very unattractive building material
- Lime stone, concrete and cement don't rot when they get wet like wood does
→ They can't be gnawed by insects or rodents either, and they're fire resistant
- Concrete doesn't corrode like lots of metals do. It does have a fairly low tensile strenght and can crack. If its reinforced with steel brds it'll be much stronger