Limestone

Limestone is mainly calcium carbonate, CaCO₃, which when heated breaks down to form calcium oxide and carbon dioxide. Calcium oxide reacts with water to produce calcium hydroxide. Limestone and its products have many uses, including being used to make cement, mortar and concrete.

Carbonates react with acids to produce carbon dioxide, a salt and water. For example:

calcium carbonate + hydrochloric acid → carbon dioxide + calcium chloride + water

CaCO₃ + 2HCl → CO₂ + CaCl₂ + H₂O

Since limestone is mostly calcium carbonate, it is damaged by acid rain. Sodium carbonate, magnesium carbonate, zinc carbonate and copper carbonate also react with acids: they fizz when in contact with acids, and the carbon dioxide released can be detected using limewater.

When limestone is heated strongly, the calcium carbonate it contains decomposes to form calcium oxide. This reacts with water to form calcium hydroxide, which is an alkali. Calcium hydroxide is used to neutralise excess acidity, for example, in lakes and soils affected by acid rain.

Sinkhole in Hemel Hempstead

The recent sinkholes in Hemel Hempstead left a lot of people shocked and surprised and the size of the hole, and how quickly it happened. 

The fact that it was occurring on people's driveways, alongside the motorways and nearly underneath people's houses was terrifying for some to understand.

The 15ft deep sinkhole closed the M2 motorway near Kent.

These sinkholes occur after heavy rainfall. Rainfall seeps through the soil absorbing carbon dioxide and reacts with decaying vegitation, creating a slightly acidic water. Water moves through spaces and cracks underground, slowly dissolving limestone and creating a network of cavities and voids. As limestone dissolves, the pores and cracks are enlarged and carry more acidic water. 

Sinkholes are therefore formed when land surface above collapses or sinks in to the cavities, or when surface materials is carried downward in to the voids. 

Limestone

Myself and Ashleigh have come together and after a few hours of research, we have decided that our topic will be around limestone and the sink holes.

We will reserch what creates sinkholes and why they appear, how limestone affects it and the bedrock of Wales.

Included in the podcast will be our visit to botonocal gardens and st fagans.

We are both very excited to create a fun and creative podcast.