Sedimentary rocks are formed by layers of rock particles and dead plant and animal material building up over millions of years. Limestone and sandstone are examples of sedimentary rocks.
3. Metamorphic Rocks
Metamorphic rocks are formed when igneous and sedimentary rocks are changed into harder rocks by high temperatures and pressure. Quartzite, slate and marble are examples of metamorphic rocks.
‘Metamorphosis’
‘Metamorphosis’ means to change from one thing to another, such as igneous or sedimentary rocks changing form. In the biological world, it refers to an animal changing into its mature form, such as a caterpillar turning into a butterfly.
Testing rocks for the presence of carbon
Geologists are scientists who study the rocks that make up the Earth. Geologists often use an acid test to find out if rocks are made up of carbon compounds.
1. Collect some small pebbles and rocks and bring them to school. Your teacher will give you a small quantity of hydrochloric acid (five to ten per cent concentration). Be extremely careful with this acid as it is corrosive.
2. Place a small drop of acid on each pebble or rock. Prepare a data collection sheet and a scale to note ‘fizziness’. Consider the following: zzWhy do some of the rocks fizz? Research the chemical reaction online.
zzWhat may you conclude from the ‘fizziness’ of the reaction?
zzWhat type of data are you recording when you are noting ‘fizziness’? How accurate do you think this data is?
