The Lithosphere C5 Flashcards
Why does graphite conduct electricity?
The carbon atoms only have three covalent bonds leaving four spare delocalised electrons to carry charge.
What is a use for graphite and why?
Pencils.
The covalent bonds are arranged in sheets with weak forces between these sheets, allowing the pencil to rub off in layers.
Describe a use for diamond and why this is a good use…
Glass-cutting tool. Diamond has a rigid structure with four covalent bonds making it the hardest structure - it can break other substances.
Percentage composition describes…
The percentages of minerals and elements in rocks.
Describe the lithosphere.
The crust and part of the mantle just below it make the Earth’s lithosphere. This mostly consists of a mixture of minerals. The elements silicon, oxygen, and aluminium are found in large amounts in the crust.
What are the features of diamond?
The carbon atoms form four covalent bonds in a very rigid giant covalent structure.
All the bonds give diamond a high melting point.
Diamond does not conduct electricity as it has no free electrons, not even when molten.
Usually insoluble.
What are graphite’s features?
Graphite is made from carbon.
It only has three covalent bonds creating sheets that can slide over each other - this makes graphite slippery so good as a lubricant.
The lagers can be rubbed off into paper leaving a black mark.
High melting point.
Spare electrons mean that graphite can conduct electricity - used in electrodes.
Describe silicon’s features…
Most silicon and oxygen in the crust exists as silicon dioxide.
This is what sand is made of.
Each grain of sand is a giant structure of silicon and oxygen.
A similar structure to diamond with four covalent bonds gives it a high melting point and means it cannot conduct electricity.
Diamond and graphite are…
Minerals of carbon atoms.
Describe giant covalent structures.
These contain uncharged atoms. The covalent bonds between the atoms are strong. They have high melting points and are usually insoluble in water.
