C5: Chemicals of the Natural Environment Flashcards
Name a gas in dry air that is a compound & give the formula.
Carbon dioxide - CO2
Explain why most molecular substances are gases
Molecular substances usually exist as small molecules, like CO2 and H20. The atoms within are held together by very strong covalent bonds. In contrast the forces of attraction between these molecules are very weak. You only need a little bit of energy to overcome the weak forces this is why they have low melting & boiling points.
DEFINE: Covalent Bonding
A covalent bond is formed between non metal atoms, which combine together by sharing electrons.
What is the earths hydrosphere?
The earths hydrosphere consists of all the water in the oceans, seas, lakes, rivers, etc and the substances dissolved in it.
What makes sea water salty?
Many of the compuonds found in water are ionic compounds called salts.
Why do solid ionic compounds form crystals?
They form crystals becaus of their gaint lattice structure. The ions with opposite charges attract each other. There are very strong ionic bonds between all the ions.
Do ionic compunds have low or high boiling points? Why?
They have high melting and boiling points this is because of the very strong forces of attraction between the ions. It would take alot of energy to break them. This is what makes them solid at room temperature.
Can ionic compounds conduct electricity when solid? Why?
They can not conduct electricity in solid form because the ions are not free to move. They conduct electricity in molten or dissolved states as the ions can move.
Carbonates give off carbon dioxide when theyre mixed with dilute acid. What is the test for CO2?
You can test for carbon dioxide is limewater. If present limewater turns cloudy.
What is the test for halides?
To identify a hallide ion, add dilute nitric acid followed by silver nitrate solution. The colour determines the hallide.
What is the Earths lithosphere?
The lithosphere is the ridgid outer layer- the crust and part of the mantle below it. Its made up of a mixture of minerals.
Name three abundant elements in the earths lithosphere
Silicon, Oxygen& Aluminium
Industrial diamonds are used in drill tips and precision cutting tools. What property makes it suitable for this?
It is the hardest natural substance
Explain how the bonding in diamond gives it this physical property
The carbon atoms in diamond each form four covalent bonds in a very ridgid giant covalent structure. These bonds are very hard to break.
Graphite conducts electricity which is unusal for a non metal. Explain why it has this property
Only three out of four of each carbon’s four outer electrons are used in bonds, so there are lots of spare electrons- this gives it the ability to conduct electricity.
