Chemistry 2 Unit 1 and 2
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What is a compound?
A compound is 2 or more elements chemically combined together
What is a covalent bond?
A covalent bond is when atoms of non-metallic elements join together by sharing electrons
What is an ionic compound?
Ionic compound is a giant structure of ions formed when metallic and non-metallic elements react with each other
What is meant by ionic bonding?
This is the electrostatic force of attraction between positive and negative ions
What is meant by a covalent bond?
This is the bond in which when 2 two atoms Share one or more pairs of electrons
Describe the structure of the atoms in a metal
The atoms in metals are closely packed together and arranged in regular layers
What force hold metal atoms in place in their structure?
The electrons in the highest energy level are delocalised. The strong electrostatic forces between these electrons and the positively charged metal ions hold the metal together
Why do ionic compounds have a higher melting point?
- They gave a giant structure
- Strong electrostatic forces that hold the ions together
- Lots of energy is needed to brake the bonds
Why can ionic compounds conduct electricity when dissolved one water?
Ionic compounds cannot conduct electricity when solid because the ions can only vibrate about fixed positions not move freely
Why do substances with simple molecules not conduct electricity?
Substances with simple molecules do not conduct electricity because the molecules do not have an overall electric charge
Why do substances with simple molecules have a Low melting and boiling point?
Substances with simple molecules have a low melting/boiling point because they have weak intermolecular forces between molecules
Why do ionic compounds have high melting/boiling point?
They have a high melting/boiling point because of the large amounts if energy needed to brake the many strong bonds
What do atoms that share electrons form?
Giant covalent structures or macromolecules
Why are diamonds hard?
Diamond is a form of carbon that had a regular 3D giant structure. Every carbon atone is covalently bonded to 4 other carbon atoms.
Why is graphite soft / softer than diamond?
In graphite, each carbon atom bonds to 3 other carbon atoms forming layers. There are no covalent bonding between the layers therefore they slide over each other
Why can graphite conduct electricity?
Graphite can conduct electricity because one electron from each carbon atom is delocalised
Why can the layers I'm graphite slide over each other easily?
Graphite has week intermolecular forces between the layers
What are fullerenes?
Fullerenes are large molecules formed from hexagon rings of carbon atoms, with different numbers if carbon atoms
What can fullerenes be used for?
- Fullerenes can be used for:
- Drug delivery into the body
- Reenforcing materials
Why can metals be bent and shaped?
Metals can be bent and shaped because the layers if atoms in metals are able to slide over each other
What are alloys?
Alloys are mixtures of metals or metals and elements
Why are alloys harder than pure metal?
Alloys are harder than pure metals because the different sized atoms in the mixture distort the layers in the metal structure and make it more difficult for them to slide over each other
What are shape memory alloys?
Shape memory alloys can return to their original shape when heated after being deformed. ( e.g. Dental braces)
Why are metals good conductors of electricity/heat?
Metal structures have delocalised electrons that move throughout the giant metallic lattice and can transfer energy quickly
What is the difference between LD and HD poly(ethene)?
They are made using different reaction conditions and catalysts. HD poly(ethene) had a higher softening temperature and is stronger than LD
What allows thermo-softening polymers to be remoulded?
Thermo-softening polymers are made up of individual polymer chains tangled together. they have week intermolecular forces
What is nanoscience?
Nanoscience is the study if small particles that are between 1-100 NM
What makes Nanoparticles useful?
They contain a few hundred atoms arranged in a particular way; their small size give them a large surface area to volume ratio
What can Nanoparticles be used for?
- Nano particles can be used for:
- High selective sensors
- Very efficient catalysts
- New coatings
- Cosmetics e.g. Sun screen and deodorants
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