C2 Chem Flashcards
Giant covalent structure
All atoms are covalently bonded in a massive network such as diamond
Are sometimes called macro molecular substances
Giant covalent structure has a high or low melting point?
High
Diamond properties
- Carbon atom is joined to four other covalent bonds
- Has high melting point because a lot of covalent bonds has to be broken
- is very hard because atoms are bonded in a rigid network
- it is an insulator because there are no free electrons to move around
Properties of graphite
- carbon atom is joined to three covalent bonds that forms layers
- very high melting point because a lot of covalent bonds have to be broke
- soft and slippery because the layers can slide over each other
- conductor because it has delocalized electrons
What are fullerenes?
How many carbon does it contain?
Are molecules made up of linked carbon rings
It contains 60 carbon atoms in a spherical shape
Simple molecular substance
- There are millions of separate but identical molecules such as water
Low melting and boiling points because it has weak intermolecular forces - Non conductive because the electrons are not free to move
What is an alloy?
A mixture of a metal with small amounts of other metals or carbon
Why can metals be bent and hammered into shape?
Because the layers of metal atoms can slide over each other easily whilst maintaining the metallic bonding
Why are alloys harder than pure metal?
Because different metal atoms in alloys jam up the metal structure that stops the layers of atoms from sliding past each other easily
What is a shape memory alloy?
Example?
An alloy that can return to its original shape after being deformed
Nitinol
What are the uses of a shape memory alloy such as nitinol?
Wires in dental braces
Structure of thermo softening polymers
- Long polymer chains are not joined up
- they soften and melt when heated because they have weak intermolecular forces
Stricture of thermosetting polymers
- polymer chains are joined to each other by strong covalent bonds that makes them not soften or melt
What are atoms?
A particle with no overall charge
What is an element?
Element is a substance made up of only 1 atom
What is a compound?
A substance made up of more than type of atom that are chemically joined together
How are compounds broken down?
By thermal decomposition or electrolysis
Rules for covalent bonding
- A pair of electrons are shared between 2 atoms
- between nonmetals only
Rules for ionic bonding
- electrons are transferred between 2 atoms
- occurs between metal and non metal
What is nanoScience?
The study of nanoparticles
Why are nanoparticles have different properties?
They have a much larger surface area to volume ratio
What are the uses of nanoparticles?
They can be used as sensors for example, to detect toxic lead ions
They can be used in clothes to kill bacteria and prevent smells
What are the concerns of nanoparticles?
- since they have different properties, they may be toxic
- they might be more reactive than bulk material
Definition of a nanoparticle?
A particle between 1 - 100 nanometer in size
How are the ions arranged in an ionic lattice?
Ions are packed in an ordered,regular structure
What is the percentage yield?
The amount that is actually produced with the amount expected in theory
How to calculate percentage yield?
Mass of product obtained/maximum theoretical mass of product * 100
What is an empirical formula?
Examples
The ratio of atoms or ions in a substance
Butane C4H10 = C2H5
Octane C8H18 = C4H9
How do you make insoluble salts?
Reacting together solutions of two soluble salts
What is a precipitate in terms of salts?
An insoluble solid (salt) formed when reacting two soluble salts together
What are the main soluble salts?
All Sodium, potassium, ammonium (carbonates and hydroxides)
All nitrates
Most chlorides, bromides and iodides
Most sulfates
What are the main Insoluble salts?
Barium,calcium and leaf sulfate
Most carbonates and hydroxides
Lead and silver chloride, bromide and iodide
How to make soluble salt?
Reacting metal with acid
What is a base?
A compound, usually metal oxide or hydroxide that reacts with acid to neutralize it
Examples of soluble salts?
Sodium nitrate
Sodium chloride
Examples of insoluble salts?
Lead sulfates
Lead chloride
What kind of ions do alkalis release when they are dissolved in water?
Hydroxide ions (OH-)
What kind of ions do acids release when dissolved in water?
Hydrogen ions (H+)
What is the neutralization reaction?
Acids and alkalis react together to produce a salt and water
H+ + OH- = H2O
Example of ionic equation for neutralization?
H+ + OH- = H20
Aqueous + Aqueous = Liquid
What is paper chromatography?
A technique that separates different dyes or pigments in a colored substance using paper
What is gas chromatography?
A method that separates chemicals in a small sample using un-reactive gases
What is mass spectroscopy?
An analytical technique that involves breaking molecules into charged fragments and measuring their mass ratio
What are key factors that affects the rate of reaction?
Temperature
Surface area
Concentration
The use of a catalyst
What is the retention time?
Time taken for substance to detector at the end of the column
What is the minimum energy required for reactions to start?
Th activation energy
What are catalysts?
A chemical compound that speeds up chemical reactions without being used up
Pros and cons of catalysts?
Are are used to speed chemical reactions up without being used up
However, some catalysts are expensive since such as the platinum used in fuel cells
What is an exothermic reaction?
Example?
Chemical reaction that give out energy (heat)
Make bonds
Metal + acid = salt + hydrogen
What is an endothermic reaction?
Example?
Reactions that take in energy
Break bonds
Photosynthesis
Examples of reversible reactions?
Hydrated copper sulfate = anhydrous copper sulfate + water
Blue White
Endothermic and exothermic
Example of reversible reaction?
Photosynthesis and respiration
What is a precipitate?
Insoluble Solid formed when 2 soluble salts react together
What is electrolysis?
Breaking down a compound using electricity
What is reduction?
Gaining electrons
What is oxidation?
Loss of electrons
Where does reduction happen in electrolysis?
On the negative electrode
Where does oxidation happen in electrolysis?
In the positive electrode
Examples of exothermic reactions?
Oxidation
Neutralization
Displacement
Combustion
Examples of endothermic reactions?
Respiration
Photosynthesis
Acid plus metal
Salt and hydrogen
Acid plus metal oxides
Salt plus water
