C2 Flashcards
What are 3 states of matter
Liquid
Solid
Gas
What is the melting point
The temperature at which a solid changes into a liquid
What is the boiling point
The temperature at which the particles gain enough energy to change from a liquid to a gas
What does the amount of energy needed to break bonds to change state depend on?
Strength of forces between particles of substance
The stronger the forces between particles…
The higher the m.p. and b.p. of substance
What does (aq) stand for
Aqueous solution
(g) meanning
Gas
(l) meanning
Liquid
(s) meanning
Solid
Describe properties of gas particles
- widely spaced
- movement of particles: in random directions at random speed
- collisions are frequent and elastic
- weak forces between particles
- have highest energy
Describe properties of liquid particles
- closely spaced but still in constant motion
-therefore constantly colliding - forces between particles are weaker than in solid
- randomly arranged
- move around eachother
- can flow and take shape of container
Describe solid particles
Solid particles can only vibrate in a fixed position
- low energy
- regular pattern
- cannot be compressed
How do you turn: solid into liquid
Melting
How do you turn: liquid into gas
Evaporating/ boiling
How do you turn: gas into liquid
Condensing
How do you turn: liquid into solid
Freezing
How do you turn: gas to solid or solid to gas
Sublimation
Example of sublimation
Solid carbon dioxide ( dry ice) and Iodine
How do substances change state
Energy must be transferred
How do substances melt. Explain in terms of energy
- particles gain energy- heating
- bonds are broken between particles
What happens when a substance boils or evaporates.
Forces of attraction between particles are overcome
The stronger the forces of attraction…
The more energy Is required to overcome forces
What happens to particles during condensation and freezing
- Energy is transferred from substance to surroundings
- This is because the forces of attraction between the particles get stronger
How do you know if a substance is solid when given its temperature
Given temperature < melting point
= solid
How do you if a substance is liquid when given the temperatures of its b.p. and m.p.
Given temperature is between melting and boiling points
=liquid
How do you know if a substance is gas when given its temperature
Given temperature > boiling point
= gas
What are limitations of particles model
- particles are not solid they are mostly empty space
- many particles are not spherical
- no forces between spheres
What does the particle model show
Particles are solid spheres with no forces between them
How can you distinguish a pure substance when given the time and temperature it takes for it to melt and boil
- pure substance will melt or boil at a fixed temperature (flat horizontal line)
- mixture will melt over a range of temperatures and not sharp melting point
Define ion
- charged atom
- when an atom loses or gains electrons to obtain full outer shell
In what compounds does ionic bonding occur between
Metals combined with non- metals
What ions do metal atoms form in ionic bonding
Positively charged ions- lose electron
What ions do non metal atoms form in ionic bonding
Negatively charged ions- gain electron
How are positive metal ions formed in ionic bonding
-When metal reacts with non-metal and loses electron from outer shell -it becomes fully stable
- positive because there is more protons than electrons
How do non metals become negatively charged ions in ionic bonding
-they gain electron
-to get fully stable outer shell
- becomes negatively charged because there is more electrons than protons
Group 1 always forms ..
1+ ions
Group 2 always forms..
2+ ions
Group 6 always form..
2- ions
Group 7 always form..
1- ions
What does a dot and cross diagram represent
Electron transfer during formation of ionic compound
What is ionic bond
Force of attraction between oppositely charged ions
Describe electron transfer between potassium oxide
- potassium atom loses electron and forms 1+ potassium ion
- oxygen gains 2 electrons and forms 2- oxide ion
2 potassium atoms react with 1 oxygen atom
For sodium chloride the ions are Na+ and Cl- . What is the formula of compound
NaCl 1+ charge cancels out 1 - charge
Magnesium fluoride the ions are Mg 2+ and F - . What is the formula of compound
MgF₂
We need 2 F- ions to cancel out the 2+ charge on Mg
Lithium oxide the ions are Li+ and O2- . What is the formula of compound
Li₂O
We need 2 lithium ions to cancel out the 2- charge on O
What are ionic compounds held together by
Strong electrostatic forces of attraction between oppositely charged ions
Properties of ionic substances
- high m.p. and b.p.
- in solid form they do not conduct electricity
Why do ionic substances have high melting and boiling point
because of large amounts of energy needed to break many strong electrostatic forces of attraction between oppositely charged ions
Why can ionic substances not conduct electricity in solid form
Because ions are in fixed position
How can ionic compounds conduct electricity
When melted or in aqueous solution because ions are free to move therefore can carry charge
what words to always use when describing ionic structures and their properties
Ions
what words to never use when describing ionic structures and their properties
- delocalised electrons
- molecules
- intermolecular forces
What is an ionic lattice
When ions have a regular repeating arrangement
What does the ball and stick diagram present in ionic bonding
Ions are arranged close seperated by sticks to eachother
- but in reality there is no gaps or sticks between ions
What is empirical formula
Simplest ratio of ions in compound
Ions with higher charge will…
have stronger forces of attraction between them, so will need more energy in order to overcome these forces
Covalent bonding occurs in what compounds?
Compounds of non- metals
What happens in covalent bonding
Atoms share pairs of electrons
Limitations of models showing covalent bonds
- none are to scale
- some do not show 3 dimensional arrangement in space
- some do not show electrons or all the shells
Properties of covalent substances
These substances:
- consist of small molecules - are usually gases or liquids that have low m.p. b.p.
- do not conduct electricity because molecules do not have overall electrical charge
What happens to forces when covalent substance heated
- weak intermolecular forces between molecules are overcome- when substance melts or boils- these require little energy to break
- STRONG COVALENT BONDS DO NOT BREAK
Explain the effect of the size of molecule on intermolecular forces
- intermolecular forces increase with size of molecule
- larger molecules need more energy to break intermolecular forces and so have higher m.p. + b.p.
- this explains why melting and boiling point Increases down group 7
What is the only word you should be using to describe covalent bonding
Intermolecular forces
What is a polymer
Very large covalent compound with many repeating units
Polymer- structure, properties and explanation
- lines show covalent bonds
- solid
- intermolecular forces between polymer molecules are relatively strong
What does n represent in polymers
A large number
Giant covalent structures properties
Solids with very high melting and boiling points
Atoms joined together by strong covalent bond
These bonds must be overcome in order to melt or boil substance
Examples of giant covalent substances
Diamond and graphite (forms of carbon)
Silicon dioxide (silica)
Diamond- structures, properties and explanations
● doesn’t conduct electricity= no delocalised electrons to cary charge
●very hard = strong covalent bond to form lattice
● very high melting point= each carbon atom forms 4 covalent bonds with other carbon atoms
large amount of energy is needed to overcome all these bonds
-
What is graphene
Single layer of graphite so one atom thick
Graphene properties
○ very strong
○ able to conduct electricity due to delocalised electrons
Graphene uses
- Electronics
- Composites
Describe the structure of fullerene
Hallow shaped, hexagonal rings of carbon atoms
Example of fullerene
Buckminsterfullerene (C ⁶⁰)
Describe Properties of fullerenes
Very strong
Hallow so can contain other other chemicals within it
Uses of fullerene
Drug delivery, lubricants
Describe structure of Carbon nanotubes
Cylindrical tubes of carbon atoms that are very long compared to their diameter
Uses of carbon nanotubes
Nanotechnology, electronics, reinforcing (e.g. tennis rackets)
Properties of carbon nanotubes
●Very strong, light and flexible
● Able to conduct electricity due to delocalised electrons
Describe structure of graphite
- each carbon forms 3 bonds to other carbon atoms
- forming layers of hexagonal rings
Why can graphite conduct electricity
Conducts electricity= 1 carbon only forms 3 bonds so one electron is delocalised
These electrons are free to move and can carry charge through the structure conducting thermal energy and electricity
Why is graphite soft and slippery
Arranged in layers with weak intermolecular forces between layers so layers can easily slide due to no covalent bonds present
What is a pure metal
● Sea of delocalised electrons with positive metal ions
● Ions are tightly packed and arranged in rows
What is an alloy
Presence of other elements between positive metal ions and delocalised electrons- distorts layers and prevents them from sliding over eachother
How are delocalised electrons and metal ions bonded together
Strong electrostatic force of attraction between positive metal ions and negatively charged electrons
Properties of metals
- have high m.p. b.p. = lots of energy needed to break strong metallic bonds between positive ions and delocalised electrons
- good conductors of electricity- delocalised electrons free to carry charge
- same with thermal energy- good conductors
- malleable- layers can slide over eachother, bent, shaped, attraction between ions and electrons prevents metal from shattering
Benefits of alloys
Different sizes of atoms in alloy distorts layers in structure of metal making it more difficult for them to slide over eachother so are harder
Nanoparticles have a …
High surface area to volume ratio
Risks of nanoparticles
- so small so can be inhaled through lungs and because if large s.a. to volume ratio they can initiate harmful reactions and toxic substances can bind to them
What charge is a cation
Positive
What charge is an ion
Negative
What charge is cathode
Negative electrode
What charge in annode
Positive
