Topic 1: Key Concepts In Chemistry Flashcards
What is ionic bonding?
When a metal and a non-metal react together, the metal atoms loses electrons to form a positive ion(cation) and the non-metal gains these electrons to form a negative ion(anion)
What are the properties of ionic compounds?
- high melting and boiling points
- don’t conduct electricity unless melted
- many dissolve easily in water-so will carry an electrical current
Why do ionic compounds have high melting and boiling points?
Due to the strong attraction between the ions. It takes a large amount of energy to overcome this attraction
Why don’t ionic compounds conduct electricity unless melted?
Because the ions are fixed in place and can’t move. But when an ionic compound melts, the ions are free to move and will carry an electric current
Why do ionic compounds dissolve easily in water and carry an electrical current?
Because the ions separate and are all free to move, so they’ll carry an electrical current
What structure do ionic compounds have?
Ionic compounds will always have a giant ionic lattice structure. The ions form a closely packed regular lattice. There are very strong electrostatic forces of attraction between oppositely charged ions, in all directions
What is a covalent bond?
A strong bond that forms when a pair of electrons is shared between two atoms
What are simple molecular substances made up of?
They are made up of molecules containing a few atoms joined by covalent bonds
What are the properties of simple molecular substances?
- the atoms with the molecules are held together by very strong covalent bonds-forces of attraction between these molecules=very weak
- melting and boiling points are very low
- most molecular substances are liquid/gases at room temp
- as molecules get bigger, the melting&boiling points increase
- molecular compounds don’t conduct electricity
- some are soluble some aren’t
What are the properties of giant covalent structures?
- all atoms are bonded to each other by strong covalent bonds
- they have very high melting&boiling points
- they generally don’t contain charged particles, so they don’t conduct electricity
- they aren’t soluble in water
What are some examples of carbon-based giant covalent structures?
- diamond
- graphite
- graphene
What are fullerenes?
Fullerenes are molecules of carbon, shaped like closed tubes or hollow balls
What is metallic bonding?
Metallic bonding is the strong electrostatic force of attraction between the metal ions and the delocalised electrons.
What are the physical properties of metals?
- the electrostatic forces between the metal ions and the delocalised sea of electrons are very strong
- mostly high melting points
Advantages of 2D presentations
Simple, show what atoms something contains, shows how atoms are connected
Disadvantages of 2D presentations
Dont show the shape of substance or size of atoms
Advantages of dot and cross diagrams
Show how compounds/molecules are formed and where the electrons came from
Disadvantages of Dot and cross diagrams
Dont show size of atoms or how they’re arranged
Advanatges of 3D models
Show arrangement of ions
Disadvantages of 3D models
Only show outer layer of substance
Advanatges of ball and stick model
Helps visualise structures in 3D, more realistic than 2D
Disadvantages of ball and stick models
Misleading, looks like big gaos between atoms, actually where electrom clouds interact and dont show correct scales of atoms/ions
What is an ionic bond
When a metal and non metal react together, the metal atom loses electrons to form a cation(+) and non metal gains these electrons to form a anion(-) . These oppositely charged ions are strong attracted by electrostatic forces
What are ions
Charged particles can be single atoms or groups
What are negative ions called
Anions
What are positive ions called
Cation
What are fullernes made of
Carbon atoms arranged in hexagons, can contain pentagons or heptagons
What type of structure are metals
Giant structure
What are the electrons in the outer shell of a metal like
Delocalised, strong forces of electrostatic attraction between the positive metal ions and shared electrons
What are the properties of metals
High melting and boiling points, shiny at room temp, arent soluble in water, more dense than non-metals, malleable(layers of atoms in oure metal can slide over eachother), good conductors of heat and electricity, lose electrons to gain full outer shell
Properties of non-metals
Dull looking, brittle, lower boiling points, dont conduct, lower density, gain electrons to gain full outer shell
What is a covalent bond
A strong bond that forms when a pair of electrons is shared between 2 atoms
What are polymers
Molecules made up of long chains of covalently bonded carbon atoms e.g polyethene
Properties of diamond
Four covalent bonds, high melting point, doesnt conduct electricity, rigid lattice structure - hard, good for cutting tools
Properties of graphite
3 covalent bonds, sheets of carbon in hexagons, no covalent bonds between layers - only held together weakly, so they’re free to move over each other, soft and slippery(good lubricant), high melting point, can conduct electrcity because it has one free electron
Properties of graphine
Type of fullerne, one layer of graphite, sheet of carbon atoms joined in hexagons, 2D substance
What is an ion?
An atom or group of atoms with a positive or negative charge
What does covalent bonding result in the formation of
Molecules
How big are simple molecules?
10(-10)m
How big are the bonds that form between simple molecules?
10(-10)m
Structure of diamond
Make up of a network of carbon atoms that each form 4 covalent bonds
Structure of graphite
In graphite, each carbon atom only forms 3 covalent bonds, creating sheets of carbon atoms arranged in hexagons
Why is diamond used at a cutting tool
Because the strong bonds hold the atoms in a rigid lattice structure, making diamond really hard
Why is graphite used as a lubricant
Because they’re aren’t any covalent bonds between the layers, they’re only held together weakly so they can move over each other
What are fullerenes
Molecules of carbon shaped like closed tubes or hollow balls
What is a property of a fullerene
It has a huge surface area
What has the formula C60
Buckminsterfullerene
What is the structure of buckminsterfullerene
Forms a hollow sphere made up of 20 hexagons and 12 pentagons
What does buckminsterfullerene form
Soft brownish-black crystals
What are nanotubes
Tiny cylinders of graphene
Properties of nanotubes
Don’t conduct electricity, high tensile strength(don’t break when stretched),
What can nanotubes be used to do
Strengthen sports equipment
What is graphene
A type of fullerene
What is a closed system
A system where nothing can get in or out
What is the conservation of mass
No atoms or destroyed and no atoms are created
What is a precipitation reaction
When 2 solutions react and an insoluble solid called a precipitate forms in the solution
How can u see that mass is always conserved
If u do a reaction in a closed system, the total mass of the system before and after doesn’t change
Why may the mass increase in an unsealed reaction vessel
One of the reactants may be a gas that’s found in air,
Steps of an experiment used to find empirical formula
1) heat a crucible to destroy bacteria and make sure it’s clean
2) Leave the crucible to cool then weigh it with its lid
3) Add some clean magnesium ribbon to the crucible and reweigh crucible, lid, magnesium ribbon.
The mass of the mag ribbon is this reading - the reading of the crucible and lid
4) Heat the crucible (10mins) until the mag has turned white
5) Allow crucible to cool, and reweigh all of it together
Mass of mag oxide = this - initial reading
How to calculate the mass of a product formed from the given mass of a limiting reactant
1) write out the balanced equation
2) work out the RFM of the reactant and product
3) find out how many moles there are of the substance u know the mass off
4) use the balanced equation to work out how many moles they’ll be of the other substance
5) use the no. Of moles to calculate the mass
What is the amount of product formed directly proportional to
The amount of the limiting reactant used up
Why is the amount of product formed directly proportional to the amount of the limiting reactant used
Because if u add more of the limiting reactant there will be more reactant particles to take part in the reaction which means more product particles are made (as long as the other reactants are in excess)
