How bonding and structure relate to properties (2.2) (M) Flashcards
What are the three states of matter?
solid, liquid and gas
Which processes take place at the boiling point?
boiling and condensing
Which processes take place at the melting point?
melting and freezing
What is the simple model of states of matter? (with diagrams for each)
particles are represented by small solid spheres
What is particle theory?
based on fact all matter is made up of tiny particles
It describes the movement of and average distance between particles
What are the properties of a solid?
- have fixed shape an volume
- cannot be compressed
- least energetic
What are the properties of a liquid
- have a fixed volume
- but can flow and take shape of container
- particles slide over each other
- occupy slightly more space than when solid (ice and water an exception)
What are the properties of a gas?
- have no fixed volume or shape
- can be easily compressed
- particles move in all directions
- most energetic
The amount of energy needed to change state from solid to liquid and from liquid to gas depends on what?
the strength of the forces between the particles of the substance
What does the nature of the particles involved in changes of state depend on?
the type of bonding and the structure of the substance
What do you call it when you go from a solid to gas?
sublimation
What do you call it when you go from a gas to solid
deposition
The stronger the forces between the particles the (…) the melting point and boiling point of the substance
higher
2 needed
What are limitations of the simple model?
- in the model there are no forces
- all particles are represented as solid inelastic spheres (particles are not spheres and particles are mostly made up of empty spaces)
In chemical equation, what are all the state symbols?
(s), (l) and (g), with (aq) for aqueous solutions
How would you describe the structure of ionic compounds? (as well as the forces within this structure)
Ionic compounds have regular structures (giant ionic lattices) (of alternating positive and negative ions)
in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions
these forces act in all directions in the lattice
What are the melting and boiling points of ionic compounds like? Why is this?
These compounds have high melting points and high boiling points
because of the large amounts of energy needed to break the many strong bonds
When can ionic compounds only conduct electricity? Explain why
When melted (molten) or dissolved in water
because the ions are free to move and so charge can flow and carry electrical charge
Substances that consist of small molecules are usually which states of matter?
gases or liquids
Substances that consist of small molecules have relatively (…) melting and boiling points
low
Describe the intermolecular forces of a simple molecule
only weak forces between the molecules (intermolecular forces)
forces within molecules are strong (intramolecular forces) so it is hard to break down these molecules into separate reactants
When the substance of simple molecules melts or boils, is it the covalent bonds or intermolecular forces that are overcome?
intermolecular forces, not the covalent bonds
The intermolecular forces (…) with the size of the molecules, so larger molecules have (…) melting and boiling points
increase
higher
Why do small molecules (covalent bonds) not conduct electricity?
because the molecules do not have an overall electric charge (no free electrons)
Why are the bulk properties of simple molecular substances different from the properties of the elements/compounds that make them up?
intermolecular forces are weak compared with (strong) covalent bonds (atoms/molecules must act together)
size
Polymers have (…) molecules. How are they described?
very large
repeating units/chains of molecules
How are the atoms in the polymer molecules are linked to other atoms?
by strong covalent bonds
strong vs weak
The intermolecular forces between polymer molecules are relatively (…)
strong
What is the state at room temperature of polymers, due to the fact they have strong covalent bonds?
therefore these polymers are solids at room temperature
What is the state of matter of giant covalent structures?
solids
What is the melting point like of giant covalent structures?
The melting point is very high
All of the atoms in giant covalent structures are linked to other atoms by…
strong covalent bonds
What needs to happen for giant covalent structures to melt or boil?
the covalent bonds must be overcome
breaking apart the structure as all atoms are covalently bonded
3 needed
What are examples of giant covalent structures?
Diamond and graphite (allotropes of carbon) and silicon dioxide (silica)
What does a giant covalent structure look like?
example for diamond, other structures have different forms
Metals have giant structures of atoms with (…) metallic bonding
strong
What does metallic bonds being strong in metal atom mean for the melting/boiling points?
It means that most metals have high melting and boiling points
How are atoms arranged in pure metals? What properties do they have because of this?
In pure metals, atoms are arranged in layers
this allows metals to be bent (ductile) and shaped (malleable)
What is the problem with pure metals? What is the solution to this?
Pure metals are too soft for many uses
so are mixed with other metals to make alloys which are harder
Why are alloys harder and stronger than metals?
In an alloy, there are atoms of different sizes.
Which distort the layers of atoms in the pure metal.
So layers can’t slide over each other
(A greater force is required the layers to slide over each other)
What is stronger, pure gold (24 carat) or an alloy of gold (e.g. 18 carat)?
18 carat gold
Why are metals good conductors of electricity?
because the delocalised electrons in the metal carry electrical charge through the metal
Why are metals good conductors of thermal energy?
because energy is transferred by the delocalised electrons moving freely throughout the metal
Explain, in terms of particles, why liquid iodine does not conduct electricity
Iodine has no delocalised electrons/ions
so cannot carry charge
4 marks
Describe the structure and bonding in a thermosoftening polymer and explain why they felt when heated
Chains or large molecules
with intermolecular forces between chains
that are weak
and are easily overcome
