3.7 bonding and physical properties Flashcards
What is a solid and what are the properties
. A state of matter where the particles are vibrating around a point, in a regular arrangement.
. The particles are very close together, and they are not easily compressed
The diffusion is very slow, and solids expand when heated
What is a liquid and what are its properties
. State of matter with a random arrangement of particles that can move past each other but are always touching each other
Liquid changes shape, and are not easily compressed
Diffusion in them is slow, and liquids can evaporate
What is a gas and what are its properties
. Random arrangement of particles which are far apart from each other, moving very rapidly
Diffusion of gases is rapid
Gases can exert a pressure
What happens when you heat a solid, why does it expand
. It supply’s energy to the particles so makes them vibrate more in a fixed position which slightly increases the distance between the particles so the solid expands
How do you turn a solid to liquid
(melting or fusion)
. Solid has closely packed vibrating particles whereas liquid has random moving particles which can still be close together.
So to change a solid to a liquid, supply more energy which can weaken the forces between the particles that hold it together in a solid shape.
This energy is called the specific latent heat of fusion, or even better, the
Enthalpy change of melting
Why doesn’t the temperature increase when the solid is melting
. The heat energy provided is absorbed as the forces between the particles are weakened .
What is enthalpy vs temperature
Enthalpy is the heat energy change measured under constant pressure
Temperature depends on the average kinetic energy of the particles and therefore is related to their speed.
The greater the energy, the faster they go
What happens when you heat a liquid
. You supply energy to the particles which makes them move faster so they have more kinetic energy.
On average, the particles move further apart so liquids also expand when heated
What is the latent heat of vaporisation
The energy needed to break all the intermolecular forces between particles in a liquid.
So it is turning a liquid into a gas
AKA Enthalpy change of vaporisation
What happens when you heat a gas
. Particles gain kinetic energy ad move faster, and get much further apart from each other
As a result the gas expands
What are crystals
What are the 4 types
Solids that have a regular arrangement of particles which are held together by forces of attraction.
Ionic, metallic, molecular or macromolecular are the 4 types
These bonds could be strong eg covalent, ionic, or metallic.
These could be weak intermolecular forces of attraction eg Van der Walls, dipole-dipole, or hydrogen bonds
The strength of these bonds affects the physical properties of the crystals, eg the stronger the force, the higher the melting point and the greater the enthalpy of fusion.
What are ionic crystals
. Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions.
Eg NaCl is a typical ionic crystal
These ionic compounds have high melting points, which are a result of the strong electrostatic forces of attraction within the structure.
A lot of energy is required to break these electrostatic forces
What are metallic crystals
. Metals exist as a lattice of positive ions embedded in a delocalised sea of electrons
This positive and negative attraction extends throughout the crystal.
As a result they have high melting and boiling points
What are molecular crystals
. Consist of molecules held in a regular array by intermolecular forces.
Covalent bonds act within the molecules to hold the atoms together
However the covalent bonds don’t act between the molecules
Describe what is happening to the molecules in ice when it is being melted
. Molecules gain kinetic energy so vibrate more
. Eventually the intermolecular forces (hydrogen bonds) are broken between the molecules, and ice becomes water
