P6 Molecules And Matter Flashcards
Density and formula
Defined as: mass per unit volume of material
-objects from low density materials have low mass
-similarly sized objects made from high density materials have high mass
Formula:
Density= mass/volume
D=m/V
Density=kgm-3
Mass=kg
Volume=m3
Density depends on the spacing of the atoms in matter:
-solids and liquids have similar densities as the space between particles does not change significantly (usually liquids have lower density than solids)
-gases have a far lower density as spacing between atoms increase x10, as particles have lots more energy to move, so volume increases greatly and therefore density decreases greatly
The particle model
-the particle model is a model that describes the arrangement and movement of particles in a substance
-solid liquid,gas
Solids,liquids and gas
Solids:
-particles closely pakced
-particles vibrate in fixed position
Solids have:
-a definite shape (rigid)
-a definite volume
Liquids:
-particles closely packed
-particles can flow over one another
Liquids have:
-no definite shape-they are able to floe and will take shape of container
-a definite volume
Gases:
-particles far apart
-particles flow randomly
Gases have:
-no definite shape-they will take shape of their container
-no fixed volume
Gases are highly compressible:
-large gaps between particles
-easier to push particles closer together than solids and liquids
Summary tablenlf solids liquid gases
State: solid,liquid,gas
Density: high,medium,low
Arrangement of particles: regular pattern, randomly arranged, randomly arranged
Movement: vibrate in fixed position, move around each other, move quickly in all directions
Energy:low,greater,highest
Chnages in state
When substance changes state:
-number of molecules in substance does not change
-therefore it made does not change
There are six changes of state that can occur between solids,liquids,gases:
Melting-solid to liquid
Boiling-liquid tk gad
Condensing-gas into a liquid
Freezing-liquid to soilf
Subliming-solid to gad
Energy and change in state- temperature-time graph
The temperature of water:
1)increases until it reaches 0 degrees when the ice start to melt at 0 degrees
2) stays constant at 0 degrees until all ice has melted
3)increases from 0 to 100 degrees until water in beaker starts to boil at 100 degrees
4) stays constant at 100 degrees as water turns to stesm
Energy transferred to a substance when it changes state is called latent heat. The energy transferred to the substance to melt or boil is ‘hidden’ by substance because temp does not change at substances melting or boiling point
Flat section of a temperature-time graph gives melting or boiling point of substance
Internal energy
Defined as: the total energy stored inside a system by the particles that make up the system due to their motion and positions
The molecules within a substance have energy in their:
-kinetic store they have due to their individual motions relative to each other
-potential store they have due to their individual positions relative to each other
So the internal energy of a substance is the total energy in kinetic and potential energy stores of all particles in the substance that is caused by their individual motions and positions
Heating-internal energy
heating a system changes a substances internal energy by increasing the kinetic energy of its particles
-the temperature of the material,therefore, is related to the average kinetic energy of molecules
-the higher the temperature, the higher the kinetic energy of the molecules
-this increase in kinetic energy can:
-cause the temperature of the system to increase
-or produce a change of state
Fhange of state-internal energy
-when a substance reaches a certain temperature,energy will stop being transferred to the kinetic store of the molecules and will be transferred to their potential store instead
-this energy goes into overcoming the intermolecular forces of attraction between the molecules,causing them to move further apart from one another leading to a change of state
When a substance changes it state:
-the potential energy of molecules increases,allowing them to overcome the intermolecular forces of attraction
-the kinetic energy remains the same, meaning the temperature will remain the same,even though substance is still being heated
Latent heat
-energy needed for a substance to change is called latent heat
-when a change of state occurs, the energy transferred to or away from a substance changes the internal energy of the substance but not its temperature
-this means whilst substances is changing state, the temperature of the substance remains constant, despite the fact that energy still is being transferred to the substance-this is because energy is being used to overcome intermolecular forces of attraction between the molecules instead of increasing the kinetic energy of molecules
-molecules in a solid are tightly bound together whereas in a liquid they are free to flow over one another-therefore to change state from solid to liquid, molecules need to gain enough energy to overcome intermolecular forces of attraction holding them in rigid solid structure
-molecules in a liquid are less tightly bound together, whereas in a gas they are free to move completely apart from each other-therefore to change state from liquid to gas, the same need tk happen
What 2 tupes does latent heat come in
Latent heat of fusion
Latent heat of vaporisation
What is specific latent heat defenition
The amount of energy required to change a state of 1kg lf a substance with no change in temperature
Difference between latent heat of fusion and vaporisation
Latent heat of fusion:
Defined as: the energy required to convert 1kg lf a substance between a solid and a liquid state eith no change in temperature
-this applies when melting a solid or freezing a liquid
-when a solid substance is melted, it temperature stays constant until all of substance has melted
-the latent heat lf fusion is the amount kg energy needed per kg for all particles in the substance to overcome intermolecular fir es of attraction holding them together in their solid state
- if a substance in it liquid state is frozen, the substance will solidify at the same temperature as its melting point
Latent heat of vaporisation:
Defined as: the energy required to convert 1kg between a liquid and a gaseous state with no change in temperature
-applies when vaporising and condensing
-when a liquid substance is vaporised, its temperature will stay constant until all of the substance has vaporised
-latent heat of vaporisation id the amount of energy per kg needed for all particles in the substance to overcome intermolecular forces of attraction holding them together in their liquid state
-if a substance is gas and is condensed, it will condense at the same temperature as its boiling poiny
Formula for specific latent fusion and vaporisation
Specific latent heat of fusion=energy/mass
Specific latent heat of fusion= j/kg
Energy=j
Mass=kg
Specific latent heat of vaporisation=energy/mass
Specific latent heat of vaporisation= Lv
Energy=J
Mass=kg
Heating graph
• When energy is transferred to a solid, the temperature starts to increase as the particles gain kinetic energy and vibrate faster
• When the temperature of the substance reaches its melting point, the energy transferred to the substance is now used to overcome the intermolecular forces of attraction holding the particles in their solid structure
• The temperature of the substance stops increasing
• This is melting and will continue until all the particles have reached the liquid state
• As energy is continually added, the temperature of the liquid starts to increase as the particles gain more kinetic energy and move over one another faster
• When the temperature of the substance reaches its bolling point, the energy transferred to the substance is now used to overcome the intermolecular forces of attraction holding the particles in their liquid structure
• The temperature of the substance stops increasing
• This is evaporation or vaporisation and will continue until all the particles have reached the gaseous state
Cooling graph
• The process is repeated backwards for cooling as energy is transferred away
• A gas turns back into liquid through condensation
• A liquid turns back into a solid through freezing
• When energy is transferred away from a gas, the temperature starts to decrease as the particles lose kinetic energy and move slower
• When the temperature of the substance reaches its boiling point, the energy transferred away from the substance is now taken from the energy used to overcome the intermolecular forces of attraction
• The temperature of the substance stops decreasing
• The particles now succumb to those intermolecular forces of attraction and are held together in their liquid structure
• This is condensing and will continue until all the particles have reached the liquid state
• When energy is transferred away from a liquid, the temperature starts to decrease as the particles lose more kinetic energy and move even slower
• When the temperature of the substance reaches its melting point, the energy transferred away from the substance is now taken from the energy used to overcome the intermolecular forces of attraction
• The temperature of the substance stops decreasing
• The particles now succumb to those intermolecular forces of attraction and are held together in their solid structure
• This is freezing and will continue until all the particles have reached the solid state
Specific heat capacity v specific latent heat
-specific heat capacity is the amount of heat required to raise the temperature of a substance by a certain amount:
-the substance will still be in the same state, just raised to a different temperature
-specific latent heat is the amount if energy needed to cause a change of state:
-the substance will be changing states, but still at the same temperature
Kinetic theory
-molecules in gas are in constant random motion at high speeds
-the temperature of the gas is related to the average kinetic energy of the molecules
Hotter the gas, the higher the average kinetic energy
Cooler the gas,lower the average kinetic energy
-random motion means that the molecule are travelling in no specific path and undergo sudden changes in their motion if they collide:
-with the walls of its container
-with other molecules
-the random motion of tiny particles in a fluid is known as Brownian motion
Temperature and pressure-kinetic theory
Temperature:
-as temperature of gas increases, the average speed lf the molecules increases
-since the average kinetic energy depends on their speed, the kinetic energy of molecules also increases if its volume remains constant
Pressure:
-molecules of gas in a container will collide with the container walls
-pressure is defined as the force exerted per unit area of the container
Equation:
Pressure=force/area
P=f/a
Pressure=Pa
Force=N
Area=m2
Therefore a gas at high temperature has more frequent collisions on the container walls and therefore overall more force per unit area
-if the gas is heated up, the molecules will travel at higher speed:
This means they will collide with the walls more often and creates and increase in pressure
-therefore at a constant volume, an increase in temperature increases the pressure of the gas and vice versa
