Particle Model Flashcards
What is density?
Density (p) = mass / volume
G/cm3 or kg/m3
What is a solid?
- strong forces of attraction hold particles together in a fixed and regular arranged position
- particles have little energy inKE stores so only vibrate in fixed position
What is a liquid?
- forces or attraction between particles are weaker
- particles are close together but can flow in irregular arrangements at low speeds
- they have more KE in stores
What is a gas?
- there are almost no forces of attraction between the particles
- more energy in their KE stores than liquids
- free to move in random directions at high speeds
Where is thermal energy stored?
The energy in a substance’s thermal energy store is held together by its particles in their kinetic energy stored
-when you heat something the extra energy is transferred into the KE stores making them move faster or vibrate more wearing the forces
What happens when there is a change in state?
Mass is conserved (particles are the same)
-these physical changes differ from some chemical changes because the material recovers its original properties if the change is reversed
What happens to the density when there is a change in state?
- it’s volume changes as particles gets further apart of closer together
- therefore seeing as D = m/v its density must too
- substances are verbally more dense as solids and least dense as gases
What is the equation for specific heat capacity?
Change in thermal energy = mass(Kg) x specific heat capacity (J/Kg°C) x temperature change (°C)
DeltaQ = m x c x delta temp
What is specific heat capacity?
Is the change in energy in the substance’s thermal energy stores needed to raise the temperature of 1KG of that substance by 1°C
What does heating do?
Increases energy in thermal energy stored or internal energy of the substance (sum of energy in KE stores and of the particles)
-temperature is in theory a way of measuring average internal energy of a substance
What is the specific heat capacity of water?
4200 J/KG°C
What is specific latent heat?
The amount of energy needed to change 1KG of it from one state to another without changing its temperature
What is specific latent heat in terms of cooling and heating?
-for cooling SLH is the energy released by a change in state
What is the name for SLH for different states?
For changing between a solid and a liquid it is called the specific latent heat of fusion
-for changing between a liquid and a gas it is the specific latent heat if vaporisation
What is the equation for specific latent heat?
Thermal energy (J) = mass (Kg) x specific latent heat (J/Kg) Q = m x L
What is 0 Kelvin equal to?
-273°C
What is the latent heat of fusion and vaporisation for water?
Melting ice = 0°
Vaporisation = 100°
On a graph which sections show latent heat?
The flat parts
What is pressure?
- colliding has particles create pressure
- when gas particles more randomly they collide and exert a force and so pressure
- in a sealed container the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the container walls
How does gas pressure vary with volume?
Increasing the volume of a gas means the particles and hit the walls of the contained less often
- this means gas pressure decreases, they are inversely proptional
- decreasing volume means they are in a smaller space so more collisions with container walls so pressure increases
What is the equation that links gas pressure and volume?
- for a gas of fixed mass at a constant temperature: p1v1 = p2v2
- p1 is the pressure at a volume 1 and p2 is the pressure at a volume v2
- pressure is measured in Pa or N/m2
What effect does temperature have on gas pressure?
The higher the temperature the faster the particles move and the more often they collide with the container.
- the force exerted by each particle during a collision also increases as the temperature increases
- increasing temperature of a fixed volume increases its pressure
What is absolute Zero?
In theory the coldest that anything can get is -273°C
- here the particles have as little energy in their kinetic stores as it’s possible to get (almost still)
- this is the start of the Kelvin scale of temperature (a temp change of 1° is a cha be of 1 Kelvin
How do you convert between kelvins and degrees?
Degrees Celsius to kelvins, just add 273
-Kelvin to degrees Celsius just subtract 273