P6 - Molecules And Matter✔️ Flashcards
What is the density?
The density of a substance is defined as its mass per unit volume - caculated by mass/volume
Equation for density?
ϱ = m/v
density = mass/volume
ϱ=density in kg/m^3
m=mass
v=volume
Does the mass of a substance change when it changes state?
When a substance changes state the number of particles in the substance stays unchanged so the mass of the substance after the change of state is the same as the mass before the change of state.
Mass of substance is conserved when it changes state
Particles of a substance in solid state?
Particles held next to each other in fixed positions - vibrate about their fixed position - solid keeps its own shape
Particles of a substance in liquid state?
Particles are in contact with each other - move about at random so a liquid doesnt have its own shape.
Particles of a substance in Gas state?
Particles move about at random - much faster then they do in a liquid-further apart so density of gas lot less then that of solid or liquid
Do particles of solid,gas and liquid all have same amount of energy?
No - they have different amounts of energy - for a given amount of substances its particles have more energy in the gas state then they have in the liquid state - more energy in liquid state then solid state
What happens to temperature of pure substance as it changes state?
Any pure substance undergoing a change of state its temperture remains the same while the change takes place
What is melting point?
Point at which a solid changes state to a liquid
What is boiling point?
Temperature at which a liquid turns to gas
What is freezing point?
Point at which a liquid changes to a solid - same temperature as melting point of solid
What effects melting point of substance?
The melting point of a liquid or solid are affected by impurities in the substance - melting pint of water is lowered if you add salt to the water
Why is salt added to the grit used for gritting roads in frezzing weather?
The salt lowers the freeing temperature of the moisture in the ice - causing it to melt away
What is latent heat?
Latent heat - energy transferred to the substance when it changes state
Whats the difference between boiling and evaporation?
Boiling occurs throughout a liquid at its boiling point - evaporation occurs from the surface of a liquid when its temperature is below it boiling point
What does the flat section on a temperature-time graph tell us?
Flat section gibes the melting point or the boiling point of a substance
What is internal energy?
Internal energy - energy stored by the particles of a substance
What causes internal energy?
Energy of particles is caused by their indivisual motion and positions - internal energy is sum of kinetic energy and potential energy
What is kinetic energy
Energy it has due to the motion of the internal particles
What is potential energy?
Energy particles have due to their position
Characteristics of a solid?
-strong forces of attraction between particles - bond particles in fixed positions
-each particles vibrates about a fixed position
-solid is heated - particles energy store increase - particles vibrate more
Characteristics of a liquid?
-forces of attraction not strong enough to hold particles in fixed position - stong enough to stop them moving away completley
-when heated - partiles break away - particles that escape are in a gas state
Characteristics of a gas?
-particle move at high speed in random directions - colliding with eachother and internal surface - which causes the pressure of gas in container
-heated - particles gain kinetic energy move faster causes pressure to increase
How does temperature affect pressure in gas?
Increase in temperature causes particles to gain kinetic energy and as a result move at higher speeds colliding with each other and the internal surface of ther container more often therefore inreasing pressure
What is specific latent heat of fusion?
The energy needed to change state of 1kg of the substance from solid to liquid at its melting point
Unit: (J/kg)
Equation for specific latent heat of fusion (Lf)?
Specific latent heat of fusion Lf = energy / mass
Specific latent heat of fusion: joules per kilogram - J/kg
Energy:Joules - J
Mass:killograms - kg
What is specific latent heat of vaporisation?
Is the energy needed to change the state of 1kg of a substance from liquid to vapour at its boiling point - without changing temp
Equation for specific latent heat of vaporisation Lv?
Specific latent heat of vaporisation Lv = energy/mass
Specific latent heat of vaporisation: joules per kilogram - J/kg
Energy:Joules - J
Mass:killograms - kg
What is boyles law?
Pressure(p) x volume(V) = constant
Pressure = Pa
Volumes = m^3
P = constant / v
Why does pressure increase if volume is reduced?
The space between each mollecules is smaller so they dont travel as far between each impact with the surface of the container
Word Equation for specific latent heat of vaporisation?
specific latent heat of vaporisation = energy / mass
Word Equation for specific latent heat of fusion?
specific latent heat of fusion = energy/mass
