P6 Molecules and Matter Flashcards
What happens when atoms absorb radiation
Electrons move to higher energy levels, further away from the nucleus
What happens when atoms emit radiation
Electrons drop to a lower energy level, closer to the nucleus
What is Thomson’s plum pudding model
Thomson modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the ‘dough’
What is Rutherford’s nuclear model
Rutherford concluded that an atom’s mass is concentrated in the atom’s centre
This was called the “nucleus” and it contained positively charged particles called protons.
What is the modern model
Niels Bohr discovered that electrons orbit (fly around) the nucleus at fixed distances
In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons
What is density
The amount of mass in a volume
What is the formula for density
ρ=m/V
What is upthrust
An object floats in a fluid if the density of the object is lower than the density of the fluid
The force that keeps the object afloat is called upthrust
What is the law of displacement
The Law of Displacement says that an object completely submerged in a fluid will replace an amount of fluid equal to its own volume.
How are particles in a solid arranged
Solids are the densest state of matter
The particles are packed tightly together
How are particles in a gas arranged
Gases are the least dense state of matter
The particles are free to move with negligible forces between particles
How are particles in a liquid arranged
Liquids are less dense than solids but denser than gases
The particles in liquids can move around each other
What is the conservation of mass
When a substance changes state, its mass is conserved
What is a physical change
Changes of state are physical changes because the material recovers its old properties if the change is reversed
What is condensation
When the temperature of a gas decreases to the boiling point, the strength of the forces between particles increases and the particles condense to become a liquid
For the same material, its boiling point is the same as its condensing point
What is boiling
If we heat a liquid, the liquid particles move more energetically until they have enough energy to escape completely from the forces between them
The particles become a gas and move completely freely
The temperature needed for this to happen is the boiling point. Boiling can be called vaporisation
What is solidifying
When the temperature of a liquid decreases to the melting point, the strength of the forces between particles increases and the liquid solidifies to become a solid
For the same material, its melting point is the same as its freezing point
What is melting
If we heat a solid, the solid particles vibrate more energetically, until they have enough energy to overcome the forces between them
This is when the solid melts
The temperature needed for this to happen is the melting point.
Melting is sometimes also called fusion
What is the internal energy store
The amount of energy in an object’s internal store is the sum of the kinetic and chemical stores of the object’s particles
What is the potential energy store
The energy in an object’s potential store comes from the potential energy stored in the bonds between particles
What is the kinetic energy store
The energy in an object’s kinetic store comes from the random motion of its particles
The temperature of a body is a measure of the energy in the kinetic stores of its particles
Increasing a body’s temperature increases the energy in the kinetic stores of the body’s particles, which means that the energy in the body’s internal store also increases
How to calculate change in internal energy
mass * specific heat capacity * temperature change
How to calculate thermal capacity
mass * specific heat capacity
What is latent heat
The energy that is transferred to a substance without the substance’s temperature changing
Where does latent heat go
Energy is absorbed to create or weaken bonds, rather than transfer kinetic energy to a substance’s particles
What is specific latent heat
Latent heat / 1kg of mass
What is latent heat of fusion
Latent heat in melting or freezing
What is latent heat of vaporisation
Latent heat in boiling or condensing
How to calculate energy change for change of state
Energy = mass * specific latent heat
What happens when gas is heated
Energy is transferred to kinetic energy store
Particles move faster
Particle collide with the container more of ten and with more force, increasing pressure
What is the equation for change in momentum
Δp = force × time = impulse
What happen when work is done on gas
Gas’ internal energy increases
