P6- Molecules And Matter Flashcards
Density Equation
Mass/volume = density (kg/m^3)
Finding the density of a regular solid (method)
- Use a ruler to measure the dimensions of the object ( or vernier calipers)
- Calculate the volume (LxWxH)
- Measure the mass of the object using scales
- Divide the mass by the volume
Finding the density of an irregular solid (method)
- Measure the mass of the object using scales
2.Fill a eureka can with water until the spout - Place a measuring cylinder under the spout
- Lower the object into the water
- The water that is displaced into the measuring cylinder is equal to the volume of the object
- Calculate the density (Mass/volume)
Finding the density of a liquid (method)
- Measure the mass of an empty measuring cylinder
- Pour a known volume of the liquid into the measuring cylinder
- Calculate the mass by subtracting the mass of the empty cylinder from the filled cylinder
- Calculate the density (Mass/volume(ml=cm^3))
What is the density of water?
1g/cm^3
Density (definition)
Mass per unit of volume
Solid (key features)
Strong forces of attraction hold the particles together in a regular arrangement
Doesn’t flow
Fixed shape
Fixed volume
Density - much higher than a gas
Particles don’t have much energy- vibrate around fixed positions
Liquid(key features)
Weaker forces of attraction between the particles. Particles are close together but can move past each other and form irregular arrangements.
Flows
Fits shape of container
Fixed volume
Density-much higher than a gas but less than solids
More energy than particles in a solid
Gas(key features)
Flows
Fills container
Volume can be changed
Density - lower than a solid or a liquid
Particles travel in Random directions at high speeds
Almost no forces of attraction between particles
Particles have more energy than solids or liquids
Conservation of mass
The mass of the substance after the change of state is the same as the mass of the substance before the change of state
Liquid to solid
Freezing
Solid to liquid
Melting
Liquid to gas
Boiling (or vaporisation)
Gas to liquid
Condensation
Solid to gas
Sublimation
Gas to solid
Deposition
Particles in a solid
Vibrate around fixed positions
Particles in a liquid
Ransom movement, can flow
Particles in a gas
Random, faster than liquids, Further apart than liquids
What is an objects melting point the same as?
The freezing point
What is an objects boiling point the same as?
The point where it condenses
Liquid to gas = boiling
Gas to liquid = condensing
The point where the changes happen is the same
How can the melting point of water be lowered?
By adding salt to the water
What is latent heat?
The energy transfereed to a substance when it changes its state
What is internal energy?
The energy stored by the particles of a substance
What is internal energy the sum of?
The kinetic energy and the potential energy
Forces of attraction between particles
Greatest in solids
Weakest in gases
Heating of a gas (in a container)
The particles gain kinetic energy
Move faster
Collide with the walls of the container more frequently and with more force
What is the specific latent heat of fusion?
The energy needed to change the state of 1kg of the substance from solid to liquid at its melting point.(without changing its temperature)
Unit for specific latent heat
Joules per kilogram
J/Kg
Specific latent heat of vaporisation
The energy needed to change the state of 1kg of the substance from liquid to vapour (gas) at its boiling point ( without changing its temperature)
What is a fluid?
A liquid or a gas
What is brownian motion?
The random motion of tiny particles in a fluid
What happens in the random motion of smoke particles in air?
Air molecules repeatedly collide at random with each smoke particle. The air molecules must be moving very fast to make this happen however they are too small to see however what you see is the random motion of the smoke particles caused by the impacts of the air molecules.
Pressure X volume
Pressure X volume is constant
Pressure equation when 3 of 4 variable are known
P1 x V1 = P2 X V2
P1 X V1/ P2 = V2
What is the relationship between pressure and volume?
Pressure is inversely proportional to volume
As pressure increases volume decreases
What does the density of an object depend on?
What it’s made of and how its particles are arranged
Density
A measure of the ‘compactness’ of a substance. It relates the mass of a substance to how much space it takes up.
What effect does heating a system have on an object’s internal energy?
It transfers energy to its particles (they gain energy in their kinetic stores and move faster), increasing the internal energy. This then leads a change in temperature or a change in state.
When does a change in state of a substance occur?
If the substance is heated enough- the particles will have enough energy in their kinetic stores to break the bonds holding them together.
Interpreting a change of state graph ( heating)
When a substance is melting or boiling, your still putting in energy and so increasing the internal energy, but the energy’s used for breaking intermolecular bonds rather than raising the temperature. There are flat spots on the heating graph where energy is being transferred by heating but not being used to change the temperature.
Interpreting a change of state graph (freezing)
When a substance is condensing or freezing, bonds are forming between particles, which releases energy. This means the internal energy decreases, but the temperature doesn’t go down until all the substance has turned to liquid (condensing) or a solid (freezing). The flat parts of the graph show this energy transfer.
