P6 Flashcards
Density of a substance is deined as …
Its mass per unit of volume
Equation of density
Mass(kg)
Density(kg/m^3)=—————-
Volume(m^3)
Ways to find the volume of a regular solid
Use a millimetre ruler
Vernier callipers
Micrometer
How to find the volume of a small irregular solid
Lower it on a thread into a measuring cylinder partly filled with water. You can work out the volume from the rise in the water level.
How to find the volume of a liquid
Use a measuring cylinder
How to find the mass of a liquid
Subtract mass of emoty beaker by total mass of the beaker and liquid.
Which states flow
Liquids and gases
Which states have a fixed shape
S-Fixed
L-Fits container shape
G-Fills container
Which states have a fixed volume
S-Fixed
L-Fixed
G-Can be changed
States density comparisons
S-Much higher than a gas
L-Much higher than a gas
G-Lower than a solid or a liquid
Changes of state are ….. changes
Physical
Why are changes of state physical changes
Beacuse no new substances are produced and if a physical change is reversed, the substance recovers its original properties.
When solid carbon dioxide (dry ice) warms up, the solid turns into … directly
gas
Why is the mass of a substance conserved when it changes state
Because the number of particles is unchanged.
When the temp of the substance is increased, the particles move…
Faster
Arrangement of particles in a solid
Regular arrangement. The particles are held next to each other in fixed positions. They vibrate around their fixed postions.
Arrangement of particles in a liquid
They are in contact with each other. They move about at random.
Arrangement of particles in a gas
The particles move about at random more quickly. On avarege are much further apart.
For a given amount of a substance, its particles have more energy on a gas state than in
Another state
For any pure substance undergoing a change of state…
Its temperature stays the same while the cange of state is taking place.
The melting point of a solid and the boiling point of a liquid are affected by…
Impurities on the substance
The melting point of water is lowered if you add
Salt, which is why salt is added to the grit that’ used for gritting roads in freezing weather, meaning roads don’t get icy until they are colder.
How to measure the melting point of a substance
Put a solid in a test tube in a beaker of water, heat until melts and record.
The enegy transerred to a substance when it changes its state is called
Latent heat. It is ‘hidden’ by the substance because its temperature doesn’t chnage at the substances’ melting point or at its boiling point.
Fusion is sometimes used to describe melting because
different solids can be joined or ‘fused together when they melt
Evaporation from a liquid happens at its surface when the liquid is below its boiling point. At its boiling point,….
a liquid boils because the bubbles of vapour form inside the liquid and rise to the surface to release the gas
The energy stored by the particles of a substance is called the substance’s..
Internal energy. This is the enrgy that is caused by their individual motion and positions.
The internal energy of a the particles is the sum of:
The kinetic energy due to their individual motions relative to each other, and the potential energy due to their individual postions relative to each other.
Conclusion: The internal energy of a substance is the total energy in the kinetic and potential energy stores of all the particles in the substance that is caused by their individual motions and positions.
Internal energy does not include
Gravitational potential energy or the kinetic energy that is caused by the motion of the whole susbtance.
Heating a substance changes the internal energy of the substance by…
increasing the energy of its particles. Because of this, the temp of the substance increases or its physical state changes .
When the temp of a substance increases or decreases…
the total kinetic energy of its particles increases or decreases.
When the physical state of a substance changes, …
the total potential energy of its particles changes.
In solids, particles are arranged in a …..
Three-dimensional structure
When a solid is heated, ….
the particles’ energy stores increase and they vibrate more.
If a solid is heated enough it melts because the particles have gained enough energy to break away from the structure.
What are the forces of attraction between particles in liquids like?
Weaker than in solids. They are not strong enough to hold the particles together in a rigid structure. However, they are strong enough to stop them moving away from each other completely at the surface.
What happens to the particles when a liquid is heated?
Some of the particles gain enough energy to break away from the other partcicles. The molecules that escape from the liquid in a gas state are above the liquid.
Describe the forces of attraction and state charactersitics of gases.
The forces of attraction between the particles are so weak, they are insignificant. The particles move about at a high speed in random directions, colliding with each other and the internal surface of the conatiner. The pressure of a gas on a solid structure such as a conatiner is caused by the force of impacts of the gas particles with the surface.
What happens to the particles in a gas when it is heated?
Its partciles gain kinetic energy and on avergae move faster. This causes the pressure pf the gas to increase because the particles collide with the container surface more often and with more force.
When a solid substance is heated at its melting point, the substance melts and turns into a liquid. Its temp. stays constant until all of the substance has melted. The energy supplied is called ……………………………..?
Latent heat of fusion. It is the energy needed by the paricles to break free from each other.
What is the specific latent heat of fusion of a substance?
The energy needed to change the state of 1kg of the substance from solid to liquid at its melting point (i.e.without changing the temperature).
What is the unit of the specific latent heat of fusion?
Joule per kilogram (J/kg)
Formula for specific latent heat of fusion
If energy E is transferred to a solid at its melting point, the mass m of the susbtamce melts without change in temeperature:
energy E (joules)
specific latent heat of fusion L (J/kg) =————————
f. mass M (kg)
Or (rearranged) : E=m L
f
