A measure of how compact a
substance is. How much mass a
substance contains per it's volume.
In a dense material the particles are tightly
packed together. In a less dense material
the particles are more spread out.
If you compressed the material, the
particles would move closer together
making it more dense.
Decreasing volume=increase in density.
REQUIRED PRACTICAL- Finding the density of regular and irregular
solids and liquids.
Regular solids- use a balance to measure it's
mass, measure the length width and height with a
ruler, then calculate the volume using the
appropriate calculation for the shape. Use the
volume and mass to find density.
Irregular solids- use a balance to measure it's mass,
submerge the object in a eureka can with a
measuring cylinder beneath the spout, the volume of
water displaced into the measuring cylinder is the
volume of the object. Use the volume and mass to
find density.
Liquids- place a measuring cylinder on a balance
and zero the balance, pour 10ml of the liquid into
the measuring cylinder and record the liquids mass,
pour another 10ml into the measuring cylinder,
repeating the process until the cylinder is full and
recording the total volume and mass each time. For
each measurement ude the formula to find density
(remember 1ml=1cm3). Find the mean for your
calculated densities.
SOLIDS
Solids have a fixed shape, cannot flow
and cannot be compressed easily.
They have a fixed volume. Their
particles are arranged in a regular
order. The particles are tightly packed
together and have strong bonds. The
particles vibrate but don't have much
room to move.
LIQUIDS
Liquids flow, have a fixed volume and cannot be
compressed. Their particles are arranged in a
random way and have weaker bonds than a
solid. The particles vibrate more than a solid but
are still tightly packed.
GASSES
Gasses completely fill and take the shape of their container.
They can be compressed and they flow. The particles are free
to move and have practically no bonds. Gasses have a lower
density than liquids and solids and their particles have no
pattern and are free to move.
LIQUIDS & GASSES =
Fluids
Changes Of State
(P3.1.2)
A change of state is a physical
change NOT a chemical change.
You don't end up with a new
substance, it's the same
substance you started with just
in a different form.
The number of particles doesn't change, they're
just arranged differently. This means mass is
conserved, no mass is lost when the substance
changes state.
Solid to liquid=melting
Liquid to gas=boiling OR
evaporating
Liquid to
solid=freezing
Gas to
liquid=condensing
Solid to
gas=sublimating
Gas to solid=deposition OR
reverse sublimation
Internal Energy
(P3.2.1)
The internal energy of a system is the total
energy that its particles have in their kinetic
and potential energy stores.
The particles in a system
vibrate or move around,
meaning they have energy
in their kinetic energy
stores.
The particles in a
system also
have energy in
their potential
energy stores
due to their
positions.
Heating the system transfers energy to it's
particles because they move faster and gain
energy in their kinetic stores. This increases
internal energy.
This leads to either a change in
temperature or a change in state.
If the temperature changes, the
size of the change depends on the
mass of the substance, the
specific heat capacity of the
substance and the energy input.
If the substance is heated enough this will lead to a
change in state because the particles will have enough
energy in their kinetic energy stores to break the
bonds and change state.