TOPIC 5 SOLIDS, LIQUIDS AND GASES Flashcards
what is the equation for density?
density = mass / volume
what are the units for density ?
grabs per cubic centimetre - g/cm3
or
kilograms per cubic metre - kg/m3
what does it mean if a solid object floats on the surface of a liquid
it has a lower density than the fluid
what does the density depend on?
the density of an object depends on what it’s made of- density doesn’t vary with the shape of size
what does the average density determine
whether the object floats or sinks
what is an experiment to demonstrate density
you can measure the volume by completely immersing the object into a measuring container of water.
the amount the volume reading on the container increases by when you add the object to the water is the volume of the object
this only works for objects denser than water though
what is density?
Density is the mass per unit volume- the measure of compactness of a substance. It relates the mass off a substance to how much space it takes up.
what is the equation for pressure?
pressure = force / area
what is pressure ?
pressure is the force acting per unit area of a surface. Pressure is a measure of the force being applied to the surface of something. It relates how much force is being applied to an object (N) to the area that it is applied over (in m2). Pressure is measured in pascals (Pa) or kilopascals (kPa). 1Pa=1N/m2
describe how pressure works
when force is concentrated on a smaller area creates a larger pressure, but with a larger area, you get a smaller pressure.
describe how pressure works in snowshoes in snow
they have a large surface area and therefore there is less force concentrated into the ground
describe how pressure affects stiletto heels marking floors
there is a small surface area and therefore more force is concentrated into the ground
describe how pressure works when walking on pebbles and sand
even though ther is a small surface area, the individual grains are combined repay her than the individual pebbles, so there is less pressure
how is it possible to lie on a bed of nails
it is possible because the total contact is spread out so there is less pressure applied
convert 1m2 to cm2 and mm2
1m2 = 10,000cm2 = 1,000,000mm2
how do you work out the pressure difference in liquids and gases
pressure difference = height x density x gravity (10)
what is pressure difference for liquids and gases?
pressure in liquids and gases depends on density. It is the difference in pressure between two points in a liquid or gas. It depends on the height difference (m) and the density (kg/m3) of the substance. Gravity also has an affect too - g is the acceleration due to gravity which is about 10m/s2
describe pressure for gases and liquids
in gases and liquids at rest, the pressure at any point acts equally in all directions. in gases and liquids, the pressure increases with depth. The pressure is higher at the bottom of the sea than the surface and it is lower high up in the atmosphere at hand close to earth
describe what happens with a water in a bag with holes
Pressure moves in all directions. It is the same throughout the water so water jets act in all directions. This is because when the water molecules move, they transmit a force to all the molecules next to them.
describe what happens on a diver (bottle experiment description)
the conpression on the bottle increases the pressure in the water. this compresses the air inside the diver. the air now displaces less water so there is less is less upthrust acting on the diver. the diver takes in more water so the weight increases
describe what happens with pressure on a spouting can
as the depth increases, the weight of the water increases so the is more pressure lower down. this increase in pressure which push the water jet out at a greater velocity
why do divers masks not break at great depth
the same pressure and force is Cting inside the mask so the resultant force is 0
describe what happens with atmospheric pressure with a card in a water beaker
the atmospheric pressure pushes up the card and holds water in place. due to the atmospheric pressure being greater than the water.
describe how atmospheric pressure affects a bottle and hot water
after heating, the bottle is full of hot air. as the air cooled, fewer particles collide with the inside of the bottle. this decreases pressure inside the bottle and reduces the density. atmospheric pressure outside the bottle is bigger is bigger so the bottle collapses
describe how atmospheric pressure affects a ruler and newspaper
air pressure is pushing down on the entire sheet of the newspaper (with a large surface area) which means it’s difficulty to flip the ruler.
describe how atmospheric pressure affects a bottle and vaccum pump
the air is removed from the bottle which reduces the pressure inside. the atmospheric pressure is larger on the outside and therefore compresses the bottle
describe how atmospheric pressure affects the Magdeburg hemispheres
air is removed from the inside of the hemispheres. the atmospheric pressure is greater than the pressure inside. hence there is a large force pushing on the spheres
describe solids
In solids, there are…
- strong forces of attraction holding it together in a fixed regular lattice arangement
- definite shape and volume
- their particles vibrate in their positions
- when heated, their particles vibrate faster and allow the to expand
descibe liquids
in liquids, there are…
- weak forces of attraction between the the particles
- randomly arranged (but they tend to stay closely together.
- the dont have a fixed shape but do have a fixed volume.
- their particles are constantly moving but when heated the expand
describe gases
in gases, there are…
- very weak forces of attraction
- move far apart from each other
- travel in straight lines between collisions
- constantly moving randomly
- don’t have definite shape of volume (they fill any container)
- when heated their particles move faster which means they expand or their pressure increases
what happens to the particles when a substance is heated
the particles gain more kinetic energy - (vibrate faster in solids)
explain what happens to the particles when a substance changes state
the state of matter depends on 3things temperature, pressure and material- the particles gain enough energy (potential energy) to break free of their inter-molecular bonds, separation increases at a constant temperature I.e. volume increases, volume of gas is about 1000x bigger than the volume of solids or liquids
what are the main assumptions for the kinetic theory of matter?
every material is made up of small particles (molecules). the sizes of particles are different for different materials. the particles are very hard (incompressible) but the separation between particles can change. the particles are always moving p (high per temp=faster). particles at the same temperature have the same kinetic energy so heavier particles move more slowly.
how is evaporation different to boiling?
in evaporation- it is gradual vaporisation…. it eventually turns to a gas overtime as some molecule have enough energy t escape the attractive forces. these molecules change to a gas and leave.
in boiling - it is a rapid vaporisation …. all the particles have sufficient energy to escape.
what is the Brownian motion and what does it illustrate
it is the constant motion of smoke particles seen with a microscope- caused by the collisions in the air which transfer energy. evidence of the random motion of air particles
give an example of the Brownian motion
the constant movement of smoke particles viewed under a microscope.
explain how the Brownian motion supports the idea that matter is made from tiny particles in continuous motion
in liquids and gases, particles have no fixed arrangement (irregular) and are free to move around. small particles hit larger particles which shows the random movement
Describe the particle arrangement in solids
Particles of solids have a fixed regular arrangement. The particles are not free to move however vibrate in their positions. If heated there is more kinetic energy and therefore vibrate faster
Describe the particle arrangement in liquids
The particles in liquids had definite volume but no definite shape. Their particles have weak attraction so a free to move past each other
Describe the particle arrangement in gases
They do not have definite shape but do have definite volume. They are free to move in straight lines between collisions so have a larger space between the particles. (more KE)
Explain what causes gas pressure in a sealed container
The particles in gases move quickly in all directions but bump into the walls of the container. If the temperature is above 0, particles have more kinetic energy. When the particles collide with the container, it exerts a force and this force acts over and area so the pressure increases. (p=fa)
Explain what happens to the pressure of a gas when heated
Increasing the temperature gives more kinetic energy to the particles. Collisions are more frequent with the walls and other particles and with a greater force. This increases pressure (pressure is proportional to its absolute temperature).
Explain the term ‘absolute temperature’
It’s lowest possible temperature at which point the atoms of a substance transmit no thermal energy (-273degrees c = 0Kelvin)
Describe and explain some applications of cooling materials to a very low temperature
Reduce the resistance of electrical components e.g MRI or LHC
Levitation and transport
What is the relationship between average kinetic energy of a molecule of gas and temperature
The average kinetic energy of a molecule of gas is directly proportional to its absolute temperature
CQ
in a sample of gas, oxygen (O2) and hydrogen (H2) molecules are both at the same temperature. The speed of oxygen molecules is 250ms-1.
Use Mr of O2 and H2
How fast are the hydrogen molecules moving?
KE = 0.5mv2
they are both at the same temperature so the average KE is the same
KE = 0.5 x 32 x (250)2 = 1,000,000
0.5 x 2 x v2 - square root 1000000 / 0.5 x 2
= 1000ms-1
What is Boyle’s law
It states that the volume of a fixed mass of a gas is inversely proportional to its pressure provided that the temperature remains constant
Describe how Boyle’s law is explained using the kinetic model
The temperature is constant so the particles have constant kinetic energy. As the volume of the gas decreases, the particles are more likely to collide to the container walls (as they have less distance to travel). This increased the rate of collisions and leads to an increase in pressure
Describe the pressure law
The pressure law states that the pressure of a fixed mass of a gas and is proportional to its absolute temperature provided they volume remains constant
