Please enable JavaScript.

Coggle requires JavaScript to display documents.

iGCSE Solids, Liquids & Gases (Pressure (Pressure in Liquids and Gases…

- - - - The metric system was designed so that water will have a density of one gram per cubic centimetre (g/cm^3)
    - - This is because Lead is about 10 times as dense as water and Styrofoam is about one tenth as dense as water.
      - If you were to look at both of these in equally sized shapes, you would realise that they both has the same volume however the Lead would be heavier
        
        This is because Lead has more particles which gives it more mass per unit of volume, This property of matter is called density.
        
        The density of a material helps to distinguish it from other materials.
        
        Since mass is usually expressed in gams and volume in cubic centimetres, density is expressed in grams/cubic centimetre
    - - density = mass / volume
    - - Fill the displacement can with water and place on a level surface covering the hole.
      - Let the excess water drain into a beaker and discard
      - Ensure the water has stopped draining before placing the irregular shaped object into the displacement can while covering the hole with a finger.
      - Place a measuring cylinder next to the hole and uncover the hole draining the water that the object has caused to overflow
      - Once the water has stopped filling the measuring cylinder, read the volume of water at eye level taking note of the meniscus, that the object has caused to drain out the displacement can.
      - Te volume is the volume of the object, and use this to work out the density in the equation: density = mass / volume
- - - - It is the force from the weight of the atmosphere above us pushing down on a unit area.
    - - This is because there is a greater weight of fluid pushing down on each unit of area.
    - - Pressure at a point in a gas or liquid which is at rest, acts equally in all directions and increases with depth.
    - - This can be expressed in pressure = height x density x g
      - g = 10 N/kg
- - - - solids
        
        The particles are held in a fixed pattern or crystal structure by strong forces of attraction between them.
        
        They vibrate about their fixed positions in the structure and are tightly packed
        
        They...
        
        have a fixed shape
        
        have a fixed size
        
        do not flow
        
        cannot be compressed
        
        have a high density
      - liquids
        
        The particles are not held in fixed positions but they are still bound together by strong forces between them
        
        The particles are tightly packed but they move at random and have less strong forces of attraction than solids
        
        They...
        
        fill the shape of their container
        
        have a fixed size
        
        can flow
        
        cannot be compressed
        
        have a medium density
      - gases
        
        The particles are very spaced out with large distances between them and very weak forces of attraction
        
        They move around very quickly with a rapid, random motion in all directions
        
        They...
        
        fill the shape of their container
        
        have the size of their container
        
        can flow
        
        can be compressed
        
        have a very low density
  - - - Melting
        
        When a solid is heated the particles vibrate more strongly as they gain kinetic energy and the particle attractive forces are weakened
        
        Eventually, at the melting point, the attractive forces are too weak to hold the particles in the structure together in an ordered way and so the solid melts
        
        The particles become free to move around and lose their ordered arrangement
    - - Boiling
        
        Bubbles of vaporised liquid form within the bulk liquid and then rise to the surface where they burst and release the gas.
        
        In order to form vapour, the molecules of the liquid must overcome the forces of attraction between them
        
        The temperature of a boiling liquid remains constant, even when more heat is added
      - Evaporation
        
        Evaporation is the process where some of a liquid becomes a gas at temperatures below the boiling point. In other words, its molecules escape the body of the liquid and move freely away as a gas
        
        The reason this happens is because some molecules have high enough energy to escape the surface tension of the liquid.
        
        Evaporation results in the liquid becoming cooler. Blowing on the liquid increases the evaporation
    - - Subliming
    - - Condensing
    - - Freezing
    - - Deposition
- - - - Temperature actually measures the average value of the kinetic energy carried by each particle in the gas.
      - The average kinetic energy of the particles has a minimum possible value. This implies that an object cannot be cooled indefinitely.
        
        the temperature -273 degrees C is the lowest possible temperature in the universe and is called the absolute zero.
        
        Nothing can be called below this temperature
        
        Kelvin is a unit of temperature
        
        A change in temperature of 1 degree Kelvin is exactly the same as a change in temperature of 1 degree Celsius (Centigrade)
        
        Where Celsius and Kelvin differ is in their zero-points, i.e. zero degrees Celsius is defined as the freezing point of pure water, while zero degrees Kelvin is defined as the lowest physically achievable temperature - known as absolute zero
        
        This corresponds to a total lack of thermal energy.
        
        The two scales can be inter-converted as follows: Temperature in K = Temperature in degrees C + 273.
  - - - If the number of particles and volume of a gas remains constant then when the gas is heated, the pressure increases
      - By increasing the temperature of the gas, the molecules' speeds increase meaning an increased amount of collisions with the container walls.
      - initial pressure / initial temperature = new pressure / new temperature
  - - - If a container with a fixed amount of molecules inside, is reduced in volume, more molecules will hit the sides of the container per unit time, causing a greater pressure.
    - - Pressure and volume can be any units as long as the same units are used on either side of the equation.