5. Solids, Liquids & Gases

• solid particles have a fixed shape and a regular arrangement and the particles are not free to move
• a barometer is an instrument used to measure atmospheric pressure
• boiling point is the temperature at which a liquid changes to a gas
• boyle's law is the law that states that at constant pressure, the volume of a gas is directly proportional to its temperature
• brownian motion is the motion of small particles suspended in a liquid or gas caused by molecular collisions
• Objects made from low density materials typically have a low mass. Similarly sized objects made from high density materials have a high mass. For example, a bag full of feathers is far lighter compared to a similar bag full of metal. Or another example, a balloon is less dense than a small bar of lead despite occupying a larger volume
• 1. Place the object on a digital balance and note down its mass
  2. Fill the eureka can with water up to a point just below the spout
  3. Place an empty measuring cylinder below its spout
  4. Carefully lower the object into the eureka can
  5. Measure the volume of the displaced water in the measuring cylinder
  6. Repeat these measurements and take an average before calculating the density
• Pressure is defined as the concentration of a force or the force per unit area
• For example, when a drawing pin is pushed downwards as it is pushed into the surface, rather than up towards the finger. This is because the sharp point is more concentrated (a small area) creating a larger pressure
• Tractors have large tyres this spreads the weight (force) of the tractor over a large area. This reduces the pressure which prevents the heavy tractor from sinking into the mud
• Nails have sharp pointed ends with a very small area this concentrates the force, creating a large pressure over a small area. This allows the nail to be hammered into a wall
• If a force is spread over a large area it will result in a small pressure. If it is spread over a small area it will result in a large pressure
• When an object is immersed in a fluid, the fluid will exert pressure, squeezing the object. This pressure is exerted evenly across the whole surface of the fluid and in all directions. The pressure exerted on objects in fluids creates forces against surfaces. These forces act at 90 degrees (at right angles) to the surface
• Specific heat capacity is a measure of the energy required to raise the temperature of 1 kg of a substance by 1oC
• Water has a higher specific heat capacity (4200 J/kg/oC) compared to air (1000 J/kg/°C), meaning a relatively large amount of energy is required to raise its temperature