5) Solids, Liquids & Gases Flashcards
Units for temperature, energy, mass, density, area, volume, velocity, acceleration, force, pressure
temperature: degree Celsius (°C) or Kelvin (K)
Energy: Joule (J)
mass: Kilogram (kg)
density: kilogram/metre cubed (kg/m3)
distance: metre (m)
area: metre squared (m2)
volume: metre cubed (m3)
velocity: metre per second (m/s)
acceleration: metre per second squared (m/s2)
force: newton (N)
pressure: pascal (Pa)
Density
The mass per unit volume of a material
Calculating density
Density (kgm^-3) = mass (kg)/ volume (m3)
Measured in g/cm3 or kg/m3
Investigating density - depending on shape
- Weight object on balance, note down mass
- Use a ruler, vernier calipers, micrometer to measure dimensions
- Repeat measurements, take the average (accuracy)
- Calculate the volume of the object (regular shape)
- Calculate density
Investigating density - irregular shape
- Weigh object on balance
- Fill the eureka can with water up to a point just below the spout
- Place an empty measuring cylinder below its spout
- Carefully lower the object into the eureka can
- Measure the volume of the displaced water in the measuring cylinder
- Repeat these measurements and take an average before calculating the density
Pressure
The concentration of a force or the force per unit area
Calculating pressure
pressure (Pa) = force (N)/ area (m^2)
Pressure in fluids
-when an object is immersed in a fluid, the fluid will exert pressure, squeezing the object
-pressure is exerted evenly across the whole surface of the fluid in all directions, creates forces against surfaces
-These forces act at 90 degrees (at right angles) to the surface
Calculating pressure difference in a liquid
Pressure (Pa) = height (m) x density (kg/m^3) x gravitation field strength (N/kg)
Solids characteristics
-high density
-regular pattern
-vibrate around a fixed position
-low energy
-definite shape
-definite volume
Liquids characteristics
-medium density
-randomly arranged
-move around each other
-greater energy
-No definite shape
-A definite volume
Gas characteristics
-low density
-randomly arranged
-move quickly in all directions
-highest energy
-No definite shape
-No fixed volume
-highly compressible - large gaps between particles
Heating a system causes:
-change energy stored in a system by increasing KE of its particles. This:
-causes temperature of system to increase
-produce a change of state
Practical: Investigating Changes of State
- Place the ice cubes in the beaker
- Place the thermometer in the beaker
- Place the beaker on the tripod and gauze, heat using bunsen burner
- take regular temperature measurements
- Continue whilst the substance changes state (from solid to liquid)
- Plot graph of temp against time
Specific heat capacity
The amount of energy required to raise the temperature of 1 kg of the substance by 1 °C
Calculate change in thermal energy
Change in thermal energy (J) = Mass (kg) × Specific heat capacity (J/kg °C) × Change in temperature (°C)
Brownian motion
The random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving atoms or molecules in the fluid
Absolute zero
-The temperature at which the molecules in a substance have zero kinetic energy
-absolute zero = -273 Celsius
The Kelvin Scale
-Begins at 0
-0K = -273C
Temperature and speed of molecules
-hotter the gas, faster the molecules move
-increase kinetic energy
-molecules collide with the surface of the walls more frequently
Kelvin temperature is proportional to average kinetic energy of its molecules
Boyle’s law
For a fixed mass of gas, at constant temperature, the pressure is inversely proportional to the volume
P1V1 = P2V2
Charles law
For a fixed mass of gas, at constant pressure, the volume is directly proportional to the temperature
V1/T1 = V2/T2
Pressure Law
For a fixed mass of gas at constant volume, the pressure is directly proportional to the temperature
P1/T1 = P2/T2
Ideal gas assumptions
-gas particles are very small - volume of particles is much smaller than volume occupied by gas
-gas particles move in random motion and in all directions with a distribution of speeds
-number of particles are large
-gas particles undergo elastic collisions and no KE is lost
-time duration of the collisions is small compared to the time in between collisions
-no forces/ interactions between the particles other than when they collide
