Topic 14 - Particle Model Flashcards
Explain solids in terms of the movement and arrangement of particles
The particles in a solid are close together in a regular arrangement and vibrate in fixed positions. They have the least kinetic energy of all states.
Explain liquids in terms of the movement and arrangement of particles
The particles in a liquid move freely. Liquids are randomly arranged. They have more kinetic energy than a solid.
Explain gases in terms of the movement and arrangement of particles
The particles in a gas are widely spaced, free to move in any direction and randomly arranged. They have the most kinetic energy of all the states of matter.
What is the equation for density?
density (kilogram per cubic metre, kg/m³) = mass (kilogram, kg) ÷ volume (cubic metre, m³)
Describe how to measure the density of a cube
Using a ruler measure the length, width and height. Then, calculate the volume.
Measure its mass (such as by using a top pan balance).
Density = mass/volume
Describe how to measure the density of a sphere
Use vernier callipers to measure the diameter of the sphere.
Measure its mass (such as by using a top pan balance).
Calculate the volume using
⁴⁄₃πr³.
Density = mass/volume
Describe how to measure the density of an irregular shaped object
Measure the object’s mass (such as by using a top pan balance).
Fill the displacement can until the water is level with the bottom of the pipe.
Place a measuring cylinder under the pipe ready to collect the displaced water.
Carefully drop the object into the can and wait until no more water runs into the cylinder.
Measure the volume of the displaced water.
Density = mass/volume
Describe how to measure the density of a liquid
Measure a measuring cylinder’s mass (such as by using a top pan balance).
Pour 50cm³ of water into the measuring cylinder and measure its new mass.
Subtract the new mass from the original mass to find the water’s mass.
density = mass/volume
Explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules
Density depends on the spacing of the atoms in matter.
Solids and liquids have similar densities because the space between particles does not significantly change.
Usually liquids have a lower density than solids (the main exception is ice and water).
Gases have far lower density. The spacing between molecules increase as the particles have lots of energy to move so volume increases greatly and therefore density decreases greatly.
Describe what occurs when substances change state
Mass is conserved.
These physical changes are reversible and not chemical because the material retains its original properties when reversed.
Explain what happens when a system is heated
The amount of energy the particles have increase so the particles vibrate more so the temperature increases or the energy is put into breaking bonds and the system changes state.
Define specific heat capacity
The energy required to raise the temperature of 1kg of a substance by 1℃
Define specific latent heat
The energy required to change the state of 1kg of a substance without a change in temperature
What is the equation for change in thermal energy?
change in thermal energy (joule, J) = mass (kilogram, kg) × specific heat capacity (joule per kilogram degree Celsius, J/kg °C) × change in temperature (degree Celsius, °C)
What is the equation for thermal for a change of state?
thermal energy for a change of state (joule , J) = mass (kilogram, kg) × specific latent heat (joule per kilogram, J/kg)
Explain ways of reducing unwanted energy transfer through thermal insulation
If thermal energy transfers out of a system some energy is lost to the surroundings and therefore wasted.
Thermal insulators/poor conductors
(-Use cladding,
-Use double thickness of the concrete
-Plant trees around wind break
-Use double glazed windows
-Close windows/door)
Use reflective coatings to reflect infrared radiation back into the system
(-Use silver/reflective/white paint)
Describe how to determine the specific heat capacity of water for the core practical to investigate the properties of water
-Measure the mass of water
-Place water in the calorimeter
-Place the immersion heater into the central hole at the top of the calorimeter.
-Clamp the thermometer into the smaller hole with the stirrer next to it.
-Record the temperature of the water.
-Connect the heater to the power supply and a joulemeter and turn it on for ten minutes. Stir the water regularly.
-After ten minutes the temperature will still rise even though the heater has been turned off and then it will begin to cool. Record the highest temperature that it reaches and calculate the temperature rise during the experiment.
specific heat capacity = energy/(mass x temperature change)
How can a calorimeter be made more effective?
By:
-Adding a lid
-Adding insulation
-Adding a stirrer
-Using a more sensitive thermometer
-Ensuring the heater is fully submerged
Describe how to obtain a temperature-time graph for melting ice for the core practical to investigate the properties of water
-Place 50g of crushed ice straight from the freezer into the calorimeter.
-Place the immersion heater into the central hole at the top of the calorimeter.
-Clamp the thermometer with its bulb in the ice but near the top of the ice.
-Record the temperature of the ice.
-Connect the heater to the power supply and joulemeter, turn it on and record the temperature every 20 seconds.
-Continue until the thermometer bulb is no longer under the level of the water.
Explain the pressure of a gas in terms of the motion of its particles
Particles in a gas move randomly in every direction.
-Pressure produces a net force at right angles to any surface
-Particles collide with a wall, changing velocity. This means they change momentum during their collision.
-They exert a force on the wall as force = momentum/time
-Pressure is the force across the area of the wall.
Explain the effect of changing the temperature of a gas on the velocity of its particles
-Increased temperature means more energy given to the particles
-The thermal energy is transferred to kinetic so particles move at faster speed, collisions with walls occur more often and the particles hit the wall with greater impact so pressure increases.
Describe the term absolute zero
0 Kelvin or -273℃
Nothing can exist at a colder temperature than this. particles at this temperature have no energy so do not vibrate at all and remain perfectly still
T Kelvin = (T-273) centigrade
Explain the effect of pressure changes on gases
-Increasing the pressure of the gas causes it to compress (have a smaller volume). Same force is exerted on walls, as temperature and energy of particles is constant. Forces need to be exerted on a smaller area and volume decreases.
pressure ∝ 1/volume
Explain how the pressure of a gas produces force
-As the gas particles move about randomly they collide with the walls of their containers
-These collisions produce a net force at right angles to the wall of the gas container (or any surface)
-Therefore, a gas at high pressure has more frequent collisions with the container walls and a greater force
-Hence the higher the pressure, the higher the force exerted per unit area
Explain the effect of changing the volume of a gas
-When volume increases there is a greater area that particles collide with. The same force is exerted on the walls as velocity is constant (only affected by temperature) and pressure decreases.
pressure ∝ 1/volume
What is the equation to calculate pressure or volume for gases of fixed mass at constant temperature?
(P₁ x V₁) = (P₂ x V₂)
Explain why doing work on a gas can increase its temperature
-Doing work on a gas means compressing or expanding the gas, so changing the volume.
-Pumping more gas into the same volume means more particles are present so more collusions occur per unit time with the walls, so pressure increases.
-Kinetic energy is transferred to the particles into thermal energy when more gas is added into the fixed volume, this heats the gas
e.g. bicycle pump gets warm when used to inflate a tyre
