What is the internal energy of a body?
The sum of all the kinetic energies and potential energies of all of its particles.
How are the Kinetic and potential energies in a body distributed?
The kinetic and potential energies are randomly distributed.
What are the two ways in which you can increase the internal energy of a system?
Do work (change it’s volume)
Increase the temperature.
When a substance changes state what type of energy is changing?
The potential energy of a system is increasing (solid to liquid to gas) or decreasing (gas to liquid to solid.)
Kinetic energy remains constant during change of state because constant temperature.
What is specific heat capacity of a substance?
The amount of energy required to raise the temperature of 1kg of substance by 1K without a change in state.
What does empirical in nature mean?
The gas laws are empirical in nature demeaning that they are not based on theory but on experimental evidence.
What does the Pressure-Volume graph look like?
Curve which decreases. At higher temp the curve is further away from the axis.
Boyle’s Law?
Charles’ Law?
Pressure Law?
Boyle’s Law PV=K
Pressure is inversely proportional to volume provided the temperature is kept constant and for a fixed mass of gas.
Charles’ Law? V/T=K
Volume is directly proportional to temperature provided that pressure is kept constant and for a fixed mass of gas.
Pressure Law? P/T=K
Pressure is directly proportional to temperature provided that the Volume is kept constant and for a fixed mass of gas.
What is absolute zero?
Absolute zero is the temperature at which particles have zero kinetic energy/no kinetic energy.
What is Brownian motion?
The random (Very important that it is random) motion of larger particles in a fluid caused by collisions with surrounding particles.
Can be observed by looking at smoke particle under a microscope.
Assumptions for the Derivation of the Kinetic Theory Model?
-No intermolecular forces act between the particles
-The Volume of the molecules Is negligible compared of the volume of the container.
-Collisions of the particles with the container walls and other particles are perfectly elastic.
-Time spent in collision with the container walls and other particles is negligible compared to the time between collisions.
-The particles follow Newton’s Laws apply
-The particles move with a range of speed/Kinetic energies in random directions.
What is interesting about an Ideal Gas?
An Ideal GAs follows the Gas Laws perfectly and adheres to the assumptions of kinetic theory model. As one of the assumptions of the kinetic theory model is that no intermolecular forces act between the molecules this means that the Ideal gas has no potential energy as intermolecular forces are associated with potential energy.
Therefore and Ideal Gas’s Internal energy is equal to the sum of the kinetic energies of all of it ‘s particles.
An ideal gas follows the gas laws perfectly, meaning that there is no other interaction other than perfectly elastic collisions between the gas molecules, which shows that no intermolecular forces act between molecules. As potential energy is associated with intermolecular forces, an ideal gas has no potential energy, therefore its internal energy is equal to the sum of the kinetic energies of all of its particles.
Statement about knowledge of Gas laws over time and how other have developed?
Knowledge and understanding of gases has changed greatly over time; the gas laws were discovered by a number of scientists and later explained by the development of the kinetic theory model, however this model was not accepted at first. Knowledge and understanding of any scientific concept changes over time in accordance to the experimental evidence gathered by the scientific community,
Specific heat capacity of a solid and of a liquid experiment?
Of a solid:
A block o metal of known mass is used. A 12V electrical heater is inserted into a hole drilled int the metal and is used to heat the metal. A thermometer is placed in another hole in the metal and a small amount of oil or water Is placed in the hole in order to improve the thermal contact between the thermometer and the metal.
Heater current x Heater p.d. x heating time+ energy supplied.
IVt=mc delta theta
so
c=IVt/m delta theta
Specific heat capacity of a liquid:
A known mass of liquid m is used in an insulated calorimeter of known mass and specific heat capacity. 12 V electrical heater is placed in the liquid and used to heat it directly. A thermometer is inserted into the liquid and is used to measure the temperature rise.
Assuming no heat loss to the surrounding so
IVt=mc delta theta ( of liquid) + mc delta theta (of calorimeter.) All quantities are known so we can rearrange to calculate specific heat capacity of the liquid.
Continuous flow heating experiment?
Do questions on it.
Cold water flows in and a heating element is switched on. This transfers thermal energy to the water and heats it up.
Assume the energy transfer from the heater is 100% efficient (all of the energy is transferred to the water). We can ensure this is true by placing some oil between the heater and water tube to ensure good thermal contact.
Insulate the heater water tube to minimise energy loss to surroundings.
Q/t=mc delta theta/t
Can work out work done on water or specific heat capacity of water.
-Let water flow at a steady rate so that the water flowing out is at a constant temperature.
-Record the flow of water and duration of the experiment which you can work out mass flow per second from.
-Calculate difference in temp from thermometer on cold water and thermometer on hot water.
- What we want to do is change the power settings go the heater and change the flow rate of the water also. We want to keep the change in temp constant.
Since c and delta theta are the same this means we can say that
Q2-Q1=(M2-M1)c x delta theta
where Q2 is energy transferred to the water in second experiment( which we can work out from knowing power setting go heater and duration of experiment) and the m is the mass of water which we can work out from knowing the flow rate and duration of the experiment.
-We can rearrange this equation of specific heat capacity(c).
Molar Mass?
The mass of one mole of the substance.
Molecular Mass?
The mass of a given molecule.
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