T H E R M A L E N E R G Y

SPECIFIC HEAT CAPACITY:

In physics the flow of energy, from a higher temperature to a lower temperature, due to conduction, convection or radiation, is what we call heat. As heat is a form of energy it is measured in the units of energy (Joules).All bodies have internal energy. This is made up of the potential energy contained within the inter-atomic bonds and the kinetic energy of the vibrations of the atoms.The potential energy depends on the energy stored in the inter-atomic bonds and the kinetic energy depends on the temperature.The temperature of a body is a measure of the mean, random, kinetic energy of its vibrating atoms.The base SI unit of temperature is the Kelvin.Absolute zero (0K) corresponds to a temperature of approximately -273 degree Celsius.Specific heat capacity is the quantity of energy needed to raise the temperature of a material, per kilogram per degree rise in temperature.E = m*c* TΔElectrical energy transferred by heater = increase in internal energy of material.I*V* t = m*c* TΔ ΔThe sources of errors while measuring the specific heat capacity of solids are:

Energy is absorbed by the heater itself Energy is lost to the surroundings, despite the lagging. A little energy will be taken by the lagging Inaccuracy of the thermometer, especially when temperature change is small Inaccuracy of the meters.

One way of making allowance for the heat transferred to the surroundings is to determine the gradient of a temperature-time graph line at the point where the line first becomes linear. Rate of electrical energy transferred by heater = rate of energy gained by block. Finding the specific heat capacity of a liquid poses a slight problem, as the liquid has to be in some form of container, such as a glass beaker. This apparent difficulty can be largely overcome by using an expanded polystyrene cup to contain the liquid.The main sources of error when dealing with a liquid are:

Energy taken by the heater itself (making c too large) Heat lost to the surroundings, mainly from the top of the cup (making c too large) Thermometer error, especially when temperature change is too small. Meter errors Small amount of energy taken by the thermometer and cup (making c too large)

INTERNAL ENERGY AND ABSOLUTE ZERO:

In an ideal gas we assume that the inter-molecular forces are negligible, except during collision. Furthermore, we assume that the collisions of the gas molecules with one another and with the walls of any container are elastic. As collisions between gas molecules take place randomly, there is a continuous interchange of kinetic and potential energy in this way.We also assume that the internal energy is entirely the kinetic energy. This means for an ideal gas temperature is a measure of the total internal energy.A hot body has a much greater concentration of internal energy compared with a cold body. We define heat as the random interchange of energy between two bodies in thermal contact, resulting in energy flowing from hot to cold.Energy can be transferred between two bodies in the form of work, irrespective of any temperature difference; this work can either be mechanical or electrical.

Energy transfer by working is an ordered process and is independent of any temperature difference.The four states of matter are: solid, liquid, gas and plasma.Because plasma is ionized, made up of charged particles, it can be controlled by magnetic fields.At the stage of phase change there is no rise in temperature although the material is still receiving heat. This energy is used to break the potential bonds within the molecules. It is called latent heat.A temperature of 0K is called absolute zero because it is the lowest temperature that can be reached.A superconductor is a material that will conduct electricity without resistance when cooled below a certain temperature.This is how magnetic levitation works:

When the magnet is dropped and falls towards the superconductor, the change in magnetic flux induces an electric current in the superconductor.

By Lenz’s law the current flows in a direction such that its magnetic field opposes that of the magnet and so the magnet is repelled.

As the superconductor has no resistance, the current in it continues to flow, even though the magnet is no longer movies.

The magnet is permanently repelled and hovers above the superconductor.Absolute zero is the temperature at which the molecules of matter have their lowest possible average kinetic energy. In practice, quantum mechanics requires that materials have a minimum kinetic energy called the zero-point energy.

GAS LAWS AND KINETIC THEORY:

Pressure = Force / AreaPressure = height * density * gThe total pressure is always PA + hpgBoyle’s law states that: the pressure of a fixed mass of gas in inversely proportional to its volume provided that the temperature is kept constant. The graph of p against V is called an isothermal curve. An isothermal is a curve that shows the relationship between the pressure and volume of a gas at a particular temperature. Charle’s law states that: The pressure of a fixed mass of gas is directly proportional to its Kelvin temperature provided that the volume is constant.The universal molar gas constant, R, has a value of 8.31.P*V = n*R*T, where n is the number of moles of a gas.P*V = N*k*T, where N is the number of molecules of the gas and k = 1.38 * 10-23

A gas that obeys this equation under all conditions is called an ideal gas and hence this equation is called the ideal gas equation or the equation of state for an ideal gas.Most gases obey the equation provided that the pressure is not too large and the gas is above a certain temperature, called its critical temperature.Pressure = density * (speed)2 / 30.5 * m * c2 = 1.5 * k * T, where T is in Kelvin.The average kinetic energy of the molecules of a gas is proportional to the absolute temperature of the gas.

Assumptions Experimental EvidenceGas molecules are in continuous random motion. Brownian motion

The volume occupied by the molecules is negligible compared with the volume of the container.

It is easy to compress a gas by a large amount.

Intermolecular forces are negligible except during a collision The molecules are very far apart relative to their size and so the intermolecular forces become very small.

The duration of collisions is negligible compared with the time spent between collisions

The molecules on average are farther apart.