TJC 12 Temperature and Ideal Gases

Temasek Junior College 1 i Unit 12: Temperature and Ideal Gases Learning Outcomes Candidates should be able to: (a) show an understanding that a thermodynamic scale of temperature has an absolute zero and is independent of the property of any particular substance. (b) convert temperatures measured in kelvin to degrees Celsius: / / 273.15T K T C   (c) recall and use the equation of state for an ideal gas expressed as pV = NkT, where N is the number of particles. (d) state that one mole of any substance contains 6.02 × 10 23 particles, and use the Avogadro constant NA = 6.02 × 10 23 mol-1 as well as the relationship Nk = nR between the Boltzmann constant and the molar gas constant, where n is the amount of substance in moles and N = nNA. (e) state the basic assumptions of the kinetic theory of gases. (f) explain how the random motion of gas particles exerts mechanical pressure and hence derive, using the definition of pressure as force per unit area, the relationship 2 3 1 cNmpV  . (A simple model considering one -dimensional collisions and then extending to three dimensions using 22 3 1 ccx  is sufficient.) (g) recall and apply the relationship that the mean kinetic energy of a molecule of an ideal gas is proportional to the thermodynamic temperature (i.e. kTcm 2 3 2 1 2  ) to new situations or to solve related problems. Name : ________________________________ Class : _________

Temasek Junior College 2 1 Temperature 1.1 Temperature and Heat From the macroscopic perspective between systems, temperature is the physical property that determines the direction of heat flow. Heat then refers to the energy transferred between two systems at different temperatures. Microscopically however, we can define temperature a s a measure of the average kinetic energy of molecules in a body. 2 Temperature Scales LO(a) 2.1 Temperature and thermometers Thermometers are devices used to measure temperature. There are many kinds of thermometers, but their operation always depends on some thermometric property.  Thermometric property: a physical property that increases or decreases continuously with temperature, such as the ones below The fact that substances change state (from solid to liquid, or from liquid to gas) at fixed temperatures is used to define reference temperatures, which are called fixed points. By taking the value of the thermometric property at t wo fixed points, and dividing the range of values into a number of equal units (or degrees) between the two points, we can set up what is known as an empirical scale of temperature for that thermometer. 2.2 Empirical Scales ‘Empiric