Lecture 3. Temperature

Relative scale – Fahrenheit ( o F) – Celsius ( o C) – Specified reference temperature = the freezing point of water = 0 o C or 32 o F – 0 o C and its equivalents are known as the values of the ‘standard conditions of temperature’.

Absolute scale – Rankine ( o R) – Kelvin (K) (not o K!) – Their zero point at the lowest possible temperature – Rankine scale based on ‘degree unit size’ of that in the Fahrenheit scale. – Kelvin scale based on ‘degree unit size’ of that in the Celsius scale. – See Figure 4.1, p. 91 and Figure 4.2, p. 94, DMH

Rankine-Fahrenheit scale Kelvin-Celsius scale

Notes Δ o C, Δ o F, ΔK and Δ o R symbols are not in standard usage. The proper meaning of the symbols o C, o F, K and o R, as either the temperature or the unit temperature difference, must be interpreted from the context of the equation or sentence being examined.

Temperature Conversion

Examples Lecture 3 (E4.1, DMH) Convert 100 o C to (a) K, (b) o F and (c) o R Ans. (a) 373 K, (b) 212 o F and (c) 672 o R

Examples Lecture 3 (E4.2, DMH) The heat capacity of sulfuric acid has the units J/(g mol)( o C), and is given by the relation heat capacity = x10 -1 T Where T is expressed in o C. Modify the formula so that the resulting expression has the associated units of Btu/(lb mol)( o R) and T is in o R. Ans. Heat capacity = x10 -2 T

Problems Lecture 3 4.4, 4.8, 4.9