Molecular Physics | Thermodynamics Answers

Suppose water clusters containing up to 50 molecules. If we add 500 water

molecules at 0c with 500 water molecules forming ice at 0c.


(a) The heat flow would be from ice to water or water to ice.

(b) Which thermodynamic property directed the heat flow for the above situation.

(c) Justify the heat flow direction from Boltzmann entropy equation.

Heat supplied to raise steam in the boiler is 3000 KJ/kg while heat rejected by the system to

the cooling water in the condenser is 2000 KJ/kg. The turbine develops power of 1500 KW and

the work required to pump the condensate back into the boiler is 50 KW.

A kettle transfers 6000 J of energy electrically. 1500 J of this is wasted. What is the efficiency of this kettle?

The volume of a small piece of metal is 5.000cm3 at 200C and 5.014cm3 at 1000C. Determine the cubic expansivity of the metal?

What substance can gain 40.0 KJ and only gain 25 C if 1.616 kg of the substance is present?

1) a 1.000 m aluminum bar at 30.00 C cools to a temperature of -50.00 C. What is the final length of the bar?


2) a large container is holding 2.50 L of mercury. What is the change in volume of the mercury if it experiences a temperature change of 78.0 C (assuming the temperature of the container remains constant)?

A 0.350 m gold bar at 20.0 C heats up to 500.0 C. What is the change in length of the gold bar?

On the Rankine temperature scale, which is sometimes used in engineering applications, the freezing point of water is at 491.67 °R and the boiling point of water is at 671.67 °R.

(i) Determine a relationship (a mathematical equation) between the Rankine and Fahrenheit temperature scales. (ii) A healthy person has an oral temperature of 98.6F. Calculate what this reading would be on the Rankine temperature scale.

Concrete sidewalks are always laid in sections, with gaps between each section. The drawing shows three identical 2.4-m sections. The outer two are against immovable walls. Two identical gaps between the three sections are provided so that thermal expansion will not create thermal stress that could lead to cracks. Calculate the minimum gap width necessary so that an increase in temperature of 32 C° will not cause cracking of the concrete sections.

Identify 3 process of thermodynamics that have an effect on global climate. Describe how they have an effect and how we could change the degree of effect that they have.