Thermodynamics- Intro and basic concepts

Question 1

What is thermodynamics?

Answer 1

Heat in motion. The science of energy.

Question 2

What is classical thermodynamics?

Answer 2

Macroscopic approach to thermodynamics that doesn’t require knowledge of the behaviour of individual particles.

Question 3

What is a system?

Answer 3

A quantity of matter or a region in space chosen for study

Question 4

What is a system’s surroundings and boundary?

Answer 4

Surroundings: the mass or region outside the system
Boundary: the real or imaginary surface that separates the system from its surroundings.

Question 5

What are the similarities and differences between a closed and open system?

Answer 5

No mass can cross the boundary of a closed system (although it can have a moving boundary). Energy can cross the boundary in both.

Question 6

What is a control surface?

Answer 6

The boundaries of a control volume (real or imaginary)

Question 7

Define specific gravity

Answer 7

The ratio of the density of a substance to the density of some standard substance at a specified temperature (usually water at 4°C)

Question 8

What is a property of a system?

Answer 8

Any characteristic of a system used to describe the state. Have numerical value and unit.

Question 9

Extensive, intensive, specific and molar properties.

Answer 9

Extensive: those whose values depend on the size (or extent) of the system.
Intensive: those whose values are independent of the mass of a system.
Specific: intensive properties per unit mass
Molar: per unit mole

Question 10

On the molecular level, what is temperature proportional to?

Answer 10

The average kinetic energy of the individual atoms (or molecules) in the system. This is related to the mean square velocity.

Question 11

What is the Ice point?

Answer 11

A mixture of ice and water that is in equilibrium with air saturated with vapour at 1atm pressure and 0°C temperature.

Question 12

What is the steam point?

Answer 12

A mixture of liquid water and water vapour (no air) in equilibrium at 1atm pressure and 100°C temperature.

Question 13

What is a thermodynamic temperature scale?

Answer 13

Independent of the properties of any substance and start at absolute 0. Kelvin and Rankine.

Question 14

What is the 0th law of thermodynamics?

Answer 14

If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.

Question 15

Define pressure and it’s different types

Answer 15

Pressure: a normal force exerted by a fluid per unit area.
Absolute (P): the actual pressure at a given position measured relative to absolute vacuum.
Gauge: the difference between absolute pressure and local atmospheric pressure.
Vacuum pressures: pressures below atmospheric pressure.

Question 16

How to calculate pressure variation with depth

Answer 16

ΔP=ρgΔh

Question 17

What is the standard atmosphere?

Answer 17

The pressure produced by a column of mercury 760mm in height at 0°C under standard gravitational acceleration.

Question 18

Formula for work done to raise an object

Answer 18

W=mg(z2-z1)

z is about distance.

Question 19

Kinetic and potential energy definitions

Answer 19

Kinetic: as a result of its motion relative to some reference frame.
Potential: as a result of its elevation in a gravitational field.

Question 20

What is work?

Answer 20

What is performed whenever a force acts through a distance. The amount performed is dependent on the path taken.

Question 21

What defines a polytropic system?

Answer 21

When PV=k

Question 22

What is heat?

Answer 22

The form of energy that is transferred between two systems (or 1 and its surroundings) by virtue of a temperature difference.

Question 23

What do q, Q and Q• (dot on top) denote?

Answer 23

Q is amount of heat transfer in a given time.
q is heat transfer per unit mass (Q/m).
Q• is heat transfer rate (Q=Q•Δt)

Question 24

What is an adiabatic system?

Answer 24

A system which exchanges no heat with its surroundings and so is perfectly insulated from them.