Lecture 1 Energy + Life Lectures 1 + 2

Question 1

Classical thermodynamics deals with the _________ properties of matter

Answer 1

macroscopic

Question 2

What is meant by an open system?

Answer 2

A system that can exchange both energy and matter with its surroundings.

Question 3

What is meant by a closed system?

Answer 3

A system that can exchange energy with its surroundings but not matter.

Question 4

What is meant by an isolated system?

Answer 4

A system that cannot exchange matter nor energy with its surroundings

Question 5

A helpful picture of all the different types of systems on the back of this card.

Answer 5

Question 6

The total energy of a system is its _________ which is represented by the symbol __.

Answer 6

internal energy; U

Question 7

What is the units of energy?

Answer 7

Joules (J)

Question 8

In which two ways can the total internal energy be used?

Answer 8

As Work (w) and as Heat (q)

Question 9

What is meant by work and heat?

Answer 9

• Heat - It’s the energy lost from a hot body to a cooler body - From a warm human body to its cooler surroundings.
• Work - Is energy that can be channelled in an organized way to do something useful.

Question 10

What is the first law of thermodynamics?

Answer 10

“the internal energy of an isolated system is constant” but I much prefer “energy cannot be created or destroyed, but only converted from one form to another” which is another way of expressing it.

Question 11

Which body has more kinetic energy?

A train moving at 70mph or a car moving at 70mph

Answer 11

A train moving at 70mph has more kinetic energy because kinetic energy also depends on mass as well as speed which is summarised in the following formula

E_k=1/2mv²

The kinetic energy of the train is also equal to the total energy required to stop the train.

Question 12

What is gravitational potential energy?

Answer 12

The energy an entity has due to its relative position with respect to Earth.

Question 13

What is chemical potential energy?

Answer 13

Chemical potential energy holds together atoms joined by ionic or covalent bonds. Chemical potential energy is stored in these bonds.

Question 14

What is the amount of chemical potential energy stored in a bond called?

Answer 14

Bond energy more formally referred to as bond enthalpy (it’s fancy name).

Question 15

Bond forming ________energy and bond breaking ________ energy.

Answer 15

Releases; consumes

Question 16

True or False: The bond energy of a bond say O-H is subject to variation depending on which compound has this O-H bond.

Answer 16

True: the O-H bond in water has bond energy of 492kJ mol^-1 whereas the O-H bond in methanol has a bond energy of 437kJ mol^-1 .

Question 17

What two things does bond energies tell us about particular bonds?

Answer 17

1. The amount of energy released when that particular bond forms.
2. The amount of energy required to break that particular bond.

A C-H bond energy of 412kJ mol^-1 tells us that 412kJ of energy is released for every mole of C-H bonds that form. Also tells us that 412kJ of energy is consumed for every mole of C-H bonds that break.

Question 18

Where do you expect heat to move towards if a system is hot but the surroundings are cold?

Answer 18

From the system to the surroundings. Heat moves from areas of a high temperature to areas of a low temperature.

Question 19

The transfer of energy as heat from a region of high temperature to a region of low temperature is an example of a spontaneous/non-spontaneous process

Answer 19

Spontaneous

A spontaneous process is one that happens without any effort or work being required to bring it about.

Question 20

The total energy of a system and its surrounding increases/decreases/remains unchanged

Answer 20

Remains unchanged.

Question 21

Heat is the transfer of energy from a ____ region to a _____ region

Answer 21

hot; cold

Question 22

A body at a higher temperature to some other body is said to have more…

Answer 22

…thermal energy

Question 23

The greater the thermal energy of a mole of atoms in a containment vessel, the less kinetic energy they have and the slower the atoms move.

True/False

Answer 23

False! Thermal energy is proportional to kinetic energy.