Lesson 2 - Enthalpy change

Question 1

Physical Change and example

Answer 1

Change in its conditions that does not change its chemical properties
Ex.) Melting, Shredding, Boiling, Chopping

Question 2

Enthalpy of solution

Answer 2

When one substance dissoles in water

Question 3

For a solute to dissolve in a solvent (3 things)

Answer 3

1. Interactions between molecules of the solute are broken to make room for solvent molecules
2. Interactions between molecules of solvent are broken to make room for solute molecules
3. Interactions form between solute and solvent molecules

Question 4

ΔHsolution =

Answer 4

ΔHsolution = ΔHsolute+ΔHsolvent+ΔHmix

Question 5

Enthalpy of phase change

Answer 5

When a substance changes phases

Question 6

What does the subscript symbol nought represent?

Answer 6

Nought represents standard conditions (1 mol at SATP)

Question 7

Some processes are equal but opposite, say examples

Answer 7

ΔHmelting = -ΔHfreezing
ΔHvaporization = -ΔHcondensation
ΔHsublimation = -Δdeposition
Endothermic = Exothermic

Question 8

Heating curve

Answer 8

Shows the amount of heat added as temperature changes

Question 9

A linear increase of a heating curve

Answer 9

Shows that the temperature of the substance is increasing within a phase, and temperature is calculated by Q=mcΔT

Question 10

A straight line on a heating curve

Answer 10

Between phases, where the intermolecular forces are being broken therefore heat is added with no change in temperature. This is the enthalpy part of the diagram

Question 11

Chemical change and example

Answer 11

A change of materials into another, new materials with different properties and one or more than one new substances are formed
Ex.) Burning wood, frying eggs, combustion of propane

Question 12

Nuclear change and example

Answer 12

A process such as fission, fusion or radioactive decay where the structure of an atomic nucleus is altered through release of energy or mass or by being broken apart
Ex.) Splitting of the uranium-235 nucleus when it is bombarded with neutrons.

Question 13

Some radioactive nuclei emit B…

Answer 13

Beta particles, identical to electrons

Question 14

Some radioactive nuclei emit A…

Answer 14

Alpha particles, identical to helium (2 protons and 2 neutrons)

Question 15

E=

Answer 15

E=mc^2

Question 16

In a nuclear change, why is the the total mass of all products smaller than the original nucleus?

Answer 16

The missing mass is converted into energy through Einstein’s equation E=mc^2

Question 17

Alpha decay

Answer 17

When a nucleus emits an alpha particle, the resulting nucleus has two less proton and two less neutron. Thus mass number is reduced by four and its atom number is reduced by two.

Question 18

Beta decay (B- particle)

Answer 18

When a nucleus emits a B- particle, a neutron becomes a proton and a electron. The resulting nucleus has one less neutron and one more proton. The electron gets released

Question 19

Beta decay (B+ particle)

Answer 19

When a nucleus emits a B+ particle, a proton becomes a proton and a positron. The resulting nucleus has one less proton and one more neutron. The positron gets released.

Question 20

Gamma radiation

Answer 20

Intense radiation given off from a radioactive decay. It carries no mass and is purely energy.

Question 21

Nuclear fission

Answer 21

Process where a heavier nucleus splits off into multiple, smaller, lighter nuclei. It can result in various combinations of new elements

Question 22

Nuclear fusion

Answer 22

Process where two very small nuclei combine to form a larger nuclei.