B.1 Thermal energy transfers

Question 1

Solid Phase Properties

Answer 1

Fixed volume, do not flow, particles in regular rows, little energy, vibrate around fixed positions, strong intermolecular forces

Question 2

Liquid Phase Properties

Answer 2

Can flow and take the shape of their container, random particle arrangement, more energy than solids, particles move around each other, weaker intermolecular forces than solids

Question 3

Gas Phase Properties

Answer 3

Fill their container, volume changes with pressure/temperature, particles far apart and random, high energy and move quickly, largest thermal expansion.

Question 4

Thermal Expansion in Phases

Answer 4

Upon heating, particles gain energy and move apart, weakening intermolecular forces. Solids expand the least, gases the most, and liquids are intermediate.

Question 5

Density Definition

Answer 5

Mass per unit volume of a substance. Higher density means particles are closer together. Calculated using ρ = m/V, with ρ in kg/m³.

Question 6

Celsius Scale

Answer 6

Measures temperature with 0°C as the freezing point and 100°C as the boiling point of water. Commonly used for everyday temperature measurements.

Question 7

Kelvin Scale

Answer 7

Absolute temperature scale with 0 K as absolute zero, the point at which particles have minimum kinetic energy. 0°C equals 273.15 K.

Question 8

Absolute Zero

Answer 8

The lowest possible temperature, 0 K or -273.15°C, where the particles of a substance have minimal kinetic energy.

Question 9

Conversion from Celsius to Kelvin

Answer 9

Add 273.15 to the Celsius temperature to convert to Kelvin. For example, 25°C + 273.15 = 298.15 K.

Question 10

Relationship between Temperature and Kinetic Energy

Answer 10

In the Kelvin scale, temperature is directly proportional to the average kinetic energy of the particles of a substance.

Question 11

Specific Heat Capacity (c)

Answer 11

The amount of energy required to raise the temperature of 1 kg of a substance by 1 K. It indicates a material’s ability to store thermal energy.

Question 12

Phase Change

Answer 12

A transition of matter from one state (solid, liquid, gas) to another without changing temperature. It involves energy changes affecting particle interaction but not kinetic energy.

Question 13

Latent Heat

Answer 13

The energy absorbed or released during a phase change. It does not increase temperature but changes the state of a substance (fusion for melting, vaporization for boiling)

Question 14

Heating Curve

Answer 14

A graph showing how a substance’s temperature changes with energy input, highlighting plateaus during phase changes where temperature remains constant despite energy addition.

Question 15

Calculating Energy for Temperature Change

Answer 15

Q is energy, m is mass, c is specific heat capacity, and ΔT is temperature change.

Question 16

Conduction

Answer 16

The transfer of thermal energy through direct contact between particles. More efficient in solids due to close particle arrangement.

Question 17

Convection

Answer 17

The transfer of heat in fluids (liquids or gases) by the movement of heated particles, creating convection currents

Question 18

Thermal Radiation

Answer 18

Transfer of energy by electromagnetic waves. It does not require a medium, thus can occur in a vacuum.

Question 19

Conductors vs. Insulators

Answer 19

Conductors allow easy thermal energy transfer (e.g., metals), while insulators resist it (e.g., wood, air).

Question 20

Fourier’s Law of Heat Conduction

Answer 20

The rate of heat transfer through a material is directly proportional to the temperature difference and the material’s thermal conductivity, inversely proportional to the material’s thickness.

Question 21

Black Body Definition

Answer 21

An idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence, and emits radiation at a rate described by Planck’s law.

Question 22

Wien’s Displacement Law

Answer 22

The peak wavelength of the emission from a black body is inversely proportional to its temperature, allowing temperature determination from peak radiation wavelength.

Question 23

Stefan-Boltzmann Law

Answer 23

The total energy radiated per unit surface area of a black body across all wavelengths is directly proportional to the fourth power of the black body’s absolute temperature.

Question 24

Luminosity of a Black Body

Answer 24

The total amount of energy emitted by a black body per unit time, dependent on its surface area and the fourth power of its temperature.

Question 25

Apparent Brightness

Answer 25

The observed brightness of a star or celestial object as seen from Earth, depending on the object’s luminosity and its distance from the observer.