# Thermal Physics J1 Orion (Due : Friday 10/6)

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Thermal Physics J1 Orion (Due : Friday 10/6)

## 1. Simple Kinetic Molecular Model of Matter (Anniqa, Ryan lee, Ting Hao, Jasriine, Sanjevene)

### 1.1. Brownian Motion

1.1.1. Random motion of particles caused by the collisions between particles

### 1.2. States of Matter

1.2.1. Solid

1.2.1.1. incompressible

1.2.1.2. fixed shape and volume

1.2.1.3. particles held together by strong intermolecular forces

1.2.1.4. particles vibrate in fixed position

1.2.2. Liquid

1.2.2.1. low compressibility

1.2.2.2. fixed volume but unfixed shape, takes the shape of the container

1.2.2.3. particles are close together and attract each other

1.2.2.4. particles vibrate vigorously and are able to move

1.2.3. Gas

1.2.3.1. high compressibility

1.2.3.2. fixed volume but unfixed shape, occupies any available space

1.2.3.3. particles are spaced out and intermolecular forces are weak

1.2.3.4. particles move at high speeds and collide with each other and the container walls

### 1.3. Kinetic Theory

1.3.1. Matter consists of tiny particles that are in constant motion.

1.3.2. When the particles collide, energy is exchanged between them.

1.3.3. Separation between particles is caused by intermolecular forces.

1.3.3.1. Forces are stronger when particles are closer together.

1.3.3.2. Forces weaken when the particles are further apart.

1.3.4. Temperature of matter is due to the average kinetic energy of the particles.

### 1.4. Energy of particles

1.4.1. Internal energy: kinetic energy + potential energy

1.4.2. Particles have kinetic energy because they are in constant motion.

1.4.3. Particles have potential energy because their constant motion opposes the bonds trying to pull them together.

1.4.4. Thermal energy: total amount of internal energy possessed by the particles in an object.

### 1.5. Heat vs Temperature

1.5.1. Temperature: the average kinetic energy of particles in an object.

1.5.2. Heat: the amount of thermal energy being transferred. 🔥

### 1.6. Thermal Equilibrium

1.6.1. Heat is transferred from a body of high temperature to a body of low temperature.

1.6.2. When a hot object is in contact with a colder object, thermal energy is transferred.

1.6.2.1. The hot object cools down and its particles lose kinetic energy.

1.6.2.2. The cold object heats up and its particles gain kinetic energy.

1.6.2.3. The transfer of energy stops when both objects have the same temperature.

1.6.2.3.1. This means the objects have reached thermal equilibrium.

### 1.7. Measuring Temperature

1.7.1. Kelvin, K

1.7.1.1. a thermodynamic scale

1.7.1.2. based on the average kinetic energy of particles

1.7.2. Celsius, °C

1.7.2.1. based on the boiling and melting point of water

1.7.3. Absolute zero

1.7.3.1. 0 K or -273 °C

1.7.3.2. It is the absolute lowest temperature an object can go.

1.7.3.3. Particles are unable to move any slower.

1.7.4. K = °C + 273

### 1.8. Vaporisation

1.8.1. Evaporation

1.8.1.1. occurs at temperatures less than boiling point

1.8.1.2. occurs at the surface of a liquid

1.8.1.4. no bubbles are formed

1.8.1.5. Factors that affect rate of evaporation (of water)

1.8.1.5.1. Surface area

1.8.1.5.2. Temperature

1.8.1.5.3. Humidity

1.8.1.5.4. Wind

1.8.2. Boiling

1.8.2.1. occurs at boiling point

1.8.2.2. occurs throughout the entire liquid

1.8.2.3. process is rapid

1.8.2.4. bubbles are formed

## 2. Thermal Properties & Temperature (Xi Ting, Sean, Sara, Willlon habishek)

### 2.1. Thermal expansion

2.1.1. When heated, the vibrations of particles in a solid vibrate faster, resulting in vibrations taking up more space. Vice versa for lowering temperatures

2.1.2. Different materials expand to different degrees

2.1.3. Allowing for expansion and contraction

2.1.3.1. Leaving space in between train rails to allow for expansion on a hot day

2.1.4. Uses

2.1.4.1. thermometer

2.1.4.1.1. liquid in thermometer expands as temperature increases (linear)

2.1.4.2. bimetal strip

2.1.4.2.1. Used to convert temperature change into mechanical displacement

2.1.4.2.2. using two metals with different degrees of expansion

2.1.5. Water and ice

2.1.5.1. Water expands when frozen, contracts when melted

2.1.5.1.1. pipe bursting

2.1.5.1.2. weathering

### 2.2. Measurement of temperature

2.2.1. A physical property that varies with temperature may be used for measurement of temperature.

2.2.2. by using Thermometers

2.2.2.1. Liquid-in-glass Thermometer

2.2.2.1.1. The liquid in a glass bulb expands up a capillary tube when the bulb is heated. Mercury and Alcohol are usually used to make these thermometers.

2.2.2.2. Thermistor Thermometer

2.2.2.2.1. A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature.

2.2.2.3. Thermocouple Thermometer

2.2.2.4. Infrared Thermometer

### 2.3. Thermal capacity

2.3.1. HEAT CAPACITY

2.3.1.1. The amount of heat required to increase the temperature of a substance by 1 °C (or 1 K).

2.3.1.2. Heat Capacity = Heat absorbed (or released) / Change in Temperature

2.3.1.2.1. C = Q / △T

2.3.1.3. Measured in J/°C or J/K

2.3.1.4. Depends on : Mass of Object & Type of Material

2.3.2. SPECIFIC HEAT CAPACITY

2.3.2.1. The amount of heat required to increase the temperature of 1 kg of substance by 1 °C (or K)

2.3.2.2. Specific Heat Capacity = Heat Capacity / Mass

2.3.2.2.1. Cs = C / M

### 2.4. Melting and boiling

2.4.1. LATENT HEAT

2.4.1.1. A substance will absorb or release heat energy without a change in temperature during a phase change

2.4.2. SPECIFIC LATENT HEAT

2.4.2.1. The amount of heat required to change the phase of 1 kg of substance at a constant temperature.

2.4.2.2. Specific Latent Heat = Latent Heat / Mass

2.4.2.2.1. L = Q / M

2.4.2.3. Measured in Jkg^-1

## 3. Thermal Processes (Erica, Raisa, Ryan woon, Gilhun, Pamela)

### 3.1. Definition

3.1.1. thermal energy refers to the energy contained within a system that is accountable for its temperature.

### 3.2. Conduction

3.2.1. the diffusion of thermal energy within one material or between materials in contact

3.2.1.1. Conductors

3.2.1.1.1. materials which speedily transfer heat

3.2.1.1.2. metals have a high thermal conductivity

3.2.1.2. Insulators

3.2.1.2.1. materials that contain tiny pockets of trapped air; heat energy cannot flow through them

3.2.1.2.2. common thermal insulation materials:

3.2.2. transfer of heat through solids

3.2.2.1. particles are arranged closely, allowing many collisions to occur

3.2.3. process of conduction (in metals):

3.2.3.1. one end of the metal is heated, heat is transferred to the kinetic energy store of the particles of that end

3.2.3.2. particles vibrate faster, collisions with neighbouring particles occur more often

3.2.3.3. process repeats, and energy is passed along the metal until heat is spread out evenly throughout

3.2.4. example: cold cast iron skillet that is placed onto a stovetop; the skillet becomes very hot due to the conduction of heat from the burner to the skillet.

### 3.3. Convection

3.3.1. the transfer of heat due to the bulk movements of molecules within fluids

3.3.1.1. convection in a liquid

3.3.1.1.1. water is being heated from the bottom of a beaker

3.3.1.1.2. particles near the heat source gain kinetic energy and expand, becoming less dense

3.3.1.1.3. it rises upwards as cooler, denser water sinks and displaces it

3.3.1.1.4. as the particles now at the bottom are being heated, the particles above lose their energy, allowing the cycle to repeat

3.3.1.1.5. the circulating stream = convection current

3.3.1.2. convection in air

3.3.1.2.1. air is heated by the Sun

3.3.1.2.2. warm air rises above the equator as it is displaced by cooler, denser air sinking to the north and south

3.3.1.2.3. results in huge convection currents in the Earth's atmosphere

3.3.1.2.4. can cause winds across oceans and continents

3.3.2. example: boiling water

3.4.1. energy in the form of electromagnetic waves is emitted by all matter in all directions and travels directly to its point of absorption at the speed of light

3.4.1.1. includes infrared waves & light, mixture of different wavelengths

3.4.1.2. all matter gives out thermal radiation; the higher the surface temperature & area, the more energy they radiate per second

3.4.1.2.1. emitters & absorbers

3.4.1.2.2. reflectors

3.4.2. transfer of heat through empty space/vacuum, without particles (unlike conduction & convection)

3.4.3. example: toasters use thermal radiation as it emits heat