Unit 3.1: Heat and Temperature Flashcards
Temperature
- Average kinetic energy of the molecules of a substance
- Faster movement, higher temperature
- Not affected by mass
When most objects are heated they ______
expand
Total Internal Energy Formula
- E(int) = E(k) + E(p)
- E(k) is kinetic energy
- E(p) is potential energy
Absolute Zero
- Avg. kinetic energy at which all molecules stop moving
- 273.15°C or 0 K
Celsius to Kelvin Conversion
T(k) = T(c) + 273.15
Heat
- The total kinetic energy of an object
- Flows from areas with highest to lowest temperature
- Affected by object’s mass
Absolute Temperature
Measured by Kelvin Scale (K)
Methods of Heat Transfer
- Conduction
- Convection
- Radiation
Conduction
Occurs between objects in direct contact
Convection
Occurs when fluids (liquids or gases) move around due to temperature differences
Radiation
- Energy transferred as waves such as visible light and infrared
- Can travel through a vacuum
Why plateaus of temperature change occur
- Bonds break as solids change to liquids (or liquids to solids)
- This requires time
Change in Kinetic vs Potential Energy
- E(k): Change in temperature of matter
- E(p): Change in phase of substance
Specific Latent Heat
Amount of energy transferred when 1 kg substance changes phase at constant temperature
Evaporation
- Occurs only at surface of liquid
- Can occur at any temperature
Latent Heat of Fusion, L(f)
From melting or freezing
Latent Heat of Vaporization, L(v)
From boiling or condensing
Kinetic Energy during Evaporation
- Some molecules have KE high enough to escape and become gas
- When these molecules lost, average KE of liquid decreases
- Results in evaporative cooling
Boiling
- Bubbles form throughout liquid
- Occurs at precise temperature
Kinetic energy during Boiling
KE is high enough for molecules to form bubbles within liquid
Conductor
A material through which energy can be easily transferred as heat
Insulator
A material that transfers energy poorly
Specific heat [energy]
Amount of energy required to raise temperature of 1 kg of substance by 1 K
Conservation of Heat
- Heat energy gained = heat energy lost
- Q1 = -Q2
Variables for conduction [A]
- ΔQ/Δt is the rate of heat transfer (J/s)
- k is the material conductivity (W/K·m)
- A is cross-sectional area (m²) perpendicular to heat flow
Variables for conduction [B]
- ΔT is temperature (K)
- Δx is length (m)
- ΔT/Δx is the temperature gradient
Formula for conduction
ΔQ/Δt = kA(ΔT/Δx)
