1.3 Making Use of Energy Flashcards
What are the primary mechanisms of heat energy transfer?
Conduction, convection, and radiation.
How does conduction occur in solids?
Through the vibration of atoms, where energy is transferred from one atom to the next as they vibrate more vigorously with increased temperature.
Why are metals better conductors of heat than non-metals?
Metals have free (delocalized) electrons that gain kinetic energy when heated and transfer energy quickly through collisions with adjacent metal ions and other electrons, facilitating faster heat diffusion.
What is convection and where does it primarily occur?
Convection is the transfer of heat in fluids (liquids and gases) where heated particles move to take the place of cooler particles, creating convection currents.
What role do surfaces play in radiation?
Black, matt surfaces are good emitters and absorbers of radiation, while light, shiny surfaces are poor emitters and absorbers.
How can heat loss be reduced in buildings?
By using methods like double glazing, cavity wall insulation, and loft insulation, which reduce conduction, convection, and radiation.
What is the payback time formula for energy-saving methods?
Payback time = Installation Cost / Annual Saving.
How does double glazing reduce heat loss?
It contains a layer of air or a vacuum between two panels of glass, reducing conduction and preventing convection.
What is cavity wall insulation and how does it work?
Insulating material placed in the gap between the outer bricks and the inside wall, containing pockets of trapped air that reduce conduction and convection.
What is the function of a thin layer of silver foil in cavity wall insulation?
To reduce heat loss via radiation by reflecting heat back into the building.
How does loft insulation reduce heat loss?
It reduces heat loss via convection and conduction through the roof, similar to cavity wall insulation.
What is the effect of heat on fluid particles?
Heated fluid particles move faster and expand, becoming less dense and causing hot material to rise.
How is the density of an object calculated?
Density is calculated as mass per unit volume: ρ = m / V.
How does convection create weather systems?
Convection cells on a large scale cause hot air to rise and cool air to fall, leading to the movement of air and weather patterns.
How does conduction differ in metals and non-metals?
In metals, conduction involves both vibration of ions and movement of free electrons, while in non-metals, it only involves the vibration of atoms.
Why are gases less dense than solids and liquids?
Gases have particles that spread out to occupy a greater volume, resulting in lower density.
How can irregular objects’ volume be measured?
By using the water displacement method in a measuring cylinder.
Why is reducing heat loss in buildings good for the environment?
It reduces the amount of energy required to heat the house, leading to lower energy consumption and reduced carbon emissions.
What is the primary method of heat transfer in solids?
Conduction.
What type of surfaces are poor emitters and absorbers of radiation?
Light, shiny surfaces.
How does the movement of hot fluid particles affect cooler areas?
Hot fluid particles move into cooler areas, transferring heat and causing convection currents.
How does heat transfer via radiation occur?
Through infrared electromagnetic waves, which can transfer energy without requiring particles.
Why is air considered a poor conductor of heat?
Air has low thermal conductivity due to the large distance between its molecules compared to solids and liquids.
What is the role of free electrons in metal conduction?
Free electrons in metals gain kinetic energy when heated and transfer energy quickly through collisions with adjacent ions and other electrons.
