Chapter 8 Science Study Notes: Convection, Conduction, and Radiation

Flashcards covering the definitions, processes, and applications of convection, conduction, and radiation.

What is conduction?

 The transfer of thermal energy through a substance or between substances in contact, by the collision of particles.

What is convection?

The transfer of thermal energy from one part of a fluid to another by circulating current of faster moving and slower moving particles.

What is radiation?

The transfer of ration energy or electromagnetic waves.

What is radiant energy?

Energy that travels in the form of electromagnetic waves through empty spaces.

How do heat sinks use conduction to dissipate heat?

are designed with materials that have high thermal conductivity, such as copper or aluminum. These materials efficiently transfer heat away from a hot source, like a computer processor, to a cooler environment, thus cooling the component.

How is heat transferred through direct contact during conduction?

the molecules in a warmer object vibrate more vigorously and collide with the molecules in a cooler object. These collisions transfer some of the energy from the warmer molecules to the cooler ones, increasing their vibration and, therefore, their temperature.

How does convection work?

it works by heating a fluid, which then expands and becomes less dense. This lighter, warmer fluid rises, displacing cooler, denser fluid, which sinks. This movement creates a circulating current that distributes heat throughout the fluid.

How is heat transferred through electromagnetic waves during radiation?

All objects emit this, with hotter objects emitting more radiation than colder ones. When this radiation strikes another object, it can be absorbed, causing the object to heat up. This transfer of energy occurs through electromagnetic waves.

How do convection ovens use fans to circulate hot air?

use fans to circulate hot air continuously around the food. This ensures that the heat is evenly distributed, leading to more uniform heating and faster cooking times compared to conventional ovens.

How do HVAC systems use forced convection?

systems utilize forced convection to distribute warm or cool air throughout a building. Fans or blowers are used to circulate air, ensuring that the temperature is consistent across different areas.

How do solar panels use radiative heat transfer?

use radiative heat transfer to absorb energy from the sun. The photons in sunlight carry energy, which is absorbed by the solar panel material (usually silicon). This absorbed energy is then converted into electrical energy through the photovoltaic effect.

How are radiative barriers used in buildings?

such as reflective films or coatings, are used in buildings to reduce heat gain or loss by reflecting thermal radiation. These barriers are particularly effective in hot climates for keeping buildings cool.

How do insulation materials minimize thermal energy transfer?

fiberglass or foam are designed to minimize thermal energy transfer by reducing conduction and convection. These materials contain air pockets that trap air, which is a poor conductor of heat, thus slowing down the rate of heat transfer.

How does technology help control heat?

it helps by allowing us to manipulate thermal energy transfer. This includes slowing it down with insulators, speeding it up with conductors, or moving it from one place to another using convection or radiation.

How do thermal energy transfers affect objects?

Thermal energy transfers can significantly affect objects. Adding heat increases temperature, which can lead to phase changes such as melting (solid to liquid) or boiling (liquid to gas). Additionally, materials may undergo thermal expansion, where they increase in size due to the increased kinetic energy of their particles.

How is heat transmitted through conduction?

Heat is transmitted through conduction when vibrating molecules in a warmer area collide with cooler ones, transferring energy without moving the material itself. The energy moves from more energetic to less energetic particles, resulting in heat transfer.

What happens on a particle level when heat is applied to a thermal conductor?

When heat is applied to a thermal conductor like metal, the atoms inside it start to vibrate more quickly because they have more energy. Free electrons help carry the heat energy through the metal, moving from one part to another and spreading the heat rapidly.

Give examples of conductors.

Examples of conductors include copper, aluminum, iron, and steel. These materials allow heat to pass through them easily.

Give examples of insulators.

Examples of insulators include wood, plastic, rubber, foam, and fiberglass. These materials resist the flow of heat.

What applications use conduction?

Applications that use conduction include cooking pans (transferring heat to food), radiators (spreading heat in a room), soldering irons (heating metal parts), and heat sinks (cooling computer parts).

What applications use insulators?

Applications that use insulators include house insulation (keeping buildings warm or cool), oven mitts (protecting hands from heat), cooler boxes (keeping food cold), and electrical wire coating (protecting from heat and shock).

How is energy (heat) transferred throughout a fluid by convection?

When a fluid is heated, its particles gain energy and move faster, spreading out and becoming less dense. The warmer, lighter particles rise, while cooler, denser particles sink, creating a circular motion called a convection current that distributes heat.

Give examples of convection currents in everyday life.

Examples of convection currents in everyday life include boiling water, hot air balloons, sea breezes, and heating systems in homes. These all rely on the movement of fluids due to temperature differences.

How is the sun's energy transferred through empty space?

The Sun's energy is transferred through empty space by radiation. This energy travels in the form of electromagnetic waves, such as light and heat (infrared rays), which do not require particles to move energy.

How can we compare the ability of an object to absorb radiant energy based on color and texture?

Dark colors (like black) absorb more radiant energy, while light colors (like white or silver) absorb less and reflect more energy. Rough or dull surfaces absorb more energy, while smooth or shiny surfaces reflect more and absorb less. Therefore, black and rough surfaces absorb the most heat, and white and shiny surfaces absorb the least heat.

List forms of radiant energy.

Forms of radiant energy include electromagnetic waves, microwaves, and X-rays. These are all part of the electromagnetic spectrum and can transfer energy through space.

Describe technologies used to reduce thermal energy flow into and out of buildings.

Technologies to reduce thermal energy flow into and out of buildings include insulation placed in walls, roofs, and floors to slow down heat flow,