Sci Chapter 10

How does a vacuum flask minimize heat transfer?

Foam insulation, double slivered glass walls , vacuum layer.

How do solar heaters absorb heat efficiently?

They’re painted black to absorb radiation.

Why are air conditioners installed high up?

Cold air sinks, as it is denser, and cools the room.

How do wool clothes keep us warm?

Wool traps air, a poor conductor of heat.

How does Styrofoam reduce heat loss?

It is a good thermal insulator, as it contains a lot of air which are poor conductors of heat.

Which surfaces reflect radiation best?

Shiny, silver, and smooth surfaces.

Which surfaces absorb and emit radiation best?

Black, dull, rough surfaces.

What affects the rate of radiation?

Temperature, surface area to volume ratio, texture, and color.

Why can radiation happen in space?

It does not need a medium to transfer energy.

What is radiation in heat transfer?

Transfer of thermal energy via electromagnetic radiation, such as infrared radiation, without the aid of a medium.

Give 2 examples of convection in daily life.

Sea breeze (day), Land breeze (night).

What causes convection currents in a fluid?

Differences in density due to heating and cooling.

What are 2 factors affecting conduction of heat?

Type of material and state of matter.

How does heat transfer differ in metals vs non metals?

Metals have free electrons that transfer heat quickly through free electron diffusion while non metals only can transfer heat through particle vibrations

Why are metals good conductors of heat?

They have free electrons that transfer energy quickly through free electron diffusion.

Why is heat conduction fastest in solids?

Particles are closely packed, allowing for more efficient heat energy transfer through vibrations.

What is conduction?

Transfer of thermal energy via particle vibrations without movement of the medium.

Which metal should be placed near the contact point in a heater?

The metal with the higher rate of thermal expansion.

How does a bimetallic strip in a thermostat work?

It bends when heated to open or close an electric circuit.

What is a bimetallic strip?

Two different metals with different expansion rates joined together.

What are key features of a good thermometer?

Easy to read, safe, responsive, sensitive, accurate over temperature range.

How does a rivet work?

Heated and hammered into place, it contracts when cooled and pulls plates together.

How does hot water help loosen a jar lid?

The metal lid expands more than the glass, making it easier to open.

Which state of matter conducts heat the best?

Solids > Liquids > Gases

Which state of matter expands the most when heated?

Gases > Liquids > Solids

Why do pipelines have expansion bends?

To allow for safe expansion of gas or oil pipelines.

What causes bread dough to rise when baking?

Air bubbles expand when heated.

Why can glass crack when hot water is poured into it?

Glass is a poor conductor of heat and expands unevenly.

Why do tiles or pavements pop out in hot weather?

Due to thermal expansion of the concrete or tiles.

What is convection?

Transfer of thermal energy in fluids via circulation of currents that direct the movement of particles in the fluid.

Why are telephone wires strung loosely?

So they don't snap when they contract in cold weather.

Why do bridges have expansion gaps or rollers?

To prevent damage from thermal expansion during hot weather.

Why do railway tracks have expansion gaps?

To allow the metal to expand on hot days without bending or twisting.

What happens to a substance when it is cooled?

It loses heat energy and contracts.

What happens to a substance when it is heated?

It gains heat energy and expands.

How do you convert Kelvin to Celsius?

Subtract 273.15 from the Kelvin value.

What happens at 0 Kelvin?

All molecular motion stops.

What is the SI unit for heat?

Joule (J).

What is the SI unit for temperature?

Kelvin (K)

What is heat?

Heat is the amount of thermal energy possessed by a substance.

What is temperature?

Measure of the hotness of an object