1. shivering to keep warm
   heat transfer
2. insulation on an airplane

Thermodynamics refers to heat transfer, where heat naturally moves to a cooler place to create an even temperature.

1. movement of atoms
   radiation from the sun
2. lighting a fire

When atoms move they create heat.

1. sound
   speed
2. size

The speed the atoms are moving at determines how much heat is produced. The faster they go, the more heat is produced.

1. absolute zero
   zero
2. at freezing point

At the temperature of absolute zero there is no atomic movement.

1. colliding particles
   colliding molecules
2. colliding atoms

When atoms collide they transfer heat. It's a bit like billiard balls colliding. When one ball hits another, the second ball picks up momentum from the first ball.

1. transfer of heat
   transfer of cold
2. transfer of electricity

Conduction refers to the transfer of heat through atom collisions.

1. plastic
   wood
2. metal

Metal is a good conductor, which is why, if you heat the end of a metal rod, the other end will quickly become hot.

1. vibration
   light
2. absorption

Infrared radiation is a form of light, but it is outside the spectrum visible to the human eye.

1. black
   white
2. blue

Black objects best absorb infrared. The absorption of infrared causes an increase in atomic motion, leading to a rise in temperature. So if you want to stay cool, it's best to wear light-colored clothing!

1. a quarter
   a half
2. all

About half of the sun's energy that makes it to Earth is infrared radiation, which we experience as warmth. The rest is visible light.

1. liquids
   gases
2. both of the above

Convection is the cycle of warm particles rising while cooler particles fill their space, heat up, and rise as the cycle continues. Convection affects both liquids and gases since, when these media get warm, the warm particles rise above both.

1. reduce
   balance
2. increase

The purpose of a thermos is to reduce the transfer of heat.

1. insulation
   encapsulation
2. obstruction

A thermos is built based on the principle of insulation.

1. metal
   stone
2. foam

Foam is a good insulator because both the plastic in it and the air trapped in it are poor conductors and because convection cannot take place effectively since air in the foam is broken into tiny bubbles.

1. Foam is hard to come by.
   Heat is sucked away.
2. There are no atoms in a vacuum.

In a vacuum there are almost no atoms, which means there cannot be conduction or convection -- ideal in a thermos. Although it is almost impossible to make a perfect vacuum with zero atoms, a good thermos can get close.

1. shaft
   mirror
2. telescope

Silvered glass acts as a mirror, reflecting infrared radiation away.

1. because the vacuum is not perfect
   because the cap allows heat to escape
2. both of the above

The heat loss in the imperfect vacuum is not significant compared to the heat lost through the cap. Also, the glass meets the walls at the top of the flask , creating a conduction path.

1. It has a sensor inside.
   You can only use it once for hot food.
2. It doesn't know.

It doesn't know -- or care. It stops heat transfer, be it inside or outside the flask.

1. metal
   plastic
2. bubble wrap

Although you might think bubble wrap would help with insulation, you need something sturdy, like metal or plastic, to protect the fragile glass inside.

1. It uses radiators.
   It uses air conditioners.
2. There is no heat, because it's in a vacuum.

A space shuttle generates a lot of heat from its engines and electronics, as well as from solar radiation. Its cargo bay doors are lined with radiators that dissipate the heat. One of the first things astronauts do once they reach orbit is turn on the radiators to cool down the ship.