Heat Transfer

What  is the original source of most of the energy that people use?

• By radiation from the Sun.
• By convection from the Sun.
• By radiation from the Earth's core.
• Conduction from Earth's core.

Which best explains how roasting marshmallows happens?

• Heat from the fire is conducted into the marshmallow.
• Heat from the fire is radiated into the marshmallow.
• The coolness of the marshmallow is conducted into the fire.
• The coolness of the marshmallow is radiated into the fire.

Which best describes heat transfer by radiation?

• A slice of bacon frying in a pan.
• A pot on a stove boiling water.
• Cooking a hotdog in a microwave.
• A hot air balloon.

When choosing materials to build a fireplace, why is brick a better choice than metal?

• Brick is a conductor.
• Brick is heat resistant.
• Metal is a conductor.
• Metal is heat resistant.

What enables firemen to enter buildings that are on fire and return from them safely?

• Convection cells keep fire away
• The heat makes the building expand so there is no more room
• Firemen wear heat resistant suits
• They are really fast

Why should space be left at the top of a plastic bottle when filling with water and then freezing?

• Because water expands when frozen.
• Because water contracts when frozen.
• Because plastic contracts when frozen.
• Because plastic expands when frozen.

Which best explains why there are gaps between the concrete sidewalks?

• When it's cold the gaps allow expanding without cracking.
• When it's hot the gaps allow expanding without cracking.
• When it's cold the gaps allow contracting without cracking.
• When it's hot the gaps allow contracting without cracking.

Popcorn is made from corn kernels. What occurs when kernels are heated in the microwave?

• The kernels expand.
• The kernels dissolve.
• The kernels become hard and brittle.
• The kernels stick together to form a ball.

Why does a balloon on top of a water bottle expand when the bottle is placed in hot water?

• Heat causes gases to expand.
• Heat causes gases to contract.
• As air cools, currents flow clockwise.
• As air cools, currents flow counterclockwise.

If you cannot open a jar, why will placing the metal lid under hot water help to loosen the lid?

• Glass contracts when it is heated.
• Metals expand when they are heated.
• Metals are easier to grip when they are warm.
• Hot water reduces friction between metal and glass.