heat conduction

what is conduction

Conduction is the transfer of thermal energy between particles of matter that are touching. Thermal energy is the total kinetic energy of moving particles of matter, and the transfer of thermal energy is called heat. Conduction is one of three ways that thermal energy can be transferred (the other ways are convection and thermal radiation). Thermal energy is always transferred from matter with a higher temperature to matter with a lower temperature.

pass it on

To understand how conduction works, you need to think about the tiny particles that make up matter. The particles of all matter are in constant random motion, but the particles of warmer matter have more energy and move more quickly than the particles of cooler matter. When particles of warmer matter collide with particles of cooler matter, they transfer some of their thermal energy to the cooler particles. From particle to particle, like dominoes falling, thermal energy moves through matter. In the opening photo above, conduction occurs between particles of metal in the cookie sheet and anything cooler that comes into contact with ithopefully, not someones bare hands!

examples of conduction

The cookie sheet in the opening image transfers thermal energy to the cookies and helps them bake. There are many other common examples of conduction. The Figure 1.1 shows a few situations in which thermal energy is transferred in this way. Q: How is thermal energy transferred in each of the situations pictured in the Figure 1.1? A: Thermal energy is transferred by conduction from the hot iron to the shirt, from the hot cup to the hand holding it, from the flame of the camp stove to the bottom of the pot as well as from the bottom of the pot to the food inside, and from the feet to the snow. The shirt, hand, pot, food, and snow become warmer because of the transferred energy. Because the feet lose thermal energy, they feel colder.

textbook_image

instructional diagrams

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questions

thermal energy can be transferred by

a) conduction.

b) convection.

c) radiation.

-->  d) all of the above

thermal energy is always transferred

a) from a cooler to warmer object.

-->  b) from a warmer to cooler object.

c) between objects that are the same temperature.

d) two of the above

only the particles of warm matter are in constant random motion.

a. true

-->  b. false

all of the following are examples of heat conduction except

a) pressing a shirt with a hot iron.

b) warming your hands by holding a cup of hot chocolate.

-->  c) warming your hands over a campfire.

d) heating soup in a pan on a stovetop.

if you hold an ice cube in your hand, your hand feels really cold because

a) cold is transferred to your hand from the ice cube.

-->  b) thermal energy is transferred from your hand to the ice cube.

c) thermal energy is transferred to your hand from the ice cube.

d) none of the above

conduction occurs when particles of matter collide.

-->  a. true

b. false

diagram questions

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