Atoms and Molecules

What are books made of? What are computers made of? Everything around you is made of atoms and molecules. Molecules are the smallest particle of matter that can exist and still have all the properties of a particular object. But what is the difference between atoms and molecules? Well, atoms are what make up molecules.

Molecules are always moving , but when an object is heated its molecules moves faster and farther apart. When an object is cooled its molecules move slower and closer together. In a solid the molecules are tightly packed together in a fixed position. But when a solid is heated the molecules move farther apart and go from a solid state to a liquid state which is called melting.

In a liquid molecules move faster and more freely than molecules in a solid. When heat is added to the water the molecules move even faster and bump into to one another. Some of the molecules ar pushed out in to space and become a gas. This is called evaporation.

In a gas, the molecules are very far apart and move freely in space. The process of boiling water and changing it quickly into a gas is called rapid evaporation.

What do molecules have to do with heat transfer? Even if it is snow, the more molecules the more heat. For example, an ice sculpture has more heat than a match. Why? Try melting a whole ice sculpture with one match. Which one last longer?

Heat Transfer Quiz

How many types of heat transfer are there?

a. 1

b.3

c.17

This is a picture of what kind of

heat transfer?

a. conduction

b. convection

c. radiation

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If you put a marshmallow directly into the what kind of heat transfer is it?

a. conduction

b. convection

c. radiation

Give an example of convection.

a. meat on hot grill

b. smell of meat cooking

c. heat given of by grill's fire

When you are licking ice cream what causes it to melt?

a. conduction

b. radiation

c. convection

d. both a and b

If you burn yourself what kind of heat transfer is it?

a. pain

b. conduction

c. injury

d. convection

Which was more heat ? A match or an ice sculpture?

a. match

b. ice sculpture

c. they both have the same amount of heat

What kind of heat transfer travels in waves?

a. conduction

b. convection

c. radiation

What is an example of conduction at the movie theater?

a. eating warm popcorn

b. smelling the buttery popcorn

c. burning your tongue on a hotdog

d. both a and c

What is an example of radiation at home?

a. the toilet

b. the radio

c. the microwave

d. the stove

e. all except a

What is an example of convection at the grocery store?

a. touching the frozen food packages

b. smelling the raw fish

c. eating free samples

Answers: 1. b 2. c 3. a 4. b 5. d 6. b 7. b 8. c 9.

Radiation Heat Transfer

The third type of heat transfer is radiation. Radiation is like the sun shining on you on a hot day. Radiation is a form of electromagnetic waves traveling through space. Whether it is radio waves, light waves, or heat waves, they are all forms of radiation. The waves travel through empty space, just like the sun's heat waves, to reach you. Just think, the sun is millions of miles away out in space, yet its heat waves still reach you. All that is because of radiation. Radiation melts everything cold like ice, and ice cream. One example of radiation is UV light. Which, of course, you can obtain naturally obtain from the sun. Another example of radiation is heating lamps that you see in reptile tanks at the pet store. One last example is the microwave which lets out radioactive waves. Radiation is important.

Convection Heat Transfer

Smell those delicious cookies in the oven?  When you are sniffing in is called convection.  Convection is heat transfer through gases or liquid cycle.  Steam cooking is also convection.  The water is heated, gets less dense and rises upward.  In the air it cools and drops back down.  Then it is heated again and thus creates a cycle.  Convection also happens with water.  If  you put a cup on a stove it will heat the water on the bottom and cause it to rises.  Then it will cool and fall back down to the bottom of the cup which will warm up.  Examples of convection are putting your hand over a hot bowl of soup.  

                                                  

Conduction Heat Transfer

Look in the kitchen. See the stove and the pot on it? This is an example of conduction. Conduction is direct heat which is heat directly transferred to the object. Now put two spoons in the pot, metal and wooden. Leave the spoons in the pot for a minute. Which one is warmer? It is the metal spoon. The hot soup in the pot heats up one of the molecules in the metal spoon. The characteristics of the metal cause the molecules to move faster and that heats up other molecules. The characteristics of a wooden spoon cause the molecules to move slower therefore making the it heat up slower. This is conduction because the heat is directly transferred to the spoons.

Some other examples of conduction are when you burn yourself on the stove and when you eat warm popcorn or when you burn your tongue on a hot dog. Ever wonder why you where oven mitts? This is also because of conduction. The pot or tray is to hot to touch so you where it to protect your hands.

Heat Transfer

Do you like popcorn, cookies, frozen pizza, and more.  All these foods are cooked and heated by heat transfer.  You may not notice, but every thing has heat even cold things like snow.  There are three types of heat transfer.  They are conduction, convection, and radiation.