Lesson plan on the Concept of Heat

Objective: Defining Heat

Everyone is familiar with heat but most are unaware of its scientific explanation. Heat is a form of energy that propagates in wave form and brings changes to the state of matter to which it is supplied. When heat is absorbed by a substance in its solid state, the substance becomes liquid form and, on further exposure to heat changes into a gaseous state. When the substance releases this additional energy, or heat, the reverse processes occur.

Instruct the students to recount some of their experiences with heat. (i.e. the sun, a blast from a subway vent, hot sand, boiling water)

Materials:

Ice-cubes

Glass bowl

Burner

Lid

Thermometers

Freezer

Procedure

• Divide the students into small groups and ask them to do the following experiment in which a change of state occurs.
• Direct them to record the changes occurring in the ice cubes and the temperature at which these changes occur.
• Place some ice-cubes in a bowl. Heat the bowl and the ice-cubes become water. Continue heating until the water changes into vapor . Now place the lid over the bowl and water droplets will form in it. Freeze the bowl and ice will form.

Recording the data

Question: How do the ice-cubes change?

Record the temperatures at which these changes occur.

Hypothesis: Allow the students to develop a hypothesis from this data.

Analyzing the data will reveal that these changes occur at particular temperatures.

Objective: How does the matter change states?

In a solid state, molecules are tightly bound together and hence have little freedom. When heat is absorbed, the molecules are raised into loosely held orbits where they have more freedom and the matter turns into its liquid state. As more heat is absorbed, this process continues and the molecules attain sufficient energy to break the bonds and thus enter into gaseous sate. If the molecules come in contact with an object at a lower temperature, they release this surplus energy and return to the more stable and tightly held orbits.

Materials

Glass Bowls

Food Coloring

Hot Water

Cold Water

Procedure:

• Take two beakers and pour cold water into one and hot water into the other.
• Add one or two drops of a food color, (for example red in one and green in the other), into each beaker.

Question: What effect does heat have on the movement of the molecules?

Hypothesis: The heat can influence the movement of the molecules.

Test the hypothesis: In the case of hot water the color merges rapidly, whereas in cold water this merging takes place very slowly.

Analysis and conclusion: Students should arrive at the conclusion that absorption of heat increases the molecules' freedom of movement.

1. What will happen when a bottle of juice is removed from a refrigerator and left at room temperature?.

2. What is the reason behind the formation of clouds?