Basic Science and Technology - Junior Secondary 2 - Condensation and sublimation

TERM: 2^ND TERM

WEEK: 10

CLASS: Junior Secondary School 2

AGE: 13 years

DURATION: 40 minutes each for 2 periods

DATE:

SUBJECT: Basic Science

TOPIC: Condensation and Sublimation

SPECIFIC OBJECTIVES: At the end of the lesson, the learners should be able to

1. ) Explain condensation and sublimation using kinetic theory
2. ) Explain cloud, mist and fog

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, story-telling, videos from source

INSTRUCTIONAL MATERIALS: Recommended Basic Science textbooks for Junior Secondary School 2

INSTRUCTIONAL PROCEDURES: PERIOD 1-2:

NOTE

CONDENSATION AND SUBLIMATION

Condensation:

• Condensation is the process in which a gas changes into a liquid when it cools down. According to kinetic theory, gas particles have high energy and move quickly in random directions. When the temperature drops, the gas particles lose energy, slow down, and come closer together. As a result, they form bonds, and the gas becomes a liquid.
• For example, when steam (water vapor) cools down on a cold surface, it condenses to form water droplets.

Sublimation:

• Sublimation is the process in which a solid changes directly into a gas without passing through the liquid phase. Kinetic theory explains that, in the solid state, particles are tightly packed and vibrate in place. When enough heat is added, the particles gain enough energy to overcome the forces that hold them together, and they escape directly into the gas phase. An example of sublimation is the transformation of dry ice (solid carbon dioxide) into carbon dioxide gas without becoming a liquid.

Clouds, Mist, and Fog

Clouds:

• Clouds are collections of tiny water droplets or ice crystals suspended in the atmosphere. They form when warm, moist air rises and cools down. As the air cools, the water vapor in the air condenses into tiny droplets, which group together to form clouds. The process is related to condensation, as the water vapor turns back into liquid when cooled.

Mist:

• Mist is similar to fog but is typically less dense. It occurs when tiny water droplets are suspended in the air, often due to cooling air near the ground. Mist usually forms in the morning when air temperatures drop and the moisture in the air condenses into small droplets that create a hazy appearance. It is generally less obstructive to visibility than fog.

Fog:

• Fog is a dense collection of water droplets suspended in the air near the Earth's surface, which significantly reduces visibility. It forms when the air temperature drops to the dew point, causing the water vapor to condense. Fog is essentially a ground-level cloud. It forms when the air becomes saturated with moisture, often in cool, calm conditions with high humidity

EVALUATION:

1. How does the kinetic theory explain the process of condensation?
2. What are the key differences between sublimation and other phase transitions like melting or freezing?
3. What factors influence the formation of clouds, and how do they relate to kinetic theory?
4. Explain why fog and mist are both forms of suspended water droplets but differ in terms of visibility.
5. Using kinetic theory, describe why evaporation occurs faster on a hot day than on a cold day.

CLASSWORK: As in evaluation

CONCLUSION: The teacher marks their books and commends them positively