Table of Contents
Activity 1.14: Exploring Evaporation Rates Under Different Conditions
Objective
To observe how various factors like wind, surface area, temperature, and humidity affect the rate of evaporation.
Materials Needed
- 5 mL of water.
- A test tube.
- An open china dish.
- A window or a fan.
- A cupboard or closed space.
- A rainy day for comparison.
Steps to Perform the Activity
Initial Setup:
- Take 5 mL of water in a test tube and place it near a window or under a fan.
- Pour another 5 mL of water into an open china dish and place it in the same area.
Evaporation in Different Conditions:
- Place the test tube and china dish in different environments:
- Near a window or under a fan for faster airflow.
- In a cupboard or enclosed space with still air.
- Repeat the same steps on a rainy day.
Observations:
- Measure the time taken for water to evaporate in each scenario.
Observations
- Under a Fan or Near a Window:
Water evaporates quickly because increased airflow carries away water molecules, reducing humidity. - In a Cupboard or Closed Space:
Evaporation is slower due to stagnant air and reduced airflow. - On a Rainy Day:
Evaporation slows down significantly because of high humidity in the air, which reduces the air’s capacity to absorb more water vapor.
Also Check – Chapter 1 -MATTER IN OUR SURROUNDINGS -Class 9 – Simplified notes
Concepts Behind the Activity
Evaporation is a Surface Phenomenon:
- Evaporation occurs at the surface of a liquid, where particles with higher kinetic energy escape into the air as vapor.
Factors Affecting Evaporation:
- Surface Area: Larger surface areas expose more liquid to air, increasing evaporation.
- Temperature: Higher temperatures provide more energy to particles, increasing their chances of escaping as vapor.
- Humidity: High humidity slows evaporation as the air already contains a lot of water vapor.
- Wind Speed: Faster winds remove water vapor from the surface, increasing the rate of evaporation.
Learning Outcomes
Effect of Surroundings on Evaporation:
The activity demonstrates how environmental factors influence the speed of evaporation.
Practical Understanding of Evaporation:
- Clothes dry faster on sunny or windy days because heat and airflow speed up evaporation.
- Humid days slow down the drying process as the air is saturated with water vapor.
Applications of Evaporation:
- Cooling effects, such as perspiration, where evaporation of sweat cools the body.
- Industrial processes like salt production, where seawater is evaporated in large open pans.
Applications of States of Matter
- Everyday activities like drying clothes, sweating, and cooking involve evaporation.
- Industrial uses include distillation and production of dried goods.
- Managing humidity in indoor spaces to control evaporation rates.
Intext and additional Question Answers on Activity 1.14: Exploring Evaporation Rates Under Different Conditions
Question 1: What do you observe when camphor is heated in a china dish?
Camphor changes directly from a solid to a gas, forming white vapors without passing through the liquid state. It leaves no residue in the dish.
Question 2: What do you infer about sublimation from this activity?
Sublimation is the process where certain solids directly transition to a gaseous state without becoming liquid. This is possible due to the weak intermolecular forces in such solids.
Additional Question: Can sublimation occur in everyday items like naphthalene balls?
Yes, naphthalene balls used to repel insects sublimate over time, disappearing as their solid particles turn into gas.
Conclusion
This activity illustrates that evaporation depends on surface area, temperature, humidity, and airflow. Understanding these factors helps explain common phenomena like drying clothes and cooling through evaporation, making it a vital concept in science and everyday life.
