Class 9 Science- Chapter 1- Matter In Our Surroundings – Activity 1.12: Heating and Observing the Melting of Ice and Boiling of Water

Activity 1.12: Heating and Observing the Melting of Ice and Boiling of Water

Objective

To study the changes in states of matter by heating ice to observe its melting (solid to liquid) and boiling water to observe its vaporization (liquid to gas).

Materials Needed

• 150 g of ice.
• A beaker.
• A thermometer.
• A heat source (like a burner).
• A glass rod for stirring.

Steps to Perform the Activity

1. Melting of Ice:
   • Place 150 g of ice in a beaker.
   • Suspend the thermometer in the beaker so that its bulb touches the ice.
   • Note the initial temperature of the ice.
   • Start heating the beaker on a low flame. Observe and record the temperature when the ice begins to melt.
   • Continue heating until all the ice converts into water. Note the temperature during this process.
2. Boiling of Water:
   • After the ice has melted, stir the water gently using the glass rod.
   • Continue heating and note the temperature at which the water starts boiling.
   • Observe the formation of steam (gas state) as the water boils.

Observations

• Melting of Ice:
  • The temperature remains constant at 0°C (273 K) while the ice melts, even though heat is being supplied.
  • This is due to the absorption of latent heat of fusion, which helps overcome the forces holding the particles in a fixed position.
• Boiling of Water:
  • The temperature of the water remains constant at 100°C (373 K) during boiling.
  • The absorbed heat is used to convert water into steam, known as the latent heat of vaporization.

Also Check – Chapter 1 -MATTER IN OUR SURROUNDINGS -Class 9 – Simplified notes

Concepts Behind the Activity

1. Melting Point and Latent Heat of Fusion:
   • The melting point is the temperature at which a solid changes to a liquid.
   • During melting, heat energy is used to overcome the forces of attraction between particles, allowing them to move freely.
   • This energy is absorbed without raising the temperature and is called the latent heat of fusion.
2. Boiling Point and Latent Heat of Vaporization:
   • The boiling point is the temperature at which a liquid changes into gas.
   • During boiling, particles absorb energy to break free from the liquid and move independently as gas.
   • The absorbed energy without a temperature change is called the latent heat of vaporization.
3. Energy and Particle Motion:
   • As heat is supplied, the kinetic energy of the particles increases.
   • In melting, particles gain enough energy to break out of their fixed positions.
   • In boiling, particles gain energy to overcome intermolecular forces and move freely as gas.

Learning Outcome

1. Change of State:
   Matter changes from one state to another (solid to liquid, liquid to gas) with the application of heat.
2. Role of Heat Energy:
   Heat energy is crucial for changing the state of matter by increasing particle motion and overcoming intermolecular forces.
3. Latent Heat:
   The concept of latent heat explains why the temperature remains constant during melting and boiling, despite continuous heating.

Applications

1. Understanding the role of latent heat in natural phenomena like melting icebergs and evaporation of water bodies.
2. Explaining industrial processes such as the use of steam for energy production.
3. Designing cooling systems that utilize the principle of latent heat.

Intext and additional Question Answers on Activity 1.12: Heating and Observing the Melting of Ice and Boiling of Water

Question 1: What happens to the temperature when ice starts melting?
The temperature remains constant at 0°C as the ice absorbs latent heat of fusion. This energy is used to break the bonds holding the particles in a fixed structure, turning the solid into a liquid.

Question 2: What happens to the temperature when water starts boiling?
The temperature remains constant at 100°C as the water absorbs latent heat of vaporization. This energy allows the liquid particles to overcome intermolecular forces and become gas.

Additional Question: Why is latent heat important during state changes?
Latent heat is the energy required to change the state of matter without changing its temperature. It is essential for breaking intermolecular forces during melting, boiling, or sublimation.

Conclusion

This activity demonstrates that heat energy causes a change in the state of matter without a temperature rise during the process. The melting of ice and the boiling of water are excellent examples of how energy influences the behavior of particles, resulting in state changes. This understanding is fundamental in physical science and its applications in daily life.