Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Thermal physics → Thermal properties of matter ↓


Boiling and Melting Point


In thermal physics, understanding the concepts of boiling point and melting point is fundamental to understanding how substances transition between different states of matter. When we explore these concepts, we delve into the thermal properties of matter, which are important for a variety of applications in daily life, science, and industry.

Introduction to thermal properties

Matter exists in different states – solid, liquid and gas. These states are determined by the temperature and pressure conditions. Thermal properties of matter are the main characteristics that determine how a substance reacts to changes in heat. The two important concepts we are focusing on here are: boiling point and melting point of substances.

Understanding the states of matter

Let us begin by briefly discussing the three states of matter:

  • Solid: The molecules are tightly packed in a definite arrangement, which gives the solid a definite shape and volume.
  • Liquids: The molecules are closely packed together, but they can move freely, allowing liquids to take the shape of their container, and their volume remains constant.
  • Gas: Molecules are far apart and move around freely, allowing gases to fill any shape or volume.

Melting point

The melting point is the temperature at which a solid becomes a liquid. At the melting point, the solid and liquid phases of a substance coexist in equilibrium. Melting is an important physical change that occurs when enough heat is applied to overcome the forces holding particles in the solid structure.

Melting process

As we increase the temperature of a solid substance, its particles vibrate with more energy. When the temperature reaches the melting point, these vibrations are so energetic that they break the fixed positions of the particles in the solid structure, causing it to turn into a liquid. The temperature at which this happens is the specific melting point of the substance. For example:

Water (H2O): Melting Point = 0°C or 32°F

Common substances and their melting points:

SubstanceMelting point (°C)
Ice (water)0
Iron1538
Gold1064
Copper1085

Factors affecting melting point

The melting point is not a fixed number and can be affected by a variety of factors:

  1. Impurities: Adding impurities to a substance can lower its melting point. This is called melting point depression. For example, adding salt to snow lowers the melting point of snow, which is why it is used to melt ice on roads.
  2. Pressure: For most substances, increasing the pressure has little effect on the melting point. However, in some cases, such as ice, increasing the pressure can lower the melting point. 
    Clausius-Clapeyron Relation: dp/dT = L / (T(Vm,l - Vm,s))
    Where:
    • dp/dT is the change in pressure with temperature
    • L is the latent heat
    • T is the temperature
    • VM,l and VM,s are the molar volumes of liquid and solid, respectively

Boiling point

The boiling point is the temperature at which a liquid turns into a gas. At this point, the vapor pressure of the liquid is equal to the atmospheric pressure surrounding it, causing the liquid to form vapor bubbles and convert to the gas phase.

Boiling process

When heat is applied to a liquid, its particles gain energy and move faster. When the particles have enough energy to overcome atmospheric pressure and form bubbles, the liquid reaches its boiling point. For example:

Water (H2O): Boiling Point = 100°C or 212°F at 1 atmospheric pressure

Common substances and their boiling points:

SubstanceBoiling point (°C)
Water100
Iron2862
Gold2856
Copper2562

Factors affecting boiling point

Several factors can affect the boiling point of a liquid:

  1. Pressure: The boiling point of a liquid decreases when the external pressure is low. This is why water boils at a lower temperature at higher altitudes due to the lower atmospheric pressure.
  2. Impurities: The presence of impurities such as salt can increase the boiling point of a liquid. This is known as boiling point elevation. 
    Boiling point elevation formula: ΔTb = iKbm
    Where:
    • ΔTb is the boiling point elevation
    • i is the van 't Hoff factor
    • Kb is the ebullioscopic constant
    • m is the molality of the solution

Comparison between boiling point and melting point

Both boiling point and melting point are intrinsic properties of substances that represent transitions between states of matter.

  • The melting point indicates the change from solid to liquid.
  • The boiling point indicates the transition from liquid to gas.

Both points are affected by changes in pressure and the presence of impurities. However, it is important to note that the role of pressure is more pronounced in boiling points than in melting points.

Phase diagram

To better understand transitions between different states of matter, phase diagrams are invaluable tools. These diagrams depict situations in which different phases exist and coexist in equilibrium.

Consider a simple phase diagram for water:

Temperature Pressure Solid Liquid Gas Triple Point

Practical example

Let us consider some real examples to understand the application of boiling point and melting point:

Kitchen scene

When you're cooking pasta, you need to boil the water so that the pasta will cook properly. At sea level, water boils at 100°C (212°F). However, if you're cooking pasta in a high-altitude city like Denver, the boiling point will be lower due to the lower atmospheric pressure.

Industrial applications

In industry, control of boiling and melting points is very important. For example, crude oil needs to be boiled at different temperatures to separate its components in order to refine it.

Metallurgy

In the production of metals, it is important to know the melting point of the various components. In making steel, iron (melting point 1538°C) is melted and mixed with other elements to produce various steel grades.

Conclusion

Understanding the boiling point and melting point of substances is essential as it affects a variety of areas, from cooking in daily life to high-level scientific research and industrial processes. By studying these thermal properties, we can better understand the underlying principles governing the state changes of matter. These principles underline the importance of thermal physics in explaining natural phenomena and developing technological solutions.


Grade 10 → 3.3.3


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Boiling and Melting Point

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