Grade 9
  1. Mechanics  1.1. Motion  1.1.1. Types of motion  1.1.2. Distance and displacement  1.1.3. Speed and Velocity  1.1.4. Acceleration  1.1.5. Graphical representation of motion  1.1.6. Equations of motion  1.1.7. Uniform and non-uniform motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Relative speed  1.1.10. Circular motion  1.2. Laws of force and motion  1.2.1. The concept of force  1.2.2. newton's first law of motion  1.2.3. Newton's second law of motion  1.2.4. Newton's third law of motion  1.2.5. Inertia and types of inertia  1.2.6. Motion  1.2.7. Conservation of momentum  1.2.8. Application of Newton's laws in daily life  1.2.9. Types of Forces (Contact and Non-Contact)  1.2.10. Friction and its effects  1.3. Gravitational force  1.3.1. Newton's law of universal gravitation  1.3.2. Importance of Gravitational Force  1.3.3. Acceleration due to gravity  1.3.4. Free fall and weightlessness  1.3.5. Mass and weight  1.3.6. Variation of g with height and depth  1.3.7. Kepler's laws of planetary motion  1.3.8. Satellites and their orbits  1.4. Work, Energy and Power  1.4.1. Concept of work  1.4.2. Positive and negative actions  1.4.3. Work done by constant and variable force  1.4.4. Energy and its forms  1.4.5. Kinetic energy and potential energy  1.4.6. Law of conservation of energy  1.4.8. Commercial unit of energy  1.4.9. Work–energy theorem  1.5. Simple machines  1.5.1. Types of simple machines  1.5.2. Mechanical advantage  1.5.3. Machine efficiency  1.5.4. Levers and their types  1.5.5. Pulleys and Inclined Planes  1.5.6. Gears and their uses
  2. Properties of matter  2.1. States of matter  2.1.1. Solids, liquids and gases  2.1.2. Properties of different states of matter  2.1.3. Change in state of matter  2.1.4. Plasma and Bose–Einstein condensate  2.2. Density and pressure  2.2.1. Concept of density and relative density  2.2.2. Pressure in solids, liquids and gases  2.2.3. Pascal's law and its applications  2.2.4. Atmospheric pressure and its variations  2.2.5. Surface tension and capillarity  2.3. Buoyancy and Archimedes' principle  2.3.1. Buoyant force  2.3.2. Archimedes principle  2.3.3. Applications of Archimedes' Principle  2.3.4. floating and sinking objects  2.3.5. Theory of Flotation and Archimedes' Principle
  3. Heat and Thermodynamics  3.1. Temperature and heat  3.1.1. Concept of heat and temperature  3.1.2. Temperature measurement  3.1.3. Temperature scales  3.2. Heat transfer  3.2.1. Conduction of heat  3.2.2. Convection of heat  3.2.3. heat radiation  3.2.4. Applications of heat transfer  3.2.5. Thermal conductivity  3.3. Thermal expansion  3.3.1. Expansion of solids, liquids and gases  3.3.2. Abnormal expansion of water  3.3.3. Applications of Thermal Expansion  3.4. Specific heat capacity and latent heat  3.4.1. Concept of specific heat capacity  3.4.2. Measurement and applications of specific heat  3.4.3. Latent heat of fusion and vaporization  3.4.4. Heat Engines and Efficiency
  4. Waves and sound  4.1. Waves and their types  4.1.1. Mechanical and electromagnetic waves  4.1.2. Longitudinal and Transverse Waves  4.1.3. Properties of Waves  4.1.4. Wavelength, frequency and speed of the wave  4.1.5. Superimposition of waves  4.2. Sound waves  4.2.1. Nature and transmission of sound  4.2.2. Speed of sound in different mediums  4.2.3. Reflection of sound and echo  4.2.4. Sonar and ultrasound  4.2.5. Resonance and pulsation  4.3. Sound characteristics  4.3.1. Intensity, loudness and quality of sound  4.3.2. Doppler effect in sound
  5. Lighting and Optics  5.1. Reflection of light  5.1.1. Laws of reflection  5.1.2. Reflection from a plane mirror  5.1.3. Reflection from a spherical mirror  5.1.4. Image formation by concave and convex mirrors  5.1.5. Applications of Reflection  5.2. Refraction of light  5.2.1. Laws of refraction  5.2.2. Refractive index  5.2.3. Refraction through a glass slab  5.2.4. Refraction in water and air  5.2.5. Lenses and their types  5.2.6. Image formation by convex and concave lenses  5.2.7. Total internal reflection and its applications  5.3. Dispersion and scattering of light  5.3.1. Spectrum of white light  5.3.2. Prisms and Dispersion  5.3.3. Tyndall effect and blue sky
  6. Electricity and Magnetism  6.1. Electric charge and static electricity  6.1.1. The concept of electric charge  6.1.2. Charging by friction, contact and induction  6.1.3. Electroscope and its working  6.2. Current Electricity  6.2.1. The concept of electric current  6.2.2. Ohm's Law and Resistance  6.2.3. Factors affecting resistance  6.2.4. Series and Parallel Circuits  6.2.5. Heating effect of electric current  6.2.6. Electric power and energy  6.3. Magnetism  6.3.1. Natural and artificial magnets  6.3.2. Properties of magnets  6.3.3. Earth's magnetism  6.3.4. Magnetic field and field lines  6.3.5. Electromagnets and their applications
  7. Modern Physics  7.1. structure of the atom  7.1.1. Atomic Structure and Subatomic Particles  7.1.2. Electrons, Protons, and Neutrons  7.1.3. Rutherford and Bohr model  7.2. Radioactivity  7.2.1. Types of radioactive emissions  7.2.2. Half-life and radioactive decay  7.2.3. Uses and Hazards of Radioactivity
  8. Space science and astronomy  8.1. The universe and its components  8.1.1. Stars and galaxies  8.1.2. Planets and Solar System  8.2. Satellites  8.2.1. Natural and artificial satellites  8.2.2. Use of satellites

Grade 9 → Heat and Thermodynamics ↓


Specific heat capacity and latent heat


Heat and thermodynamics is a fascinating field of physics that allows us to understand the principles of heat energy transfer and its effects. In particular, we delve into two very important concepts: specific heat capacity and latent heat. Understanding these concepts will help us explain how substances react to heat, how they absorb or release energy when they change state, and much more.

Specific heat capacity

Specific heat capacity, often called specific heat, is a property that tells how much heat energy is needed to change the temperature of a substance. It is defined as the amount of heat needed to raise the temperature of one kilogram of a substance by one degree Celsius (or one Kelvin).

Formula for specific heat capacity

The formula for specific heat capacity is given as:

        Q = mcΔT

Where:

  • Q is the heat energy absorbed or released (in joules, J)
  • m is the mass of the substance (in kilograms)
  • c is the specific heat capacity (in joules per kilogram per degree Celsius, J/(kg°C))
  • ΔT is the change in temperature (in degrees Celsius or Kelvin)

Example: heating water

Suppose we want to heat 2 kg of water from 20°C to 100°C. The specific heat capacity of water is about 4,186 J/(kg°C). We can use the formula to find out how much heat is needed:

        Q = mcΔT
Q = 2 kg * 4,186 J/(kg°C) * (100°C - 20°C)
Q = 2 * 4,186 * 80
Q = 669,760 J

Therefore, 669,760 joules of heat energy are required to heat the water.

Understanding specific heat through pictures

Iron (low specific heat) Water (high specific heat)

In the SVG illustration above, imagine two bars that represent different substances. The red bar represents a substance like water that has a very high specific heat capacity, meaning it requires a lot of heat energy to change its temperature. In contrast, the blue bar represents a substance like iron that has a low specific heat capacity, meaning it heats up quickly with less heat energy.

Latent heat

Latent heat is another essential concept in thermodynamics. It is the heat energy needed to change the state of a substance without changing its temperature. This means that even if you provide heat to a substance, when it changes state, such as from solid to liquid or liquid to gas, its temperature will remain constant.

Types of latent heat

There are mainly two types of latent heat:

  • Latent heat of fusion: It is the heat energy required to change a substance from solid to liquid or vice versa at constant temperature.
  • Latent heat of vaporization: It refers to the thermal energy required to convert a liquid into a gas or vice versa without any change in temperature.

Formula for latent heat

The formula to calculate latent heat is:

        Q = mL

Where:

  • Q is the heat energy absorbed or released (in joules, J)
  • m is the mass of the substance (in kilograms)
  • L is the specific latent heat (in joules per kilogram, J/kg)

Example: melting ice

Suppose you have 1 kg of ice at 0°C and you want to melt it completely at the same temperature to form water. The specific latent heat of fusion for ice is about 334,000 J/kg. The heat required to melt the ice is:

        Q = mL
Q = 1 kg * 334,000 J/kg
Q = 334,000 J

Therefore, 334,000 joules of energy are required to convert 1 kilogram of ice at 0°C into water at 0°C.

Understanding latent heat through pictures

snow melting Water

In the diagram above, as the ice receives heat, it begins to melt into water at a constant temperature (shown by the dashed line). Even though heat is still being applied, the temperature does not increase until the phase change is complete.

Conclusion

Understanding specific heat capacity and latent heat helps us explain and predict how different substances absorb and release heat. It helps us understand energy transformations during heating and cooling processes and provides information about how energy is conserved during phase changes. Whether you're heating a pot of water or watching ice melt on a hot summer day, these concepts reveal the invisible dance of heat and energy in everyday life.


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Specific heat capacity and latent heat

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