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 ↓


Temperature and heat


Understanding the concepts of temperature and heat is a fundamental part of physics and is important in various aspects of our daily lives. From knowing how the thermostat works at home to understanding the weather report or even cooking, temperature and heat are always at play.

What is the temperature?

Temperature is a measure of how hot or cold something is. It quantitatively expresses the amount of heat present in a substance or object. Temperature is a scalar physical quantity and is usually measured in degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K).

To get a clearer picture, think about how temperature affects a simple activity like making tea. When water is heated, its temperature rises. You know the water is ready for tea when it reaches a certain temperature, usually around 100 degrees Celsius, where it begins to boil.

Visual example of temperature

100 degrees Celsius

How is temperature measured?

Temperature is usually measured using a device called a thermometer. There are different types of thermometers, such as mercury thermometers and digital thermometers. Each type uses a different method to measure temperature. For example, mercury thermometers use the expansion and contraction of mercury to give a temperature reading.

What is heat?

Heat is a form of energy that is transferred between substances or systems due to a difference in temperature. It flows from a hotter object to a cooler object until both reach the same temperature, which is called thermal equilibrium.

Imagine you have a cup of hot coffee. When you place it on the table, the heat of the coffee slowly transfers to the cold environment. Eventually, the coffee cools down to room temperature.

Heat transfer

Conductivity

Conduction is the process by which heat is transmitted directly through a substance when there is a difference in temperature, without the substance moving. Metal is a good conductor of heat, which is why metal spoons heat up quickly when put into a pot of boiling water.

Convection

Convection is the transfer of heat through fluids (liquids and gases) due to molecular motion. Warm air rising and cool air falling is an example of convection. This principle allows heaters and air conditioners to effectively control room temperature.

Radiation

Radiation is the transfer of heat via electromagnetic waves. Unlike conduction and convection, radiation requires no medium to transfer heat, with the sun's heat reaching Earth through the vacuum of space.

Visual example of heat transfer

conductivity Convection Radiation

Relation between temperature and heat

While temperature is a measure of the average kinetic energy of the particles in a substance, heat refers to the transfer of thermal energy between systems. They are related, but not the same. For example, a large pot of lukewarm water contains more heat than a cup of boiling water, even though the boiling water has a higher temperature.

Specific heat capacity

Specific heat capacity is the amount of heat required to change the temperature of a substance by one degree Celsius. Different substances have different specific heat capacities.

Q = mcΔT

In this formula:

  • Q = heat energy (joules)
  • m = mass (in kilograms)
  • c = specific heat capacity (joule/kg°C)
  • ΔT = Change in temperature (°C)
For example, water has a very high specific heat capacity, meaning it takes a lot of heat to change its temperature.

Practical example

Let's consider heating water. If you have 1 kg of water, and you want to raise its temperature by 20°C, knowing that the specific heat capacity of water is 4,186 J/kg°C, you can calculate the amount of heat needed:

Q = mcΔT = 1kg × 4186 J/kg°C × 20°C = 83,720 J

This means that you need 83,720 joules of energy to heat the water to 20°C.

Conclusion

Understanding temperature and heat is an ongoing journey in the study of thermodynamics. It forms the basis of how energy is transferred and transformed in various systems and processes. This understanding helps us with everything from managing energy consumption in our homes to understanding environmental changes on a global scale.

With these basic concepts, one can explore more complex phenomena, such as the efficiency of heat engines, the behavior of gases, and more.


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Temperature and heat

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