heat temperature and internal energy class 9 physics | FBISE | KPK textbook board

Welcome to my channel ''Lectures of Physics". This channel contains lectures of physics on class 9th, 10th, 11th and 12th in easy way. This video is about heat temperature and internal energy class 9 physics FBISE KPK textbook board. Temperature, internal energy, and heat are three closely related but distinct physical quantities that describe the energy and thermal behavior of matter. Understanding their differences is very important in physics because they explain how energy is stored, transferred, and measured in different systems. Temperature is a measure of the degree of hotness or coldness of a body. It tells us how hot or cold something is but does not directly tell us the total amount of energy it possesses. On the microscopic level, temperature is defined as the average kinetic energy of the particles of a substance. In solids, liquids, and gases, particles are constantly moving — vibrating, rotating, or translating. The faster the particles move, the higher the temperature. For example, boiling water has faster-moving particles than ice, which means its temperature is higher. Temperature is measured in degrees Celsius (°C), Kelvin (K), or Fahrenheit (°F). The Kelvin scale is used in scientific work because it starts from absolute zero, the lowest possible temperature where molecular motion almost stops. Internal energy is the total energy contained within a system due to the motion and arrangement of its particles. It includes both kinetic energy (from particle motion) and potential energy (from forces between particles). Therefore, while temperature only measures the average kinetic energy, internal energy represents the sum of all microscopic energies inside the substance. For example, if you have two cups of water at the same temperature, the one with more mass has greater internal energy because it contains more particles and therefore more total energy. Internal energy is a state function—it depends only on the state of the system (its temperature, pressure, and volume), not on how it reached that state. Heat, on the other hand, is the energy in transit between bodies due to a temperature difference. When two objects at different temperatures come into contact, heat flows from the hotter body to the colder one until both reach the same temperature — a state called thermal equilibrium. Heat always flows spontaneously from hot to cold objects, never the reverse (according to the second law of thermodynamics). Heat is not a substance; it is a form of energy transfer. Once transferred, it changes the internal energy of a substance — either by raising its temperature, changing its state (like melting or boiling), or doing both. The SI unit of heat is the joule (J), the same as energy, though it is sometimes measured in calories. To summarize: Temperature measures the average kinetic energy of particles. Internal energy is the total microscopic energy (kinetic + potential) of all particles. Heat is the transfer of energy from one body to another due to a temperature difference. For example, when you heat water on a stove, heat energy flows from the flame to the pot and then to the water. This energy increases the internal energy of the water, causing its temperature to rise. Thus, while heat causes a change in internal energy, temperature tells us how fast the particles are moving on average. These three concepts together explain how energy moves and changes form in all thermal processes. In daily life, we often confuse temperature, heat, and internal energy, but scientifically they are very different. Temperature tells how hot or cold something feels, internal energy tells how much total energy is stored inside, and heat tells how energy is moving from one place to another. For instance, a large bucket of warm water can have more internal energy than a small cup of boiling water because it contains more particles, even though its temperature is lower. When heat is added to a system, it can either raise the temperature or cause a phase change like melting or boiling. For more amazing lectures please subscribe our channel.    • class 9 physics chapter 7 | Properties of ...      • class 9 physics chapter 6 | Work  and ener...      • class 9 physics chapter 5 | gravitation  |...   For more lectures of class 9th visit link below    • class 9 physics chapter 1 | physical quant...   For more lectures of class 10th visit link    • class 10 physics chapter 10 | simple harmo...   For more lectures of class 11th visit link    • Physics Class 11   #lecturesofphysics #heat #temperature #internalenergy #physics #inter physics #matric level physics #school level physics #fsc physics