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thermal expansion of liquids class 9

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 thermal expansion of liquids class 9 physics chapter 8 thermal properties of matter. The main reason for the thermal expansion of liquids is the increase in the kinetic energy of the molecules. When a liquid is heated, its molecules move faster and their average separation increases. This increased movement makes the liquid expand. Since the amount of expansion depends on how much the temperature rises, we can say that thermal expansion of liquids is directly proportional to the rise in temperature. However, not all liquids expand equally for the same rise in temperature. Different liquids have different degrees of thermal expansion. For example, alcohol expands more than water when both are heated through the same temperature difference. Types of Thermal Expansion in Liquids In solids, we study three types of expansion — linear, areal, and cubical. But in liquids, we only deal with volume or cubical expansion, because liquids do not have a fixed shape. They take the shape of the container, so only the change in volume can be observed. Therefore, thermal expansion of liquids mainly refers to cubical or volume expansion. Apparent and Real Expansion of Liquids When we heat a liquid in a container, both the container and the liquid expand. The expansion we observe directly is called apparent expansion. But since the container also expands, the actual expansion of the liquid is a bit greater than what we see. The actual or total expansion of the liquid itself is called real expansion. Apparent Expansion: The observed increase in the volume of a liquid when heated in a container. Real Expansion: The true increase in the volume of the liquid itself if the container did not expand. Mathematically, Real Expansion = Apparent Expansion + Expansion of Container For example, when we heat water in a glass flask, both the glass and the water expand. The rise in water level inside the flask shows apparent expansion, but the real expansion is actually greater than that, because the flask itself expands outward. Anomalous Expansion of Water Water shows an unusual behavior between 0°C and 4°C, called anomalous expansion of water. When water is cooled from 4°C to 0°C, instead of contracting, it expands. This means that the volume of water decreases as it is cooled down to 4°C, but below 4°C, the volume starts increasing again. This is called the anomalous expansion of water. It is an important phenomenon in nature because it helps aquatic life survive in cold climates, as ice floats on the surface of water. Applications of Thermal Expansion of Liquids Thermometers: The working of mercury and alcohol thermometers depends on the thermal expansion of liquids. The liquid expands when the temperature rises and contracts when it falls. Industrial Uses: Knowledge of thermal expansion of liquids is important in designing containers, boilers, and storage tanks, to allow space for expansion. Nature: The anomalous expansion of water helps maintain aquatic life in winter by preventing ponds and lakes from freezing completely. Conclusion In summary, the thermal expansion of liquids is an important physical property that occurs because of the increased movement of molecules when heated. It results in an increase in volume with rise in temperature. The concept of real and apparent expansion, as well as the anomalous expansion of water, are key ideas in understanding the behavior of liquids under temperature changes. This topic not only explains daily life phenomena but also forms the basis for instruments like thermometers, which rely on the predictable thermal expansion of liquids. For more amazing lectures please subscribe our channel.    • Class 9th physics chapter 8 thermal proper...      • Properties of matter class 9 physics      • Work  and energy class 9 physics      • Gravitation class 9 physics   For more lectures of class 9th visit link below    • class 9 physics chapter 1 physical quantit...   For more lectures of class 10th visit link    • Physics Class 10th   For more lectures of class 11th visit link    • Physics Class 11   For more lectures of class 12th visit link    • Physics Class 12th   #lecturesofphysics #thermalexpansion #thermalexpansionofliquids #class9physics #physics #inter physics #matric level physics #school level physics #fsc physics