|
Profile
Elizabeth Tan Seok Hui (34) 3B2 This is a physics blog :D  Chapters Chapter 7- Kinetic Model Of Matter Chapter 8- Transfer of Thermal Energy Chapter 9- Thermal Properties of Matter 3B2 Physics Tay Shuying Eileen Chia Lim Ern Huei Dawn Chiam Fu Jinting Samantha Yeap Yap Xin Ying Jovee Gan Deborah Loo Vani Hilary Fong Victoria Lee Amanda Teo Janice Yoong Phyllis Quan Wilma Heng Aiswary 3B1 Physics Sheryl Tan Stephanie Loo Jolene Ek Layout: hearteditorials Codes: -ambulance Icon: biconcave |
Wednesday, September 3, 2008
Thermal Properties of Matter.
1. Heat is the amount of thermal energy that flows from a hotter region to a cooler region. The unit for thermal energy is the JOULE (J) Thermal energy supplied to the water leads to a gain in the internal energy of the water molecules. Internal energy comprises of two components :  -Kinetic Energy (Picture on the right) -Potential En  ergy
Therefore, the kineticc component of internal energy is due to the vibration of the particles. It is directly related to temperature. -The higher the temperature, the more vigorous the vibrations of the particles. The potential component of internal energy is due to the stretching and compressing of the intermolecular bonds as the particles vibrate.
http://www.y  outube.com/watch?v=JAQmIuUoH5U ( Watch)When a solid changes to liquid upon heating, this change of state is called melting. For a pure substance, melting occurs at a definite or constant temperature. -This particular temperature is known as the melting point of the substance. How does a solid melt? The molecules in a solid are held by strong intermolecular bonds. For the solid to melt, these bonds have to be broken. Once the intermolecular bonds are broken, the molecules can now move out of their fixed positions. We say the solid has melted, that is, the change of state from solid to liquid has occured.  Freezing is simply changing a liquid=solid. The reverse process of melting is called solidification- changing from a liquid to a solid. A pure substance will solidify or freeze at a temperature equal to its melting point. For example, water freezes to form ice at 0 degrees. During solidification, the temperature remains constant at the freezing point. Thermal energy is released by the substance. Boiling  When a pure liquid is heated and it changes to a vapour at a fixed or constant temperature, we call this change of state boiling. This particular temperature is known as the boiling point of the substance. The reverse of boiling is condensation. It is the change of state from vapour to liquid when a substance is cooled at the same constant temperature as in boiling. -During boiling, the temperature remains constant at its boiling point. thermal energy is being absorbed by the substance.  ( Click on it to enlarge the picture) Evaporation Evaporation is the change of state from liquid to gas. The different between boiling and evaporation is that evaporation can occur at any temperature. Boiling Evaporation 1. Occurs at fixed temperature 1. Occurs at any temperature 2. quick process 2.Slow process 3.Takes place throughout the liquid 3. Takes place only at the liquid surface. 4.Bubbles are formed in the liquid 4. No bubbles are formed in the liquid 5.Temperature remains constant 5.Temperature may change 6.Thermal energy supplied by an 6.Thermal energy supplied by the surroundings. energy source 
Applications of evaporation   Perfume ( Cooling sensation ) - Wet clothes can dry rather fast.Others include; Your refrigerator at home & even sponging a sick person with fever. Factors affecting the rate of evaporation
|