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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
If you only do what you know you can do - you never do very much-Tom Krause quotes. Try and fail, but don't fail to try. -Stephen keggwa quotes. Thats why, everyone go do your physics blog :D Transfer of Thermal Energy. Thermal energy is transferred only when there is a difference in temperature. Thermal energy always flows from a region of higher temperature to a region of lower temperature. Thermal energy is transferred by any of these three processes;
Conduction is the transfer of energy from one molecule to another. This transfer occurs when molecules hit against each other, similar to a game of pool where one moving ball strikes another, causing the second to move. Conduction takes place in solids, liquids, and gases, but works best in materials that have simple molecules that are located close to each other. For example, metal is a better conductor than wood or plastic. Conduction is the process of thermal energy transfer without any flow of the material medium.
Convection is the movement of heat by a liquid such as water or a gas such as air. The liquid or gas moves from one location to another, carrying heat along with it. This movement of a mass of heated water or air is called a current. Convection currents occur only in fluids such as liquids and gases but not in solids. This is because convection involves the bulk movements of the fluid which carry thermal energy with them. For solids, the thermal energy is transferred from one particle to another through vibrations, without any bulk movement of the particles themselves. Convection is the transfer of thermal energy by means of currents in a fluid (liquid of gases)
Heat travels from the sun by a process called radiation. Radiation is the transfer of heat by When infrared rays strike a material, the molecules in that material move faster. In addition to the sun, light bulbs, irons, and toasters radiate heat. When we feel heat around these items, however, we are feeling convection heat (warmed air molecules) rather than radiated heat since the heat waves strike and energize surrounding air molecules. Radiation is the continual emission of infrared waves from the surface of all bodies, transmitted without the aid of a medium. Unlike conduction and convection, radiation does not require a medium for energy transfer. This means that radiation can take place in a vacuum. Factors affecting rate of infrared radiation
Common applications of conduction Uses of good conductors of heat. If thermal energy has to be transferred quickly through a substance, good conductors of heat such as metals are used. Some examples of the uses of metals are:
3.Heat exchanges, such as those used in a large laundry facility, help save energy. Uses of bad conductors of heat (Insulators) Insulators are very useful if we want to minimise loss of thermal energy, or prevent thermal energy from being transferred quickly. Some common uses of insulators are:
END OF CHAPTER 8. Kinetic Model Of Matter Matter is anything occupying space and having mass; it is the material of the universe. Matter is also made out of particles. In room temperature, matter can be in different states of matter, such as Solid, Liquid or Gas. The particles in different states have different properties & arrangements. Solid.
 eo on states of matter; click here! :D An example of particles in a gaseous statewould be the steam in the picture on the right. A pictorial example of particles in a solid state would be the pebbles in the picture on the left. Particles in a liquid state would be the water shown in the picture on the left. AT the microscopic level, all matter is made up of tiny particles called atoms or molecules. These particles are always in continuous motion. This assumption of tiny particles in continuous motion is known as the kinetic model of matter.  From left to right, Solid, Liquid & Gas. Solid - The particles are closely packed together, usually in a regular pattern, resulting in solids having high densities. -The particles vibrate about fixed positions only and are held in positions by very strong intermolecular bonds, which explains why solids have fixed volumes and shapes. Liquid - They are randomly arranged with the particles slightly further apart as compared to that of solids, resulting in liquids having relatively high densities -The particles are free to move about the confined space and have attractive forces between particles., explaining why liquids have fixed volumes but will take the shape of the vessels containing them Gas -The particles are very far apart and are randomly arranged, occupying any free space, resulting in very low densities. Solid has a strong intermolecular force whereas gas has a weak intermolecular force. * Did you know there is actually more than just 3 states of matter? Most people only know the gaseous, liquid and solid states. One other well-known state of matter is plasma, found in plasma televisions or plasma spheres. Brownian motion  Brownian motion is the random or irregular motion of smoke particles in air. Brownian motion only occurs in fluids. A fluid is a substance that has the ability to flow or has particles that can move freely. Learn more about brownian motion here. End of Chapter 7.  Physics is the study of the natural world around us-from the very large, such as the solar system, to the very small, such as the atom. The study of physics is commonly divided into major topics such as General Physics, Thermal Physics, Light, Waves and Sound, Electricity and Magnetism. All these topics are related to two main ideas: matter and energy. However, this blog will cover Thermal Physics, which is chapter 7,8 & 9 of the textbook. |
