Chapter 9 Thermal Properties Of Matter

Internal energy consists of mainly two parts, kinetic energy and potential energy. In this case, kinetic energy is due to the vibration of particles, directly related to temperature. The higher the temperature, the more vigorous the particles would vibrate, therefore, the kinetic energy in this case would mean the movement of the particles and not the vibrations. The amount of potential energy would depend on the force between each particle and how far apart they are.

Melting, it refers to the change of state from a solid to a liquid and it occurs at a particular temperature known as the melting point. It happens when the heat gained by the solid is used to break the intermolecular bond between the molecules. When the bond breaks, the molecules would be able to move around and the change of state occurs. There is no change in temperature while the thermal energy is used to break the intermolecular bond. When the entire solid melts, temperature would then continue to increase.

Solidification would be the opposite of melting. It refers to the change of state from liquid to solid and for solidification the melting point would be the freezing point too. Temperature would reamin constant as the thermal energy is given out as the intermolecular bonds are formed. It happens when the liquid molecules come together and solidifies, therefore forming intermolecular bonds. Temperature changes would only occur when the substance is cooled.

Boiling, it refers to the change of state from a liquid to a gas and it also occurs at a particular temperature known as the boiling point. During boiling, the temperature remains constant at the boiling point as thermal energy is being absorbed by the liquid to separate the molecules and to push back on the atmosphere surrounding it. The molecules are now further apart.

Condensation would be the opposite of boiling. It refers to the change of state from gas to liquid. The boiling point would also be the condensation point. Alike to boiling, during condensation, the temperature remains constant at the condensation point as thermal energy is released by the substance.

Evaporation, like boiling, it’s the change of state from liquid to gas. However, evaporation, unlike boiling, could happen at any temperature. It is often confused with boiling. However, only evaporation has the following properties which could differ to boiling. In short, evaporation is a cooling process.

Evaporation:

• Occurs at any temperature
  
• Slow process
  
• Takes place only on liquid surface
  
• No bubbles are formed in the liquid
  
• Temperature may change
  
• Thermal energy supplied by surroundings
  
  Factors affecting the rate of evaporation:
  
• Temperature
• Humidity of surrounding air
• Surface area of liquid
• Movement of air
• Pressure
• Boiling point of liquid

After reading up on these processes, I feel that they play a very huge role in our lives. This is probably due to the fact that these processes uses up or gives out energy. Hence, they can be used as methods to absorb energy and to give out energy. Water is used to cool down machineries as condensation makes use of a large amount of energy, which in this case is thermal energy. The melting of metal allows it to be easily bent into many shapes for other purposes. In fact, they play a important role in our bodies. Our sweat evaporates off to cool down our body temperature when we exercise is just one of the many examples available. I feel that physics is not only about theories but it can be applies into almost every part of our lives, which I find astonishing and which is also why I love physics.

Chapter 8 Transfer Of Thermal Energy

Transfer of thermal energy consists of conduction, convection and radiation.

Conduction occurs in all three states of matter, solid, liquid and gas.It is the transfer of heat energy due to the transfer of kinetic energy. Particles vibrate more vigorously after being heated forming a chain effect resulting in the particles of the whole objects vibrates more vigorously as a whole. However, the ability for an object to conduct heat through conduction is determined by how the particles align themselves. Hence metal will conduct heat better than a piece of wood.

For convection, it works by the theory that hot gas/liquid rises and cold gas/liquid sinks. When an object is being heated unevenly, a hot and cold region will be formed. Hence convection will occur. However, it only applies for gas/liquid as the particles in them are not in a fixed position as the force of attraction between them is weaker. Hence the mobility allows convection to occur.

For radiation, it is due to the electromagnetic wave. Infra-red waves allow the transfer of heat and it is not restricted by any medium unlike conduction and convection. However, the absorption of radiation is affected by several factors such as colour, texture of the object and surface area.

Having said so, the theory of thermal conduction has benefited man-kind in a lot of ways. For conduction, the cooking pans we use make full use of the theory of conduction. The metal part of the pan allows heat conduction to cook food and also allow even distribution of heat throughout the pan. The plastic handles protect us from the heat and let us handle the pan when we are cooking. Without which, we will not have the luxury to being able to cook our food so efficiently.

For convection, ill relate it to cooking again since I aspire to be a good housewife. When we cook our noodles or soup, the heat in the water is transferred through convection. Without which, the process of conduction will be very slow. Just imagine if everyone is to take over one hour to cook a packet of noodles, wont my future husband starved to death by the time I finish? Hence convection plays a very important role in our daily livelihood and also in many industries.

For radiation, using cooking as an example again, our microwave oven makes use of this aspect of thermal conduction. The microwave oven produces microwave which heats up our food quickly. This provided much convenience and saved a lot of our time.

In conclusion, making use of the physics theory of conduction, convection and radiation in our daily lives helps to reduce a lot of troubles. Not only in our household, but these theories are also proved useful in many industries and factories.

Chapter 7 Kinetic Model Of Matter

Solid, liquid and gas. These 3 states are the basic science anyone would learn. Every matter is bound to be in one of the 3 states.

Let’s talk about the properties for each state.

Solid. It has a fixed shape and volume, normally hard and rigid which means it would need a large force to change its shape, has a high density and is incompressible.

Liquid. It has a fixed volume but not a fixed shape, has high density and is also incompressible.

Gas. It does not have a fixed shape or volume unlike solid or liquid, has low density and also unlike solid nor liquid it is compressible.

It is due to the arrangement of particles that cause the properties for each state.

In solid, the particles are arranged closely together, usually in a regular pattern, occupying the most minimum space which gave solid the property of having high density. As it is closely packed together, the particles could only vibrate about their fixed position as they are held in place by very strong intermolecular bond which is why solids have fixed volumes and shapes.

In liquid, particles are arranged randomly, slightly further apart as compared to solid which results in liquids having rather high density. Particles are free to move about but are confined within the container, it has attractive forces between particles which explains why liquid has a fixed volume but not a fixed shape.

In gas, particles are very far apart from each other as they are randomly arranged and would occupy any available space, resulting in gas having low density. Particles have very little attraction between each other and move about randomly at high speed which explains why gases have no fixed volume nor shape and yet are highly compressible.

Physics is not only about theories. It can be applied in our daily lives. In fact, it plays an extremely important role in building our world. Every structure we see, roads, bridges, houses, etc. They are all build on physics theories and formulas. Having said so, the fundamental of matters, the three states fascinates me a lot too. After reading up on it, I realize that these concepts can be applied in our daily lives to a very large extent. Let’s just take water as an example. In its solid state, it helps us to cool down things. Our drinks such as coke or sprite, ice makes them chilled hence more enjoyable to be consumed in a hot sunny weather. As for water in its liquid state, it helps to hydrate our bodies, can be used to bath, cook, wash and many more. It is even known as the source of life. Hence we can see how important it is to us. As for water in its gaseous state, steam machineries, factories, steam plays a very important role in driving these machineries to work to provide us with the luxury of not having to do the hard labour ourselves.