A phenomenon related to temperature and heat

1. A phenomenon related to temperature and heat Mentee: Le Tran Hieu

2. There are many phenomena related to temperature and heat in our life. They cause some effects that make us have to attend much. The picture behind is an example. The rain in Asburg park, Newsey became deformed because of high temperature.

3. The example is an usual phenomenon in Science: If you heat a substance, you can realize that its size is developed. • We can conduct an experiment: Prepare a cup and a metallic sphere that can be put tightly in the cup. Heat the sphere for about 4 or 5 minutes. After that, we put it again in the cup. We can see that the sphere cant be put in the cup. This means that the sphere is bigger than it before being heated.

4. We can explain this phenomenon qualitatively: When you heat the object you increase its energy by providing thermal energy. As we know everthing is created from atoms so the energy of atoms of the object also increase. The thermal energy turns into kinetic energy of the atoms  the atoms move faster  the distance among atoms increases → the volume of object increases

5. We can infer another conclusion: if we make a substance colder, its size will decrease. ( In our experiment after heating the sphere if we put the sphere in water for few minutes we will be able to put it in the cup again). We can find some applications about this phenomenon in our life: - There is a slit between two bars (used to link two rails). - Each bridge has a bridge pier held tightly(cant move) but the another one can be moved thanks to small wheel

6. All things that are made hotter (colder) will develop (decrease) their size. • But there is a liquid that not follow this conclusion. It is water. With temperature higher than 4 Celsius degrees, water develops when it is heated. However from 0 to 4 Celsius degrees, it decreases when temperature increases. This character of water explains why fish can live in cold areas even when the temperature is lower than 0.

7. We can know that statement succinctly: When the temperature is decrease to near 4 Celsius degree, the volume of the water above decrease so its density increase → this part of water will sink and the water below will come to the surface.(the convection happens) • But when the temperature decrease from 4 to 0 Celsius degree the water above increases its volume so its density is smaller than the below water’s.(the convection doesn’t happen). Therefore, the water freezes from top to bottom and fish can live in the water below the ice.

8. Conclusion: - Everything will bigger (smaller) if it is warmer (colder), except water. - This phenomenon is applied a lot in our life such as in building bridges or making rails.

9. When the fluorescent light is turned on, the electric arc happens: an electric current causes a big difference of voltage between two electrodes. The hairsprings of two electrodes will be heated and radiate electrons. The electrons move in the tube with high speed and hit inert gas atoms (neon, argon…) and emit more ions.This process spread the warmth and make Hg in the tube turn into gas atoms. The ions and electrons hit Hg atoms and make Hg atoms emit ultra-violet ray photons (we cant see it). The violet ray photons hit phosphorus atoms on the tube (phosphorus is used to make flourescent). They release infared photons and white-light photons (we can see these light) and produce a low calorie. Therefore the lamp can emit light at such low temperature.