Physics Library

Teori Atom J. J. Thomson

Berdasarkan penemuan tabung katode yang lebih baik oleh William Crookers, maka J.J. Thomson meneliti lebih lanjut tentang sinar katode dan dapat dipastikan bahwa sinar katode merupakan partikel, sebab dapat memutar baling-baling yang diletakkan diantara katode dan anode. Dari hasil percobaan ini, Thomson menyatakan bahwa sinar katode merupakan partikel penyusun atom (partikel subatom) yang bermuatan negatif dan selanjutnya disebut elektron.
Atom merupakan partikel yang bersifat netral, oleh karena elektron bermuatan negatif, maka harus ada partikel lain yang bermuatan positif untuk menetrallkan muatan negatif elektron tersebut. Dari penemuannya tersebut, Thomson memperbaiki kelemahan dari teori atom dalton dan mengemukakan teori atomnya yang dikenal sebagai Teori Atom Thomson. Yang menyatakan bahwa:

“Atom merupakan bola pejal yang bermuatan positif dan didalamya tersebar muatan negatif elektron”

Model atom ini dapat digambarkan sebagai jambu biji yang sudah dikelupas kulitnya. biji jambu menggambarkan elektron yang tersebar marata dalam bola daging jambu yang pejal, yang pada model atom Thomson dianalogikan sebagai bola positif yang pejal. Model atom Thomson dapat digambarkan sebagai berikut:

                                                                 atom thomson

Kelemahan:

Kelemahan model atom Thomson ini tidak dapat menjelaskan susunan muatan positif dan negatif dalam bola atom tersebut.

ATOM

Atom berasal dari bahasa yunani “atomos” yang berarti tidak dapat dipotong. Sesuai pengertian tersebut,Atom-atom adalah partikel penyusun semua benda yang berukuran sangat kecil. Di dalam atom juga terdapat sub-atom, yaitu partikel penyusun atom yang ukurannya lebih kecil. Sulit bagi kita untuk membayangkan seberapa kecil atom ini

Setiap atom memiliki inti, yang terdiri dari proton dan neutron, serta elektron yang bergerak cepat di sekitar inti. Elektron-elektron ini terdapat pada tingkatan energi yang berbeda-beda, yang disebut kulit, tiap kulit memiliki jumlah batas untuk elektron, apabila elektron di kulit pertama sudah memenuhi batas, maka elektron akan memenuhi kulit kedua dan seterusnya.

4 C6H5 COOH + 18 H2 O ------ 15 CH4 + CO2

GLOBAL WARMING

Definition of Global Warming


 along with the increasing temperature of the earth in the world , then we need to provide information that is essential to all communities that exist throughout the world to find a very large negative impact as a result of global warming . so let us think together after skimming the information about global warming and its impacts to our planet .

Global warming is the increase in the average temperature of the atmosphere , ocean , and land earth caused by several factors . most likely caused by increased concentrations of greenhouse gases resulting from human activity through the greenhouse effect global warming will be followed by Climate Change , such as increased rainfall in some parts of the world , causing flooding and erosion . Meanwhile , in the other hemisphere will experience a prolonged dry season caused by rising temperatures.

Causes of Global Warming

Greenhouse Effect

All energy sources that exist on Earth comes from the Sun . When this energy arrives Earth 's surface , the light turns into heat that warms the Earth . Earth's surface will absorb some of the heat and reflect repopulating the rest . Some of this heat tangible long-wave infrared radiation into space . Some of this heat tangible long-wave infrared radiation into space . However, some of the heat remains trapped in Earth's atmosphere as a result of accumulated amount of greenhouse gases include water vapor , carbon dioxide , and methane that trap this radiation. These gases absorb and reflect radiation emitted waves heat the Earth and consequently will be stored on the surface of the Earth . This situation occurs continuously , resulting in an annual average temperature of the earth continues to rise . These gases serve as the gas in the greenhouse. With the increasing concentration of these gases in the atmosphere , the more heat is trapped beneath it .

Feedback Effects


Feedback process that occurs affects of global warming . An example is the process of water evaporation . In the case of warming due to increasing greenhouse gases such as CO2 , initially warming will cause more of water to evaporate into the atmosphere . Because water vapor is itself a greenhouse gas , warming will continue and increase the amount of water vapor in the air until it reaches equilibrium with the water vapor concentration . The resulting greenhouse effect greater than the effect of CO2 alone . ( Although this feedback increases the absolute water content in the air , the relative humidity of the air is almost constant or even decreases slightly because the air becomes warmer ) . This feedback effect only slowly as CO2 has a long time in the atmosphere .

Another important feedback is the loss of reflectance ( albedo ) of ice. As global temperatures increase, ice near the poles melts at an increasing rate . Along with the melting of ice, land or water below it will open . Both land and water has the ability to reflect light much less when compared to ice , and consequently will absorb more solar radiation . This will add to the warming and lead to even more ice to melt, causing a continuous cycle .

Positive feedback due to release of CO2 and CH4 from the softening of frozen ground ( permafrost ) are other mechanisms that contribute to warming . In addition, the melting ice will also release CH4 are also positive feedback .

The ability of oceans to absorb carbon will also be reduced when it warms up , this is caused by the decreased levels of nutrients in the mesopelagic zone thus limiting the growth of phytoplankton diatoms than a carbon sink that low .

Deforestation


Rampant cases of deforestation is one of the causes of global warming . Deforestation that reduces carbon sequestration by trees , causing the increase of carbon emissions by 20 % , and change the local micro-climate and hydrological cycle , thus affecting soil fertility . Forests are the lungs into the Earth now can not function to its full potential because it has a very reduced number of existing trees . The number of existing trees can not balance the number of CO2 on Earth .

Due to Global Warming

Unstable Climate Change

It has been predicted by scientists , the northern regions of the Northern Hemisphere will heat up more than other regions on Earth . This will result in the melting of icebergs and land will shrink . It would be a bit of ice floating in the waters . . Areas that previously experienced mild snow , probably will not experience it again . In the mountains in temperate regions, snow covered sections will shrink and will melt faster . Growing seasons will be longer in some areas . Temperatures in winter and at night will tend to increase.

Warm regions will become more humid as more water evaporates from the oceans . High humidity will increase rainfall , on average , about 1 percent for each degree Fahrenheit warming . Storms will become more frequent . In addition , the water will evaporate more quickly than soil . As a result, some areas will become drier than ever . The wind will blow harder and probably with different patterns . Hurricanes ( hurricane ) which draws its strength from the evaporation of water , will be greater . Contrary to the warming that happens , some very cold periods might occur . Weather patterns become less predictable and more extreme .

Rising Sea Level

When the atmosphere warms , the surface layer of the oceans will also warms , it expands and causes the volume will raise the sea level . Warming also resulted in the melting of the polar ice , especially around Greenland .

Changes in sea level will greatly affect the life on the beach . Some areas will sink . Erosion of cliffs , beaches and sand dunes will increase . Even the slightest rise in sea level will greatly affect coastal ecosystems , for example, would drown coastal marshes half .

Ecological disturbance

Animals and plants into living creatures that are difficult to avoid the effects of global warming because most of the land is controlled by humans . In global warming , animals tend to migrate toward the poles and up the mountains . Plants will change the direction of growth , seeking new areas as old habitats become too warm . However , human development will obstruct this movement . Species migrate north or south is blocked by the cities or farms may be dead . Some types of species that are not able to quickly move towards the poles may also be destroyed .

Some kind of way to lessen the negative impact of Global Warming

The damage that has occurred can be addressed in several ways . The beach area is protected by didnding and barrier to prevent the entry of sea water . As another way , the government helps populations in coastal areas to move to higher ground . There are two ways to slow the increase in greenhouse gases . First, it prevents the carbon dioxide released into the atmosphere by storing the gas elsewhere . This method is called carbon sequestration ( removing carbon ) . The second way is to reduce the production of greenhouse gases .

Other ways that can be done is as follows :

- Plant more trees

- Traveling with environmentally friendly vehicles , for example: bicycle

- Use energy saving electronics

- Reduce the use of air conditioning

- Recycling organic waste

- Separate Waste Paper , Plastic , and cans that can be recycled