What is the minimum total energy released when an electron and its antiparticle (positron) annihilate each other?


Answer 1
Answer: Energy, in a form of gamma rays, is released when an electron and its antiparticle (positron) annihilate each other. 
Answer 2


the minimum total energy released when an electron and its antiparticle (positron) annihilate each other is:-

2 mc^2.    [Mass of electron m and c is the velocity of light.]  

m=1*10^(-30) kg., c =3*10^ 8 m/s  

energy released = 2 *9* 10 ^(-14) j  

1 j =6*10^(18) eV.  

Energy released = 6*18*10^4 eV

                               =104*10^4 eV  

                                 =1.04 MeV.

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IV. Can transport varying ions.


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Similarly fossils have helped scientists categorise species. Study of the chromosomes (in cases with available chromosomes) can help scientists figure out a lot about the subjects and categorise them. 

A student used 10 mL water instead of 30mL for the extraction of the NaCl from the mixture. How would this affect the calculated percentage of NaCl in the sample?


In this problem, the solute is sodium chloride, the salt while the solvent which comprise of a larger mass in the solution is water. When the solvent volume is decreased which is related to its mass, with the solute mass being held constant, then the concentration of salt increases. This is called concentration method. 

How does the calorie compare to the metric unit the joule? How do you calculate a calorie? Is it the same for all types of food?


Answer: One calorie is an energy unit of measure equal to about 4.184 joules. As such calorie is a fixed amout of energy and is the same for all types of food.


A calorie is defined as the amount of heat that must supplied to 1 gram of liquid water to increase its temperature 1°C.

The unit calore was established for the metric system, but the current standard SI system of measures use the joule as the the unit for energy.

As said the equivalence between calories and joules is 1 cal = 4.184 joules.

The energy content of the food is usually referred as calories, although it is really kilo calories. For instance, when you say that a snack contains 250 calories, it actually has 250 kilocalories (250,000 calories).

Food calories (the energy content of food) may be measured with a calorimeter, which is the original method. A calorimeter is a device  utilised to burn a sample of food and measure the temperature change in the surrounding water. Although you can use that method in a laboratory, nowadays the energy content is measured indirectly by adding up the energy provided by the energy-containing nutrients (protein, carbohydrates and fats).

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