The answer is A) Water has surface tension.
This is the correct answer because water allows animals and really light items to rest upon the top of the water.
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Half-life of a radioactive substance is the time required to reduce the amount of substance to half of its initial amount.
In present case, half-life is material is given as 1000 years and initial amount of material is given as 400 kg
Answer 1) Since, half-life of radio-active substance is 1000 years, therefore after 1st half life, amount of the material will be left to half the initial amount. Hence, amount of substance left after 1000 years = 400/2 = 200 kg.
Answer 2) For 2000 years, radioactive material has crossed 2 times the half life. Therefore , amount of the material will be left to 1/4 the initial amount. Hence, amount of substance left after 2000 years = 400/4 = 100 kg.
Answer 3) For 4000 years, radioactive material has crossed 4 times the half life. Therefore , amount of the material will be left to 1/16 the initial amount. Hence, amount of substance left after 4000 years = 400/16 = 25 kg.
It is A. Quanta, have a nice day!!
Answer:
I guess B They have a charge
Answer:
2Mg + 2CO₂ → 2MgO + C
Option a.
Explanation:
The chemical reactions are balanced in order to verify compliance with the Law of conservation of mass. This law states that in any chemical reaction, the mass of the reagents must be equal to the mass of the products