Answer:
b. independent/manipulated variable
Explanation:
Independent/manipulated variable - refers to the variable that is changed by the scientist or an experimenter. Only one variable that is independent is required to ensure a fair test in an excellent experiment. As the independent variable is being changed by an experimenter or scientist, data is being recorded simultaneously as they are collected.
Main advantages of DDT are the insecticide property and the knoledge about its chemical synthesis.
Explanation:
At that time in 1939 it was discovered that DDT have insecticide properties. It is a useful property because it allows inhibition of insects populations in large areas. Killing insects will reduce the diseases transmitted by them as typhus and malaria. More over you prevent the destruction of the agricultural crops by the harmful insects.
However the synthesis of the molecule was known way back in 1874. From that time it was plenty of time in which chemistry knowledge evolved so the synthesis at kilograms scale was implemented. High quantities of DDT molecule become available for the market so that in 1945 was available as agricultural insecticide.
It was discovered that DDT have bad effects for human health and also over time some insects developed resistance and their were not affected anymore by the molecule.
You may find the chemical structure of DDT in the attached figure.
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about DDT
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Direct electron transfer from a a singlet reduced species to a triplet oxidizing species is quantum-mechanically forbidden.
<h3><u>Transfer from singlet to triplet:</u></h3>
- Either an excited singlet state or an excited triplet state will occur when an electron in a molecule with a singlet ground state is stimulated (through radiation absorption) to a higher energy level.
- All electron spins in a molecule electronic state known as a singlet are coupled.
- In other words, the ground state electron and the stimulated electron's spin are still coupled (a pair of electrons in the same energy level must have opposite spins, per the Pauli exclusion principle).
- The excited electron and ground state electron are parallel in a triplet state because they are no longer coupled (same spin).
- It is less likely that a triplet state would arise when the molecule absorbs radiation since excitation to a triplet state necessitates an additional "forbidden" spin transfer.
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Answer:
Labor unions were created in order to help the workers with work-related difficulties such as low pay, unsafe or unsanitary working conditions, long hours, and other situations. ... Sometimes the unions organized strikes in order to try to change the conditions of the workers.
Explanation:
