Answer:
d. may melt if heat is transferred to it from hot mantle rock rising up into the crust.
Explanation:
Hot, solid rock in the Earth's crust is a solid outer region of the Earth, Underneath the Earth Structure lies the mantle which is composed of solid rocks especially granite and basalt. The mantle is very hot and may melt if heat is transferred to it from hot mantle rock rising up into the crust therefore forming a molten magma. It may even be hotter (and not cooler as it was stated in the option A which makes it the wrong answer) than the surface lava because of the pressure of the overlying rock. As such, This effect is seen when a volcanic eruption occurs.
The given formula for heat, Q=mc(Tf-Ti), is the best way to solve such problems with changes in temperature. It can be said that m is the mass of the substance. C is the specific heat of the substance. The term (Tf-Ti) is the change in temperature.
Q = mc(Tf-Ti) = 480g(0.96 J/g-C)(234-22) = 97689.6 Joules of heat
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.
Lean more:
about DDT
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