Answer:
The true statement is option D. The two major factors determining the Earth's temperature are the Earth-Sun distance and the concentration of oxygen in the atmosphere.
Explanation:
The distance between the sun and the Earth is one of the factors that determines the temperature of the planet. The energy from the sun travels to the Earth, increasing the temperature.
The other fact that has a role in the Earth's temperature is the concentration of oxygen in the atmosphere. It can increase or decrease the temperature according to the amount of this. Oxigen contributes to the greenhouse effect, which helps to keep the temperature in a range that allows life to happen.
Answer:
B and C
Explanation:
B. In a given rock sample, the amount of Silicon-32 isotopes gets divided in half about every 170yrs.
This is the concept of half-life. Half life is the time take for half of a radioactive isotope to disintegrate. The shorter the half life the faster the isotope disintegrates.
From the question, we were told that it would take 170yrs for half of the isotope of Silicon to disintegrate to Phosphorus. This is the half life.
C. The half life can be used to determine the amount of Si-32 that has decayed from the time closure temperature was reached.
The closure temperature is very important in radioactivity. It is the temperature at which a system has cooled and there is no resulting disintegration of parent and daughter isotopes.
From first order kinetics, we know that the rate at which radioactive elements decay at any time is directly proportional to the number of radioactive atoms present. A knowledge of the half life helps to figure out the number of atoms that has decayed in time.
C. it cannot be used again!
