To answer the first question, we need to understand what nuclear fusion is. Nuclear fusion is the process in which two or more atomic nuclei combine to form a single, heavier nucleus, releasing a large amount of energy in the process.
Now let's look at the options:
A - starts when two atoms slam together, causing the larger atom to split into two smaller atoms: This describes nuclear fission, not fusion.
B - starts when a neutron slams into an atom, causing two atoms to form one, heavier atom: This also describes nuclear fusion backward. In fusion, two atoms combine to form a heavier atom, not the other way around.
C - starts when a neutron slams into an atom, causing the larger atom to split into two smaller atoms: This describes nuclear fission, not fusion.
D - starts when two atoms slam together to form one, heavier atom: This describes nuclear fusion, where two atoms combine to form a heavier atom.
Therefore, the correct answer is D - starts when two atoms slam together to form one, heavier atom.
Moving on to the second question, we need to understand what nuclear fission is. Nuclear fission is the process in which the nucleus of an atom is split into two or more smaller nuclei, releasing a significant amount of energy.
Now let's analyze the options:
A - starts when two atoms slam together, causing the larger atom to split into two smaller atoms: This describes nuclear fission, which is the correct answer.
B - starts when a neutron slams into an atom, causing the larger atom to split into two smaller atoms: This also describes nuclear fission, which is the correct answer.
C - starts when a neutron slams into an atom, causing two atoms to form one heavier atom: This describes nuclear fusion, not fission.
D - starts when two atoms slam together to form one heavier atom: This describes nuclear fusion, not fission.
Therefore, the correct answer is B - starts when a neutron slams into an atom, causing the larger atom to split into two smaller atoms.
Now let's move on to the third question. The Big Bang theory is a scientific explanation for the origin of the universe. The evidence supporting the Big Bang theory assumes certain conditions about the universe when it began. Let's examine the options:
A - It was composed of ice: This is not correct. The composition of the early universe is believed to be different, consisting of high-energy particles and radiation, but not ice.
B - It was very tiny: This is correct. The Big Bang theory suggests that the universe was extremely compact and dense at its beginning.
C - It was contracting: This is not a direct assumption of the Big Bang theory. The theory describes the expansion of the universe, not contraction.
D - It was extremely hot: This is correct. The Big Bang theory proposes that the early universe was extremely hot and dense, with temperatures reaching billions of degrees Celsius.
Therefore, the two correct answers are B - It was very tiny, and D - It was extremely hot.
I hope this helps clarify the concepts and answers your questions!