The answer is A warm air rises cool air sinks
Nuclear reaction: ¹¹C → ¹¹B + e⁺(positron) + ve(electron neutrino).<span><span><span><span>
</span></span></span></span>Beta
decay is radioactive decay<span> in which
a beta ray and a neutrino are emitted from an atomic
nucleus.
There are two types of beta
decay: beta minus and beta
plus. In beta minus decay, neutron is converted to a
proton and an electron and
an electron antineutrino and in beta
plus decay, a proton is converted to a neutron and positron and an electron neutrino, so mass number does not change.</span>
Answer: a)
: negative
b)
: positive
c)
: positive.
d)
: negative
e)
: positive.
f)
: positive.
Explanation:
Entropy is the measure of randomness or disorder of a system. If a system moves from an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.
is positive when randomness increases and
is negative when randomness decreases.
a) 
As ions are moving to solid form , randomness decreases and thus sign of
is negative.
b) 
As solid is changing to gas, randomness increases and thus sign of
is positive.
c) 
As 2 moles of reactants are converted to 4 moles of products , randomness increases and thus sign of
is positive.
d) 
As gas is changing to solid, randomness decreases and thus sign of
is negative.
e) 
As 7 moles of reactants are converted to 8 moles of products , randomness increases and thus sign of
is positive.
f)
As solid is changing to gas, randomness increases and thus sign of
is positive.