Which of the following could result from a substance that undergoes a physical change? a. it changes irreversibly. b. it undergoes phase change. c. it’s elements composition is altered. d. its atoms rearrange to form a new molecule.

The answer is: B. It undergoes phase change.

A physical change occurs when a substance changes phase.  

For example, evaporization is phase change process in which the water changes from a liquid to a gas (water vapor).  

Condensation is phase change process in which the water changes from a gas to a liquid.

If the arrangement of particles is changed, that is chemical change or chemical reaction (new substance is formed).

The correct answer is option B, that is, it undergoes a phase change.  

Explanation:

A physical change occurs when a substance changes phase. The term phase change or phase transition is most generally used to illustrate transitions between the liquid, solid, and gaseous states of matter.  

At the time of a phase change of a given medium, some of the features of the medium change, generally intermittently, as an outcome of the change of external conditions like pressure, temperature, or others. For example, a liquid may turn into a gas by getting heated to the boiling point, leading to a sudden change in volume.  

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years