If a substance decreases in temperature from 270k to 220k, the kinetic energy of that substance increases.

No, the kinetic energy of the substance does not increase with decrease in temperature as kinetic energy is directly proportional to temperature.

False

Explanation:

Kinetic energy, the energy exhibited by a moving object or when it gains some external energy.

If the external energy is in the form of heat, then the heat will lead to increase in temperature of the object which will transfer energy to the molecules in the object and thus the molecules will be moving faster leading to increase in the kinetic energy.

So in the given case, the temperature decreases from 270 K to 220 K, that means energy is lessened so the molecules will be moving slow leading to decrease in the kinetic energy and not increase in the kinetic energy.

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.