The force that holds atoms together in a molecule is called: MCQ with Answer and Explanation

Explanation:
According to the law of conservation of mass, the mass of a substance remains constant during any physical change, including the interconversion of states. Density, volume, and shape change as the intermolecular spaces and arrangement alter during phase transitions, but the total number of atoms and mass is conserved.

Explanation:
The salt bridge (e.g., KCl-agar) allows migration of ions between half-cells, completing the circuit and maintaining charge neutrality. Without it, charge buildup would stop the reaction. It does not increase current or electrode potential. It prevents mixing of solutions. A porous membrane can also serve. Ions in the bridge must have similar mobility and not interfere with cell reactions.

Explanation:
The half-life is the time required for half of the radioactive atoms to decay. After 10 years (1 half-life), 1/2 remains. After 20 years (2 half-lives), 1/4 remains. After 30 years (3 half-lives), the fraction remaining is (1/2)^3 = 1/8. Thus, one-eighth of the original sample will remain.