Chapter 30, Problem 1CQ

Name three different types of evidence for the existence of atoms.

To determine

The three different types of evidence for the existence of atoms.

Explanation of Solution

Introduction:

Atom is defined as the smallest constituent of matter. Every solid, liquid, gas and plasma is made up of atoms, which can be either neutral or ionized.

The evidences that supports the existence of atoms are as follows:

1. In case of chemical reaction, the reactant masses combine in fixed mass ratio, which provides evidence of presence of basic units that have mass ratios. These basic units are atoms.
2. According to Greek evidence, matter can be divided to infinitely small divisions, and atoms cannot be further divided. Thus, atoms are smallest indivisible particle.
3. Robert Brown observed the movement of pollen grains in still water, which is possible due to thermal motion of fluid molecules, which undergo collision with the particles floating in water. This led to the conclusion that fluid is made up of fundamental units, referred to as atom.

Conclusion:

Hence, the evidences that proves the existence of atoms have been mentioned.