Q.(a) What do you understand by the term 'dissociation'? Explain its various forms.

Dissociation Chemistry – From Intuition to Precision

Imagine you have a salt crystal sitting in a glass of water. The crystal is a neat, orderly stack of sodium ions and chloride ions held together by strong electrostatic forces. Drop it into water, and something remarkable happens: the crystal breaks apart. Not into smaller crystals, but into individual ions that drift freely through the liquid. That process — the splitting of a compound into its constituent ions or molecules when dissolved in a solvent — is dissociation.

The key intuition is this: dissociation is a separation, not a destruction. The compound doesn't vanish; it simply unpacks into its charged or neutral building blocks, which then move independently.

The Precise Statement

In chemistry, dissociation is the reversible or irreversible process in which a molecule (or ionic compound) splits into two or more smaller chemical species — typically ions, radicals, or neutral fragments — under the influence of a solvent, heat, or an electric field.

For ionic compounds like sodium chloride ($\text{NaCl}$) in water, dissociation is complete and immediate:

For covalent molecules that can ionise, like acetic acid ($\text{CH}_3\text{COOH}$), dissociation is partial and reversible:

What Drives Dissociation?

Two factors matter most:

1. Solvent polarity — Water, with its high dielectric constant, weakens the electrostatic attraction between ions in a crystal or between polar groups in a molecule. The solvent molecules literally pull the species apart.

2. Bond strength — Weak bonds (like the $\text{O–H}$ bond in a carboxylic acid) break more easily than strong ones. That's why strong acids like $\text{HCl}$ dissociate almost completely, while weak acids like acetic acid dissociate only slightly. …

Hyperactivity Characteristics – A First Look

The Intuition

Imagine a classroom. Most students sit reasonably still, listen, and raise their hands before speaking. Now picture a student who seems to be driven by a motor — they can't stay seated, they fidget constantly, they blurt out answers, and they talk excessively. That restless, excessive, and often poorly controlled movement and speech is what we call hyperactivity.

The key intuition: hyperactivity is not just "being active." It is activity that is inappropriate for the situation — too much, too fast, and too hard to control. A child running on a playground is normal; the same child running in a library during a test is hyperactive.

The Precise Statement

In clinical and educational psychology, hyperactivity is one of the two core symptom domains of Attention-Deficit/Hyperactivity Disorder (ADHD) (the other being inattention). The characteristics of hyperactivity are:

Hyperactivity refers to a persistent pattern of excessive motor activity, restlessness, and impulsivity that is developmentally inappropriate, occurs across multiple settings, and interferes with functioning or development.

The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th edition) lists these specific hyperactivity-impulsivity symptoms (for children aged 17 or younger, at least 6 of the following must have persisted for ≥6 months):