NDA Chemistry · Chemistry in Everyday Life

Medicines and Health Chemistry

The drug classes the NDA names by their job — antacid, analgesic, antibiotic, antiseptic versus disinfectant — plus the calcium compound in tooth enamel and the radioisotope used to treat cancer.

All Chemistry in Everyday Life notes NDA Chemistry strategy

Why this matters

The smaller subtopic — about three PYQs, all EASY/MODERATE, each a single recall fact: which medicine class treats a complaint, what tooth enamel is made of, which radioisotope treats cancer. The classic traps live here: antiseptic versus disinfectant (skin versus surfaces) and analgesic versus antipyretic (pain versus fever). Learn the class↔use table.

Concept 1 of 3

Drug classes by their job

Intuition

Each medicine class is named by what it does — relieves acidity, kills pain, kills bacteria, prevents infection. The bank asks 'which type of medicine treats X?'. Learn the class↔use pairs and keep the look-alike classes apart.

Definition

The high-frequency drug classes:

Antacid — neutralises excess stomach acid; treats indigestion / acidity (e.g. milk of magnesia, sodium bicarbonate).
Analgesic — relieves pain (e.g. aspirin, paracetamol).
Antipyretic — reduces fever (e.g. paracetamol). (Paracetamol is both analgesic and antipyretic.)
Antibiotic — kills or stops bacteria (e.g. penicillin). Does not work on viruses.
Antiseptic — kills microbes on living tissue / skin (e.g. Dettol, tincture of iodine).
Disinfectant — kills microbes on non-living surfaces / floors (e.g. phenol, chlorine). Too harsh for skin.
Antihistamine — relieves allergy symptoms.

Class	Job	Example
Antacid	Treats indigestion / acidity	Milk of magnesia, NaHCO₃Q Antacid is the answer for indigestion — it neutralises excess stomach acid.
Analgesic	Relieves pain	Aspirin, paracetamol
Antipyretic	Reduces fever	Paracetamol
Antibiotic	Kills bacteria	Penicillin
Antiseptic	Kills microbes on living skin/tissue	Dettol, tincture of iodine Antiseptic is for the BODY (cuts, skin). Disinfectant is for SURFACES (floors). Same idea, different place.
Disinfectant	Kills microbes on non-living surfaces	Phenol, chlorine, bleach

Practice this concept5 quick reps

Practice — Level 1 (5 reps)

Quick reps to lock in the method. Try each, then check.

1.
Which type of medicine is used to treat indigestion?
2.
Which class of drug relieves pain?
3.
Which class of drug reduces fever?
4.
Which medicine is applied to a cut on the skin to prevent infection?
5.
Which chemical is used to clean floors and toilets to kill germs?

From the bank · past-year question

Example 1Chemistry in Everyday LifeEASY

Which one of the following type of medicines is used for treating indigestion ?

[Q98 · Sep · 2025]

Antiseptic (skin) versus disinfectant (surfaces)

Both kill microbes, but an antiseptic is mild enough for living tissue (applied to skin, cuts), while a disinfectant is harsher and used on non-living surfaces (floors, instruments). Tincture of iodine and Dettol are antiseptics; phenol and bleach are disinfectants.

Analgesic (pain) versus antipyretic (fever)

An analgesic relieves pain; an antipyretic reduces fever. Paracetamol happens to do both, but the class names mean different jobs — match the name to the symptom in the question.

Antacid treats acidity, not infection

An antacid neutralises stomach acid (indigestion). It is not an antibiotic or antiseptic. The cue word 'indigestion / acidity' points to antacid.

Concept 2 of 3

Radioisotopes and elements in medicine

Intuition

Some elements' radioactive isotopes are used to diagnose or treat disease. The bank's recurring fact is the isotope used to treat cancer — cobalt-60, whose gamma rays destroy tumour cells.

Definition

The medical-isotope recall facts:

Cobalt-60 (Co-60) — its gamma radiation is used in radiotherapy to treat cancer ('cobalt therapy').
Iodine-131 (I-131) — used to diagnose and treat thyroid disorders.
Sodium-24 (Na-24) — used to study blood circulation.
Phosphorus-32 (P-32) — used in treating some blood disorders.

Isotope	Medical use
Cobalt-60	Radiotherapy for cancer (gamma rays)Q Cobalt-60 is the cancer-treatment isotope the bank asks for ('cobalt therapy').
Iodine-131	Thyroid diagnosis and treatment
Sodium-24	Tracing blood circulation
Phosphorus-32	Treating certain blood disorders

Practice this concept3 quick reps

Practice — Level 1 (3 reps)

Quick reps to lock in the method. Try each, then check.

1.
Which element's isotope is used in the treatment of cancer?
2.
Which radioisotope is used for thyroid disorders?
3.
Which radioisotope is used to study blood circulation?

From the bank · past-year question

Example 2Chemistry in Everyday LifeEASY

Which one of the following elements' isotopes is used in the treatment of cancer?

[Q123 · Sep · 2021]

Cobalt-60 treats cancer; iodine-131 treats the thyroid

Cobalt-60 is for cancer radiotherapy. Iodine-131 is for the thyroid. The bank pairs the wrong organ with the isotope as a distractor.

Concept 3 of 3

Chemistry of the body — bones and teeth

Intuition

A few facts about the chemicals that make up the body. The bank's recurring one is what tooth enamel is made of — a calcium phosphate (hydroxyapatite), the hardest substance in the body.

Definition

The body-chemistry recall facts:

Tooth enamel is made of calcium phosphate (hydroxyapatite) — the hardest tissue in the human body.
Bones are also mainly calcium phosphate, with some calcium carbonate.
Acids dissolve calcium phosphate, which is why acidic food and bacterial acid cause tooth decay — fluoride toothpaste forms acid-resistant fluorapatite.

Body part	Main chemical
Tooth enamel	Calcium phosphate (hydroxyapatite)Q Tooth enamel = calcium phosphate. Not calcium carbonate or calcium chloride.
Bones	Calcium phosphate (with some carbonate)

Practice this concept2 quick reps

Practice — Level 1 (2 reps)

Quick reps to lock in the method. Try each, then check.

1.
Tooth enamel is made of which calcium compound?
2.
Bones are made mainly of which calcium compound?

From the bank · past-year question

Example 3Chemistry in Everyday LifeEASY

Tooth enamel is made up of which one of the following calcium compounds?

[Q109 · Apr · 2019]

Tooth enamel is calcium phosphate, not calcium carbonate

Enamel and bone are mainly calcium PHOSPHATE (hydroxyapatite). Calcium carbonate (chalk, eggshell) is the distractor — do not pick it for tooth enamel.

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Reference tables (3)

Drug classes by their job6 rows

Class	Job	Example
Antacid	Treats indigestion / acidity	Milk of magnesia, NaHCO₃Q Antacid is the answer for indigestion — it neutralises excess stomach acid.
Analgesic	Relieves pain	Aspirin, paracetamol
Antipyretic	Reduces fever	Paracetamol
Antibiotic	Kills bacteria	Penicillin
Antiseptic	Kills microbes on living skin/tissue	Dettol, tincture of iodine Antiseptic is for the BODY (cuts, skin). Disinfectant is for SURFACES (floors). Same idea, different place.
Disinfectant	Kills microbes on non-living surfaces	Phenol, chlorine, bleach

Radioisotopes and elements in medicine4 rows

Isotope	Medical use
Cobalt-60	Radiotherapy for cancer (gamma rays)Q Cobalt-60 is the cancer-treatment isotope the bank asks for ('cobalt therapy').
Iodine-131	Thyroid diagnosis and treatment
Sodium-24	Tracing blood circulation
Phosphorus-32	Treating certain blood disorders

Chemistry of the body — bones and teeth2 rows

Body part	Main chemical
Tooth enamel	Calcium phosphate (hydroxyapatite)Q Tooth enamel = calcium phosphate. Not calcium carbonate or calcium chloride.
Bones	Calcium phosphate (with some carbonate)

Watch out for (5)

Antiseptic (skin) versus disinfectant (surfaces)
→ Drug classes by their job
Analgesic (pain) versus antipyretic (fever)
→ Drug classes by their job
Antacid treats acidity, not infection
→ Drug classes by their job
Cobalt-60 treats cancer; iodine-131 treats the thyroid
→ Radioisotopes and elements in medicine
Tooth enamel is calcium phosphate, not calcium carbonate
→ Chemistry of the body — bones and teeth

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