Science — Food — CTET Mathematics & Science
A child who can recite "carbohydrates give energy, proteins help growth" from memory has not necessarily understood food the way NCERT wants them to. NCERT's Class VI textbook introduces this entire topic through activities — testing a chapati, a potato, and a drop of milk with iodine solution and watching the colour change — because the constructivist philosophy behind the syllabus treats a nutrient as something a learner discovers by testing, not a fact handed down from a teacher. CTET tests this chapter the same way: expect a described experiment or a classroom scenario at least as often as a bare "which vitamin causes X" recall question.
1. What CTET actually asks
Science — Food carries weightPct 5 of the 60-question Mathematics & Science elective section, which works out to roughly 3 of those 60 questions, sitting inside the section's ~30-question Science sub-block. Each question is worth 1 mark with no negative marking, so — as with every CTET Paper 2 question — an educated guess after eliminating even one option is always at least as good as leaving the question blank.
The chapter draws on five connected strands, and CTET splits its questions roughly 70% pure content and 30% pedagogy-of-teaching-this-topic — expect most questions to test the science itself, but expect at least one question per attempt that asks how you'd teach food and nutrition to a Class VI-VIII learner, not just what the facts are:
- Sources of food — which everyday foods come from which part of a plant, and which come from animals.
- Components of food — carbohydrates, proteins, fats, vitamins, minerals, roughage, and water, and the specific job each one does in the body.
- Balanced diet and deficiency diseases — what happens when one of those components falls short, and how a balanced diet is defined.
- Testing food for nutrients — the iodine, Biuret, and fat-translucency classroom tests NCERT treats as central, not supplementary.
- Cleaning, cooking, and preserving food — why we cook, and how salting, sugaring, drying, oiling, and refrigeration each stop food from spoiling.
2. Sources of food — plant-based and animal-based
Every food item traces back to a plant or an animal, and NCERT's Class VI treatment specifically drills which part of the plant a familiar food comes from — this "part-of-the-plant" mapping is one of the most repeatable question types in this section:
| Plant part | Examples |
|---|---|
| Root | Carrot, radish, turnip, beetroot |
| Stem | Potato, ginger, sugarcane, onion (a modified underground stem, though its layers are technically leaf bases) |
| Leaf | Spinach, cabbage, lettuce, coriander, mint |
| Flower | Cauliflower (an unopened flower cluster), broccoli, banana flower |
| Fruit | Apple, tomato, brinjal, mango, cucumber |
| Seed | Wheat, rice, pulses (gram, lentils), mustard |
The classic trap here is potato — students reflexively call it a root because it grows underground, when it is in fact a stem tuber (it stores food and can sprout new shoots from "eyes," which roots cannot do). Ginger and turmeric are also underground stems (rhizomes), not roots.
Animal-based sources include milk (and its products — curd, ghee, paneer, cheese), eggs, meat, fish, and honey. Animals themselves are classified by diet as herbivores (eat only plants — cow, goat, deer), carnivores (eat only other animals — lion, tiger), and omnivores (eat both — humans, crow, bear); this classification occasionally crosses over into a food-chain or food-web question that pairs with this chapter.
3. Components of food and their functions
NCERT groups the components of food into six categories, each with a distinct job:
- Carbohydrates — the body's primary, quick-access energy-giving nutrient. Found in rice, wheat, potato, sugar. Present mainly as starch (in grains and tubers) and simple sugars (in fruits, honey, table sugar).
- Proteins — the body-building nutrient, essential for growth, tissue repair, and forming enzymes and antibodies. Found in pulses, milk, eggs, meat, fish, soybean, and paneer — plant-based proteins (pulses, soy) and animal-based proteins (milk, egg, meat) both count.
- Fats — a concentrated energy-giving nutrient (roughly double the energy per gram of carbohydrates or proteins), also needed to absorb the fat-soluble vitamins (A, D, E, K) and to insulate the body. Found in ghee, butter, oil, nuts, and meat.
- Vitamins — protective nutrients needed only in small quantities, but essential for specific body functions; NCERT covers Vitamins A, B-complex, C, D, E, and K, each linked to specific foods and specific deficiency effects (Section 4).
- Minerals — also protective, but chemically distinct from vitamins: minerals are inorganic elements (calcium, iron, iodine, phosphorus) drawn from soil and water into food, whereas vitamins are organic compounds. Calcium and phosphorus build bones and teeth; iron builds haemoglobin; iodine supports the thyroid gland.
- Roughage (dietary fibre) — found in whole grains, vegetables, and fruits. Roughage is not digested and provides no nutrients or energy at all, but it adds bulk to food, helps peristalsis (the gut's muscular movement), and prevents constipation — its value lies entirely in what it does mechanically, not chemically.
- Water — makes up over half the body's weight; carries digested nutrients around the body, helps regulate body temperature, and removes waste through sweat and urine.
A genuinely useful nuance for CTET: NCERT typically calls carbohydrates, proteins, fats, vitamins, and minerals nutrients, while treating roughage and water as essential components of food that are not themselves nutrients — a distinction examiners occasionally test directly ("which of the following is a component of food but not classified as a nutrient?").
4. Balanced diet and deficiency diseases
A balanced diet contains all the nutrients — carbohydrates, proteins, fats, vitamins, and minerals — in the right proportions and quantities needed by the body, along with adequate roughage and water. What counts as "right proportion" is not fixed: it varies with age, sex, activity level, health condition, and climate — a growing child, a pregnant woman, and a manual labourer each need a different balance, which is exactly why NCERT frames "balanced" as proportional and person-specific rather than as one universal plate.
When a component is chronically missing or insufficient, the body shows a specific, nameable deficiency disease — this table is one of the highest-yield memorisation targets in the chapter:
| Deficient component | Deficiency disease / effect |
|---|---|
| Vitamin A | Night blindness (poor vision in dim light); dry skin |
| Vitamin B1 (Thiamine) | Beriberi (weakness, nerve damage) |
| Vitamin C | Scurvy (bleeding and swollen gums, slow wound healing) |
| Vitamin D | Rickets in children (soft, bent bones) |
| Calcium | Weak bones and teeth |
| Iron | Anaemia (fatigue, pale skin, low haemoglobin) |
| Iodine | Goitre (swelling of the neck from an enlarged thyroid) |
| Protein (severe, in children) | Kwashiorkor (swollen belly, stunted growth, thin limbs) |
| Protein and energy together (infants) | Marasmus — together with kwashiorkor, both fall under the umbrella term Protein-Energy Malnutrition (PEM) |
5. Testing food for nutrients — NCERT's hands-on method
NCERT's Class VI "Components of Food" chapter is built around three simple, low-cost classroom tests, and the pedagogy point matters as much as the chemistry: these tests exist so a student can personally verify a nutrient's presence rather than take the textbook's word for it — the defining move of NCF 2005's activity-based, inductive approach to science teaching.
| Test | Method | Positive result |
|---|---|---|
| Starch (iodine test) | Add 2-3 drops of dilute iodine solution to the food sample | The sample turns blue-black |
| Protein (Biuret test) | Add a few drops of copper sulphate solution, then several drops of caustic soda (sodium hydroxide) solution, to a paste of the food sample | The sample turns violet/purple |
| Fat | Rub a small piece of the food firmly on a sheet of paper | An oily, translucent patch appears and does not dry up |
The order matters for the Biuret test — copper sulphate is added first, sodium hydroxide second — and the colour cue is specific enough that CTET frequently swaps it with the wrong test's colour as a distractor (a blue-black result belongs to starch, not protein; a violet result belongs to protein, not starch).
The pedagogical case for this activity-based method over textbook-only teaching is direct: performing the test builds process skills (careful observation, recording, inference) alongside content knowledge, makes an invisible property (a nutrient's presence) concrete and checkable, and lets the generalisation ("different everyday foods contain different nutrients in different amounts") emerge from the students' own evidence rather than being delivered as a fact to memorise. A lesson that only shows a video of someone else performing these tests, without students handling the materials themselves, does not deliver the same constructivist benefit — CTET's pedagogy questions on this topic specifically probe that distinction between hands-on and merely observational teaching.
6. Cleaning food, cooking, and preservation
Cooking makes many foods easier to digest, kills harmful microorganisms, destroys certain natural toxins, and improves taste and texture — but it is not cost-free: prolonged or excessive cooking destroys heat-sensitive nutrients, especially Vitamin C, which is why NCERT recommends minimal cooking time for vegetables rich in it.
Food spoils because microorganisms (bacteria, fungi) grow in it, and every common preservation method works by denying microbes something they need to grow:
- Drying/dehydration — removes moisture (sun-drying grains, fish, papad, pickles); microbes cannot grow without water.
- Salting and sugaring — a high concentration of salt or sugar draws water out of microbial cells by osmosis, preventing their growth; used for pickles, salted fish and meat, jams, and squashes.
- Using oil and vinegar — coating food in oil creates a barrier against air and moisture, while vinegar's acidity is hostile to most microbes; the basis of pickling.
- Refrigeration/cold storage — low temperature slows down, but does not eliminate, microbial growth and enzymatic activity — refrigerated food still spoils eventually, just far more slowly. Treating refrigeration as "killing germs" is a common and testable misconception; it is a slowing method, not a sterilising one.
- Pasteurisation — specifically used for milk: heating to around 70°C for a short time, then rapid cooling, kills most disease-causing microbes without curdling the milk or destroying its taste.
- Chemical preservatives — substances like sodium benzoate or sodium metabisulphite, used commercially in jams and squashes to inhibit microbial growth over long shelf life.
7. Solved PYQ-style examples
Q1. Which of the following food items is obtained from the stem of a plant? Solution. Potato is a modified underground stem (a stem tuber), not a root — it stores food and can sprout new shoots from its "eyes." Answer: Potato.
Q2. A student's diet is chronically low in Vitamin C. Which condition is this most likely to cause? Solution. Vitamin C deficiency causes scurvy, marked by bleeding and swollen gums and slow wound healing. Answer: Scurvy.
Q3. A food sample turns blue-black when a few drops of dilute iodine solution are added to it. This indicates the presence of: Solution. A blue-black colour change with iodine solution is the specific, standard positive indicator for starch. Answer: Starch.
Q4. Which component of food provides no energy or nutrients but is still essential for healthy digestion? Solution. Roughage (dietary fibre) is not digested or absorbed and contributes no nutrients or energy, but adds bulk that helps peristalsis and prevents constipation. Answer: Roughage.
Q5. Why does milk kept in a refrigerator eventually spoil, even though it lasts much longer than milk left at room temperature? Solution. Refrigeration lowers the temperature enough to slow down microbial growth substantially, but it does not kill the microorganisms already present — given enough time, they still multiply and spoil the milk. Answer: Because refrigeration only slows, rather than stops, microbial growth.
Q6. A Class VI teacher asks students to test a piece of roti, a slice of potato, and a drop of milk using iodine solution, copper sulphate/sodium hydroxide, and the paper-rubbing method, and to record their own observations before the teacher states any conclusion. This teaching choice is best explained by which principle? Solution. This is a direct application of NCF 2005's activity-based, constructivist approach — letting learners generate and verify the generalisation ("foods differ in nutrient content") from their own evidence, rather than receiving it as a stated fact. Answer: Activity-based, inductive (constructivist) science teaching.
8. Common traps
- Calling potato, ginger, or turmeric a root — all three are underground stems (potato: tuber; ginger and turmeric: rhizomes), identifiable by their ability to sprout new shoots, which true roots cannot do.
- Swapping the colour cues of the starch and protein tests — blue-black belongs to the iodine/starch test; violet/purple belongs to the copper sulphate-sodium hydroxide/protein (Biuret) test. Under time pressure these two are the most frequently interchanged facts in this chapter.
- "Fat is always bad and should be avoided" — fats are one of the six essential components, providing concentrated energy and enabling absorption of Vitamins A, D, E, and K; the correct teaching correction is moderation, not elimination.
- Treating vitamins and minerals as interchangeable terms — vitamins are organic compounds; minerals are inorganic elements drawn from soil and water. Both are "protective," but they are chemically distinct categories with distinct deficiency diseases.
- Assuming roughage is "useless" because it isn't digested — its value is entirely mechanical (adding bulk, aiding peristalsis), not nutritional; "not digested" does not mean "not needed."
- Believing refrigeration kills microorganisms — it only slows their growth and activity; it is not a sterilising method, and refrigerated food still spoils, just more slowly.
- Assuming any classroom demonstration counts as "activity-based" teaching — NCF 2005's constructivist approach specifically favours learners handling materials and recording their own observations; watching a teacher (or a video) perform the same test is a weaker, more passive substitute.
- Confusing "nutrient" with "component of food" — carbohydrates, proteins, fats, vitamins, and minerals are nutrients; roughage and water are essential components of food that NCERT does not classify as nutrients.
9. Training protocol
Because this chapter is worth only about 3 marks, the efficient approach is a single tight pass rather than deep, repeated revision: fix the plant-part-to-food mapping (root/stem/leaf/flower/fruit/seed) and the deficiency-disease table as flashcard-style recall, since both are tested almost verbatim year to year. Rehearse the three food tests by their colour cue, not just their reagent name — under exam time pressure, the fastest way to answer a food-test question is to recall "blue-black = starch, violet = protein, oily translucent patch = fat" as a single fixed triple. For the roughly 30% of questions in this chapter framed as pedagogy, default to the option that has students handling materials and recording their own observations — that is almost always NCF 2005's preferred answer over lecture, textbook-reading, or passive demonstration. Finally, since CTET carries no negative marking, never leave a question in this chapter blank once you've ruled out even one option — a plausible-sounding deficiency disease or a swapped test colour is easy to eliminate even under uncertainty.
