Indian Army GD / Technical Recruitment General Science Syllabus

What does a seismograph measure and what does a hygrometer measure?

A seismograph measures the intensity and magnitude of earthquakes; a hygrometer measures humidity (water vapour) in the air.

Convert 0°C and 100°C to the Kelvin scale.

0°C = 273.15 K (≈273 K); 100°C = 373.15 K (≈373 K). To convert: K = °C + 273.

What are the three common states of matter and their key property differences?

Solid (definite shape and volume), liquid (definite volume, no fixed shape), gas (neither definite shape nor volume). Particle freedom increases solid→liquid→gas.

What is sublimation? Give one example.

The direct change of a solid into gas (or gas to solid) without passing through the liquid state. Examples: camphor, naphthalene balls, dry ice (solid CO₂).

Differentiate an element, a compound, and a mixture.

An element has one type of atom; a compound has two or more elements chemically combined in a fixed ratio; a mixture has substances physically combined in any ratio, separable by physical means.

What is the difference between a physical change and a chemical change?

A physical change alters form but not composition and is usually reversible (e.g., melting ice); a chemical change produces a new substance and is usually irreversible (e.g., burning paper).

What are the main types of chemical reactions?

Combination (synthesis), decomposition, displacement, double displacement, and redox (oxidation-reduction) reactions.

Define oxidation and reduction.

Oxidation is the gain of oxygen or loss of electrons; reduction is the loss of oxygen or gain of electrons. They occur together in a redox reaction.

What is the chemical formula of water, common salt, and baking soda?

Water is H₂O, common salt (sodium chloride) is NaCl, and baking soda (sodium bicarbonate) is NaHCO₃.

On the pH scale, what values indicate acids, bases, and neutral substances?

pH below 7 = acidic, pH 7 = neutral, pH above 7 = basic (alkaline). The scale runs from 0 to 14.

List three properties of metals and three properties of non-metals.

Metals: lustrous, malleable/ductile, good conductors of heat and electricity. Non-metals: dull, brittle, poor conductors (insulators).

Which is the most reactive metal and which metals are least reactive (noble)?

Potassium/sodium are among the most reactive metals; gold and platinum are the least reactive (noble) metals.

Name the two main gases in air and their approximate percentages.

Nitrogen (≈78%) and oxygen (≈21%); the remaining ≈1% includes argon, carbon dioxide, and other gases.

Which gas is essential for breathing, and which gas do plants use during photosynthesis?

Oxygen is essential for respiration (breathing); plants absorb carbon dioxide (CO₂) during photosynthesis.

Who discovered the cell, and what is the cell's basic definition?

Robert Hooke discovered the cell (in cork). The cell is the basic structural and functional unit of life.

What is the main difference between prokaryotic and eukaryotic cells?

Prokaryotic cells lack a true (membrane-bound) nucleus and organelles (e.g., bacteria); eukaryotic cells have a membrane-bound nucleus and organelles (e.g., plant and animal cells).

Which organelle is called the 'powerhouse of the cell' and why?

The mitochondrion, because it produces energy in the form of ATP through cellular respiration.

Name two structures present in plant cells but absent in animal cells.

Cell wall and chloroplasts (containing chlorophyll); plant cells also have a large central vacuole.

Which organ system in the human body transports blood, and which one controls body activities?

The circulatory system transports blood; the nervous system controls and coordinates body activities.

How many chambers does the human heart have, and what are they?

Four chambers: two upper atria (left and right) and two lower ventricles (left and right).

What is the normal number of bones in an adult human body, and how many in a newborn?

An adult has 206 bones; a newborn has about 300 bones, which fuse with age.

Which organ filters blood and produces urine, and what is the basic unit of the kidney?

The kidney filters blood and produces urine; its basic functional unit is the nephron.

What are the major food nutrients the human body needs?

Carbohydrates, proteins, fats, vitamins, minerals, and water (and dietary fibre).

Which deficiency causes scurvy and which causes night blindness?

Vitamin C deficiency causes scurvy; vitamin A deficiency causes night blindness.

Differentiate communicable and non-communicable diseases with one example each.

Communicable diseases spread from person to person (e.g., tuberculosis, malaria); non-communicable diseases do not spread (e.g., diabetes, cancer).

Who is the father of genetics, and what carries hereditary information in cells?

Gregor Mendel is the father of genetics. Genes, made of DNA on chromosomes, carry hereditary information.

How many chromosomes are in a normal human body cell, and which pair determines sex?

46 chromosomes (23 pairs). The 23rd pair determines sex: XX is female, XY is male.

What is a food chain, and what are the producers in an ecosystem?

A food chain shows the transfer of energy through organisms by feeding. Producers are green plants that make their own food via photosynthesis.

Which gas in the atmosphere protects Earth from harmful UV rays, and which gases cause global warming?

The ozone layer (O₃) protects against UV rays. Greenhouse gases like carbon dioxide, methane, and water vapour cause global warming.

What is RAM, and how does it differ from ROM in a computer?

RAM (Random Access Memory) is volatile temporary working memory lost when power is off; ROM (Read Only Memory) is permanent, non-volatile memory that stores fixed instructions.