🧊 Matter in Our Surroundings – Full Breakdown

AMU Class 11 Science Chemistry June 2026

        This is the first chapter in the AMU Chemistry syllabus and honestly? It's a free 4–5 marks if you understand the patterns. The questions are mostly direct — states of matter, evaporation, sublimation, latent heat. AMU loves asking tricky True/False style MCQs and "which of the following" comparison questions. I've broken down everything in a way that you'll never mix up solid/liquid/gas properties again. Written by someone who cracked AMU 11 Science in 2026 — trust me, this chapter is pure memory + one simple trick.
    

1) What is Matter?

Definition: Anything that has mass and occupies space (volume) is called matter.

Examples: Chair, air, water, cold drink, smell of perfume, almonds — all matter.

Non-examples: Love, hate, thought, cold, smell (the sense of smell — not the actual gaseous particles). AMU loves this trick: "Smell of perfume" is matter (it's gaseous particles), but "love" or "thought" is NOT matter.

⚠️ AMU loves this: "Which of the following is NOT matter?" Options usually have a mix of love, smell of perfume, chair, cold drink. Answer = love / thought / hatred. Anything that doesn't have mass or occupy space is not matter.

2) Physical Nature of Matter

Particle Nature — 3 Characteristics (NCERT + AMU fav)

Particles of matter have:

Intermolecular space — gaps between particles
Intermolecular force — attraction between particles (max in solids, min in gases)
Kinetic energy — they are always in motion (min in solids, max in gases)

🧠 Shortcut — The "Diver" Question: AMU loves asking: "A diver can cut through water in a swimming pool. Which property does this show?" Answer: Particles of matter have space between them. Not "particles are small" — specifically intermolecular space. This exact question has appeared multiple times!

Diffusion

Spontaneous mixing of particles of two substances due to their motion.

Rate of diffusion: Gas > Liquid > Solid (because kinetic energy decreases)
Temperature ↑ → Rate of diffusion ↑ (more kinetic energy)
Example: Smell of hot sizzling food reaches you metres away — hot food has more kinetic energy → faster diffusion

⚠️ AMU Pattern: "Why does smell of hot food travel faster than cold food?" Answer: Higher temperature → more kinetic energy of particles → faster diffusion. This is a guaranteed MCQ.

3) States of Matter — The Comparison Table You Need

Property	Solid	Liquid	Gas
Shape	Definite	No definite (takes shape of container)	No definite
Volume	Definite	Definite	No definite (fills container)
Compressibility	Negligible	Very low	High
Intermolecular force	Strongest	Moderate	Weakest
Intermolecular space	Minimum	Moderate	Maximum
Kinetic energy	Minimum	Moderate	Maximum
Rigidity / Fluidity	Rigid	Fluid	Fluid
Density	Highest (except H₂O)	Moderate	Lowest

🧠 Trick to remember — "SVK" mnemonic:
S → Solid: Shape + Volume fixed, Kinetic energy lowest
V → Vapour (Gas): Variable shape + Variable volume, Kinetic energy highest
L → Liquid: Volume fixed, Shape variable, Kinetic energy in between

For density: S > L > G (EXCEPT water — ice < water. More on this below!)

Extra Point — Plasma & BEC

AMU usually doesn't go deep into plasma/BEC for Class 11 science, but knowing these 2 extra states is good:

Plasma: Superheated gas with charged particles (found in stars, neon signs). Most abundant state in the universe.
Bose-Einstein Condensate (BEC): Supercooled gas near absolute zero where particles act like one big atom (predicted by Bose & Einstein).

4) Can Matter Change Its State?

The 6 Phase Changes (Know the names!)

Change	Name	Heat Absorbed / Released
Solid → Liquid	Fusion / Melting	Absorbed (endothermic)
Liquid → Gas	Vaporisation / Boiling / Evaporation	Absorbed (endothermic)
Solid → Gas (direct)	Sublimation	Absorbed (endothermic)
Gas → Liquid	Condensation	Released (exothermic)
Liquid → Solid	Freezing / Solidification	Released (exothermic)
Gas → Solid (direct)	Deposition	Released (exothermic)

⚠️ AMU Favourite: "Which of the following is a sublimable substance?" Answer: Camphor, Naphthalene, Ammonium Chloride, Iodine, Dry Ice (solid CO₂). These directly go from solid to gas without becoming liquid. Also the reverse: "Which gas on cooling directly becomes solid?" → Iodine vapour / Ammonium chloride vapour.

Effect of Temperature & Pressure

Temperature ↑ → Kinetic energy ↑ → particles overcome forces → state changes from S→L→G
Pressure ↑ → particles pushed closer → state changes from G→L→S (e.g., LPG — gases compressed to liquid)
Boiling point: Temperature at which vapour pressure = atmospheric pressure
Melting point: Temperature at which solid changes to liquid at 1 atm

Key Formula for AMU:
Boiling Point of Water = 100°C (at sea level, 1 atm)
Melting Point of Ice = 0°C (at 1 atm)

At higher altitudes → lower atmospheric pressure → water boils at <100°C
At higher pressure → boiling point increases (pressure cooker principle!)

5) Latent Heat — The "Hidden" Heat

When a substance changes state, temperature remains constant — the heat supplied is used to overcome intermolecular forces, NOT to raise temperature. This heat is called latent heat (hidden heat).

Two Types

Latent Heat of Fusion (L_f)

Heat required to convert 1 kg of solid → liquid at its melting point, without temperature change.

For ice: L_f = 3.34 × 10⁵ J/kg (or 80 cal/g)

Latent Heat of Vaporisation (L_v)

Heat required to convert 1 kg of liquid → gas at its boiling point, without temperature change.

For water: L_v = 22.6 × 10⁵ J/kg (or 540 cal/g)

⚠️ AMU Classic: "Why does ice at 0°C cool better than water at 0°C?" Answer: Ice has latent heat of fusion — it absorbs extra heat (336 J/g) from the surroundings to melt, providing more cooling than water at the same temperature. This question is practically guaranteed every few years!

🧠 Quick Trick — L_v > L_f
Always remember: Latent heat of vaporisation is MUCH larger than latent heat of fusion. Why? Because converting liquid to gas requires breaking all intermolecular forces (particles fly apart), while melting only partially breaks them. So L_v ≈ 7× L_f for water.

6) Evaporation — The Most Asked Topic in AMU

Evaporation: Conversion of liquid into vapour at any temperature below its boiling point, occurring only at the surface of the liquid.

Factors Affecting Rate of Evaporation (AMU Loves These)

Surface area ↑ → Rate ↑ (more molecules can escape from surface)
Temperature ↑ → Rate ↑ (more kinetic energy)
Wind speed ↑ → Rate ↑ (carries away vapour molecules, preventing saturation)
Humidity ↑ → Rate ↓ (air already has more water vapour, less space for more)

Evaporation causes Cooling — Why?
The molecules with the highest kinetic energy escape from the liquid surface first. This leaves behind molecules with lower average kinetic energy → temperature of the remaining liquid decreases → cooling effect.

Evaporation vs Boiling — AMU Trick Comparison

Feature	Evaporation	Boiling
Temperature	Any temperature (below boiling point)	Fixed (boiling point)
Where it occurs	Only at surface	Throughout the liquid (bulk)
Rate	Slow	Fast
Bubbles	No bubbles	Bubbles of vapour form inside
Cooling effect	Yes (causes cooling)	No net cooling (temperature constant)

⚠️ AMU PYQ Pattern: "Why does a desert cooler cool better on a hot dry day?"
Answer: Hot day → high temperature → evaporation rate ↑. Dry day → low humidity → evaporation rate ↑. More evaporation → more cooling. This two-factor answer is what AMU expects!

7) The Ice Floats on Water — The Exception

Question: Liquids generally have lower density than solids, but ice floats on water. Why?

Answer: In ice, water molecules form a cage-like structure (hydrogen bonding) with more empty spaces → less dense (0.92 g/cm³) than liquid water (1 g/cm³). This is unique to water — almost every other substance is denser in solid state.

🧠 Remember: Water is the ONLY substance where solid is LESS dense than liquid. This is why:

Ice floats on water
Ponds freeze from top to bottom (ice on top insulates water below → aquatic life survives!)
Water has maximum density at 4°C, not 0°C

8) Common AMU-Style MCQs with Answers

Q1:

Which of the following is NOT matter?

(a) Chair (b) Smell of perfume (c) Love (d) Cold drink

Answer: (c) Love — does not have mass or occupy space. Smell of perfume is matter (gaseous particles).

Q2:

A diver can cut through water in a swimming pool. This shows that:

(a) Water is a liquid (b) Particles of water have spaces between them (c) Water has high density (d) Water is compressible

Answer: (b) Particles of water have spaces between them

Q3:

Which of the following is a sublimable substance?

(a) Salt (b) Sugar (c) Camphor (d) Sand

Answer: (c) Camphor

Q4:

An example of solid-gas sublimation is:

(a) Dry ice (b) Water ice (c) Salt (d) Iron

Answer: (a) Dry ice (solid CO₂ directly converts to CO₂ gas)

Q5:

The rate of evaporation increases with:

(a) Decrease in surface area (b) Decrease in temperature (c) Increase in humidity (d) Increase in wind speed

Answer: (d) Increase in wind speed

Q6:

When we heat a solid, its temperature:

(a) Always increases (b) First increases, then becomes constant during phase change (c) Always decreases (d) None of these

Answer: (b) — during phase change, temperature remains constant (latent heat is being used).

Q7:

Latent heat of fusion of ice is:

(a) 80 cal/g (b) 540 cal/g (c) 100 cal/g (d) 22.6 × 10⁵ J/kg

Answer: (a) 80 cal/g (or 3.34 × 10⁵ J/kg). L_v of water is 540 cal/g.

Q8:

The temperature at which a liquid boils depends on:

(a) Atmospheric pressure (b) Volume of liquid (c) Surface area (d) Colour of liquid

Answer: (a) Atmospheric pressure

Q9:

Ice at 0°C is more effective for cooling than water at 0°C because:

(a) Ice is colder (b) Ice absorbs latent heat of fusion from surroundings (c) Ice has lower density (d) Ice is a solid

Answer: (b) Ice absorbs latent heat of fusion

Q10:

Which of the following has the highest kinetic energy?

(a) Solid (b) Liquid (c) Gas (d) All equal

Answer: (c) Gas

9) Quick One-Liner Revision — Last 5 Min Before Exam

Matter = mass + volume. Love/thought/hatred = NOT matter.
Particles of matter have: intermolecular space, force, and kinetic energy.
Diffusion rate: Gas > Liquid > Solid. Temperature ↑ → Diffusion ↑.
Solids: fixed shape + volume. Liquids: fixed volume, variable shape. Gases: variable shape + volume.
Density order: Solid > Liquid > Gas (EXCEPT water — ice is less dense).
Sublimable substances: Camphor, Naphthalene, NH₄Cl, Iodine, Dry Ice.
Evaporation = surface phenomenon at any T. Boiling = bulk phenomenon at fixed T.
Evaporation causes cooling (high KE molecules escape first).
Factors ↑ evaporation: ↑ surface area, ↑ temp, ↑ wind speed, ↓ humidity.
Latent heat of fusion (L_f) = melting/freezing. Latent heat of vaporisation (L_v) = boiling/condensation. L_v > L_f.
During phase change → temperature constant (latent heat used to overcome forces).
Ice at 0°C cools better than water at 0°C because of L_f.
Water max density at 4°C (not 0°C!) → ice floats.

🧠 From a 2026 AMU topper — my final tips for this chapter:
1. Memorise the 3 characteristics of particles — this is asked directly or indirectly in 90% of AMU questions from this chapter.
2. The comparison table (solid/liquid/gas) is your best friend. Draw it once a day for a week before the exam.
3. Evaporation vs Boiling difference is AMU's favourite 1-mark MCQ. Never mix up "surface" vs "bulk".
4. Sublimation examples — just remember C-N-A-I-D (Camphor, Naphthalene, Ammonium Chloride, Iodine, Dry ice).
5. Latent heat questions are always about "Why does temperature remain constant?" or "Why ice cools better?" — prepare 2-3 line answers for these.