Matter and Materials
1. States of Matter
MATTER is anything that has MASS and takes up SPACE. Everything around you is made of matter!
'The air you breathe, the water you drink, the chair you sit on — ALL are matter. But light and sound are NOT matter because they have no mass and do not take up space.'
The Three States of Matter
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed shape | Takes the SHAPE of its container | No fixed shape — fills ALL available space |
| Volume | Fixed volume | Fixed volume | No fixed volume |
| Particles | Tightly packed. Can only VIBRATE. | Loosely packed. Can SLIDE past each other. | Very loosely packed. Move FREELY and FAST. |
| Compressibility | Hard to compress | Hard to compress | EASY to compress |
| Examples | Ice, wood, stone, metal | Water, milk, oil | Oxygen, steam, carbon dioxide |
Particle Arrangement
'Solids have the STRONGEST force of attraction between particles. Gases have the WEAKEST. That is why solids keep their shape and gases spread everywhere.'
| State | Particle Arrangement | Force Between Particles |
|---|---|---|
| Solid | Regular, closely packed | Very STRONG |
| Liquid | Irregular, close but not tight | MODERATE |
| Gas | Far apart, random | VERY WEAK |
2. Changing States of Matter
Matter can change from one state to another by HEATING or COOLING.
| Change | From → To | Process | Example |
|---|---|---|---|
| Melting | Solid → Liquid | HEAT is added | Ice melts into water |
| Freezing | Liquid → Solid | HEAT is removed (cooled) | Water freezes into ice |
| Evaporation | Liquid → Gas | HEAT is added | Water boils into steam |
| Condensation | Gas → Liquid | HEAT is removed | Steam on a cold lid turns to water |
| Sublimation | Solid → Gas (directly) | HEAT is added | Camphor, dry ice (solid CO₂) |
'Melting and evaporation need HEAT. Freezing and condensation release HEAT. Sublimation is SPECIAL — a solid turns directly into a gas WITHOUT becoming a liquid first.'
3. Solubility — What Dissolves?
A substance that DISSOLVES in a liquid (usually water) is called SOLUBLE. One that does NOT is called INSOLUBLE.
| Soluble | Insoluble |
|---|---|
| Salt | Sand |
| Sugar | Chalk powder |
| Lemon juice | Oil |
| Baking soda | Wood |
| Vinegar | Plastic |
Factors That Affect Solubility
| Factor | Effect |
|---|---|
| Temperature | HOT water dissolves MORE sugar than cold water. |
| Stirring | Stirring SPEEDS UP dissolving but does NOT increase the maximum amount. |
| Particle size | Smaller particles dissolve FASTER (sugar dissolves faster than a sugar cube). |
Solutions
When a solute (the substance being dissolved) mixes completely with a solvent (the liquid), it forms a SOLUTION.
'If you stir SALT into water, the salt seems to DISAPPEAR. But it is still there — you can taste it. That is because the salt particles have spread out EVENLY between the water particles.'
- Solute + Solvent = Solution
- Salt + Water = Saline solution
- Sugar + Water = Sugar solution
4. Floatation — Why Things Float
Whether an object FLOATS or SINKS depends on its DENSITY compared to the density of the liquid.
'Density is how tightly packed the matter is in an object. If it is LIGHTER than water, it floats. If it is HEAVIER than water, it sinks.'
| Object | Does It Float? | Reason |
|---|---|---|
| Wood | FLOATS | Less dense than water |
| Stone | SINKS | More dense than water |
| Oil | FLOATS on water | Oil is LESS dense than water |
| Iron nail | SINKS | More dense than water |
| Iron SHIP | FLOATS | Hollow shape — overall density LESS than water |
| Cork | FLOATS | Very low density |
Why a Ship Floats
'A huge iron ship weighing THOUSANDS of tonnes floats — but a small iron nail sinks. How? The ship is shaped like a HOLLOW bowl. It contains a lot of AIR, which makes its AVERAGE density less than water.'
5. Transparent, Translucent, and Opaque
Materials behave DIFFERENTLY with light.
| Type | Light Passes Through | Can You See Clearly? | Examples |
|---|---|---|---|
| Transparent | FULL light passes | YES — see objects clearly | Glass, clear water, air, cellophane |
| Translucent | SOME light passes | BLURRY / unclear | Frosted glass, wax paper, thin cloth |
| Opaque | NO light passes | CANNOT see through | Wood, metal, brick, cardboard |
'If you hold a TRANSPARENT object up to your eye, you can read a book through it. If it is TRANSLUCENT, you see a blur. If it is OPAQUE, you see NOTHING but the object.'
6. Physical and Chemical Changes
Physical Changes
A PHYSICAL change alters the FORM or appearance of a substance but NOT its chemical composition.
| Feature | Description |
|---|---|
| No NEW substance is formed | The substance REMAINS the same chemically |
| Usually REVERSIBLE | Can often be UNDONE |
| Only shape, size, or state changes | Ice → Water → Steam (all are still H₂O) |
Examples of physical changes:
- Melting ice (H₂O solid → H₂O liquid)
- Cutting paper (paper is still paper)
- Dissolving sugar in water (sugar is still sugar)
- Breaking a glass (glass is still glass)
Chemical Changes
A CHEMICAL change produces ONE or MORE NEW substances with different properties.
| Feature | Description |
|---|---|
| A NEW substance is FORMED | The original material CHANGES into something different |
| Usually IRREVERSIBLE | Difficult or impossible to REVERSE |
| Often involves heat, light, or gas | Signs that a reaction happened |
Examples of chemical changes:
- Burning wood (wood → ash + smoke + gases)
- Cooking an egg (raw egg → cooked egg — cannot go back)
- Rusting of iron (iron + oxygen → iron oxide / rust)
- Digestion of food (food → simpler nutrients)
Comparing Physical and Chemical Changes
| Physical Change | Chemical Change |
|---|---|
| NO new substance formed | NEW substance is formed |
| Usually REVERSIBLE | Usually IRREVERSIBLE |
| Change in shape, size, or state | Change in chemical composition |
| Melting, freezing, dissolving | Burning, rusting, cooking |
'Some changes are HARD to classify. When you POP popcorn, the kernel changes shape (physical) AND new flavours form (chemical). Many real-world changes are a MIXTURE of both types!'
Key Facts to Remember
- Matter exists in THREE states: solid, liquid, gas.
- 'In a physical change, the substance stays the SAME. In a chemical change, it becomes SOMETHING NEW.'
- Soluble substances DISSOLVE in water; insoluble ones do NOT.
- Whether something floats depends on its DENSITY.
- Transparent materials let ALL light through; translucent let SOME; opaque let NONE.
Common Mistakes
| Mistake | Why It Is Wrong | Correct Understanding |
|---|---|---|
| Thinking steam is visible | Steam (gas) is INVISIBLE. What you see above boiling water is tiny WATER DROPLETS (condensed steam). | True steam is a colourless, invisible gas |
| Believing evaporation and boiling are the same | Evaporation happens at ANY temperature (surface); boiling happens at a SPECIFIC temperature (throughout the liquid) | Both change liquid to gas but in different ways |
| Confusing melting and dissolving | Melting is state change (solid to liquid). Dissolving is mixing (one substance in another). | Ice MELTS. Sugar DISSOLVES in water. |
| Saying a chemical change is always reversible | Most chemical changes are NOT reversible | You cannot 'unburn' wood or 'unrust' iron |
Exam Focus (ICSE Class 5)
| Topic | Marks (Typical) | Question Type |
|---|---|---|
| States of matter — properties | 3-4 marks | Compare solids, liquids, gases |
| Changes of state | 3-4 marks | Identify melting, freezing, evaporation, condensation |
| Soluble vs insoluble | 2-3 marks | Classify substances |
| Transparent / Translucent / Opaque | 2-3 marks | Identify and give examples |
| Physical vs chemical changes | 4-5 marks | Differentiate with examples |
Self-Test: 5 Questions
Q1. List three differences between solids and gases.
Q2. What happens to the particles of water when it evaporates?
Q3. Why does a steel ship float in water but a steel nail sinks?
Q4. Classify as transparent, translucent, or opaque: frosted glass, clear water, wood, wax paper, air.
Q5. Is the following a physical or chemical change? Give a reason for each. (a) Rusting of iron (b) Cutting a piece of paper (c) Burning of wood
Answers
A1. (1) Solids have FIXED shape; gases have NO fixed shape (fill the container). (2) Solids have tightly packed particles; gases have widely spaced particles. (3) Solids are hard to compress; gases are easy to compress.
A2. When water evaporates, the particles gain HEAT ENERGY and move FASTER. They overcome the force of attraction between them and ESCAPE into the air as water vapour (gas).
A3. The steel ship is hollow and contains air, making its AVERAGE density less than water. The solid steel nail has higher density than water because it has no air inside.
A4. Frosted glass — TRANSLUCENT. Clear water — TRANSPARENT. Wood — OPAQUE. Wax paper — TRANSLUCENT. Air — TRANSPARENT.
A5. (a) Chemical change — a NEW substance (rust/iron oxide) is formed. (b) Physical change — the paper is still paper, only its SHAPE changed. (c) Chemical change — wood becomes ASH and new gases; it CANNOT be reversed.
