Properties of Matter

What Are Properties of Matter?

Every substance has special features that help us identify it and understand how it behaves. We call these features properties. When you look at sugar, you can see it is white, sweet, and dissolves in water. These are some of its properties.

Scientists divide properties of matter into two main groups: physical properties and chemical properties. Both types give us important information about substances.

Physical Properties

Physical properties are characteristics you can observe or measure without changing what the substance is made of. When you measure physical properties, the substance remains the same substance.

Types of Physical Properties

1. Color: What the substance looks like to your eyes. Examples: Sulfur is yellow, copper is brown-red, water is colorless.

2. Odor (Smell): How the substance smells. Examples: Ammonia has a sharp smell, perfume smells sweet, gold has no smell.

3. Taste: How a substance tastes (never taste unknown chemicals). Examples: Salt is salty, sugar is sweet, lemon juice is sour.

4. State of matter: Whether solid, liquid, or gas at room temperature. Examples: Iron is solid, water is liquid, oxygen is gas.

5. Melting point: The temperature at which a solid becomes liquid. Examples: Ice melts at 0°C, candle wax melts around 60°C, aluminum melts at 660°C.

6. Boiling point: The temperature at which a liquid becomes gas. Examples: Water boils at 100°C, alcohol boils at 78°C, mercury boils at 357°C.

7. Density: How much mass fits in a certain volume. A small piece of iron is heavier than the same size piece of wood because iron has higher density.

8. Solubility: How well a substance dissolves in a liquid. Sugar dissolves easily in water (soluble), sand does not (insoluble).

9. Hardness: How easily the substance can be scratched or dented. Diamond is very hard, while chalk is soft.

10. Electrical conductivity: How well electricity passes through. Metals conduct electricity well, plastic does not.

11. Magnetic properties: Whether a magnet attracts the substance. Iron is magnetic, aluminum is not.

Nigerian Examples of Physical Properties

• Garri: White or yellow color, characteristic smell, granular texture, swells in water
• Palm oil: Red-orange color, thick liquid, does not mix with water, solidifies in cold weather
• Naira notes: Different colors for different values, specific texture, water resistant
• Aluminum cooking pot: Silver color, lightweight, good conductor of heat, does not rust easily

Chemical Properties

Chemical properties describe how a substance interacts with other substances to form new substances. You can only observe chemical properties when the substance undergoes a chemical change.

Common Chemical Properties

1. Combustibility (Flammability): Whether the substance can burn in air or oxygen. Examples: Wood, paper, and petrol can burn. Water and sand cannot burn.

2. Reactivity with acids: How a substance reacts when mixed with acid. Examples: Metals like zinc react with acids to produce hydrogen gas. Gold does not react with most acids.

3. Reactivity with bases: How a substance behaves with bases. Examples: Aluminum reacts with sodium hydroxide, releasing hydrogen.

4. Oxidation: How easily a substance combines with oxygen. Examples: Iron rusts (reacts with oxygen and moisture), gold does not rust.

5. Stability: Whether a substance breaks down easily. Examples: Hydrogen peroxide slowly breaks down into water and oxygen. Gold remains stable for thousands of years.

6. Reactivity with water: How a substance behaves when it touches water. Examples: Sodium reacts violently with water. Iron reacts slowly (rusting). Gold does not react.

Nigerian Examples of Chemical Properties

• Kerosene: Burns easily (used in stoves), does not react with water
• Iron nails: Rust when exposed to air and moisture, react with acids
• Limestone (for building): Reacts with acids, breaks down when heated strongly
• Cooking gas (LPG): Very flammable, burns cleanly with oxygen

Comparison of Physical and Chemical Properties

Physical Changes

A physical change is one where the appearance or state of matter changes, but no new substance forms. The particles stay the same, just arranged differently.

Characteristics of Physical Changes

• Usually easily reversible
• No new substance forms
• Only physical properties change
• Usually involves small energy changes
• The mass remains the same

Examples of Physical Changes

Nigerian context examples:

• Melting candle wax: Wax changes from solid to liquid when heated, back to solid when cooled. Still wax throughout.
• Dissolving sugar in tea: Sugar seems to disappear but is still there. You can get it back by evaporating the water.
• Breaking a plate: The pieces are still made of the same material, just in smaller bits.
• Freezing pure water in sachets: Water becomes ice but remains H₂O.
• Grinding pepper at the market: Fresh pepper becomes powder, but it is still pepper.
• Boiling water for pap: Water becomes steam but is still H₂O.
• Bending aluminum roofing sheet: Shape changes but still aluminum.
• Mixing garri with sugar: Both substances remain unchanged, just mixed.

Chemical Changes

A chemical change produces one or more new substances with different properties from the starting materials. The particles rearrange to form completely different substances.

Characteristics of Chemical Changes

• Usually not easily reversible
• New substance(s) form
• Chemical properties change
• Usually involves large energy changes (heat, light)
• May involve color change, gas production, or precipitate formation

Examples of Chemical Changes

Nigerian context examples:

• Rusting of iron: Iron gates or nails turn brown and weak. Iron combines with oxygen to form iron oxide (rust). Cannot easily reverse.
• Burning wood or charcoal: Wood turns to ash and smoke. Cannot get the wood back from ash.
• Frying akara or puff-puff: Raw bean paste changes chemically when heated in hot oil. Cannot reverse to raw paste.
• Cooking rice or yam: Heat causes chemical changes that make food softer and tastier. Raw starch changes structure.
• Battery running down: Chemical reactions in phone or car battery produce electricity. Chemicals change permanently.
• Milk going sour: Bacteria cause chemical changes that turn fresh milk sour. Cannot make it fresh again.
• Photosynthesis in plants: Plants use sunlight to change carbon dioxide and water into sugar and oxygen.
• Digesting food: Your body breaks down jollof rice, beans, and meat into simpler substances for energy.
• Cement setting: When you mix cement powder with water and sand for building, chemical reactions make it harden permanently.

How to Identify Physical vs Chemical Changes

Ask these questions:

1. Can you easily reverse it? If yes, likely physical. If no, likely chemical.
2. Is it still the same substance? If yes, physical. If no, chemical.
3. Can you get the original material back easily? If yes, physical. If no, chemical.
4. Did color change permanently? Permanent color change often means chemical.
5. Was there a big release or absorption of energy? Large energy changes suggest chemical.
6. Did gas bubbles form or disappear? Gas production often indicates chemical change.

Energy Changes in Physical and Chemical Changes

Physical changes usually involve small amounts of energy. Melting ice absorbs heat, freezing water releases heat, but these energy changes are moderate.

Chemical changes usually involve larger energy changes:

• Exothermic reactions: Release energy (heat, light). Examples: Burning wood, rusting iron, respiration in your body.
• Endothermic reactions: Absorb energy from surroundings. Examples: Photosynthesis in plants, decomposition of limestone when heated.

Common Exam Mistakes

Practice Questions

Multiple Choice

1. Which of the following is a chemical property?
a) Melting point
b) Density
c) Flammability ✓
d) Color

2. Which process represents a physical change?
a) Rusting of iron
b) Burning of paper
c) Melting of ice ✓
d) Souring of milk

3. A substance that can be scratched easily is said to have:
a) High density
b) Low melting point
c) Low hardness ✓
d) High solubility

4. Which of the following shows that a chemical change has occurred?
a) Change in shape
b) Change in state
c) Formation of new substance ✓
d) Change in size

Theory Questions

1. (a) Define the following terms: (i) Physical property (ii) Chemical property (4 marks)
(b) Give THREE examples each of: (i) Physical properties (ii) Chemical properties (6 marks)

Tip: For definitions, mention whether the substance changes identity. For examples, use common substances like iron, water, or wood.

2. (a) Distinguish between physical change and chemical change. (4 marks)
(b) Classify each of the following as physical or chemical change:
(i) Melting of butter (ii) Burning of kerosene (iii) Dissolving salt in water (iv) Ripening of mango (v) Magnetizing iron (5 marks)
(c) State TWO ways to identify if a chemical change has occurred. (2 marks)

Tip: For (b): Physical changes: (i), (iii), (v). Chemical changes: (ii), (iv). Explain your reasoning.

3. (a) Explain why rusting of iron is considered a chemical change. (4 marks)
(b) A student mixed sand and salt, then added water and filtered the mixture. State whether each step involves physical or chemical change and explain why. (6 marks)

Tip: For (a), mention that iron combines with oxygen and moisture to form iron oxide (rust), a new substance with different properties. For (b), all steps are physical – no new substances form.

4. (a) List FOUR physical properties of water. (4 marks)
(b) Describe an experiment to determine the melting point of a solid substance. (6 marks)

Tip: For (a): colorless, odorless, boiling point 100°C, melting point 0°C, density 1 g/cm³, good solvent. For (b): Use heating curve method with thermometer.

Memory Aids

Physical properties: “COMDS BET” – Color, Odor, Melting point, Density, Solubility, Boiling point, Electrical conductivity, Taste

Chemical properties: “FROS” – Flammability, Reactivity with acids, Oxidation, Stability

Physical vs Chemical change: “If it’s NEW, it’s chemical; if it’s the SAME, it’s physical” (NEW substance = chemical)

Signs of chemical change: “CGEP” – Color change (permanent), Gas produced, Energy change (large), Precipitate forms

Related Topics

Understanding properties of matter connects to:

• States of matter and particle behavior
• Separation techniques (based on physical properties)
• Chemical reactions and equations
• Elements, compounds, and mixtures
• Acids, bases, and salts (chemical properties)