Welcome, future scientists! Today, we’re diving into the fundamental building blocks of everything around us: matter. From the air we breathe to the chair you’re sitting on, everything is made of matter. Understanding its nature is the very first step in unraveling the mysteries of chemistry.
Sub-topic 1: Definition of Matter
What exactly is matter?
Definition: Matter is anything that has mass and occupies space (has volume).
Simple Test: If you can weigh it and it takes up room, it’s matter!
Examples: A rock, water, air, you, a tree, a car.
Non-Examples (What isn’t matter?): Light, heat, sound, thoughts, emotions. These are forms of energy or abstract concepts, not matter.
Sub-topic 2: States of Matter and their Properties
Matter exists in different physical forms, called states. The three most common states you’ll encounter are solid, liquid, and gas. There’s also plasma, but we’ll focus on the main three for now.
A. Solids
Arrangement of Particles: Particles (atoms or molecules) are tightly packed together in a regular, fixed pattern (like bricks in a wall). They vibrate in fixed positions.
Shape: Have a definite shape (they keep their shape).
Volume: Have a definite volume (they take up a specific amount of space).
Compressibility: Very difficult to compress (squeeze) because particles are already so close.
Flow: Do not flow.
Examples: Ice, wood, iron, salt.
B. Liquids
Arrangement of Particles: Particles are close together but randomly arranged. They can slide past each other.
Shape: Do not have a definite shape; they take the shape of their container.
Volume: Have a definite volume.
Compressibility: Difficult to compress, but more so than solids.
Flow: Flow easily.
Examples: Water, oil, milk, mercury.
C. Gases
Arrangement of Particles: Particles are very far apart, randomly arranged, and move rapidly in all directions.
Shape: Do not have a definite shape; they fill the entire volume of their container.
Volume: Do not have a definite volume; they expand to fill their container.
Compressibility: Easily compressible because there’s so much empty space between particles.
Flow: Flow very easily.
Examples: Air, oxygen, nitrogen, steam.
Summary Table: States of Matter
Property
Solid
Liquid
Gas
Particle Spacing
Close
Close
Far apart
Particle Motion
Vibrate in fixed pos.
Slide past each other
Random, rapid motion
Shape
Definite
Indefinite
Indefinite
Volume
Definite
Definite
Indefinite
Compressibility
Very low
Low
High
Changes of State (Physical Changes)
Matter can change from one state to another when energy is added or removed. These are physical changes because the substance itself doesn’t change its chemical identity; only its form changes.
Melting: Solid
rightarrow Liquid (e.g., ice to water). Occurs when heat energy is absorbed.
Freezing: Liquid
rightarrow Solid (e.g., water to ice). Occurs when heat energy is released.
Boiling/Vaporization: Liquid
rightarrow Gas (e.g., water to steam). Occurs when heat energy is absorbed at a specific boiling point.
Evaporation: Liquid
rightarrow Gas (e.g., puddle drying up). Occurs at any temperature below the boiling point, as heat energy is absorbed from the surroundings.
Condensation: Gas
rightarrow Liquid (e.g., dew on grass, water droplets on a cold glass). Occurs when heat energy is released.
Sublimation: Solid
rightarrow Gas directly, without passing through the liquid state (e.g., dry ice, camphor). Occurs when heat energy is absorbed.
Deposition: Gas–> Solid directly, without passing through the liquid state (e.g., frost formation). Occurs when heat energy is released.
Classification of Matter
Matter can be broadly classified into two main categories: pure substances and mixtures.
A. Pure Substances
Definition: Have a fixed chemical composition and distinct properties. They cannot be separated into simpler substances by physical means.
Types of Pure Substances:
Elements:
Definition: The simplest pure substances. They cannot be broken down into simpler chemical substances by ordinary chemical means.
Composition: Made up of only one type of atom.
Examples: Oxygen (O), Hydrogen (H), Gold (Au), Iron (Fe). You can find all known elements on the Periodic Table.
Compounds:
Definition: Pure substances formed when two or more different elements are chemically combined in a fixed ratio.
Composition: Made up of two or more different types of atoms bonded together.
Properties: Have properties entirely different from the elements they are made from.
Separation: Can only be separated into their constituent elements by chemical reactions, not physical means.
Examples: Water (
textH_2
textO, from Hydrogen and Oxygen), Carbon Dioxide (
textCO_2, from Carbon and Oxygen), Salt (NaCl, from Sodium and Chlorine).
B. Mixtures
Definition: Combinations of two or more pure substances that are physically mixed but not chemically combined.
Composition: The components retain their individual properties.
Ratio: The components can be present in varying proportions.
Separation: Can be separated into their components by physical means.
Types of Mixtures:
Homogeneous Mixtures (Solutions):
Definition: Mixtures where the components are uniformly distributed, making it appear as a single substance. You cannot see the individual components.
Examples: Saltwater (salt dissolved in water), air (mixture of gases), brass (alloy of copper and zinc).
Heterogeneous Mixtures:
Definition: Mixtures where the components are not uniformly distributed, and you can see the individual components or distinct phases.
Examples: Sand and water, oil and water, granite (you can see different mineral grains), salad.
Diagram: Classification of Matter
MATTER
|
——————————
| |
Pure Substances Mixtures
| |
—————– ————————
| | | |
Elements Compounds Homogeneous Mixtures Heterogeneous Mixtures
(e.g., O, Fe) (e.g., H2O, NaCl) (e.g., Saltwater, Air) (e.g., Sand & Water, Salad)
Sub-topic 5: Distinguishing between Mixtures and Compounds
This is a crucial distinction!
Feature
Compound
Mixture
Composition
Fixed ratio of elements
Variable ratio of components
Bonding
Chemically bonded
Physically mixed (no chemical bonds)
Properties
New properties different from components
Components retain their original properties
Separation
Only by chemical means
By physical means
Energy Change
Usually involves significant energy change during formation
Little or no energy change during formation
Formula
Has a fixed chemical formula (e.g.,
textH_2
textO)
No fixed chemical formula
Melting/Boiling Point
Fixed melting/boiling point
Range of melting/boiling points
Sub-topic 6: Physical and Chemical Changes
Matter can undergo two types of changes:
A. Physical Changes
Definition: Changes in the form or appearance of a substance, but not its chemical composition. No new substance is formed.
Reversibility: Often easily reversible.
Examples:
Changes of state (melting ice, boiling water).
Dissolving salt in water.
Cutting paper.
Bending a metal.
B. Chemical Changes (Chemical Reactions)
Definition: Changes that result in the formation of one or more new substances with different chemical properties. The original substances are transformed.
Reversibility: Often difficult to reverse.
Indicators of a Chemical Change:
Formation of gas (bubbles).
Formation of a precipitate (a solid formed in a liquid solution).
Change in color.
Change in temperature (release or absorption of heat).
Production of light or sound.
Change in odor.
Examples:
Burning wood (wood turns to ash and smoke).
Rusting of iron (iron reacts with oxygen and water).
Digesting food.
Baking a cake.
Explosion of fireworks.
Sub-topic 7: Laws of Chemical Combination (Brief Introduction)
These laws describe how elements combine to form compounds. You’ll delve deeper into these later, but it’s good to know they exist within the context of matter’s behavior.
Law of Conservation of Mass: “Matter cannot be created or destroyed in a chemical reaction.” This means the total mass of the reactants equals the total mass of the products.
Law of Definite Proportions (or Constant Composition): “A given chemical compound always contains its component elements in fixed ratio by mass.” For example, water (
textH_2
textO) always contains hydrogen and oxygen in a 1:8 mass ratio, no matter where the water comes from.
Law of Multiple Proportions: “When two elements form more than one compound, the ratios of the masses of the second element that combine with a fixed mass of the first element can be expressed in small whole numbers.” (This one is a bit more advanced, but good to know its name.)
Conclusion
Understanding the nature of matter – its states, how it’s classified, and how it changes – is the bedrock of chemistry. This knowledge will help you grasp more complex concepts as you progress. Keep practicing identifying different types of matter and changes, and you’ll be a chemistry whiz in no time.
WAEC & JAMB Focus Areas:
Definitions: Matter, element, compound, mixture (homogeneous, heterogeneous).
Properties of States of Matter: Be able to describe and compare solids, liquids, and gases based on particle arrangement, shape, volume, and compressibility.
Changes of State: Know the names and definitions of all state changes (melting, boiling, condensation, sublimation, etc.) and whether heat is absorbed or released.
Classification of Matter: Be able to classify given examples as elements, compounds, homogeneous mixtures, or heterogeneous mixtures.
Distinguishing Mixtures from Compounds: Crucial for both objective and theory questions.
Physical vs. Chemical Changes: Be able to identify and differentiate between physical and chemical changes, listing indicators for chemical changes.
Good luck with your studies!