Types of Substances

Types of Substances

A. Pure Substances

Pure substances are materials that have a uniform composition and definite chemical properties. They cannot be separated into simpler substances by physical methods.

1. Elements

Elements are the simplest form of matter consisting of only one type of atom. They cannot be broken down into simpler substances by chemical means. Elements are classified into three types:

(a) Metals

• Good conductors of heat and electricity

• Malleable (can be beaten into sheets) and ductile (can be drawn into wires)

• Lustrous (shiny appearance) and high melting points

• Example: Iron (Fe), Copper (Cu), Gold (Au), Aluminum (Al)

(b) Non-Metals

• Poor conductors of heat and electricity

• Brittle and non-ductile

• May exist in solid, liquid, or gaseous states at room temperature

• Example: Oxygen (O₂), Carbon (C), Sulfur (S), Nitrogen (N₂)

(c) Metalloids

• Have properties of both metals and non-metals

• Semi-conductors, used in electronics

• Example: Silicon (Si), Boron (B), Arsenic (As), Germanium (Ge)

2. Compounds

Compounds are pure substances composed of two or more elements chemically combined in fixed proportions. They have unique properties different from their constituent elements and can be broken down into simpler substances by chemical means.

Examples of Compounds:

• Water (H₂O): Composed of hydrogen and oxygen; essential for life.

• Carbon Dioxide (CO₂): Composed of carbon and oxygen; a gas involved in respiration and photosynthesis.

• Salt (Sodium Chloride, NaCl): Made of sodium and chlorine; commonly used in food.

B. Mixtures

A mixture is a combination of two or more substances that are physically combined and can be separated by physical methods. Unlike pure substances, mixtures do not have a fixed composition or definite properties.

Mixtures are classified into two main types:

1. Homogeneous Mixtures

2. Heterogeneous Mixtures

1. Homogeneous Mixtures

Homogeneous mixtures have a uniform composition throughout, meaning the components are evenly distributed and cannot be distinguished by the naked eye.

(a) Solutions

• A solution consists of a solute (substance dissolved) and a solvent (substance in which the solute is dissolved).

• Particles are very small and do not settle down.

• Example: Sugar in water, salt in water, air (a mixture of gases).

(b) Alloys

• An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.

• Alloys have enhanced properties compared to their individual components.

• Example: Brass (Copper + Zinc), Steel (Iron + Carbon), Bronze (Copper + Tin).

2. Heterogeneous Mixtures

Heterogeneous mixtures have a non-uniform composition, meaning the different substances remain separate and can often be seen distinctly.

(a) Suspensions

• A suspension is a mixture in which solid particles are dispersed in a liquid or gas but do not dissolve.

• Particles are large and can settle down over time.

• Example: Mud in water, flour in water, sand in water.

(b) Colloids

• A colloid is a mixture where tiny particles of one substance are dispersed in another but do not settle down.

• Colloidal particles are larger than in a solution but smaller than in a suspension.

• Example: Milk, fog, blood, jelly.

Comparison of Solutions, Suspensions, and Colloids

Mixtures are an essential part of our daily lives, from the air we breathe to the food we eat, and they can be separated using various physical techniques like filtration, evaporation, and distillation.