8.1 What Are Mixtures?

Look around — almost nothing near you is made of just one substance. Your poha, a sprout salad, lemonade, sugar in water: all are several things combined. When we put substances together like this, we make a mixture.

What Is a Mixture? A mixture is formed when two or more substances are mixed and each keeps its own properties. The individual substances are the components of the mixture, and they do not react chemically with one another. Because there’s no chemical reaction, a mixture can usually be separated back into its components.

Two kinds of mixture

Uniform vs Non-Uniform - In a non-uniform mixture, the components are not evenly spread and you can often see them separately (the green gram, onion and tomato in a sprout salad). - In a uniform mixture, the components are evenly distributed and cannot be told apart, even under a microscope (sugar dissolved in water).

Sort these mixtures into uniform or non-uniform.

Uniform or non-uniform mixture?
Click each card to toggle. Then press Check.

A Step Further: Alloys (and Mishraloha) Stainless steel is a mixture! It blends iron, nickel, chromium and a little carbon so uniformly that you can’t see the separate metals. Such uniform mixtures of metals are called alloys — brass (copper + zinc) and bronze (copper + tin) are others. Ancient India knew them as Mishraloha: texts like the Charaka Samhita describe Kamsya (bronze: 4 parts copper, 1 part tin) used to aid digestion and immunity.

Is air a mixture?

Air is a uniform mixture of mainly nitrogen (about 78%), oxygen, argon, carbon dioxide and water vapour.

Activity 8.1 — Proving CO₂ is in the air Make lime water (stir calcium oxide into water, then filter) and leave the clear solution exposed to air. It slowly turns milky — because the carbon dioxide in the air reacts with the calcium hydroxide to form insoluble white calcium carbonate. The milkiness proves CO₂ is present in air.

Air also carries dust — leave a clean black sheet by a window (Activity 8.2) and tiny particles settle on it. These suspended dust particles aren’t really part of the air; they’re pollutants, and their amount varies from place to place (tracked by the Air Quality Index, AQI, from Chapter 6).

Types of Mixtures Mixtures come in every combination of states: gas + gas (air), gas + liquid (soda water), solid + gas (smoke), liquid + liquid (vinegar; oil & water), solid + liquid (seawater), and solid + solid (alloys). In science, the components of a mixture are taken to be pure substances — which brings us to our next question.