Revision: Elements, Compounds and Mixtures >> Mixture Chemistry ICSE ICSE Class 6 CISCE

• Matter is defined based on its physical and chemical structure. It occupies space and has mass, particularly as opposed to energy.
• Atoms and molecules are the building blocks of matter, consisting of positively charged protons, neutral neutrons, and negatively charged electrons, respectively.

Chemical properties of matter tell us how a substance changes when it interacts with other substances. These properties describe how matter reacts and forms new substances. When a chemical change happens, the matter changes into something new. The atoms in a substance rearrange themselves, and a new substance is formed. For example:

• When wood burns, it turns into ash and smoke.
• When iron is exposed to air and water, it forms rust.

Examples of Chemical Properties:

• Flammability: This describes if a substance can burn. For example, wood is flammable because it can catch fire.
• Reactivity: This tells us how a substance reacts when mixed with others. For example, if you mix vinegar with baking soda, they react to create bubbles.
• Rusting: Some metals, like iron, will form rust when they come in contact with water and air.
• Acidity and Basicity: Some substances are acidic (like lemon juice), while others are basic (like soap). Acids and bases can react with each other to form new substances.

An emulsion is a colloid in which minute droplets of one liquid are dispersed in another liquid which is not miscible with it. Examples are milk and butter.

Anything that has mass and occupies space is called matter.

Atom — An atom is the smallest part of an element that takes place in a chemical reaction.

Matter—Anything that has mass and occupies space is called matter.

The matter is defined as anything that has mass and takes up space. The matter is found in solid, liquid and gas.

Compounds: Compounds are pure substances composed of two or more elements in definite proportion by mass and has a definite set of properties. The compound is made up of only one kind of molecules

Homogeneous mixture: “A mixture in which its constituents are uniformly distributed throughout its volume and cannot be seen separately is called a homogenous mixture.”

Mixtures are formed when two or more substances are mixed together without participating in a chemical change. A mixture has a variable composition. A mixture shows the properties of the constituent substances. Physical methods can easily separate the constituents.

• Atoms/molecules of a mixture are of two or more types.
• The constituent molecules of a mixture are different from each other and are not joined by chemical bonds.
• Components in a mixture retain their original properties because they are not chemically combined.
• The proportion of constituent substances in a mixture can change.
• The properties of constituent substances are retained in the mixture. 
• Unlike compounds, mixtures do not have a fixed ratio of their components.

For Examples,

Air is a mixture containing nitrogen (N₂), oxygen (O₂), and other gases.

Types of mixture

1. Homogeneous Mixtures: Homo means same. A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture. For example, salt in water. It has a uniform composition, and it can’t be separated out physically.
2. Heterogeneous Mixture: Hetero means different. A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. For example, vegetable soup. It has a non-uniform composition and can be separated out physically.

Alloy: “A homogeneous solid mixture of two or more metals or a metal and a non-metal is called an alloy.”

Impure substance: “A substance in which some other substances are also present in smaller or larger amounts is called an impure substance. Mixtures are impure substances. An example of an impure substance is air.

Pure substance: “Pure Substance is either element or compound. It contains the same kind of atom or molecules and has a definite set of physical and chemical properties.”

Immiscible liquids : Heterogeneous liquid-liquid mixtures are called immiscible liquids.

Miscible liquids : Homogeneous liquid-liquid mixtures are called miscible liquids.

Heterogeneous mixture: “A mixture in which the components are not uniformly distributed through its volume and can be easily seen separately is called a heterogeneous mixture.”

Solution: “The homogeneous mixture of water (or any other solvent) and a substance soluble in it is called a solution.”

The change of state from solid to gas directly is called sublimation.

The change of a solid substance directly into a gas or vapour without first changing into a liquid is called sublimation.

OR

The change from solid state to vapour state without passing through the liquid state is called sublimation, and the substance is said to sublime.

Evaporation: Evaporation is a process which is used to separate a solid substance dissolved in liquid. It is based on the fact that liquids vaporize easily whereas solids do not.

Evaporation Is the process of converting a liquid into its vapour state either by exposing it to air or by heating.

Evaporation : Is the process ~of converting a liquid into its vapours state either by exposing it to air or by heating.

The process in which liquid is converted into its vapor phase at its boiling point and the vapor is then condensed back to liquid on cooling is known as distillation.

Distillation : Distillation is the method of getting a pure liquid from a solution by evaporating and then condensing the vapours.

• Based on difference in solubility of the compound and impurities at different temperatures.
• Compound more soluble in hot solvent → dissolved at high temperature → cooled → pure crystals form → impurities remain in solution (mother liquor).
• Common solvents: water, alcohol, ether, chloroform, acetone, benzene, petroleum ether.
• Example: Benzoic acid (slightly soluble in cold water, completely soluble in hot water) → separated from naphthalene.
• Fractional crystallisation: Used when two compounds have different solubilities in the same solvent → less soluble crystallises first on cooling (e.g., K₂CO₃ and KCl).

• Used for separation of a mixture of two or more miscible liquids with close boiling points (difference < 25°C).
• Uses a fractionating column for repeated vaporisation and condensation.
• Distillate collected in fractions at different temperatures.
• Example: Acetone (b.p. 330 K) and methyl alcohol (b.p. 338 K); benzene and toluene.
• Cannot be used to separate azeotropic mixtures (constant boiling point mixtures).