Is Matter Around Us Pure

Table of Contents

Matter and Particle Arrangement:
- Matter is composed of particles arranged in a specific way.
- Gases have well-separated particles that can move freely, while solids have tightly packed particles with limited mobility.
Pure Substances:
- Pure substances are either elements or compounds.
- They consist of only one kind of entity and have a fixed composition.
- Pure substances cannot be broken down into simpler entities by chemical or physical means.
- Example: Diamond, carbon dioxide.
Elements:
- Elements are substances composed of only one type of atom.
- They cannot be altered through physical or chemical means to form new substances.
- Majority of elements are metals, nonmetals, or metalloids.
- Examples: Hydrogen (H), Carbon (C), Silicon (Si), etc.
Compounds:
- Compounds are substances formed by chemically combining two or more different elements in fixed ratios.
- The chemical composition of compounds is always constant.
- Compounds are always homogeneous in nature, and they have different properties from their individual elements.
- Examples: Water (H2O), Hydrogen Peroxide (H2O2).
Mixtures:
- Mixtures are substances made up of two or more unrelated chemical components.
- They can be categorized as heterogeneous or homogeneous.
- Heterogeneous mixtures have physically distinct parts with a non-uniform composition, while homogeneous mixtures have uniform composition throughout.
- Examples: Crude oil (heterogeneous), Saltwater (homogeneous).
Solutions:
- Solutions are homogeneous mixtures of two or more substances.
- A solute is the substance dissolved in the solvent, and the solution contains more solvent than solute.
- Solutes can include sugar, dissolved gases (carbon dioxide, oxygen), etc.
- Solvents are the components in which the solutes are dissolved, typically in liquid form.
- Example: Sugar in water (homogeneous solution).
Solubility:
- Solubility is the property of a substance (solute) to dissolve in a solvent.
- It is measured as the maximum amount of solute that can dissolve in a given amount of solvent at equilibrium.
- Factors affecting solubility include temperature and pressure.
- Solubility is essential in determining the concentration of a solution.
Separation Techniques:
- Mixtures can be separated into their components using various methods.
- Homogeneous mixtures can be separated by evaporation, distillation, and chromatography.
- Heterogeneous mixtures can be separated by handpicking, sieving, filtration, and centrifugation.
- Fractional distillation is used for separating components based on their melting points.
- Crystallization is a technique to separate solids from a solution by evaporating the solvent.
- Chromatography is used to separate different components in a liquid mixture based on their properties.
Colloidal Solutions:
- Colloidal solutions are mixtures where substances are suspended in a fluid.
- They include foams (gas dispersed in a solid/liquid), sols (solid dispersed in a liquid), and emulsions (liquid dispersed in a liquid).
- Colloids can exhibit the Tyndall effect, which is the scattering of light by the particles in the colloid or suspension.
Elements, Metals, Nonmetals, and Metalloids:
- Elements are species of atoms with the same number of protons in their atomic nuclei.
- Metals are solid materials that are hard, shiny, malleable, fusible, ductile, and have good electrical and thermal conductivity.
- Non-metals are brittle and poor conductors of heat and electricity.
- Metalloids exhibit properties of both metals and nonmetals.

Mixtures are formed by simply mixing two or more pure substances (components) without any chemical reactions, allowing each substance to retain its own chemical identity.

Types of Mixtures:

Homogeneous Mixture (Solution):
- A homogeneous mixture has a uniform composition throughout, and its components are evenly distributed.
- Examples: Sugar dissolved in water, salt dissolved in water.
Heterogeneous Mixture:
- A heterogeneous mixture contains physically distinct parts and has a non-uniform composition.
- Examples: A mixture of salt and iron filings, sand and sugar.

Physical vs Chemical Changes:

In a physical change, the nature of the substance, its particles, and the quantity of particles remain unaltered. Only physical properties like shape, size, color, or state change.
- Example: Melting of ice, boiling water.
In a chemical change, new compounds with different properties from the original ones are formed, and there may be changes in the number of particles.
- Example: Burning of wood or paper, souring of milk.

Solutions:

Solutions are homogeneous mixtures where one or more substances (solutes) are dissolved in a solvent.
Solutes can include various substances like sugar, dissolved carbon dioxide, oxygen, and more.
The solvent is the component of the solution in which the solute is dissolved.
Examples of solvents include water, ethanol, methanol, and acetone.

Solutions exhibit certain properties:

Their particles are very tiny, with a diameter of less than 1 nm.
The particles are not visible to the naked eye.
Solutions do not scatter a beam of light, and they do not show the Tyndall effect.
Solute particles do not settle down on keeping the solution undisturbed.
The components of a solution cannot be separated using filtration.

Alloys:

Alloys are homogeneous mixtures of metals or a mixture of a metal and another element that cannot be separated into their components by physical methods.
Examples of alloys include steel (iron and carbon), bronze (copper and tin), and brass (copper and zinc).

Concentration of Solutions:

The concentration of a solution is the amount of solute that has dissolved in a specific amount of solvent or solution.
A concentrated solution contains a significant amount of dissolved solute, while a diluted solution contains a small amount of dissolved solute.

Solubility:

Solubility is the property that shows the ability of a given substance (solute) to dissolve in a solvent.
It is measured as the maximum amount of solute dissolved in a solvent at equilibrium.
Solubility is affected by temperature and pressure. Generally, solubility increases with temperature for most solutes, while for gases, it decreases with an increase in temperature.

Types of Solutions based on the Concentration of the Solution:

Dilute Solution: Contains a small amount of solute.
Concentrated Solution: Contains a large amount of solute.
Saturated Solution: Contains the maximum quantity of solute that can be dissolved at a particular temperature and pressure.

Suspensions:

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.
Suspensions can be separated from the mixture by filtration due to the large size of solute particles.

Colloidal Solutions:

Colloidal solutions, also known as colloids, are mixtures in which substances are regularly suspended in a fluid.
They have particles smaller than those in suspensions but larger than those in true solutions.
Colloidal solutions include foams (gas dispersed in a solid/liquid), sols (solid dispersed in a liquid), and emulsions (liquid dispersed in a liquid).

Tyndall Effect:

The Tyndall effect is the scattering of light by particles in a colloid or a very fine suspension.
It makes the path of a beam of light visible when passing through a colloidal solution, indicating the presence of suspended particles.

Overall, mixtures are an essential part of our daily life, and understanding their types and properties is crucial in various scientific and industrial applications.

Dispersed Phase and Dispersion Medium in Colloidal Solutions:

Dispersed Phase: The dispersed phase in a colloidal solution refers to the solute-like component of the dispersed particles. It is the substance that is uniformly distributed in the colloid and forms tiny particles or droplets. These particles are dispersed throughout the dispersion medium, giving the colloid its characteristic properties.
Dispersion Medium: The dispersion medium, also known as the dispersing medium, is the component in which the dispersed phase is suspended. It is the continuous phase that surrounds and holds the dispersed particles or droplets. The dispersion medium provides the medium in which the dispersed phase remains stable.

Dispersed Phase	Dispersing Medium	Type	Example
Liquid	Gas	Aerosol	Fog, clouds, mist
Solid	Gas	Aerosol	Smoke, automobile exhaust
Gas	Liquid	Foam	Shaving cream
Liquid	Liquid	Emulsion	Milk, face cream
Solid	Liquid	Sol	Milk of magnesia, mud
Gas	Solid	Foam	Foam, rubber, sponge, pumice
Liquid	Solid	Gel	Jelly, cheese, butter
Solid	Solid	Solid Sol	Coloured gemstone, milky glass

Types of Colloidal Solutions:

Aerosol: An aerosol is a colloidal solution in which the dispersed phase is either solid or liquid, and the dispersion medium is a gas. An example of an aerosol is clouds, where tiny water droplets or ice crystals are dispersed in the air.
Foam: In foam, the dispersed phase is gas, and the dispersion medium is either solid or liquid. Shaving cream is an example of foam, where gas bubbles are dispersed in a liquid medium.
Sol: A sol is a colloidal solution in which the dispersed phase is solid, and the dispersion medium is a liquid. An example of a sol is milk of magnesia, where solid magnesium hydroxide is dispersed in water.
Gel: A gel is a colloidal solution in which the dispersed phase is liquid, and the dispersion medium is a solid. Gels have a semisolid consistency and often appear like a jelly-like substance. Fruit jellies are examples of gels.
Emulsion: An emulsion is a colloidal solution in which the dispersed phase is liquid, and the dispersion medium is also a liquid. Emulsions can be of two types: oil dispersed in water (O/W) or water dispersed in oil (W/O). Mayonnaise is an example of an emulsion, where oil is dispersed in water.

Evaporation:

Evaporation is the process of converting a liquid into vapor or gas state. It occurs when the molecules at the liquid surface gain enough energy to break free and enter the gaseous phase. Evaporation is a cooling process because the high-energy molecules leave the liquid, leading to a decrease in temperature.
Examples of evaporation include clothes drying in the sun, tea and other hot liquids cooling down, ice cubes melting, and the process of obtaining pure water from impure water.
Evaporation can be used to separate the volatile component (solvent) from its non-volatile solute in a mixture.

Separation Techniques:

Handpicking: Separating substances by hand based on their physical properties.
Sieving: Using a sieve to separate particles of different sizes.
Filtration: Passing a mixture through a filter to separate solid particles from a liquid or gas.
Separating Funnel: Used to separate immiscible liquids based on their density.
Centrifugation: Using centrifugal force to separate components based on their density.
Sublimation: The transition of a substance from solid to gaseous state without passing through the liquid phase.
Chromatography: Separating components in a liquid mixture based on their different properties in two phases (stationary and mobile phases).
Distillation: Separating substances from a liquid mixture by selective evaporation and condensation.
Fractional Distillation: Separating components of a mixture based on their boiling points.

Separation of Air into Its Components:

Air is a homogeneous mixture of gases. It can be separated into its components through fractional distillation. Fractional distillation takes advantage of the different boiling points of the gases in the air to separate them.

The process of obtaining different gases from the air is essential for various industrial and medical applications, including the production of oxygen, nitrogen, and other gases.

Mixtures and their Types:

Mixtures are substances composed of two or more different kinds of materials. They can be separated physically, as their components retain their individual properties.
There are two types of mixtures:
1. Homogeneous Mixtures: These mixtures have a uniform composition throughout, and their components are evenly distributed at the particle level. They are also called solutions. Example: Sugar dissolved in water.
2. Heterogeneous Mixtures: In these mixtures, the components are not uniformly distributed, and there is no particle-level homogeneity. The components in a heterogeneous mixture can be visibly distinct. Example: Mixture of salt and sand.

Separation Methods for Heterogeneous Mixtures:

Heterogeneous mixtures can be separated into their individual components using various physical methods. Some popular separation methods for heterogeneous mixtures include:
1. Sieving: Using a sieve to separate particles based on their size.
2. Filtration: Passing the mixture through a filter to separate solid particles from a liquid or gas.
3. Hand-picking: Physically picking out individual components by hand based on their properties.

Special Separation Techniques for Homogeneous and Heterogeneous Mixtures:

When dealing with both homogeneous and occasionally heterogeneous mixtures, specialized separation techniques are required. Some of these techniques include:
1. Evaporation: Separating a volatile component (solvent) from a non-volatile solute by converting the liquid into vapor and leaving behind the solid solute.
2. Centrifugation: Using centrifugal force to separate components based on their density.
3. Chromatography: Separating components in a liquid mixture based on their different properties in two phases (stationary and mobile phases).
4. Sublimation: Transition of a substance from solid to gaseous state without passing through the liquid phase.
5. Separating Funnels: Used to separate immiscible liquids based on their density.

Crystallization:

Crystallization is a separation technique used to separate solids from a solution. In this process, the solvent molecules start evaporating, leaving behind the solutes, which eventually form crystals when the solution cools down.
Crystallization is preferable to evaporation because some solids may decompose or get charred during direct evaporation. Additionally, crystallization helps remove impurities that might remain dissolved in the solution after filtration.

Applications of Crystallization:

Crystallization has various applications, including:

Water Purification: Purifying seawater or contaminated water by separating dissolved salts through crystallization.

Separation of Alum Crystals: Obtaining pure alum crystals from impure samples using crystallization.

Which separation techniques will you apply for the separation of the following? (a) Sodium chloride from its solution in water. (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c) Small pieces of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e) Butter from curd. (f) Oil from water. (g) Tea leaves from tea. (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in water.

Let's explore the separation techniques for each of the given scenarios:

(a) Sodium chloride from its solution in water:

The separation technique for this scenario is evaporation. By heating the solution, the water will evaporate, leaving behind the solid sodium chloride.

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride:

The separation technique used here is sublimation. Ammonium chloride can be separated from the mixture by heating it. Ammonium chloride sublimes, meaning it changes from a solid to a gas directly, and can be collected separately.

The separation technique in this case is magnetic separation. Since metals are typically magnetic, passing a magnet over the mixture will attract and separate the metal pieces from the oil.

(d) Different pigments from an extract of flower petals:

The separation technique here is chromatography. Chromatography is a method that separates different components based on their varying affinities for a solvent. As the solvent moves through the mixture, it carries the different pigments along at different rates, allowing for their separation.

(e) Butter from curd:

The separation technique used here is centrifugation. Centrifugation involves spinning a mixture at high speed, which causes the denser component (butter, in this case) to separate from the lighter component (curd).

(f) Oil from water:

The separation technique for this scenario is decantation or using a separating funnel. Oil and water do not mix, and if left to stand, they will separate naturally. Decantation involves carefully pouring off the top layer (oil) from the bottom layer (water) in a container. Alternatively, a separating funnel can be used to separate the two liquids more efficiently.

(g) Tea leaves from tea:

The separation technique used here is filtration. Pouring the tea through a fine mesh or a filter will separate the tea leaves from the liquid tea.

(h) Iron pins from sand:

The separation technique for this scenario is magnetic separation. As with the small pieces of metal, passing a magnet over the mixture will attract and separate the iron pins from the sand.

(i) Wheat grains from husk:

The separation technique used here is winnowing. Winnowing is a traditional method of separating grains from husks by using wind or blowing air. The lighter husks are blown away, and the heavier grains fall down.

(j) Fine mud particles suspended in water:

The separation technique for this scenario is sedimentation and decantation. Allowing the mixture to stand will cause the heavier mud particles to settle at the bottom. The clear water can then be carefully poured off, leaving behind the mud at the bottom.

These separation techniques are essential in various fields and industries, enabling us to isolate and purify different components of mixtures for further use or analysis.

Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue.

Steps for Making Tea:

Boil water to create the solvent, which is the liquid part of the solution.
Add tea leaves or tea bags to the hot water, making the solute, which is the substance being dissolved.
Stir the tea to help the tea leaves or tea bags dissolve in the water. Tea is a soluble substance, meaning it readily dissolves in water.
Allow the tea to steep for a few minutes, allowing the flavor compounds to dissolve fully into the water.
Once the desired strength is achieved, use a strainer or a tea infuser to separate the insoluble tea leaves or tea bags (the residue) from the tea solution (the filtrate).
Pour the tea filtrate into cups, and your tea is ready to be served and enjoyed!

In this process, water acts as the solvent, while the tea leaves or tea bags act as the solute. As the tea steeps, the flavor compounds from the tea leaves dissolve in the water, creating the tea solution. After straining, the insoluble tea leaves or bags are left behind as the residue, and the clear liquid tea becomes the filtrate that we drink.

Explain the following giving examples. (a) saturated solution (b) pure substance (c) colloid (d) suspension

(a) Saturated Solution: A saturated solution is a solution in which the maximum amount of solute has been dissolved in a given amount of solvent at a specific temperature and pressure, and no more solute can dissolve. At this point, the solution is in a state of dynamic equilibrium, where the rate of dissolution of solute equals the rate of precipitation or crystallization of the solute. Adding more solute to a saturated solution will not cause it to dissolve further; instead, the excess solute will remain undissolved at the bottom.

Example: If you keep adding sugar to a glass of water and stirring until no more sugar can dissolve, you will have a saturated sugar solution. Any additional sugar you try to add will settle at the bottom of the glass.

(b) Pure Substance: A pure substance is a substance that consists of only one type of particle, either a single element or a single compound, and has a uniform and definite composition. Pure substances cannot be separated into simpler substances by physical means. They have distinct chemical and physical properties that remain constant throughout the substance.

Example: Elements like gold (Au) and compounds like water (H2O) are pure substances because they are composed of only one type of particle with a fixed ratio of atoms.

(c) Colloid: A colloid is a type of mixture where one substance (the dispersed phase) is finely dispersed or suspended as tiny particles or droplets in another substance (the dispersing medium). The particles of the dispersed phase are intermediate in size between those of a solution and a suspension. Colloids do not settle out, and their particles remain dispersed throughout the medium due to Brownian motion.

Example: Milk is an example of a colloid, where tiny fat droplets are dispersed in water. Another example is whipped cream, where air bubbles are dispersed in a liquid.

(d) Suspension: A suspension is a heterogeneous mixture in which solid particles or liquid droplets are dispersed in a liquid or gas. Unlike colloids, the particles in a suspension are relatively large and can settle out over time due to gravity. They need constant agitation to remain dispersed and do not form a homogeneous mixture.

Example: A mixture of sand and water is a suspension. When the mixture is allowed to stand, the sand particles settle at the bottom, forming a visible layer of sediment. The cloudy appearance of orange juice with pulp is also due to suspended particles of pulp in the liquid.

Classify each of the following as a homogeneous or heterogeneous mixture. soda water, wood, air, soil, vinegar, filtered tea.

Let's classify each of the following substances as either a homogeneous or heterogeneous mixture:

Soda water: Homogeneous mixture Explanation: Soda water, also known as carbonated water, is a homogeneous mixture because carbon dioxide gas is uniformly dissolved in water. It appears the same throughout and has a uniform composition.
Wood: Heterogeneous mixture Explanation: Wood is a heterogeneous mixture because it is composed of different components, such as cellulose fibers, lignin, and other organic and inorganic materials. These components are not uniformly distributed throughout the wood, making it non-uniform in appearance.
Air: Homogeneous mixture Explanation: Air is a homogeneous mixture because it is a combination of gases (mostly nitrogen, oxygen, carbon dioxide, etc.) that are uniformly mixed in the atmosphere. The composition of air remains consistent throughout its volume.
Soil: Heterogeneous mixture Explanation: Soil is a heterogeneous mixture because it consists of a variety of components, such as minerals, organic matter, water, air, and living organisms. The distribution of these components is not uniform, resulting in different layers and textures within the soil.
Vinegar: Homogeneous mixture Explanation: Vinegar is a homogeneous mixture because it is a solution of acetic acid in water. The acetic acid molecules are uniformly dispersed in the water, making the solution appear consistent throughout.
Filtered tea: Homogeneous mixture Explanation: Filtered tea is a homogeneous mixture because the solid tea leaves have been removed through the filtration process. The remaining liquid is uniform and has a consistent composition.

How would you confirm that a colourless liquid given to you is pure water?

We can confirm if a colorless liquid is pure by setting it to boil. If it boils at 100°C, it is said to be pure. But if there is a decrease or increase in the boiling point, we infer that water has added impurities, hence not pure.

Which of the following materials fall into the category of “pure substance”? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Brick (e) Wood (f) Air.

Following substances are pure substances:

Iron
Ice
Hydrochloric acid
Calcium oxide
Mercury

Which of the following will show the “Tyndall effect”? (a) Salt solution (b) Milk (c) Copper sulphate solution (d) Starch solution

Tyndall effect is exhibited by only milk and starch solution from the above-mentioned list of solutions.

Classify the following into elements, compounds and mixtures. (a) Sodium (b) Soil (c) Sugar solution (d) Silver (e) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (l) Carbon dioxide (m) Blood Solution:

Let's classify each of the given substances as elements, compounds, or mixtures:

(a) Sodium: Element Explanation: Sodium is a chemical element and is composed of only one type of atom.

(b) Soil: Mixture Explanation: Soil is a mixture of various components, such as minerals, organic matter, water, air, and living organisms.

(c) Sugar solution: Mixture Explanation: A sugar solution is a mixture of sugar (a compound) dissolved in water (a solvent). It is not a pure compound but rather a homogeneous mixture.

(d) Silver: Element Explanation: Silver is a chemical element and is composed of only one type of atom.

(e) Calcium carbonate: Compound Explanation: Calcium carbonate is a compound composed of calcium, carbon, and oxygen atoms in a fixed ratio.

(f) Tin: Element Explanation: Tin is a chemical element and is composed of only one type of atom.

(g) Silicon: Element Explanation: Silicon is a chemical element and is composed of only one type of atom.

(h) Coal: Mixture Explanation: Coal is a complex mixture of carbon, organic compounds, minerals, and impurities.

(i) Air: Mixture Explanation: Air is a mixture of various gases, primarily nitrogen, oxygen, carbon dioxide, and traces of other gases.

(j) Soap: Mixture Explanation: Soap is a mixture of various chemicals, including sodium or potassium salts of fatty acids, water, and sometimes additional additives.

(k) Methane: Compound Explanation: Methane is a compound composed of carbon and hydrogen atoms in a fixed ratio.

(l) Carbon dioxide: Compound Explanation: Carbon dioxide is a compound composed of carbon and oxygen atoms in a fixed ratio.

(m) Blood: Mixture Explanation: Blood is a complex mixture of water, blood cells, proteins, nutrients, hormones, and other substances.

Which of the following are chemical changes? (a) Growth of a plant (b) Rusting of iron (c) Mixing of iron filings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of candle

The following are chemical changes:

(b) Rusting of iron: Rusting is a chemical change as iron reacts with oxygen and moisture in the presence of air to form iron oxide (rust). It involves the formation of a new substance.

(d) Cooking of food: Cooking is a chemical change as it involves various chemical reactions, such as denaturation of proteins, caramelization of sugars, and the breakdown of complex carbohydrates and fats, resulting in the transformation of raw food into cooked food.

(e) Digestion of food: Digestion is a chemical change as it involves the breakdown of complex molecules in food into simpler substances through various enzymatic reactions in the digestive system.

(g) Burning of candle: Burning a candle is a chemical change as it involves a combustion reaction between the wax (hydrocarbons) and oxygen in the air, resulting in the release of heat, light, carbon dioxide, and water vapor.

The following are physical changes:

(a) Growth of a plant: Plant growth is a physical change as it involves an increase in size and mass of the plant through cell division and elongation. It does not involve the formation of new substances.

(c) Mixing of iron filings and sand: Mixing iron filings and sand is a physical change as it does not alter the chemical composition of the substances. It is a simple physical blending of two materials.

(f) Freezing of water: Freezing is a physical change as it involves the change of the state of water from a liquid to a solid without any alteration in its chemical composition. Ice is still composed of water molecules, just in a different arrangement.

Is Matter Around Us Pure | NCERT Solutions for Class 9 | Science Chapter 2