Is Matter Around Us Pure

Chapter 2: NCERT

Types of Matter

Matter

Substance

Elements

Metals

Non-metals

Metalloids

Iron

Sodium

Chlorine

Compounds

Sulphuric Acid

Ammonia

Carbon dioxide

Mixture

Homogeneous

Solutions

Salt water

Mouthwash

Air

Heterogeneous

Suspension

Colloidal

Muddy Water

Cloud / Smog / Jelly

Constant

composition

Can it be broken down by ordinary chemical

means?YesNo

Is the composition uniform?

Yes No

Pure form of matter is known as substance

If two or more substances (elements or compounds) are mixed together in any proportion, do not undergo any chemical change but retain their properties, the resulting substance is called mixture

A solution is a homogeneous mixture of two or more substances

Elements are substances that cannot be chemically broken down into simpler substances. So an element is made up of only one kind of atoms. Elements are the building blocks of all matter.

A Compound is a substance made up of two or more elements chemically combined in a fixed ratio by weight. They are homogeneous and exhibit definite physical and chemical properties

Mechanical mixture – can be separated by hand

Non-homogeneous mixtures in which solids are dispersed in liquids

In colloids, one substance (dispersed phase) is evenly dispersed in another (continuous phase). It is also called Sol

Difference between

Metals Non-metals1. They have luster (shine) 1. They are not lustrous

2. They have silvery-grey or golden-yellow colour 2. They display a variety of colors

3. They conduct heat and electricity 3. They are poor conductors of heat and electricity

4. They are ductile (can be drawn into wires) 4. They are not ductile

5. They are malleable (can be hammered into thin sheets) 5. They are not malleable

6. They are sonorous (make a ringing sound when hit) 6. They are not sonorous

7. Examples are gold, silver, iron, potassium 7. Examples are carbon, chlorine, oxygen, iodine

Metalloids have properties between Metals and Non-metals. Examples are Boron, silicon, germanium

Compound MixtureIt is made up of two or more elements that are chemically combined.

It is made up of two or more pure substances that are mixed physically

A compound has definite melting and boiling points and density

A mixture has no definite melting or boiling points and density

The properties of a compound are entirely different from those of its constituents

A mixture retains the properties of the components

A compound is always homogeneous A mixture is heterogeneous, and some are homogeneous

The constituents of a compound cannot be separated by physical means

The components of a mixture can be separated by simple physical means,( eg. dissolving, magnetic separation, etc)

Difference between

Homogeneous Mixtures Heterogeneous Mixtures1. Homogeneous mixtures have uniform composition. 1. Heterogeneous mixtures have non uniform composition

2. It has no visible boundaries of separation between its constituentsParticles Not visible to unaided eye

2. It has visible boundaries of separation between its constituentsParticles may be visible to unaided eye

3. All solutions are homogenous mixture 3. All suspensions are heterogeneous mixture

4. Some examples of homogeneous mixtures are: salt in water, sugar in water, air, blood

4. Some examples of heterogeneous mixtures are: water and sand, oil and water, soup

Solute Solvent1. Present in lesser proportion in the solution 1. Present in greater proportion in the solution

2. Dispersed phase 2. Medium of dispersion in a solution

3. Solution may or may not be in the same state of matter as the solute

3. Solution will be in the same state of matter as the solvent.

QuestionsQ. What is meant by a substance?R. Pure form of matter is known as substance.

Q. What is a solution?R. A solution is a homogeneous mixture of two or more substances.

Type Example Solute Solvent

Gas solutions

Gas in gas Air Oxygen (gas) Nitrogen (gas)

Liquid solutions

Gas in LiquidLiquid in LiquidSolid in Liquid

Soda WaterVinegarSea waterTincture of Iodine

Carbon dioxide gas (gas)Acetic acid (liquid)Salt (solid)Iodine (solid)

Water (liquid)Water (liquid)Water (liquid)Alcohol (liquid)

Solid solutions

Liquid in solidSolid in solid

Dental amalgamBrassSteel

Mercury (Liquid)Zinc (solid)Carbon (solid)

Silver (solid)Copper (solid)Iron (solid

Alloys are mixtures of two or more metals or non-metals and cannot be separated into their components by physical methods.But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition.Example: steel (carbon + Iron), brass (zinc + copper)

Questions: SolutionQ. Give the properties of a solution?R. (i) A solution is a homogeneous mixture. (ii) The particles of solution are smaller than 1nm in diameter and hence cannot be seen by naked eyes. (iii) because of their very small size, they do not scatter beam of light passing through them. So, path of light is not visible in a solution. (iv) the solute particles cannot be separated from the solution by the process of filtration. (v) A true solution is clear and transparent; solution is stable.

Q. What is meant by solute and solvent?S. A solution is obtained when a substance is dissolved in another substance. The

substance which is dissolved to obtain a solution is called solute, whereas the substance in which the solute is dissolved is called solvent

Q. Concentration of a solution : Dilute / concentrated solution:-A dilute solution is a solution in which there is a small amount of solute, compared to the total amount of possible solute that can be dissolved in the solvent.A concentrated solution is when there is a lot or all solute that can possibly fit in the solvent.

Questions: SolutionQ. What is meant by solubility?A. The maximum amount of the solute that can be dissolved in a given amount of the

solvent is termed its solubility at that temperature

Q. What factors affect the solubility of solvent and solute?R. Temperature: For majority of solutions of solid-in-liquid and liquid-in-liquid types,

solubility increases with temperature. However for solutions of gases-in-water type, solubility decreases with increase in temperature.

• Pressure: It is applicable to gas-in-liquid solutions. An increase in pressure increases the solubility of a gas. For example, aerated drinks contain carbon dioxide gas under pressure.

• Mechanical Stirring: Mechanical stirring increases solubility. For example, sugar dissolves faster on stirring with a spoon.

• Size of Solute Particles: Smaller the particle size of solute, greater is the solubility. For example, it is easier to dissolve powdered sugar than granules of sugar.

Q. What is a saturated solution?A. When no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution

Q. What is a unsaturated solution?A. When the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution

Questions: Solution

Q. What is an aqueous solution?A. Solutions that contain water as a solvent eg. Sugar in water

Q. What is a non-aqueous solution?A. Solutions that contain a solvent other than water are called non-aqueous solutions. Ether, benzene, petrol, carbon tetrachloride etc., are some common solvents.

Unsaturated Solution Saturated Solution Supersaturated Solution

Does not have enough solute; more solute can dissolve

Has as much solute as the solvent will dissolve; no more solute dissolves

Has too much solute; becomes unstable and crystals are formed

Dilute Concentrated

Q. Concentration of a solution : 1. Percentage by mass: It is defined as number of parts by mass of the solute

dissolved per hundred parts by mass of the solution2. Percentage by volume: It is defined as the number of parts by volume of the solute

dissolved in hundred parts by volume of the solution.

Questions: Suspension

Q. What is a suspension?A. Non-homogeneous (heterogeneous) mixtures in which solids are dispersed in

liquids / gas. Particles of suspension are visible to naked eye.• Eg. Dust in air, muddy water

Q. Give the properties of a suspension?R. (i) A suspension is a heterogeneous mixture. (ii) The particles of suspension can be seen by naked eyes. (iii) Particles of a suspension scatter beam of light passing through them and

makes the path of light visible. (iv) the solute particles settle down when a suspension is left undisturbed, thus a

suspension is unstable. (v) Mixture can be separated by the process of filtration.

Questions: Colloids

Q. What is a colloidal solution?A. Particles of colloid are uniformly spread throughout the solution. As the particles are

very small, the mixture appears to be homogenous. But actually is heterogeneous. Eg. Milk, fog, jelly, whipped cream

• Scattering of beam of light by a colloid is called the Tyndall effect

Q. Give the properties of a colloid?R. (i) A colloid is a heterogeneous mixture. (ii) The particles of colloid are too small to be seen by naked eyes. (iii) Colloids are big enough to scatter beam of light passing through it and makes the path of light visible. (iv) They do not settle down when left undisturbed, thus a colloid is quite stable. (v) They cannot be separated by the process of filtration, but by special technique

called centrifugation.

Difference between

Solution Sol Suspension

1. Homogeneous mixture 1. Heterogeneous mixture 1. Heterogeneous mixture

2. Particles are less than 1 nm, not visible to naked eye

2. Particles so small that they are not visible to naked eye

2. Particles are visible to unaided eye

3. They do not scatter a beam of light

3. They scatter a beam of light passing through them, hence show Tyndall effect

3. They do not scatter a beam of light passing through them

4. Solute particles cannot be separated by the process of filtration and sedimentation

4. Solute particles cannot be separated by the process of filtration and sedimentation

4. Solute particles can be separated by the process of filtration and sedimentation

5. Solute particles diffuses rapidly

5. Solute particles diffuses slowly

5. Solute particles does not diffuse

6. They are very stable 6. They are quite stable 6. They are unstable

7. example: salt in water 7. example: milk 7. example: dust in air

8. Transparent 8. Translucent 8. Opaque

Separating the Components of a Mixture

Evaporation:Separate the volatile component of the mixture from its non-volatile component.Example: dye from ink

Centrifugation:Denser particles are forced to the bottom and lighter particles stay on top when spun.Example: cream from milk

Chromatography:Separate solutes that dissolve in same solvent according to their solubility (adsorption)Example: colors in a dye

Distillation:Separate two miscible liquids that boil without decomposing and have sufficient difference in their boiling points.Example: Acetone from water

Layering:Immiscible liquids separate out in layers depending on their density.Example: kerosene oil from water

Fractional distillation:Homogeneous mixture can be separated into its component as per the difference in their boiling pointExample: Air, crude oil

Crystallisation:The process that separates a pure solid in the form of its crystals from a solution.Example: Salt from seawater

Sedimentation:Used to separate heterogeneous mixture where solid constituent is heavier.Example: sand from water

Hand picking:When components are bigger in size and distinctly visible eg. Stones and rice

Separating the Components of Solid Mixtures

Q. What are the reasons for separating the constituents of a mixture?• To remove any harmful or undesirable constituent. • To obtain a pure sample of a substance. • To obtain useful constituent from a mixture.

Sieving:When particle size of components are different eg. Gram and wheat flour

Sublimation:When one of the component sublimes on heating eg. Iodine and table salt

Magnetic separation:When properties of constituent particles are different eg. Sulphur and iron filings

Physical and Chemical changes

Physical Change Chemical Change1. Physical change rearranges molecules but doesn't

affect their internal structures1. Chemical change is any change that results in the

formation of new chemical substances

2. A physical change is reversible 2. a chemical change is not

3. A physical change is a change in which no new substance is formed

3. a chemical change results in the formation of one or more new substances

• Texture• Color• Temperature• Shape• Change of State

• Change in Temperature• Change in Color• Noticeable Odor (after reaction has begun)• Formation of a Precipitate• Formation of Bubbles