Selina Concise Solutions for ICSE Class 6 Chemistry Chapter 5 Pure Substances and Mixtures Separation of Mixtures

POINTS TO REMEMBER

1. Element is made up of atoms of the same kind i.e. atoms of gold are similar in every respect i.e. have same melting point and same boiling pts. same colour, mass and odour.
2. Molecules of a compound are similar in every respect i.e. same composition taste, colour and odour i.e. compound water is made up of similar molecules.
3. Pure substances are either elements or compounds have definite set of properties.
4. Pure substances are required to maintain good health of human beings. Chemists, technologists and scientists need pure substances for manufacture of medicines, chemicals in industry and for scientific purposes.
5. Milk, air, bronze, sugar and water solution, salt and water solution, salt, iron filings and sand, petrol are all mixtures.
6. Mixtures, two or more components mixed in any ratio, undergo ho chemical change and retain their individual properties, can be separated by simple physical methods.
7. Mixture has no formula, no change in volume, no change in mass, energy is neither needed nor produced.
8. Mixture is impure substance.
9. Homogeneous mixture : in which constituents are uniformaly distributed throughout its volume, e.g. salt and water solution.
10. Heterogeneous mixture: The components are not uniformly distributed through its volume and components can be easily seen separately, e.g. water, oil solution.
11. Milk is emulsion but this mixture cannot be separated. Oh shaking a mixture of mustard oil and water vigorously mixture becomes milky and is called an emulsion after some time water and oil get separated.
12. Alloys are homogeneous mixtures of metal with metals or metal with non-metals.
13. Salt and sand can be seperated by solvent extraction method where one of the solid component (salt) is soluble in liquid.
14. Coagulation or loading : When alum (a chemical) is added to mixture dissolves in water and form clusters with clay and fine dust particles making them heavier, increases the rate of sedimentation.
15. Centrifugation method is used to separate solids from liquids where mixture is homogeneous. Cream is separated being lighter on churning floats on a liquid (milk).
16. Loading : The process of adding a chemical substance to help the suspended solid particles in liquid to form a sediment is called loading.

EXERCISE - I

Question 1: Select homogeneous and heterogeneous mixtures from the following:
Salt solution, petrol and water, sand and charcoal, alcohol and water, air dissolved in water, air, sea water, fruit juices, mist, brass.

Answer:
Homogeneous mixture : Salt solution, alcohol and water, air dissolved in water, sea water, brass.
Heterogeneous mixture: Sand and charcoal, air, fruit juice, mist, petrol and water.
A homogeneous mixture has the same composition throughout, like salt completely dissolved in water. A heterogeneous mixture contains physically distinct parts, like sand sitting at the bottom of a charcoal pile.
Teacher's Tip: Think of "Homo" as "Same" and "Hetero" as "Different" to remember if a mixture looks the same or different throughout.
Exam Tip: Always group your answer into two distinct columns or headings to help the examiner see your classification clearly.

Question 2: Define the following :
(a) Pure substance
(b) Impure substance
(c) Alloy
(d) Solution
(e) Heterogeneous mixture
(f) Homogeneous mixture

Answer:
(a) 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.”
(b) 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 substance. Example of impure substance is air.
(c) Alloy : “A homogeneous solid mixture of two or more metals or a metal and a non-metal is called an alloy.”
(d) Solution : “The homogeneous mixture of water (or any other solvent) and a substance soluble in it is called a solution.”
(e) Heterogeneous mixture : “A mixture in which the components are not uniformally distributed through its volume and can be easily seen separately is called heterogeneous mixture.”
(f) Homogeneous mixture : “A mixture in which its constituents are uniformly distributed throughout its volume and cannot be seen separately is called a homogenous mixture.”
Pure substances have a fixed composition, whereas impure substances (mixtures) can have components in any ratio. Solutions and alloys are specific types of homogeneous mixtures that appear uniform to the naked eye.
Teacher's Tip: Remember that all alloys are mixtures, but not all mixtures are alloys because alloys must involve metals.
Exam Tip: When defining terms, always include one example (like air for impure substances) to make your answer more complete.

Question 3: List four characteristics of a mixture.

Answer:
Four characteristics of a mixture :
1. Mixture has no fixed composition.
2. To form a mixture energy is neither produced nor evolved.
3. Mixture has no fixed melting’point and boiling points.
4. Mixture retain the properties of its components.
5. Components of mixtures can be seperated by simple physical methods.
Mixtures are unique because the components do not react chemically, allowing them to keep their original traits. Because there is no chemical bond formed, we can use physical tricks like filtration to pull them apart again.
Teacher's Tip: Think of a fruit salad; the grapes and apples stay grapes and apples even when they are mixed in the bowl.
Exam Tip: If a question asks for four points, always try to provide five if you know them, just in case one point is not perfectly accurate.

Question 4: Give reasons :
(a) Why do sugar and water retain their individual properties in a sugar solution ?
(b) Why do petrol and water form a heterogeneous mixture ?
(c) Why sulphur does dissolve when carbon disulphide is added to a mixture of iron and sulphur but not when it is added to iron sulphide ?

Answer:
(a) As sugar solution is a mixture and mixtures has not any specific set of properties. They show the properties of the individual components from which they are formed.
(b) Petrol and water forms a heterogeneous mixture as its constituents can be seen separately and are not uniformly distributed throughout its volume.
(c) Sulphur has the property to dissolve in carbon disulphide whereas iron does not dissolve and retains its individual property. However, On heating Iron and Sulphur, they chemically combined forming Iron Sulphide. In this, Iron and Sulphur particles do not exists separately as such they loose their individual property.
In a mixture, components are just sitting together without changing into something new. In a compound like iron sulphide, the elements have bonded chemically to create a completely new substance with new rules.
Teacher's Tip: Use the "Dissolving Test" to see if a substance is still its original self or if it has changed chemically.
Exam Tip: When a question asks "Why," always start your answer by addressing the chemical nature (mixture vs compound) of the substances involved.

Question 5: Give two examples for each of the following types of mixture.
(a) solid-solid
(b) solid-liquid
(c) liquid-gas
(d) gas-gas

Answer:
Two examples of :
(a) solid - solid -
1. sand and sugar
2. sand and iron filling.
(b) solid - liquid -
1. salt and water
2. charcoal and water.
(c) liquid - gas -
1. coca cola
2. mist.
(d) gas - gas -
1. air
2. helium and hydrogen in air balloon,
3. perfumes and air.
Mixtures can exist in any state of matter combined with another. For example, mist is tiny liquid water droplets hanging in the gaseous air around us.
Teacher's Tip: For liquid-gas, think of anything "fizzy" or "foggy" as a quick mental shortcut.
Exam Tip: Mention the state of each component in brackets next to your example to show the examiner you truly understand the classification.

Question 6: Name the components present in the following mixtures:
(a) Brass
(b) Duralumin
(c) Tap water
(d) Bronze
(e) Crude petroleum oil .

Answer:
(a) Brass -> Copper and Zinc.
(b) Duralumin -> Aluminium + Copper with little manganese and magnesium.
(c) Tap water -> air, dissolved salts.
(d) Bronze -> Copper, Tin and zinc.
(e) Crude petroleum oil -> petrol, kerosene, diesel, LPG, mixed with salt, water and earth particles.
Alloys like brass and bronze are created by melting metals together to make a stronger material. Even tap water is not "pure" because it contains natural minerals and gases that our bodies need.
Teacher's Tip: Remember "Brass has Zinc" (both have the letter 's' or 'z' sound) and "Bronze has Tin".
Exam Tip: For complex mixtures like crude oil, listing at least three major components is usually enough to get full marks.

Question 7: State:
(a) Three differences between water and air.
(b) Four differences between compounds and mixtures.

Answer:
(a) Water :
1. The components of water are hydrogen and oxygen which are chemically combined in a fixed ratio of 1 : 8 by mass.
2. The chemical composition of water remains same from whatever source it is obtained.
3. The properties of water are completely different from the properties of elements from which it is formed i.e. hydrogen and oxygen.
4. Energy change occurs in the formation of water.
5. A molecule of water is represented by a definite formula H₂O.
Air :
1. The main components of air are nitrogen, oxygen, carbon -dioxide, water vapour which are not chemically combined.
2. The composition of air varies from place to place. During rainy season the air becomes humid due to presence of more water vapour. Some impurities like sulphur dioxide, hydrogen sulphide etc. also changes its composition at some places.
3. The components of air retain their individual properties but not air.
4. No energy change occurs when components of air are mixed together.
5. Air cannot be represented by any chemical formula.
(b) Compound :
1. A compound is a pure substance.
2. Compounds are always homogeneous.
3. A compound has a fixed composition, i.e., it is formed when two or more pure substances chemically combine in a definite ratio by mass.
4. Formation of a compound involves change in energy.
5. Compounds have specific set of properties.
6. Components of compounds can be separated only by complex chemical processes.
Mixture :
1. A mixture is an impure substance.
2. Mixtures may be homogeneous or heterogeneous.
3. A mixture has no fixed composition, i.e., it is formed by mixing two or more substances in any ratio without any chemical reaction.
4. Formation of a mixture does not involve any change in energy.
5. Mixtures do not have any specific set of properties.
6. Components of mixtures can be separated by simple physical methods.
Compounds like water are chemically locked together in a perfect ratio, while mixtures like air are just a loose collection of gases. This is why you can breathe the oxygen in air, but you cannot breathe the oxygen trapped inside a water molecule.
Teacher's Tip: Use a "Comparison Table" to organize these points side-by-side; it's much easier to memorize!
Exam Tip: When stating differences, always contrast the same property for both items (e.g., talk about composition for both, then energy for both).

EXERCISE - II

Question 1: Define:
(a) Filtration
(b) Sublimation
(c) Evaporation
(d) Crystallisation
(e) Miscible liquids
(f) Immiscible liquids

Answer:
(a) Filtration : The process of separating solid particles from liquid by allowing it to pass through a filter paper is called filtration.
(b) Sublimation : The process in which a solid changes directly into its vapours on heating is called sublimation.
(c) Evaporation : Is the process of converting a liquid into its vapours state either by exposing it to air or by heating.
(d) Crystallisation : Evaporation of liquid from a homogeneous liquit-solid mixture and collecting solid in the form of crystals is called crystallisation.
(e) Miscible liquids: Homogeneous liquid-liquid mixtures are called miscible liquids.
(f) Immiscible liquids : Heterogeneous liquid-liquid mixtures are called immiscible liquids.
These terms describe the different ways we can pull mixtures apart based on their physical states and behaviors. For example, oil and water are "immiscible" because they refuse to mix and stay in separate layers.
Teacher's Tip: Think of "Miscible" as "Mixable" to remember that these liquids blend perfectly together.
Exam Tip: For "Sublimation," always mention that the solid skips the liquid phase entirely to get the full definition point.

Question 2: Why do we need pure substances?

Answer:
We need pure substances because of the following reasons:
1. A pure substance has a fixed melting and fixed boiling point.
2. A pure substance has its characteristic taste, colour and odour.
3. Pure substances can not be broken further into more simple substances by any physical means.
Pure substances are essential for science and medicine because they react in predictable ways every single time. If a medicine was a random mixture, we wouldn't know exactly how it would affect a patient's body.
Teacher's Tip: Think of "Pure" as "Reliable" – it always behaves the same way under the same conditions.
Exam Tip: Focus your answer on "predictability" and "fixed properties" as these are the most important scientific reasons.

Question 3: Give one example for each of the following types of mixtures.
(a) Solid-solid heterogeneous mixture
(b) Solid-liquid heterogenous mixture
(c) Solid-liquid homogeneous mixture

Answer:
(a) Iron and sulphur.
(b) Sand and water, rice and water.
(c) Sugar from its solution in water.
Heterogeneous mixtures like sand and water are easy to see with your eyes, as the parts stay separate. Homogeneous mixtures like sugar water look like a single, clear liquid because the sugar particles are tiny and spread out perfectly.
Teacher's Tip: If you can see "bits" or "layers," it is definitely heterogeneous.
Exam Tip: Use common household items like "Salt water" or "Sand in water" as examples so you don't forget them during the test.

Question 4: Name the process by which the components of following mixtures can be separated.
(a) Powdered glass and sugar
(b) Chalk powder and iron filings
(c) Chaff and grain
(d) Salt and water
(e) Wheat and sugar
(f) Sand and camphor
(g) Sugar and water

Answer:
(a) FILTRATION : Glass and sugar on dissolving in water and filtering, glass separates out as residue on the filter paper. Filtrate of sugar solution is heated to remove water by evaporation, sugar is collected as crystals.
(b) MAGNETIC SEPERATION : With the help of a magnet, iron filings can be separated leaving behind chalk powder.
(c) WINNOWING : It separates chaff (lighter) from heavier grains in two different heaps.
(d) EVAPORATION : This method is used to separate the components of a homogeneous solid-liquid mixture, like salt from sea water. Sea water is collected in shallow beds and allowed to evaporate in the sun. When all the water is evaporated, salt is left behind.
(e) EVAPORATION : Wheat and sugar are put in water in a beaker. Sugar dissolves and mixture is passed through strainer and separated and dried. Sugar is obtained by evaporating sugar solution.
(f) SUBLIMATION : Camphor sublimes on heating leaving behind sand.
(g) CRYSTALLISATION : Pure sugar is obtained from its solution in water by the process of crystallisation. At first the sugar solution is heated to evaporate Water at a faster speed. When very less of water is left the solution is cooled. On cooling sugar dissolved in it starts separating out in the form of crystals.
Separation techniques take advantage of the different physical properties of substances, such as magnetism or solubility. For instance, winnowing uses the wind to blow away light husks while the heavy grain falls straight down.
Teacher's Tip: Ask yourself: "Does one part dissolve? Is one part magnetic? Does one part turn into gas?" to find the right method.
Exam Tip: Always name the process in CAPITAL LETTERS at the start of your answer to make it stand out.

Question 5: Name:
(a) two substances which can sublime
(b) two substances soluble in water
(c) two substances insoluble in water
(d) four substances that can be used as filters.

Answer:
(a) Camphor and Naphthalene
(b) Sugar and salt (NaCl)
(c) Sand and chalk powder.
(d) (i) Filter paper, (ii) A bead of sand, (iii) Charcoal, (iv) A piece of muslin cloth.
Subliming substances like mothballs (naphthalene) disappear over time because they turn directly into gas. Soluble substances like salt vanish into water, while insoluble ones like sand stay visible as solids.
Teacher's Tip: Remember that "muslin cloth" is just a fancy name for a thin, breathable fabric used for basic straining.
Exam Tip: When naming substances, try to use their chemical names (like NaCl for salt) to show extra knowledge.

Question 6: Give reasons:
(a) Sand and saw dust cannot be separated by hand picking.
(b) Magnet is used to separate a mixture of iron and sulphur.
(c) Alum is used in purification of river water.

Answer:
(a) Because in hand picking method substances should be large enough in size to be recognized and picked out by hand but sand and saw dust particles are very small in size so they can’t be picked by hand. It can be separated by filtration.
(b) Mixtures of iron and sulphur can be separated by moving a magnet over them. Iron gets attached to the magnet is separated.
(c) Water from a river, pond or lake contains very fine clay particles. To make them settle at a faster rate, a chemical substance called alum in powdered form is added to such mixtures. It dissolves in water and forms clusters with clay and dust particles making them heavier and increasing the rate of sedimentation.
Hand picking only works for large items like stones in rice. For tiny particles or magnetic ones, we need more advanced physical tools like magnets or chemicals like alum to help group small particles together.
Teacher's Tip: Think of Alum as a "Glue" that sticks tiny pieces of dirt together so they fall to the bottom of the water.
Exam Tip: Use the word "Sedimentation" when explaining how alum helps clean water; it's a key scientific term.

OBJECTIVE TYPE QUESTIONS

1. Fill in the blanks

(a) The substances that make a mixture are called its constituents or components.
(b) Evaporation or crystallisation is a process to separate solids dissolved in liquids.
(c) Mist is a heterogeneous (liquid in gas) mixture of droplets of water and air.
(d) Clay is separated from water by the method of loading and decantation.
(e) When cereals are washed before cooking, water is separated from the cereals by decantation.
(f) Crystallisation is a process to obtain a very pure form of a solid dissolved in a liquid.
(g) Ammonium chloride can be separated from common salt by the method of sublimation.
(h) The solid particles which remain on the filter paper are called residue and the liquid which passes through it is called filtrate.
(i) The process of transferring the clear liquid layer above the solid particles which settle at the bottom of the container is known as decantation.
(j) Filtration is a method used for the separation of an insoluble solid from a solid-liquid mixture.

2. Write “true” or “false” for the following statements

(a) A pure substance consists of only one kind of atom or molecule.
Answer: True
Pure substances have a uniform identity throughout their entire mass. This means every single molecule in a glass of pure water is identical to the next one.
Teacher's Tip: If you see the word "only one kind," it is almost always a pure substance.
Exam Tip: For True/False questions, read every single word carefully, as one small "not" can change the entire meaning.

(b) Common salt is separated from its solution in water by decantation.
Answer: False
Correct : Common salt is separated from its solution in water by evaporation.
Decantation only works for heavy solids that sink to the bottom, but salt is dissolved and hidden in the water. We must turn the water into steam to leave the salt behind.
Teacher's Tip: Remember that decantation is for "sinkers" and evaporation is for "dissolvers."
Exam Tip: If a statement is False, always provide the "Correct" version to ensure you get full credit.

(c) Winnowing is a process to remove small stones from grains.
Answer: False
Correct : Winnowing is a process to remove husk from grains.
Stones are heavy and won't blow away, so winnowing won't help remove them. Hand-picking is the right way to get stones out of your grain.
Teacher's Tip: Imagine the wind blowing – only the light stuff (husk/chaff) flies away!
Exam Tip: Link the separation method to the "weight" of the impurity in your mind.

(d) Jewellery gold is a homogeneous mixture of metals.
Answer: False
Correct : Jewellery gold is a heterogeneous mixture of metals.
(Note: Most textbooks consider alloys homogeneous, but the provided text marks this as false and heterogeneous. Follow the text provided.)
Pure gold is too soft for rings, so other metals are mixed in to make it harder. This mixture creates a solid material used for making beautiful ornaments.
Teacher's Tip: Pure gold is 24 Karat; anything less is a mixture!
Exam Tip: Follow your textbook's specific classification even if you see different information online.

(e) Air can be separated from water by filtration.
Answer: False
Correct : Air can be separated from water by heating.
Air is dissolved in water, so it passes right through the holes in a filter paper. When you boil water, the bubbles you see are the dissolved air escaping.
Teacher's Tip: Think of a boiling kettle; the first bubbles are the air leaving the water.
Exam Tip: Remember that filtration only catches "insoluble" solids, not dissolved gases.

(f) Salt and air dissolved in water add taste to water.
Answer: True
Pure distilled water tastes very flat and strange because it has nothing else in it. The minerals and gases in normal water give it the refreshing taste we recognize.
Teacher's Tip: Tap water has "character" because it's a mixture, not just pure H₂O.
Exam Tip: Note that "taste" in water usually comes from the impurities, not the water itself.

(g) Steel is an alloy of iron and aluminium.
Answer: False
Correct: Steel is an alloy of iron and carbon.
Carbon makes the iron much stronger and prevents it from bending too easily. This strong mixture is what we use to build skyscrapers and cars.
Teacher's Tip: Steel = Iron + Carbon. (Think of it as adding a "C" for strength).
Exam Tip: Be careful with alloy components; mixing up aluminium and carbon is a common mistake.

MULTIPLE CHOICE QUESTIONS

1. The process of adding a chemical substance to help the suspended solid particles to deposit as sediment fastly is called
1. loading
2. sedimentation
3. decantation
4. filtration

Answer: 1. loading
Loading uses a chemical "helper" like alum to speed up the natural process of sinking. Without loading, tiny clay particles might stay floating in the water for days.
Teacher's Tip: Loading is like "loading" weight onto the particles so they sink faster.
Exam Tip: Look for keywords like "chemical substance" and "fastly" to identify Loading.

2. Salt is separated from sea water by
1. evaporation
2. sublimation
3. crystallisation
4. filtration

Answer: 1. evaporation
The sun's heat turns the sea water into vapor, leaving the salt behind in large pans. This is the primary way we get the salt we use on our food every day.
Teacher's Tip: If you want the solid and don't care about losing the liquid, choose evaporation.
Exam Tip: If the options include both "evaporation" and "crystallisation," choose evaporation for general salt production from sea water.

3. A mixture of mustard oil and water forms
1. a compound
2. a homogeneous mixture
3. an alloy
4. a heterogeneous mixture

Answer: 4. a heterogeneous mixture
Oil and water are "immiscible," meaning they will eventually separate into two distinct layers. Even if you shake them, they will eventually move apart again.
Teacher's Tip: Oil always floats on top because it is lighter (less dense) than water.
Exam Tip: Any mixture with visible layers is always classified as heterogeneous.

4. A heterogeneous mixture is
1. made up of only one kind of atom
2. made up of only one kind of molecule
3. made up of different kinds of atoms and molecules.
4. that looks uniform

Answer: 3. made up of different kinds of atoms and molecules.
(Note: Choice 3 is the provided answer, though technically it's a mixture where components are not uniform.)
In these mixtures, you have different substances mixed together that don't blend perfectly. You can usually pick out the different ingredients if you look closely enough.
Teacher's Tip: If it doesn't look the same from top to bottom, it's heterogeneous.
Exam Tip: Read all options! Choice 4 is for homogeneous mixtures, so don't mix them up.

5. Example of a homogeneous mixture is
1. distilled water
2. tap water
3. sand and water
4. sawdust and water

Answer: 2. tap water
Tap water has minerals dissolved in it so perfectly that the whole glass of water looks clear and uniform. Distilled water isn't a mixture at all—it's a pure substance!
Teacher's Tip: Distilled water is H₂O only; Tap water is H₂O + minerals.
Exam Tip: Be careful! Distilled water is a "pure substance," not a mixture.

6. A set of mixture is
1. gold, common salt, water, alloy
2. alloy, ink, honey, ice cream
3. alloy, mercury, air, sea water
4. milk, duralumin, brass, silver

Answer: 2. alloy, ink, honey, ice cream
Every item in this list is made of two or more different things mixed together. For example, honey contains various sugars and water, and ice cream has milk, sugar, and flavors.
Teacher's Tip: If an item is on the Periodic Table (like Gold or Silver), it's not a mixture!
Exam Tip: Eliminate sets that contain elements (like gold or mercury) to find the correct answer fast.

7. A gas dissolved in a liquid can be separated by :
1. filtration
2. boiling
3. using magnet
4. by crystallisation

Answer: 2. boiling
Heat reduces the ability of a liquid to hold onto dissolved gases, forcing them out as bubbles. This is why boiled water tastes "flat"—all the air has been driven out.
Teacher's Tip: Think of a soda going flat in the sun; heat pushes the gas out!
Exam Tip: Remember "Boiling for Gases" and "Evaporation for Solids" when separating things from liquids.

8. Copper is not a part of the alloy :
1. brass
2. bronze
3. steel
4. duralumin

Answer: 3. steel
Steel is strictly a mixture of iron and carbon, with no copper added. The other three alloys all rely on copper for their specific properties.
Teacher's Tip: Steel is iron-based; most "yellowish" metals like brass have copper.
Exam Tip: Memorize the components of common alloys like brass, bronze, and steel, as they appear in exams frequently.

9. Which is not a mixture?
1. sugar solution
2. tap water
3. milk
4. distilled water

Answer: 4. distilled water
Distilled water has had all its impurities removed, leaving only pure water molecules behind. Therefore, it is a pure compound, not a mixture.
Teacher's Tip: "Distilled" means "Purified" in the context of water.
Exam Tip: Whenever you see "not a mixture," look for elements or pure compounds like distilled water.

10. Give one word name for the following
(a) The solid which is left on the filter paper after filtration residue.
(b) The solid particles which separate out from the solution on slow evaporation crystals.
(c) The solid particles that settles at the bottom of the beaker in a heterogeneous mixture of a solid and a liquid decantation. (Note: The term for the particles is actually sediment, but the text lists decantation as the answer.)
(d) The clean liquid which is poured out after sedimentation supernatant liquid.
(e) The technique used to separate the light particles from heavy particles using the flow of wind winnowing.

ADDITIONAL QUESTIONS FOR PRACTICE

Question 1: Explain the term mixtures. Give an example of mixtures of -
(a) two elements
(b) two compounds
(c) elements and compounds.

Answer:
Mixture : A mixture is an impure substance made up of two or more elements or compounds mechanically mixed together in any proportion.
Examples
(a) Of two elements
Element (Iron) + Element (Sulphur) -> Mixture (Iron + Sulphur)
(b) Example Of two compounds
Compound (Potassium chloride) + Compound (Water) -> Mixture (Potassium chloride solution)
(c) Of elements and compounds
Element (Sulphur) + Element (Carbon) + Compound (Potassium nitrate) -> Mixture (Gun powder)
Mixtures are formed when substances just hang out together without making new chemical bonds. Because they aren't bonded, you can always pull them apart using physical tricks like magnets or dissolving.
Teacher's Tip: Use the "+" sign to show a mixture (they stay separate) and an arrow to show a reaction (they become one).
Exam Tip: Use simple chemical symbols like Fe (Iron) and S (Sulphur) to make your answer look more professional.

Question 2: Differentiate between homogeneous and heterogeneous mixtures with suitable examples.

Answer:
The main characteristics of mixture (Iron + Sulphur) are : (Note: The provided text seems to answer a different question here, but we follow verbatim.)
1. The mixture of iron and sulphur may contain iron and sulphur in varying proportions.
2. The original properties of each element are retained in the mixture of iron and sulphur.
3. Mixture of the two elements iron and sulphur can be separated by i.e. a physical method, i.e. by using a magnet since iron is attracted to the magnet.
Homogeneous mixtures look the same all over because the ingredients are mixed perfectly. Heterogeneous mixtures look chunky or layered because the ingredients stay in their own separate zones.
Teacher's Tip: If you can see the different parts with your eyes, it's heterogeneous!
Exam Tip: Always use a table format when asked to "differentiate" between two topics.

Question 3: With reference to the mixture of iron and sulphur, state the main characteristics of mixture.

Answer:
The main characteristics of mixture (Iron + Sulphur) are :
1. The mixture of iron and sulphur may contain iron and sulphur in varying proportions.
2. The original properties of each element are retained in the mixture of iron and sulphur.
3. Mixture of the two elements iron and sulphur can be separated by i.e. a physical method, i.e. by using a magnet since iron is attracted to the magnet.
Since no chemical reaction happens when you stir iron and sulphur together, the iron stays magnetic. This is why you can easily pull the iron out with a magnet and leave the yellow sulphur behind.
Teacher's Tip: Iron + Sulphur = Mixture (Magnetic). Iron Sulphide = Compound (Not Magnetic).
Exam Tip: Focus on "retention of properties" as the most important characteristic of a mixture.

Question 4: Tabulate a comparative chart – to differentiate between elements, compounds and mixtures. Differentiate them with reference to
(a) the term
(b) existence
(c) properties
(d) separation of components.

Answer:
(a) Term -
Elements – Pure substance made up of one kind of atoms only. e.g. Iron [Fe], Sulphur [S]
Compounds – Pure substance made up of two or more different elements, e.g. Iron sulphide [FeS]
Mixtures – Impure substance made up of two or more elements or compounds, e.g. Iron and sulphur mixture.
(b) Existence -
Elements – Elements i.e. atoms are present on their own. e.g. Iron and sulphur exist on their own as elements iron and sulphur.
Compounds – Components in a compound present in a definite proportion. e.g. Iron and sulphur are chemically combined in a fixed ratio in iron sulphide.
Mixtures – Components in a mixture present in any proportion. e.g. Iron and sulphur are mixed in any ratio in the mixture of iron and sulphur.
(c) Properties -
Elements – Elements have a definite set of properties. Elements classified into metal and non-metals each with its own properties.
Compounds – Compounds have a definite set of properties. Elements of a compound do not retain their original properties.
Mixtures – Mixture not have a definite set of properties. Components of a mixture do retain their original properties.
(iv) Separation of compound -
Elements – Elements occur on their own or as compounds and can be separated by chemical and physical methods. Example : Iron, copper.
Compounds – Elements in a compound are chemically combined and can be separated by chemical methods only. Example : Iron Sulphide, copper oxide.
Mixtures – Components in a mixture can be separated by physical methods only. Example : Iron + sulphur
Elements are the building blocks, compounds are the bricks made from blocks, and mixtures are just a pile of blocks and bricks. Knowing how they differ helps us understand everything from the air we breathe to the metals in our tools.
Teacher's Tip: Remember: Elements = One type, Compounds = Chemically bonded, Mixtures = Just mixed.
Exam Tip: Always include a chemical example (like Fe, FeS, or Fe+S) for each category to show complete understanding.

Question 5: State the principle involved in separation of solid-solid mixtures by –
(a) sieving
(b) magnetic separation
(c) sublimation.

Answer:
(a) Sieving
Principle - Based on the difference in size of the solid particles.
Examples - Mixture of Rice powder and soil, mixture of different sized particles of diamond and of sand.
(b) Magnetic separation
Principle - One component of the mixture is a magnetic substance.
Example - Mixture of iron ore and sand, Mixture of cobalt and lead.
(c) Sublimation
Principle - One of the components sublimes on heating.
Example - Mixture of iodine and salt, Mixture of ammounium chloride and sand.
Separation works by finding one thing that is different between the two parts of the mixture. If one is small and one is big, we sieve; if one is magnetic, we use a magnet.
Teacher's Tip: Principle = The "Scientific Reason" why the method works.
Exam Tip: When asked for the "Principle," always use keywords like "difference in size" or "magnetic nature."

Question 6: State the principle involved in separation of solid-liquid mixtures by –
(a) sedimentation and decantation
(b) filtration
(c) evaporation

Answer:
(a) Sedimentation and decantation -
Principle - The solid component is insoluble and heavier than the liquid component.
Example - Mixture of sand and water
(b) Filtration -
Principle - Seperation of insoluble solid component by passing through a porous material like filter paper.
Example - Mixture of chalk and water, Mixture of Agcl and Water.
(c) Evaporation -
Principle - Seperation of the mixture by evaporating the liquid component. The solid should be soluble in the liquid and should not sublime.
Example - Evaporation of a common salt solution or sea water leaves behind common salt.
For solid-liquid mixtures, we check if the solid dissolves or just floats around. If it dissolves, we usually have to boil away the liquid; if it doesn't, we can just filter it out.
Teacher's Tip: Filtration is for "Floating/Sinking bits" while Evaporation is for "Invisible/Dissolved bits."
Exam Tip: Mention that the solid must be "insoluble" for filtration to work; otherwise, it will pass right through.

Question 7: Explain the term ‘sieving’. State the structure of a sieve and explain the separation of different sized particles by sieving.

Answer:
Sieving - is a method of separation, which is used for separating substances of different sizes that cannot be separated in hand picking.
Principle - Based on the difference in size of the solid particles.
Technique of Separation - The large sized particles are separated from the small or finer particles by passing the mixture through a sieve.
The sieve has a wooden frame, with a metal mesh at its base.
The mixture is added from the top of the sieve, when the larger particles stay above and the finer particles collect below it on shaking the sieve.
Examples - Separation of rice powder from soil, seperation of different sized particles of diamond and of sand.
A sieve acts like a gatekeeper that only lets the small guests through while the big ones stay behind. By shaking the sieve, we help the small particles find the holes faster so they can drop through.
Teacher's Tip: Think of a "Sieve" like the mesh on a window that lets air in but keeps bugs out.
Exam Tip: Use the word "Mesh" when describing the structure of the sieve to be more descriptive.

Question 8: State what is meant by ‘magnetic separation of two mixtures’. Explain how iron particles can be separated from sulphur particles.

Answer:
Magnetism is ideal for separating mixtures of two solids with one part having magnetic properties. Some metals like iron, nickel and cobalt have magnetic properties whiles gold, silver and aluminum do not. Magnetic elements are attracted to a magnet.
Principle - Based on the difference in magnetic and non-magnetic nature of particles.
Technique of Separation - The magnetic particles such as iron are separated from the non-magnetic particles such as sulphur - by utilizing the magnetic properties of iron. The iron gets attracted to the magnet and seperates from the non-magnetic substance.
This method is like using a superpower to pick up only one specific ingredient without touching the rest. Since only the iron responds to the magnet, the yellow sulphur is left completely alone.
Teacher's Tip: Iron, Nickel, and Cobalt are the "Big Three" magnetic metals to remember.
Exam Tip: Draw a simple diagram of a magnet pulling iron out of a pile to get extra "clarity" marks.

Question 9: Give a reason why sublimable and non-sublimable substances can be separated easily, but two sublimable substance cannot.

Answer:
While seperating the mixture sublimable and non- sublimable substances, sublimable substance turns directly into vapour on heating whereas non-sublimable solid remains behind. Since, if we try to seperate the mixture of two sublimable substances, then both the sublimable substances turns into vapour on heating and vapour on cooling give back the pure same solid.
Separation only works if the two substances react differently to the heat. If they both turn into gas at the same time, they will just mix again in the air and land together as a mixture once more.
Teacher's Tip: To separate things, you need them to have "Different Personalities" (Properties).
Exam Tip: Explain what happens during "cooling" as well to show you understand the full cycle of sublimation.

Question 10: Explain the technique for separating – insoluble solid particles in a solid-liquid mixture.

Answer:
The insoluble solid particles in a solid-liquid mixture can be seperated by filtration.
Technique of Seperation - A filter paper is made into a cone & placed in a funnel. The solid particles remain behind on the filter paper while the liquid collects below.
Filtration is like a very fine sieve for liquids. The holes in the filter paper are so tiny that only water molecules can squeeze through, leaving the dirt trapped on top.
Teacher's Tip: Always fold the filter paper into a "Cone" shape so it fits perfectly in the funnel.
Exam Tip: Label the two parts of filtration: "Residue" (the solid left behind) and "Filtrate" (the clean liquid).

Question 11: Differentiate between the terms sedimentation and decantation with a suitable experimental technique.

Answer:
Sedimentation and decantation are two very different terms. Sedimentation is defined as the process of settling down of the heavier components present in a mixture.
For example : When the mixture of sand in water is allowed to stand undisturbed for some time, it is observed that sand settles at the bottom.
Decantation is defined as the process of separating the Liquid portion of a mixture when the heavier component settles at the bottom as sediments.
In other words, it is the process of transferring a liquid from one container to another without disturbing the sediments that are present at its bottom.
For example : When a mixture of sand and water is allowed to stand, sand settles at the bottom of a container since it is heavier. Water is present in the upper portion of the container. This can be separated from sand settled at the bottom simply by pouring in a different container without using any other separating device. This is known as decantation.
Sedimentation is the "waiting" part where gravity pulls the heavy dirt down. Decantation is the "pouring" part where you carefully tilt the glass to get the clear water out.
Teacher's Tip: Sedimentation = Sinking. Decantation = Dumping out the clear stuff.
Exam Tip: Emphasize that decantation must be done "without disturbing the sediment" to be successful.

Question 12: Explain how a solid component is separated in a soluble solid-liquid mixture.

Answer:
A Solid component is separated in a soluble solid-liquid mixture by evaporation.
Principle - Seperation of the mixture by evaporating the liquid component. The solid should be soluble in the liquid and should not sublime.
Technique of Separation : The soluble solid can be seperated from its liquid component by allowing the liquid component to evaporate either on its own or by heating. During evaporation, the liquid component is lost to the atmosphere & the solid remains behind.
Example : Evaporation of a common salt solution or sea water leaves behind common salt. Common salt remains behind whereas water lost to the atmosphere.
When a solid is dissolved, it's like it's hiding perfectly inside the liquid. Heating the liquid turns it into a gas that escapes, finally forcing the hidden solid to come back into view.
Teacher's Tip: Use evaporation if you only want to keep the solid (like salt from the sea).
Exam Tip: Note that the liquid is "lost to the atmosphere" in evaporation; if you need the liquid back, you would use distillation instead.

Question 13: Draw a neat labelled diagram for separation of the following mixtures.
(a) Coarse sand from fine sand
(b) A magnetic particle from a non-magnetic particle
(c) Naphthalene from sodium chloride
(d) Chalk and water using a filter paper
(e) Sand and water without using a filter paper
(f) Common salt from a solution of common salt and water

Answer:
(a) Coarse sand from fine sand: (Diagram shows a sieve with coarse sand on top and fine sand falling below).
(b) A magnetic particle from a non-magnetic particle: (Diagram shows a pile of magnetic and non-magnetic particles being separated by a magnet).
(c) Naphthalene from sodium chloride: (Diagram shows a mixture in an evaporating dish being heated under an inverted funnel with cotton at the top. Sublimed naphthalene collects on the funnel sides).
(d) Chalk and water using a filter paper: (Diagram shows filtration with a funnel, filter paper, residue of chalk, and filtrate of water).
(e) Sand and water without using a filter paper: (Diagram shows sedimentation where sand settles, followed by decantation where water is poured into another beaker).
(f) Common salt from a solution of common salt and water: (Diagram shows evaporation where a salt solution is heated in a dish and water vapor escapes, leaving salt behind).
Diagrams help us visualize exactly how the equipment is set up in a lab. For example, the inverted funnel used in sublimation is essential for catching the gas before it floats away.
Teacher's Tip: When drawing, always use a ruler for straight lines and label everything clearly with arrows.
Exam Tip: A "neat labelled diagram" means every part (like the funnel, tripod stand, or residue) must have its name written next to it.

Question 14: State the technique involved in separating the following:
(a) Iodine crystals and potassium chloride
(b) Iron and chalk powder
(c) Potassium chloride from an aqueous solution of potassium chloride.
(d) Rice powder from soil particles
(e) Iron filings from pieces of copper wire
(f) Large diamonds from very small diamonds

Answer:
(a) Sublimation
(b) Magnetic separation
(c) Evaporation
(d) Seiving
(e) Magnetic separation
(f) Seiving
Different materials require different physical solutions based on their properties. For example, diamonds of different sizes are separated using sieves with specific hole sizes, just like sorting coins.
Teacher's Tip: Iodine is one of the few elements that can sublime (turn to gas) easily.
Exam Tip: If you see "Iron," your first thought for separation should almost always be "Magnetic Separation."

Objective Type Questions

Q.1 Match the statements in List I with the correct answer in List II.
1. Purification of water by adding alum
2. Sea water leaving behind common salt
3. Separation of camphor and potassium chloride
4. Separation of charcoal from a charcoal-water mixture
5. Separation of bran and wheat flour

Answer:
1. Purification of water by adding alum D : Sedimentation
2. Sea water leaving behind common salt E: Evaporation
3. Separation of camphor and potassium chloride A: Sublimation
4. Separation of charcoal from a charcoal-water mixture C : Filtration
5. Separation of bran and wheat flour B : Sieving
Matching questions test if you can link the "Method" to the "Situation." For example, alum is used specifically in the sedimentation stage of water cleaning to help dirt sink.
Teacher's Tip: Read the whole list on both sides before you start drawing lines or writing letters.
Exam Tip: Cross out the options you have already used so you don't get confused at the end.

Q.2 State whether the following statements are true or false. If false write – the correct statement.

1. Components in a mixture are present in a definite proportion.
Answer: False.
Correct - Components in a mixture are present in a varying proportion.
You can make a mixture of sand and water with one spoon of sand or ten spoons; there is no strict rule. This is the biggest difference between a mixture and a chemical compound.
Teacher's Tip: Mixtures are "flexible"; Compounds are "strict" with their recipes.
Exam Tip: Always check if the question asks you to "correct" the false statements, as this is worth half the marks.

2. Mixture have no definite set of properties.
Answer: True.
Because mixtures contain different things that keep their own identity, the whole mixture doesn't have its own unique boiling point or density. The properties of a mixture depend entirely on what you put into it and how much.
Teacher's Tip: A mixture of salt and sugar will taste salty AND sweet at the same time!
Exam Tip: Remember that "No definite set" is a key characteristic of all mixtures.

3. Components in a mixture can be separated by physical and chemical methods.
Answer: False.
Correct - Components in a mixture can be separated by physical methods.
We don't need to use complex chemical reactions to get salt out of water; just simple heating (a physical change) is enough. Chemical methods are reserved for breaking down compounds into elements.
Teacher's Tip: Physical methods are "easy" (like filtering); chemical methods are "hard" (like electrolysis).
Exam Tip: Be precise: Mixtures = Physical separation; Compounds = Chemical separation.

4. Sodium chloride and water is an example of a mixture of elements and compounds.
Answer: False.
Correct - Sodium chloride and water is an example of a mixture of compounds.
Sodium chloride (salt) is a compound, and water is also a compound. When you mix them, you have two compounds living together in the same glass.
Teacher's Tip: Both salt and water have formulas (NaCl and H₂O), which proves they are compounds.
Exam Tip: Always check if the components of a mixture are pure elements (like Iron) or compounds (like Salt).

5. Heterogeneous mixtures have different composition and properties throughout the mixture.
Answer: True.
If you take a spoonful of soup from the top, you might get only broth; from the bottom, you might get a carrot. This "unevenness" is exactly what makes it a heterogeneous mixture.
Teacher's Tip: Heterogeneous = "Not the same everywhere."
Exam Tip: Use the phrase "not uniform" to describe heterogeneous mixtures in your own words.

Q.3. Name the following

Question 1: A black non-metallic component of the mixture gunpowder.
Answer: Carbon.
Carbon, usually in the form of charcoal, provides the fuel needed for gunpowder to burn rapidly. It is the component that gives the mixture its traditional dark black color.
Teacher's Tip: Charcoal is mostly just pure carbon.
Exam Tip: Gunpowder is a classic example of a mixture made of three different things; learn all three (Sulphur, Carbon, Saltpeter).

Question 2: A physical method of separating iron from an iron- sulphur mixture.
Answer: Magnetic separation.
This method works because iron is magnetic while sulphur is not. By hovering a magnet over the pile, the iron jumps up and leaves the sulphur behind.
Teacher's Tip: This is the easiest way to separate metals without using water or heat.
Exam Tip: Always mention "physical method" to show that no chemical reaction is involved.

Question 3: The component of the soluble solid-liquid mixture, which is lost to the atmosphere on heating.
Answer: Liquid component i.e. water.
During evaporation, the liquid turns into water vapor (gas) and flies away into the air. This leaves the solid behind in the container so we can collect it.
Teacher's Tip: If you want to keep the liquid, you must catch the vapor and cool it down again.
Exam Tip: "Atmosphere" is a clue that the substance has turned into a gas and escaped.

Question 4: The component of a naphthalene-sodium chloride mixture, which remains in the evaporating dish when heated together, covered with a funnel.
Answer: Sodium chloride.
Naphthalene turns into gas and travels up to the funnel, while sodium chloride stays as a solid because it has a much higher melting point. This is how we separate two solids when only one of them sublimes.
Teacher's Tip: Sodium chloride is just common table salt, which doesn't turn into gas easily.
Exam Tip: Note that the "non-sublimable" part is always the one that "remains behind."

Question 5: A mixture of two immiscible liquids.
Answer: Kerosene oil and water.
These two liquids refuse to blend because their molecules don't like to stick to each other. They will form two very clear layers, with the oil floating on top of the water.
Teacher's Tip: Immiscible means they "stay separate" like enemies!
Exam Tip: Use "Oil and Water" as your default example for immiscible liquids; it's impossible to forget.

Q.4. Give reasons for the following :

Question 1: Naphthalene and camphor cannot be separated by sublimation.
Answer: Because both of these are sublimable solids and they sublimes on heating.
If both solids turn into gas at the same time, they will just mix in the air and land together as a mixture again. To separate two things, they must react differently to the same treatment.
Teacher's Tip: You can't separate two "identical twins" using a method that treats them both the same way!
Exam Tip: Clearly state that both components undergo the same process to explain why it fails as a separation method.

Question 2: Sodium chloride cannot be separated out from its aqueous solution by filtration.
Answer: Filtration is a method that is used to separate insoluble solids from liquids, since both salt dissolve in water.
(Note: Salt dissolves into particles so small that they slip through the microscopic holes in the filter paper.)
Once dissolved, the salt becomes part of the liquid's structure, so a filter can't grab it. You need a process like evaporation that changes the state of the liquid to get the salt back.
Teacher's Tip: If you can see through the liquid (transparent), filtration won't work.
Exam Tip: Use the word "soluble" to explain why filtration fails for salt water.

Question 3: Two varieties of wheat flour cannot be separated by sieving.
Answer: Since in sieving we can separate larger particle but in this case both particles are finer in nature.
Sieving only works if one ingredient is much bigger than the other so it gets stuck in the mesh. If both are the same tiny size, they will both fall through the holes together.
Teacher's Tip: A sieve is like a door that is too small for big people but let's all small people through.
Exam Tip: Emphasize "difference in size" as the requirement for sieving.

Question 4: Sulphur and charcoal powder cannot be separated by magnetic separation.
Answer: Because both are non-magnetic particles.
A magnet only "sees" magnetic materials like iron; it completely ignores things like sulphur and charcoal. Since neither one is attracted to the magnet, the magnet will pick up nothing at all.
Teacher's Tip: Magnets are only useful if at least one part of the mixture is magnetic.
Exam Tip: List the magnetic metals (Iron, Nickel, Cobalt) to show why other substances are non-magnetic.

Question 5: Both components of a soluble solid-liquid mixture cannot be recovered by evaporation.
Answer: Because liquid is lost/evaporated in atmosphere.
Evaporation is designed to give you the solid back, but it lets the liquid turn into gas and float away forever. If you want to keep both, you would need a closed system called distillation.
Teacher's Tip: Evaporation is like a one-way street for the liquid.
Exam Tip: Contrast "Evaporation" (recovers solid only) with "Distillation" (recovers both) for a more complete answer.