Mix Example - IS MATTER AROUND US PURE? Questions in English

(A) Mass by percentage formula is given by: $\text{Mass percentage} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$
Given:
Mass of solution $= 250 \, g$
Mass percentage of glucose $= 40 \%$
Substituting the values:
$40 = \frac{\text{Mass of glucose}}{250} \times 100$
Mass of glucose $= \frac{40 \times 250}{100} = 100 \, g$
Now,calculate the mass of water:
Mass of water $= \text{Mass of solution} - \text{Mass of glucose}$
Mass of water $= 250 \, g - 100 \, g = 150 \, g$
Therefore,the mass of glucose is $100 \, g$ and the mass of water is $150 \, g$.

(N/A) Sedimentation tank: This tank allows heavy,insoluble solid particles to settle down at the bottom due to gravity.
$(b)$ Loading tank: This tank is used to add coagulants like alum to the water,which helps in settling down fine suspended impurities that do not settle easily by sedimentation.
$(c)$ Chlorination tank: This tank is used to add chlorine to the water to kill harmful bacteria and microorganisms,making the water safe for consumption.

(II, III) Burning of a candle: When a candle burns,the wax melts,which is a physical change. Simultaneously,the wax reacts with oxygen to produce $CO_2$ and $H_2O$ vapor,which is a chemical change. Thus,both changes occur together.
$(b)$ The chemical changes are:
$(ii)$ Growth of plant: This involves complex metabolic processes and permanent changes in the organism's structure.
$(iii)$ Rusting of iron: This is a chemical reaction where iron reacts with oxygen and moisture to form hydrated iron$(III)$ oxide.

(N/A) $(i)$ Immiscible liquids.
$(ii)$ The liquid with higher density will form the lower layer.
$(iii)$ The principle behind this method is that immiscible liquids separate out into distinct layers based on their differences in densities.

(N/A) $(i)$ The technique used is fractional distillation.
$(ii)$ The fractionating column is a glass tube packed with glass beads or other materials that provide a large surface area. It is fitted between the distillation flask and the condenser.
It is used because it provides a large surface area for the vapours to cool and condense repeatedly,allowing for better separation of liquids with boiling points close to each other.

(A-D) $(i)$ Sublimation.
$(ii)$ Paper chromatography.
$(b)$ Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
The crystallisation technique is better than the simple evaporation technique because:
$1$. Some solids decompose or may get charred (e.g.,sugar) upon heating to dryness.
$2$. Some impurities may remain dissolved in the solution even after filtration; evaporation would cause these impurities to contaminate the solid,whereas crystallisation leaves them in the mother liquor.

(N/A) Separating funnel.
$(b)$ It is used to separate a mixture of two immiscible liquids.
$(c)$ The principle involved is that immiscible liquids separate out into distinct layers based on their densities.

(C) '$C$' has made the desired solution.
The formula for mass by volume percentage is:
$\text{Mass by volume } \% = \frac{\text{Mass of solute (g)}}{\text{Volume of solution (mL)}} \times 100$
For student '$C$':
$\text{Mass by volume } \% = \frac{50\, g}{100\, mL} \times 100 = 50\%$
Student '$A$' prepared a solution where the total volume is likely greater than $100\, mL$ (as $50\, g$ of $NaOH$ occupies volume),and student '$B$' prepared a mass by mass solution,not mass by volume.

(A-D) $(i)$ $(a)$ Chromatography: This technique is used to separate solutes that dissolve in the same solvent.
$(b)$ Centrifugation: This method is used to separate suspended particles from a liquid based on density.
$(c)$ Sublimation: This process is used to separate a sublimable volatile component from a non-sublimable impurity.
$(d)$ Magnetic separation: This method is used to separate magnetic substances from non-magnetic substances.
$(ii)$ The principle of centrifugation is that when a mixture is rotated at high speed,the denser particles are forced to the bottom and the lighter particles stay at the top.

(N/A) Fog: Dispersed phase is liquid and dispersing medium is gas.
$(b)$ Cheese: Dispersed phase is liquid and dispersing medium is solid.
$(c)$ Coloured gemstone: Dispersed phase is solid and dispersing medium is solid.

(N/A) Evaporation: Sodium chloride is a non-volatile solute,so it can be recovered from its aqueous solution by evaporating the water.
$(b)$ Filtration: Tea leaves are insoluble solids that can be separated from the liquid tea using a filter or sieve.
$(c)$ Magnetic separation: Iron pins are magnetic,while sand is not; therefore,a magnet can be used to attract and separate the pins.
$(d)$ Chromatography: This technique is used to separate different pigments based on their differential solubility in a solvent.
$(e)$ Centrifugation: Butter particles are lighter than the liquid in curd; spinning the mixture at high speed forces the denser components outward,separating the butter.
$(f)$ Decantation and filtration: Fine mud particles can be allowed to settle (sedimentation) followed by decantation,or removed directly using filtration.

(N/A) $1$. Metals: Property: They are lustrous (shiny). Example: Iron $(Fe)$.
$2$. Non-metals: Property: They are poor conductors of heat and electricity. Example: Oxygen $(O_2)$.
$3$. Metalloids: Property: They exhibit properties intermediate between those of metals and non-metals. Example: Germanium $(Ge)$.

(A) At room temperature,the iron filings and sulphur powder exist as a mixture. When treated with dilute sulphuric acid,the iron reacts to produce hydrogen gas $(H_2)$.
$(b)$ When the mixture is heated strongly,iron and sulphur react to form a chemical compound,iron sulphide $(FeS)$. When this compound is treated with dilute sulphuric acid,it produces hydrogen sulphide gas $(H_2S)$,which has a characteristic rotten egg smell.
$(c)$ The difference in results occurs because in the first case,the substances exist as a mixture,retaining their individual properties. In the second case,heating causes a chemical reaction that forms a new compound with entirely different chemical properties compared to its constituent elements.

(N/A) The difference based on particle size is as follows:

Type of Mixture	Particle Size
True Solution	$< 1 \, nm$
Colloidal Solution	$1 - 100 \, nm$
Suspension	$> 100 \, nm$

$(b)$ To test if the solution is saturated or unsaturated,add a small amount of additional sodium chloride to the solution at the same temperature. If the added salt dissolves,the original solution was unsaturated. If the added salt does not dissolve and settles at the bottom,the original solution was saturated.
$(c)$ The solubility of most solid solutes in a liquid solvent increases with an increase in temperature. Therefore,by heating the solution,we can increase the solubility and dissolve more solute.

(N/A) Mass of solute $(w) = 34.2\, g$
Mass of solution $(W) = 214.2\, g$
Concentration of sugar in the syrup $= \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$
$= \frac{34.2}{214.2} \times 100 = 15.96\%$
$(b)$ $A$ solution is a homogeneous mixture of two or more substances.

(N/A) Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
$AIM$: To obtain crystals of pure copper sulphate from an impure sample.
Procedure:
$(i)$ Take some impure sample of copper sulphate in a china dish (approximately $5 \ g$).
$(ii)$ Dissolve the contents in a minimum amount of water and filter the impurities out.
$(iii)$ Evaporate water from the solution to get a saturated solution of copper sulphate.
$(iv)$ Cover the solution with a filter paper and leave it undisturbed at room temperature to cool slowly for a day.
Observation: The crystals of copper sulphate can be seen in the china dish.
Conclusion: The process of formation of crystals of a pure solid from a solution is called crystallisation.

(N/A) $(i)$ Magnetic separation: Pass a magnet over the mixture. The iron filings will be attracted to the magnet and can be separated from the mixture.
$(ii)$ Sublimation: Heat the remaining mixture. Camphor,being a sublimable substance,will change directly from a solid to a gas and can be collected by cooling it on a cold surface (like an inverted funnel),leaving behind the common salt.
$(iii)$ Dissolution and Filtration/Evaporation: Add water to the remaining residue (common salt). The salt will dissolve in the water. Filter the solution to remove any impurities if necessary,then evaporate the water to obtain the common salt.

(C) Comparison between metals and non-metals:

Metals	Non-metals
$(1)$ Metals are malleable and ductile.	$(1)$ Non-metals are brittle.
$(2)$ Metals are sonorous,i.e.,they produce a ringing sound when struck.	$(2)$ Non-metals are not sonorous.
$(3)$ Metals are good conductors of heat and electricity.	$(3)$ Non-metals are poor conductors of heat and electricity (except diamond and graphite).
$(4)$ Metals are generally solids at room temperature (except mercury).	$(4)$ Non-metals can be solids,liquids,or gases at room temperature.

$(b)$ Elements that exhibit properties intermediate between those of metals and non-metals are called metalloids. Examples: Boron $(B)$ and Silicon $(Si)$.
$(c)$ Among the given elements,sodium $(Na)$ and mercury $(Hg)$ are metals.

(N/A) Let the mass of potassium chloride required be $x \, g$.
The mass of the solution is $(x + 100) \, g$.
Given that the concentration is $40 \%$,we use the formula:
$\text{Concentration} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$
$40 = \frac{x}{x + 100} \times 100$
$40(x + 100) = 100x$
$40x + 4000 = 100x$
$60x = 4000$
$x = \frac{4000}{60} = 66.67 \, g$
$(b)$ Solubility is defined as the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature to form a saturated solution.
Effect of temperature:
$1$. For most solid solutes,solubility increases with an increase in temperature.
$2$. For gaseous solutes,solubility generally decreases with an increase in temperature.

(N/A) Properties of colloids:
$(a)$ $A$ colloid is a heterogeneous mixture. The size of particles of a colloid is too small to be individually seen by the naked eye.
$(b)$ Colloidal particles are big enough to scatter a beam of light passing through them and make the path of light visible (Tyndall effect).
$(c)$ They do not settle down when left undisturbed,i.e.,a colloid is quite stable. However,centrifugation techniques can be used to separate the colloidal particles.
Categorization of examples:
- Jelly: Gel
- Fog: Aerosol
- Milk: Emulsion
- Shaving cream: Foam

(N/A) Differences between a mixture and a compound:

Mixtures	Compounds
$(1)$ Elements or compounds just mix together to form a mixture.	$(1)$ Elements react to form a new substance called a compound.
$(2)$ Variable composition.	$(2)$ Composition is fixed.
$(3)$ Show the properties of its constituents.	$(3)$ Show the properties of the compound and not the constituent elements.
$(4)$ Constituents can be separated easily by physical methods.	$(4)$ Cannot be separated by physical methods.

$(b)$ Procedure to separate the mixture of sand,iron filings,naphthalene,and sodium chloride:
$(1)$ Use a magnet to move it over the mixture. The iron filings will be attracted to the magnet and can be separated.
$(2)$ The remaining mixture (sand,naphthalene,and sodium chloride) is heated. Naphthalene undergoes sublimation (changes directly from solid to gas) and can be collected separately.
$(3)$ Add water to the remaining mixture of sand and sodium chloride. Sodium chloride dissolves in water,while sand does not.
$(4)$ Filter the mixture. Sand remains as the residue on the filter paper,while sodium chloride solution passes through as the filtrate.
$(5)$ Finally,evaporate the filtrate (sodium chloride solution) to obtain solid sodium chloride.

$(a)$ The water evaporates, and sugar remains as a solid residue.
$(b)$ The solubility of potassium chloride decreases with temperature, causing crystals of potassium chloride to form.
$(c)$ Iron reacts with sulphur to form a new compound, iron$(II)$ sulphide $(FeS)$, which is a black-coloured solid.
$(d)$ The path of the light becomes visible due to the scattering of light by colloidal particles, known as the Tyndall effect.
$(e)$ $A$ colourless gas, hydrogen sulphide $(H_2S)$, is evolved, which has a characteristic smell of rotten eggs.

(N/A) Differences between homogeneous and heterogeneous mixtures:

Homogeneous mixture	Heterogeneous mixture
$(i)$ Composition is uniform throughout.	$(i)$ Composition is not uniform throughout.
$(ii)$ No visible boundaries of separation.	$(ii)$ Distinct boundaries of separation are visible.
$(iii)$ Components are not easily separated (e.g.,sugar in water).	$(iii)$ Components can be easily separated (e.g.,oil and water).

$(b)$ Reasons to support that water is a compound and not a mixture:
$(i)$ Water has a fixed chemical composition $(H_2O)$ and its components can be separated only by chemical methods like electrolysis,not by physical means.
$(ii)$ The properties of water are entirely different from the properties of its constituent elements,hydrogen (a combustible gas) and oxygen (a supporter of combustion).

(N/A) The separation techniques are:
$(i)$ Filtration: Used to separate solid particles from a liquid.
$(ii)$ Centrifugation: Used to separate fine suspended particles.
$(iii)$ Separating funnel: Used to separate immiscible liquids like oil and water.
$(iv)$ Evaporation: Used to separate a dissolved solid from its solvent.
$(v)$ Sublimation: Used to separate a sublimable solid (camphor) from a non-sublimable one (salt).
$(vi)$ Winnowing: Used to separate lighter husk from heavier grains.
$(b)$ Classification of changes:
Chemical change: $(ii)$ Burning of paper and $(iii)$ Rusting of an almirah (new substances are formed).
Physical change: $(i)$ Boiling of water and $(iv)$ Making a fruit salad (no new substances are formed,only physical state or appearance changes).

(N/A) Differences between suspension and true solution:

Suspension	True solution
$(i)$ Opaque in nature.	$(i)$ Transparent in nature.
$(ii)$ Particles can be separated by filtration.	$(ii)$ Particles cannot be separated by filtration.
$(iii)$ Unstable; particles settle down on keeping.	$(iii)$ Stable; particles do not settle down.

$(b)$ Colloids from the given list are: Milk,smoke,butter,and face cream.

(N/A) The differences are tabulated below:

Property	Suspension	True Solution
$(i)$ Filtration	Particles can be separated by filtration.	Particles cannot be separated by filtration.
$(ii)$ Transparency	Opaque.	Transparent.
$(iii)$ Stability	Unstable (particles settle down).	Stable (particles do not settle).

$(b)$ Two examples of the Tyndall effect in daily life are:
$(i)$ $A$ beam of light entering a dark room through a small hole,making dust particles visible.
$(ii)$ Sunlight passing through the canopy of a dense forest,where tiny water droplets in the mist scatter the light.

(C) The three characteristics of a colloid are:
$(i)$ It is a heterogeneous mixture.
$(ii)$ The particles of a colloid scatter a beam of light passing through it (Tyndall effect).
$(iii)$ It is a stable mixture,meaning the particles do not settle down when left undisturbed.
$(b)$ The two components of a colloid are:
$(i)$ Dispersed phase
$(ii)$ Dispersing medium
$(c)$ Among the given mixtures,the colloids are: Ink,blood,and foam.

(C) Colloids are heterogeneous mixtures where the particle size is intermediate between true solutions and suspensions $(1-1000 \ nm)$. They appear homogeneous but are actually heterogeneous. Suspensions are heterogeneous mixtures where the solute particles do not dissolve but remain suspended throughout the bulk of the medium and are large enough to be seen by the naked eye $(> 1000 \ nm)$.
From the given list:
$1$. Soda water: Solution.
$2$. Milk: Colloid.
$3$. Sponge: Colloid (solid foam).
$4$. Clouds: Colloid (aerosol).
$5$. Mixture of alcohol and water: Solution.
$6$. Jelly: Colloid (gel).
Therefore,the colloids are: Milk,sponge,clouds,and jelly.

(N/A) Concentration of a solution is the amount of solute present in a given amount of solvent or solution at a specific temperature.
Solubility is the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature to form a saturated solution.

(N/A) $(i)$ When a saturated solution is heated,its solubility increases,making it capable of dissolving more solute. Consequently,the solution becomes unsaturated.
$(ii)$ When a saturated solution is cooled slowly,the solubility of the solute decreases. As a result,the excess solute precipitates out of the solution,often forming crystals of the pure compound.

(N/A) Heating of $NH_4Cl$ (ammonium chloride) and sugar are different processes because they involve different physical and chemical changes.
$1$. $NH_4Cl$ is a sublime substance. When heated,it undergoes sublimation,meaning it changes directly from a solid state to a gaseous state without passing through the liquid phase.
$2$. Sugar $(C_{12}H_{22}O_{11})$ is not a sublime substance. When heated,it undergoes a chemical change called dehydration and thermal decomposition,which results in charring (turning into black carbon residue) rather than sublimation.

(N/A) $(i)$ Mercury and water: Since they are immiscible liquids with different densities,a separating funnel is used.
$(ii)$ Coloured components from blue ink: Chromatography is used as it separates components based on their different solubilities in a solvent.
$(iii)$ Ammonium chloride and potassium chloride: Sublimation is used because ammonium chloride sublimes upon heating,while potassium chloride does not.
$(iv)$ Mixture of alcohol and water: Fractional distillation is used because they are miscible liquids with different boiling points.

(N/A) To separate the mixture of common salt,camphor,and iron filings,follow these steps:
$1$. Magnetic Separation: Move a magnet over the mixture. Since iron filings $(C)$ are magnetic,they will be attracted to the magnet and can be separated from the mixture.
$2$. Sublimation: The remaining mixture contains common salt and camphor. Heat the mixture in a china dish. Camphor $(B)$ is a sublimable substance,meaning it changes directly from a solid to a gas upon heating. Place an inverted funnel over the dish to collect the camphor vapors,which will solidify on the cool inner walls of the funnel.
$3$. Residue: The common salt $(A)$ does not sublime and will remain as a residue in the china dish.

(N/A) $(i)$ The chemical composition of the substance remains unchanged during the process.
$(ii)$ No new chemical substance is formed; the identity of the matter remains the same.
$(iii)$ The change is often reversible,and the substance exhibits different physical properties (like shape or state) while maintaining its original chemical identity.

(N/A) The particles of a colloidal solution are very small,so they cannot be seen with the naked eye. Therefore,the colloidal solution appears to be homogeneous.
However,these particles are large enough to scatter a beam of visible light,i.e.,they exhibit the $Tyndall$ effect. Because they exhibit this property,which is characteristic of mixtures with distinct phases,the colloidal solution is actually heterogeneous.

(N/A) $(i)$ $A$ mixture of two coloured components: Ink (which contains various dyes).
$(ii)$ $A$ mixture of two volatile components with a boiling point difference of less than $25\ K$: Air (which is a mixture of gases like nitrogen,oxygen,and argon).
$(iii)$ $A$ mixture of a volatile and a non-volatile solid component: Salt and water (or camphor and sand).

(B)

Pure substance	Mixture
$(i)$ It is made up of only one kind of particles (atoms or molecules).	$(i)$ It consists of two or more pure substances mixed together in any proportion.
$(ii)$ It has a fixed composition with fixed melting and boiling points. e.g.,Gold,water,carbon dioxide.	$(ii)$ It does not have a fixed composition or fixed melting and boiling points. e.g.,Air,soil,sea-water.

(N/A) $(i)$ When iron filings and sulphur are heated together,they undergo a chemical reaction to form iron$(II)$ sulphide,represented by the formula $FeS$.
$(ii)$ When dilute hydrochloric acid $(HCl)$ is added to iron$(II)$ sulphide $(FeS)$,a chemical reaction occurs to produce hydrogen sulphide gas $(H_2S)$.
The chemical equation is: $FeS(s) + 2HCl(aq) \rightarrow FeCl_2(aq) + H_2S(g)$.
Two properties of hydrogen sulphide $(H_2S)$ gas are:
$(a)$ It is a colourless gas.
$(b)$ It has a characteristic smell of rotten eggs.

(N/A) Salt solution ($NaCl$ in water) is a solid-liquid homogeneous mixture where salt dissolves completely in water.
$(b)$ Air is a gas-gas homogeneous mixture consisting of nitrogen,oxygen,argon,and other gases.
$(c)$ Alloys like brass (copper and zinc) or bronze (copper and tin) are solid-solid homogeneous mixtures.
$(d)$ Muddy water or chalk powder in water are examples of solid-liquid heterogeneous mixtures.
$(e)$ $A$ mixture of oil and water is a liquid-liquid heterogeneous mixture as they form separate layers.

(N/A) Tincture of iodine: Solute $=$ Iodine,Solvent $=$ Alcohol.
$(b)$ Soda water: Solute $=$ Carbon dioxide $(CO_2)$,Solvent $=$ Water.
$(c)$ Sugar solution: Solute $=$ Sugar,Solvent $=$ Water.
$(d)$ Polluted air: Solute $=$ Pollutant gases (e.g.,$NO_2, SO_2, CO$),Solvent $=$ Air (mainly Nitrogen and Oxygen).
$(e)$ Dilute hydrochloric acid: Solute $=$ Hydrogen chloride gas $(HCl)$,Solvent $=$ Water.

(N/A) $(i)$ Mixture of common salt and water (True solution).
$(ii)$ Mixtures of chalk powder with water (Suspension) and milk with water (Colloid).
$(iii)$ Mixture of common salt and water (True solution).
$(iv)$ Mixture of chalk powder and water (Suspension).
$(v)$ Mixture of chalk powder and water (Suspension).

(N/A)

Elements	Compounds
$(i)$ Made up of only one type of atoms.	$(i)$ Made up of two or more types of atoms chemically combined in a fixed ratio.
$(ii)$ Cannot be broken down into simpler substances by chemical reactions.	$(ii)$ Can be broken down into simpler substances (elements) by chemical reactions.

Classification:
Elements: Iodine,$24$ carat gold,Oxygen gas,Carbon.
Compounds: Sodium chloride,Water.

(N/A) $solution$ is a homogeneous mixture of two or more substances.
$(i)$ Tincture of iodine: Solute is $iodine$ and solvent is $alcohol$.
$(ii)$ Polluted air: Solute is $pollutants$ (like $SO_2$, $NO_2$, dust) and solvent is $air$ (mixture of gases).
$(iii)$ Soda water: Solute is $CO_2$ and solvent is $water$.
$(iv)$ Dilute hydrochloric acid: Solute is $HCl$ and solvent is $water$.

(A) pure substance is defined as a substance that consists of only one type of particles. These particles can be atoms (in the case of an element) or molecules (in the case of a compound). All constituent particles in a pure substance have the same chemical properties.

(N/A) mixture consists of two or more substances mixed in any proportion. Because the composition of a mixture is variable,the intermolecular forces and the energy required for phase transitions are not constant. Therefore,a mixture does not have a fixed melting or a fixed boiling point; instead,it melts or boils over a range of temperatures.

(N/A) The elements which exhibit properties intermediate between those of metals and non-metals are called metalloids or semimetals.
Examples include Silicon $(Si)$,Germanium $(Ge)$,Arsenic $(As)$,Antimony $(Sb)$,and Tellurium $(Te)$.

(C) substance or compound is considered pure if it consists of only one type of particles and exhibits a fixed melting point and a fixed boiling point under standard atmospheric pressure.
If a substance is impure,it will typically show a range of temperatures for melting or boiling rather than a sharp,fixed value.

(B) The "Tyndall effect" is the phenomenon of scattering of a beam of light by particles in a colloid or a fine suspension.
$1$. Copper sulphate solution, sugar solution, and salt solution are all true solutions, where the solute particles are very small (less than $1 \, nm$ in diameter) and do not scatter light.
$2$. A soap solution is a colloidal solution. In a colloid, the particle size is between $1 \, nm$ and $1000 \, nm$, which is large enough to scatter a beam of light passing through it, thus exhibiting the "Tyndall effect".
Therefore, the correct option is $B$.

(A) saturated solution is one in which no more solute can be dissolved at a given temperature.
When a saturated solution is cooled,the solubility of the solute decreases.
As a result,the solution becomes supersaturated,and the excess solute typically crystallizes out of the solution.

(B) compound is a substance formed when two or more chemical elements are chemically bonded together in a fixed proportion by mass.
Water $(H_2O)$ is a compound because it consists of hydrogen and oxygen atoms chemically combined in a fixed ratio of $2:1$ by volume or $1:8$ by mass.
Air is a mixture of various gases like nitrogen,oxygen,argon,and carbon dioxide.
Soda water is a mixture of carbon dioxide gas dissolved in water.
Pond water is a mixture containing water,dissolved minerals,organic matter,and microorganisms.
Therefore,water is the correct answer.