Is Matter Around Us Pure-Exercise

1. Which separation techniques will you apply for the separation of the following?

Solution:

1. Sodium chloride from its solution in water
   Method: Evaporation or Crystallization
   Explanation: Water is evaporated, leaving solid sodium chloride crystals behind.
2. Ammonium chloride from a mixture containing sodium chloride and ammonium chloride
   Method: Sublimation
   Explanation: Ammonium chloride sublimates on heating, changing directly to gas and then solidifies upon cooling, separating it from sodium chloride.
3. Small pieces of metal in the engine oil of a car
   Method:
   Filtration or maybe Magnetic Separation if pieces are iron. Explanation: Solid metal pieces can be filtered out or separated using a magnet.
4. Different pigments from an extract of flower petals
   Method: Chromatography
   Explanation: Pigments are separated based on their different movement rates on the chromatography medium.
5. Butter from curd
   Method: Churning/Centrifugation
   Explanation: Butter is separated from curd by churning, which aggregates fat globules.
6. Oil from water
   Method: Separating funnel (decantation)
   Explanation: Due to immiscibility, oil and water separate into layers and can be separated by decanting.
7. Tea leaves from tea
   Method: Filtration
   Explanation: Tea leaves are separated from liquid tea using filtration.
8. Iron pins from sand
   Mathos: Magnetic separation
   Explanation: Iron pins are attracted and separated using a magnet.
9. Wheat grains from husk
   Method: Winnowing
   Explanation: Lighter husk is separated from heavier wheat grains by blowing air.
10. Fine mud particles suspended in water
    Method: Sedimentation and decantation/Filtration
    Explanation: Mud settles at the bottom, and clear water is poured off; filtration can also be used.

3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution)

Substance Dissolved	Temperature in K
	283	293	313	333	353
	solubility
Potassium nitrate	21	33	62	106	167
Sodium chloride	36	36	36	37	37
Potassium chloride	35	35	40	46	54
Ammonium chloride	24	37	41	55	66

1. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?

   Solution:
   Solubity of potassium nitrate at 313k in 100 gm of water = 62
   therefore Solubility in 50 gm = 62/2 = 31 gm

2. Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

   Solution:
   The primary observation is the formation of KCl crystals as the solution cools.
   This process is called crystallisation and is used industrially for the recovery and purification of potassium chloride.
   So, the cooling of a saturated potassium chloride solution leads to the visible development of KCl crystals because their solubility in water decreases with a decrease in temperature.

3. Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?

   Solution:
   

   Solubility	Temperture (293K)
   Potassium nitrate	32
   sodium chloride	36
   Potassium chloride	35
   Ammonium chloride	37

   
   Ammonium chloride has the highest solubility at 293K

4. What is the effect of a change in temperature on the solubility of a salt?

   Solution:
   The solubility of most solid salts increases as the temperature rises. This means that more of the salt can dissolve in a given amount of water at higher temperatures.

Explain the following, giving examples.

1. Saturated solution:
   At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution.
2. Pure substance:
   A single form of matter consisting of only one type of particle (either atoms or molecules) and having a definite and uniform chemical composition.
3. Colloid:
   The particles of a colloid are uniformly spread throughout the solution. Due to the relatively smaller size of particles, as compared to that of a suspension, the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture
4. Suspension:
   A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.

5. Classify each of the following as a homogeneous or heterogeneous mixture.

Substance	Solution Type
Soda Water	Homogeneous
Wood	Heterogeneous
Air	Heterogeneous
Vinegar	Homogeneous
Filtered Tea	Homogeneous

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

Solution: The most practical methods involve testing boiling/freezing points, electrical conductivity, or looking for residues after evaporation. A combination of tests can give a stronger indication that the liquid is pure water.

7. Which of the following materials falls in the category of a “pure substance”?

Solution:

• Ice: Ice is a Pure Substance \((H_2O)\)
• Milk: Milk is a mixture (Colloid of Water, Fat, Protiens etc)
• Iron: Iron is an element hence it is a pure substance.
• Hydrochloric Acid: Hydrochloric Acid is gas form is pure substance
• Calcium Oxide: Calcium Oxide is a compound, hence it is a pure substance
• Mercury: Mercury is an element hence it is a pure substance
• Brick: Brick is a mixture of clay, sand, lime, etc, hence it is not a pure substance
• Wood: Wood is not a pure substance, rather a mixture of cellulose, lignin, water, rsin etc.
• Air: Air is a mixture of mainly \(O_2,~CO_2,~N_2,~etc.\) hence it is not pure

8. Identify the solutions among the following mixtures.

Solution:

• Soil: Not a solution (heterogeneous mixture of minerals, sand, clay, organic matter).
• Sea water: Solution (salt + water, though it also has suspended impurities, the main part is a true solution).
• Air: Solution (salt + water, though it also has suspended impurities, the main part is a true solution).
• Coal: Not a solution (complex heterogeneous mixture of carbon, hydrocarbons, minerals).
• Soda Water: Solution \((CO_2)\) dissolved in water under pressure, homogeneous.

9. Which of the following will show "Tyndall effect"?

• Salt Solution: Salt Solution is a true homogeneous solution, hence it will not scatter light
• Milk: Milk, although a colloid has constituents like fats, proteins, etc, that are too big to scatter light
• Copper Suphate Solution: Copper Sulphate is a homogeneous Solution hence it will not scatter light.
• Starch Solution: Particles of starch in solution are small and able to scatter Light, hence Starch Solution will exhibit the Tyndall effect.

10. Classify the following into elements, compounds and mixtures.

1. Sodium: Element (Na, Metal)
2. Soil: Mixture (Sand, Clay, Humus etc.)
3. Sugar Solution: Mixture (Sugar and Water- Homogeneous Solution)
4. Silver: Element (Ag, Metal)
5. Calcium carbonate: compound \((CaCO_3)\)
6. Tin: Element (Sn, Metal)
7. Silicon: Element (Si, Mettaloid)
8. Coal: Mixture (Carbon and Hydrocarbons)
9. Air: Mixture \((O_2, N_2, CO_2 ~etc.)\)
10. Soap: Mixture (Sodium Salt of Fatty Acids + Additives + Perfumes)
11. Methane: Compund \((CH_4)\)
12. Carbon Dioxide: compound \((CO_2)\)
13. Blood: Mixture (Plasma, cell, protiens)

11. Which of the following are chemical changes?

1. Growth of a plant: Chemical change (new substances form by photosynthesis, respiration, cell formation).
2. Rusting of iron: Chemical change (iron reacts with oxygen and moisture → hydrated iron oxide, irreversible).
3. Mixing of iron filings and sand: Physical change (no new substance, can be separated by physical methods).
4. Cooking of food: Chemical change (complex reactions form new substances, irreversible).
5. Digestion of food: Chemical change (enzymatic breakdown into new, simpler substances).
6. Freezing of water: Physical change (state change, no new substance formed, reversible).
7. Burning of a candle: Wax melting \(\Rightarrow\) Physical change but Wax burning \(\Rightarrow\) Chemical change (produces \(CO_2,~H_2O\), heat, light).