Science Answer the questions.[Che-5M]

1. By using a magnet: Moving a magnet over the mixture will result in iron fillings getting stuck to the magnet. Thus, iron will be separated from the mixture.
   
2. Sublimation: The remaining mixture is heated in a china dish. Ammonium chloride is a sublimating substance and hence it will evaporate without passing through the liquid phase. Crust of ammonium chloride can be collected by placing an inverted funnel on top of the china dish.
   
3. Sedimentation, decantation and filtration: The remaining mixture is dissolved in water and allowed to settle for some time. Sand, being insoluble in water, settles at the bottom. The liquid is decanted in another beaker. The liquid is then filtered to remove any traces of sand.
   
4. Evaporation: The liquid is now a solution of salt in water. This is heated in a beaker so that the water evaporates. Once all the water evaporates, salt remains in the beaker.
   

1. Sodium chloride from its solution in water → Evaporation.
2. Ammonium chloride from a mixture containing sodium chloride and ammonium chloride → Sublimation.
3. Small pieces of metal in the engine oil of a car → Centrifugation or filtration or decantation.
4. Different pigments from an extract of flower petals → Chromatography.
5. Butter from curd → Centrifugation.
6. Oil from water → Using separating funnel.
7. Tea leaves from tea → Filtration.
8. Iron pins from sand → Magnetic separation.
9. Wheat grains from husk → Winnowing.
10. Fine mud particles suspended in water → Centrifugation.

1. Group of materials P is element.
2. Q is a non-metal.

Examples: Carbon(s), and bromine (l)

3. R is a metal, as most of them are good conductors of heat and electricity.

Examples: Copper, and aluminum

4. S is a metalloid, as they have intermediate properties of those of metals and non-metals.

Examples: Arsenic, and antimony

5. R is a metal, therefore, it is malleable and ductile.

1. ​​Substance X does not have a fixed melting or boiling point. Moreover, it shows the properties of its constituents. So, it must be a mixture. Sugar solution in water is a substance like X.
2. Substance Y has a fixed melting or boiling point but it cannot be split into simpler substances by chemical processes. Hence, it must be an element. Hydrogen is a substance like Y.
3. Substance Z is also a pure substance whose properties are entirely different from those of its constituents. Hence, it must be a compound. Sugar is a substance like Z.
4. Formation of Z(a compound) involves absorption or release of an appreciable amount of energy.
5. The three groups are metals, non-metals and metalloids. All the substances like Y are divided into these groups on the basis of their properties.

1. Mass of potassium nitrate required to produce a saturated solution in 100g of water at 313K = 62g

Mass of potassium nitrate required to produce a saturated solution in 50g of water = ?

Required amount = 62 × 50100 = 31

Hence 31g of potassium nitrate is required.

2. When the solution cools down, Pragya observes salt crystals of potassium chloride precipitating.

3. Solubility of each salt at 293K is as follows:

• Potassium nitrate → 21g
• Sodium chloride → 36g
• Potassium chloride → 35g
• Ammonium chloride → 24g

It is observed that the potassium chloride salt has the highest amount of solubility when compared to any other salt at 293K.

4. Effect of change of temperature in the solubility of salts:

It is observed from the given table that the solubility of the salt increases with the increase in temperature. This means that when a salt reaches its saturation point at a particular temperature, more salt can be dissolved yet by increasing the temperature of the solution.

1. Pre-Treatment: Pumps bring "raw" or untreated water, often from lakes or rivers, into the purification plant through screens that exclude fish, weeds, branches and large pieces of debris. Screening may not be necessary for groundwater. The plant may aerate the water at this point to increase the oxygen content and thus help remove problematic odors and tastes.
2. Coagulation & Flocculation: The purpose of these two steps is to clear water of the small particles that cause it to be turbid or cloudy. Turbidity renders the water hard to disinfect. The water is rapidly agitated to disperse coagulant chemicals throughout it. The small particles, including many bacteria, begin to form large clumps called flocs or floccules. In flocculation, the water is mixed gently so that these clumps combine and precipitate out further.
3. Sedimentation: The water and flocs are pumped into sedimentation basins. Here, the flocs settle beneath the water so that they can be removed. About 85 to 90 percent of the suspended particles responsible for turbidity are removed at this point, including large amounts, but not all, of the bacteria.
4. Filtration: In filtration, the water flows through a multilayer medium such as quartz sand, activated carbon or anthracite coal in order to remove up to 99.5 percent of the solid materials remaining in it, whether flocs, microbes or minerals. This step usually is the last one in the process of removing solids from the water.
5. Disinfection: Disinfection kills off disease-bearing organisms in the water. Most water treatment plants use chemicals, generally chlorine compounds, as disinfectants. Although chlorine is still one of the most common disinfectants, ultraviolet radiation and ozone gas are becoming more widespread. Chlorine is increasing in cost and has some known toxic effects on humans and fish. In addition, some disease-carrying microbes like Giardia and Cryptosporidium resist chlorine.
6. Corrosion & Scale Control: The pH of the water is adjusted so that it neither corrodes nor deposits too much scale in pipes. Excessive amounts of scale can disrupt plumbing systems, but small quantities help pipes to function at their best. However, no amount of corrosion in the water distribution system is desirable. As well as causing leaks and other damage, corrosion releases pipe metals like lead and copper that jeopardize human health.
7. Taste & Odor Control: Unpleasant tastes and odors remaining in the water, such as those from algae, often do not pose any health hazards. Yet consumers prefer to do without them. So water purification plants often remove tastes and odors through additional chemical treatment, ozonation or filtration. At this stage, some municipalities also require the addition of fluoride to the water for dental health.

• Fill half of the beaker with water
• Place a watch glass on the mouth of beaker.
• Put a few drops of ink on the watch glass.
• Now, let start heating the beaker.

1. Sol: Sol is a colloid in which tiny solid particles are dispersed in a liquid medium.

Examples are ink and soap solution.

2. Aerosol: Aerosol is a colloid in which a solid or liquid is dispersed in a gas.

Examples are hairspray and fog.

3. Emulsion: An emulsion is a colloid in which minute droplets of one liquid are dispersed in another liquid which is not miscible with it.

Examples are milk and butter.

4. Foam: A foam is a colloid in which a gas is dispersed in a liquid medium.

Examples are soap bubbles and shaving cream.

• Cutting of trees → Physical change.
• Melting of butter in a pan → Physical change.
• Rusting of almirah → Chemical change.
• Boiling of water to form steam → Physical change.
• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change.
• Dissolving common salt in water → Physical change.
• Making a fruit salad with raw fruits → Physical change.
• Burning of paper and wood → Chemical change.

1. It should possesses metallic lustre and can be polished.
2. It should be good conductors of heat and electricity.
3. It should be ductile.
4. It should be malleable.
5. It should has high tensile strength.
6. It should has high densities and melting point/boiling point too.
7. It should be hard (except sodium and potassium which are soft metals).
8. It should be solid at room temperature (except mercury, which is liquid at room temperature).

1. Non-metals are neither malleable nor ductile and do not conduct electricity.
2. Metalloids show some properties of metals and some other properties of non-metals.

1. The milk sample was illuminated because milk is a colloidal solution and its particles are big enough to scatter the light, hence, they scatter the light passing through it. The phenomenon observed is called “Tyndall effect”.
2. As salt solution is a true solution i.e., solute particle size is too small to scatter the light, hence, it does not show “Tyndall effect”.
3. Examples of colloid are gold sol, arsenius sulphide (As₂S₃) sol., Blood etc.