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Showing posts with label Ncert. Show all posts
Showing posts with label Ncert. Show all posts

Thursday, 19 May 2016

May 19, 2016

The Letter Class 10

"The Letter" is a touching story of Ali who is all alone and waits for his only daughter's letter for five long years. He receives that letter only at his grave. 
Ali was a brilliant hunter who derived pleasure from the terror of the dying birds. But his daughter hated his merciless hunting desire. After his daughter's marriage, he was left alone. His daughter, Miriam left home with her husband, a soldier in a regiment in Punjab. Having understood the meaning of love and separation, he could no longer enjoy the screams of dying birds. Therefore, he stopped hunting. 

Since then, he had been regularly visiting post office in the early morning expecting a letter from his daughter Miriam. However, it did come and he returned home disappointed. The post office staffs often made fun of him. The clerk even called out his name; jokingly even there was no letter for him. Suddenly, for several days, Ali did not come to the post office. Everyone was curious to know the reason behind this. 

At last, he did come. But now it was difficult for him even to breathe and there were clear signs of his nearing death. Finally, he met the post master and asked him for Miriam's letter. The post master scolded Ali because he was very busy. Consequently, Ali called a clerk and gave him five golden guineas and asked him to deliver his letter, if it would come, to his grave. Then he slowly left him and was not seen by any one after that. 

One day, the post master's daughter fell ill and he was anxious to hear from her. He searched for the letter from his daughter from the pile of letters and picked up a letter of the name he expected. It was addressed to "Coachman Ali". Now he realized about his mistake. He called Lakshmi Das, a clerk and asked him to find out Ali. That day he did not receive his letter and decided that he would hand over Ali's letter by himself. 

In the post office, the next morning he opened the door and saw Ali leaning on a stick with tears in his eyes. His eyes had a light so unearthly that the post master was scared. But, suddenly he disappeared. Lakshmi Das, the clerk was shocked to hear the postmaster call out the name of Coachman Ali who had now been dead for three months. The letter was found near the door. Lakshmi Das tells him about his last meeting with Ali to convince him. 

That evening both of them went to place the letter on Ali's grave. The post master repented for his attitude and thought that he should have been more sympathetic and helpful towards Ali. He was no longer ill-tempered as he was in the beginning.
May 19, 2016

Mrs Packletide's Tiger Class 10

Mrs. Packletide's Tiger is a humorous story. The author makes fun of almost all the characters. Mrs. Packletide is an important character who wanted to outshine Loona, a boastful lady. Loona had a joy- ride in an Algerian aviator. Mrs. Packletide was jealous of Loona's adventurous trip. She planned to kill a tiger to do something more exciting and adventurous than Loona. 

Mrs. Packletide offered a thousand rupees to villagers for arranging an Opportunity to shot a tiger without much risk or exertion. An old tiger that had given up hunting and confined himself to eating domestic animal was chosen for this purpose. They posted children at the outskirt of the jungle to keep a watch on the tiger in case he wanders off to new hunting grounds. Goats were scattered to keep him satisfied and to prevent him from straying. Mothers with babies walked quietly through the jungle so as to not o disturb its sleep. 

Miss Mebin was a paid companion was acquired in order to witness the shooting of the tiger. Mrs. Packletide did manage to shot an animal although it was only the goat. The tiger merely died of a heart-failure caused by the sound of the gun shot. Miss Mebin intended to blackmail Mrs. Packletide with this piece of information. 

Louisa Mebin blackmailed Mrs. Packletide into buying her the weekend cottage or else she would tell Loona Bimberton that it was not he tiger but a mere goat that Mrs. Packletide had shot. Finally, she buys a weekend cottage for Louisa Mebin to prevent her from telling anybody that it was not he tiger but a goat she had shot because the tiger merely died of a heart attack. The story ends with a note by Mrs. Packletide, "The incidental expenses are so heavy,"

Thursday, 31 March 2016

March 31, 2016

Chemistry chapter1 class 10 cbse

1. Chemical reactions- Chemical changes or chemical reactions are the changes in which one or more new substances are formed.

2. Chemical Equations– Representation of a chemical reaction in terms of symbols and formulae of the reactants and products is known as chemical equation.

3. Balanced Chemical equation– The chemical equation in which the no. of atoms of different elements is same on both sides of the arrow is called balanced chemical equation.

4. The chemical reactions can be classified into different types such as

(a) Combination reactions- The reactions in which two or more substances combine to form a new substance are called combination reactions. For example,
2Mg(s) + O2 (g) → 2 MgO (s)

(b) Decomposition reactions– The reactions in which a single compound breaks up into two or more simpler substances are called decomposition reactions. 
For example,
2Pb (NO3)2 (s) → 2PbO(s) + 4NO2 (g) + O2 (g)

The decomposition of a substance on heating is known as thermal decomposition. The decomposition of a substance by passing electric current through it is known as electrolysis.

For example, when electric current is passed through acidified water, it decomposes into hydrogen and oxygen. Electric current
2H2O (l) → 2H2 (g) + O2 (g)


Certain compounds when exposed to light undergo decomposition
For example, Silver chloride when exposed to sunlight turns grey due to its decomposition into silver and chlorine. Sunlight 2AgCl(s) → 2Ag(s) + Cl2 (g)


The decomposition of a substance by absorbing light energy is called photolysis or photochemical decomposition.

(c) Displacement Reactions- The chemical reactions in which a more reactive element displaces a less reactive element from a compound are known as displacement reactions.
For Example,
(i) Zn(s) + CuSO4 (aq) → ZnSO4 (aq) + Cu(s)
(ii) Cu(s) + 2AgNO3 (aq) → Cu (NO3)2 (aq) +2Ag(s).
(d) Double Displacement Reactions- The chemical reactions in which compounds react to form two different compounds by mutual exchange of ions are called double displacement reactions. These reactions take place in solution. Two common types of double displacement reactions are precipitation reactions and neutralization reactions.

(i) Precipitation reaction : In precipitation reactions, aqueous solution of two salts are mixed whereby some salts precipitate due to mutual exchange of ions between the two salts. For example
AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3
(ii) Neutralization reaction: In this type of reaction an acid reacts with a base to form salt and water by exchange of ions. NaOH (aq) + HCl (aq) → NaCl (aq) + H2O


(e) Redox reaction : If a substance gains oxygen or looses hydrogen during a reaction it is oxidized. On the other hand if a substance loses oxygen or gains hydrogen during a reaction, it is reduced. Both oxidation and reduction take place simultaneously and hence these are called redox reaction. Oxidation

ZnO C→ Zn + CO
Reduction Oxidation
Cl2 + H2S → 2HCl + S
Reduction

(f) Exothermic reaction and endothermic reaction : On the basis of energy changes during chemical reaction, they can be classified as
(i) Exothermic reactionA chemical reaction in which heat energy is produced is called exothermic reaction .For e.g. (i) C (s) + O2 → CO2 (g) + Heat
(ii) Endothermic reactionA chemical reaction in which heat energy is absorbed is called endothermic reaction. CaCO3 + Heat → CaO + CO2

5. Effects of some oxidation reaction in everyday life:

(a) Corrosion – The process of slow conversion of metals into their undesirable compounds due to their reaction with moisture and other gases present in the atmosphere is called corrosion of metals. Some common examples of corrosion are rusting of iron, formation of green layer on the surface of copper, tarnishing of silver etc. Formation of brown layer on the surface of iron is called rusting of iron. Formula of rust is Fe2O3.xH2o. Rusting of iron is a serious problem.

 (b) Rancidity- The taste and odour of food materials containing fat and oil changes when they are left exposed to air for a long time. This is known as rancidity. Rancidity is caused due to oxidation of fat and oil present in food materials. Rancidity can be prevented by using various methods such as by adding antioxidants to the food materials, storing food in air tight container and by flushing out air with some inert gases like nitrogen.

Friday, 11 March 2016

March 11, 2016

GPA Weighted Scales , Learn GPA in a easy way

Most students think a lot about GPA in high school. There’s no doubt that GPA is one of the most important pieces of information colleges will consider in your application. However, it can vary drastically in the way it’s calculated at different schools. Some high schools use unweighted GPAs and some use weighted GPAs.
 

What is GPA? 

In simple , GPA stands for Grade point average. Bytheway if you still wanted to know about GPA checkout this YouTube Video. 

 
 

Weighted GPA
 
Weighted GPA is often employed by high schools to better represent students’ academic accomplishments. Weighted GPA takes into account course difficulty rather than providing the same letter grade to GPA conversion for every student. Usually, weighted GPA is measured on a scale of 0 to 5.0, Weighted GPA Scale And gpa weighted scale , although some scales go up higher. An A in an Honors or AP class may translate into a 5.0 weighted GPA, while an A in a low level class will give you a 4.0 weighted GPA. Many schools also have mid-level classes where the highest weighted GPA you can earn is a 4.5.

Calculate GPA Weight On GPA Weighted Scale



So with all this in mind, how do you calculate your weighted GPA? It’s pretty easy if you know your grades so far in high school and the levels of classes you’ve taken. The simplest way to translate grades into weighted GPA is to follow the gpa weighted scale for low level classes, add 0.5 to the unweighted scale for mid level classes, and add 1.0 to the unweighted scale for high level classes.

Here’s the gpa weighted scale for reference:
Grade GPA
A+ 4.0
A 4.0
A- 3.7
B+ 3.3
B 3.0
B- 2.7
C+ 2.3
C 2.0
C- 1.7
D+ 1.3
D 1.0
F 0.0


First Semester Freshman Year

Class Level Letter Grade Unweighted GPA Weighted GPA
1 Mid B+ 3.3 3.8
2 Mid B 3.0 3.5
3 Mid B 3.0 3.5
4 Low A 4.0 4.0
5 Low A- 3.7 3.7
The weighted GPA for this semester is the average of all the numbers in the last column. Your first semester freshman year weighted GPA would be a 3.7. For the second semester, let’s say you continued to take the same level classes but improved your grades.

Second Semester Freshman Year

Class Level Letter Grade Unweighted GPA Weighted GPA
1 Mid A 4.0 4.5
2 Mid B+ 3.3 3.8
3 Mid B+ 3.3 3.8
4 Low A 4.0 4.0
5 Low A 4.0 4.0

    • Weighted Scales GPA
    • GPA weighting scales
    • UNWEIGHTED AND WEIGHTED DIFFERENCE 
    • GPA difference between them 
    • gpa weight scale 
     
  • Now that you know about weighted GPA
Weighted GPA is a way for high schools to create a measure of academic achievement that takes into account the difficult of a student’s course load and not just his or her grades alone. On a weighted GPA scale, GPAs typically range from 0 to 5.0, with a 5.0 representing all As in the highest level classes. Weighted GPA is important to take into consideration because it gives you a way to gage your progress throughout high school based on both grades AND willingness to take on intellectual challenges.




Monday, 1 June 2015

June 01, 2015

He coloured deeply under his sunburn, then grew pale

He coloured deeply under his sunburn, then grew pale. 

Answer: The statement shows that the boys were shy. Nicola felt embarressed when the narrator enquired about their earnings and what they do with the money. 

He was not used to such questions. Therefore, he grew pale.

Saturday, 23 May 2015

May 23, 2015

Why air is a mixture not a compound? Give reasons

Why air is a mixture not a compound? Give reasons. 

Air is a mixture for of the following reasons: 

1. Air does not have a fixed composition. Its composition varies from place to place. 

2. The components of air can be separated by a physical method such as fractional distillation of liquid air. 

3. Liquid air does not have a definite boiling point. 

4. We can prepare air artificially by mixing the various components of air in the same proportions in which they occur at a place. This is a physical process because no energy changes occur.

                                                              

Friday, 22 May 2015

May 22, 2015

What are suspensions? Explain with an example.

NCERT What are suspensions? Explain
with an example.

Answer: 
A suspension is a heterogeneous mixture in which very fine particles (about 10-5 m size) of solid are dispersed in any medium (liquid or gas). 

In suspension, the solute particles are visible to the naked eye, and remain suspended throughout the bulk of the medium. 

The Tyndall effect is observed in this mixture. Muddy pond water, smoke coming out of a chimney, chalk-water mixture, coarse lime particles in water
are examples of suspension.
May 22, 2015

What are suspensions? Explain with an example

What are suspensions? Explain with an example. 

Answer: 
A suspension is a heterogeneous mixture in which very fine particles (about 10-5 m size) of solid are dispersed in any medium (liquid or gas). 

In suspension, the solute particles are visible to the naked eye, and remain suspended throughout the bulk of the medium. 

The Tyndall effect is observed in this mixture. Muddy pond water, smoke coming out of a chimney, chalk-water mixture, coarse lime particles in water are examples of suspension.
May 22, 2015

What are the properties of a colloid?

What are the properties of a colloid? 

Answer: Properties of a colloid are: 

1. Heterogeneous nature: Colloid or Sol is heterogeneous in nature i.e. it can be seen only with a powerful microscope. 

2. Particle Size: Colloid particle size lies between 1nm (10-9 m) to 100 nm (10-7 m) 

3. Separation of colloidal particles by filtration: Colloidal particles cannot be separated from the mixture by the process of filtration. But, a special
technique of separation known as centrifugation. 

4. Brownian Motion: When seen under microscope, the colloidal particles in a colloid are seen to be moving in a random fashion, called Brownian motion. 

5. Stability: They do not settle down when left undisturbed, that is, a colloid is quite stable. 

6. Tyndall effect: Colloid exhibit Tyndall  effect. When a light is passed through sol kept in dark room, the path of light beam is visible. It is due to scattering of light by colloidal particles and this effect is called
Tyndall effect. 

7. Electrophoresis: Man colloidal particles may have electrical charge (+ve or -ve) on them. When an electric current passes through a sol, colloid particles move towards opposite charged electrodes. This process is called electrophoresis.
May 22, 2015

Concentration Of Sodium Chloride And Water At 293 K

To make a saturated solution, 36 g
of sodium chloride is dissolved in 100 g of water at 293K. Find its concentration at this temperature. 

Answer:  
Concentration of a solution (mass %) 
=mass of solute × 100 / mass of solution.
mass of solute (NaCl) = 36g
mass of solvent (Water) = 100g
mass of solution = 
mass of solute + mass of solvent 

= 100 + 36 = 136g
mass by % concentration 

= 36 × 100 / 136 = 26.47%

Thursday, 21 May 2015

May 21, 2015

What principle is applied in centrifugation

What principle is applied in centrifugation? Give examples where this
method is applied to separate mixtures. 

Answer: Centrifugation works on the principle that that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. 

Examples are: 

1. Separating cream from milk (cream comes as top layer) 

2. Used in diagnostic laboratories for blood and urine
tests. 

3. Used in washing machines to squeeze out water from wet clothes. 

4. Used in preparing lactic cultures to prepare cheese (paneer) from milk in dairies.
May 21, 2015

How crystallization is better than evaporation?

Q51: How crystallization is better than
evaporation? 

Answer: The process of evaporation gives residue which may contain impurities. When there is requirement to obtain solid without impurity, crystallisation method is preferred. 

In general practice, impure solids are obtained by evaporation and are further purified by crystallisation. e.g. salt obtained from sea is further purified by this method. 

In some cases e.g. sugar crystal cannot be obtained by simple evaporation technique because sugar gets charred on heating to dryness. In such cases, crystallisation technique is applied.
May 21, 2015

A boy buys common salt from the market which is contaminated with Ammonium Chloride (NH4Cl) and sand

A boy buys common salt from the market which is contaminated with Ammonium Chloride (NH4Cl) and sand. 

The procedure he should adopt to obtain pure NaCl is the following : 

(a) to mix the sample in water and evaporate the solution

(b) to mix the sample in water and evaporate the decanted solution

(c) to mix the sample in acetone and evaporate the decanted solution 

(d) to heat the sample, then mix in water and evaporate the decanted solution 

Answer: (d) to heat the sample, then mix in water and evaporate the decanted solution Ammonium chloride sublimes, it can be separated from the mixture of salt and sand by sublimation method. 

Sand can be separated from the mixture of sand and salt by dissolving salt in water and then by filtration. Salt can be separated through the process of evaporation
May 21, 2015

Which separation techniques will you apply for the separation of the following

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

(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals. 
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.
(h) Iron pins from sand.
(i) Wheat grains from husk.
(j) Fine mud particles suspended in water. 


Answer: 

(a) Sodium chloride from its solution in water. (Evaporation)

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (Sublimation)

(c) Small pieces of metal in the engine oil of a car. (Filtration)

(d) Different pigments from an extract of flower petals. (Chromatography)

(e) Butter from curd. (Centrifugation)

(f) Oil from water. (Separating Funnel)

(g) Tea leaves from tea. (Filtration) 

(h) Iron pins from sand. (Magnetic Separation)

(i) Wheat grains from husk. (Winnowing)

(j) Fine mud particles suspended in water.
(Sedimentation →Loading →Filtration)