Q&A Exam class 10 Science

1 and 2 mark questions:

Q1. If an object is placed in front of a concave mirror of 20 cm focal length, what is the position of the object when it will give a real and diminished image?

Q2. An object is placed in front of a concave mirror such that its image also formed at the same place at 10 cm in front of the mirror. What is the focal length of the mirror?

Q3. We wish to obtain an erect image of an object using a concave mirror of focal length 15 cm. 

a. What should be the range of distance of the object from the mirror?

b. What is the nature of the image?

Q4. An object is placed in front of a concave mirror such that its image also formed at the same place at 10 cm in front of the mirror. What is the focal length of the mirror?

Q5. At what distance from a concave mirror of focal length 20 cm, should an object 1.5 cm long be placed in order to get an erect image 4.5 cm tall?

Q6. Between which two points of concave mirror should an object be placed to obtain a magnification of m = - 2.

Q7. Why does a concave mirror cannot be used as a rear view mirror in vehicles?

Q8. Two spherical mirrors A and B produce images with linear magnifications + 1.5 and + 0.5 respectively. Identify which one of them is a a convex mirror and why?

Q9. State two effects caused by the refraction of light?

Q10. The refractive index of water with respect to air is 4/3. What is the refractive index of air with respect to water?

Q11. The refractive indices of kerosene, turpentine and water are 1.44, 1.47 and 1.33 respectively. In which of these materials does light travel fastest?

Q12. A virtual, erect and magnified image of an object is to be obtained with a convex lens. For this purpose, where should the object be placed?

Q13. If an object is placed at the centre of curvature in front of a concave lens, what kind of image it will produce?

Q14. A spherical lens has a power of, - 2.5 D. What is the focal length and nature of the lens?

Q15. Explain the spectrum of white light. 

Q16. While passing through a prism, which colour deviates least ?

Q17. Why do the stars always appear to be twinkling?

Q18. What is tyndall effect?

Q19. Why does the sky always appear to be blue?

Q20. Name any two effects of atmospheric refraction.

4 mark questions:

Q21. If the magnification of a mirror is +4,

a. What type of mirror is this?

b. If the focal length of the mirror is 5 cm, what is the the object distance?                 1 + 3

Q22. Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark (i) incident ray, (ii) emergent ray, and (iii) angle of deviation.                             2½ + 1½

Q23.  A virtual image at a distance of 20 cm in front of the lens is produced when an object is placed 100 cm from the lens. Calculate (i) focal length of the lens and (ii) magnification produced. (iii) Also calculate the power of the lens.                                                2 + 1 + 1

Q24. An object is placed at a distance of 6 cm from a convex lens of focal length 4 cm. If the the height of the object is 5 cm, find

(i) position, (ii) nature and (iii) height of the image.                                           2 + 1 + 1

Q25. An object is placed at a distance of 20 cm from a convex mirror of radius of curvature 60 cm. If the the height of the object is 3 cm, find (i) position, (ii) nature and (iii) height of the image.                                          2 + 1 + 1

Q26. A real image of 6 cm height is produced when an object of 2 cm height is placed at a distance of 16 cm from a concave mirror. 

(i) what is the focal length of the mirror?

(ii) find the position of the image?         2 + 2 

LECTURE 3 : TYPES OF CHEMICAL REACTIONS (CLASS X)

TYPES OF CHEMICAL REACTIONS

FOR 1 TO 1 ONLINE CLASSES OVER ZOOM PLATFORM AT REASOBLE PRICE

BOOK YOUR CLASS, CALL AT 7002561074

There are many types of Chemical reaction. Some of the most important types of Chemical Reaction are:

1. Combination Reaction

2. Decomposition Reaction

3. Displacement Reaction

4. Double Displacement Reaction

5. Oxidation and Reduction Reaction

A. COMBINATION REACTION

Those reactions in which two or more substances combine to form a single substance, are called combination reaction.

Examples: 

1. Burning of Magnesium in air.

2. Formation of water from hydrogen and oxygen.

3. Burning of carbon to form carbon dioxide.

4. Reaction between hydrogen and chlorine to form hydrochloric acid. 

5. Sodium metal burns in chlorine to form sodium chloride.

6. When iron powder is heated with sulphur, iron sulphide is formed. 

7. Calcium oxide reacts vigorously with water to form calcium hydroxide.  

8. Ammonia reacts with hydrogen chloride to form ammonium chloride. 

9. Carbon monoxide reacts with oxygen to form carbon dioxide. 

10. Sulphur dioxide reacts with oxygen to produce sulphur trioxide. 

B. DECOMPOSITION REACTIONS

Those reactions in which a compound splits up into two or more simpler substances are known as decompostion reactions. It always needs energy either in form of heat, light or electricity to carry out a decompostion reaction. 

When a decompostion reaction is carried out by heating, it is called "thermal decomposition". 

Examples. 

1. When calcium carbonate (CaCO₃) is heated, it decomposes to give calcium oxide (CaO) and carbon dioxide (CO₂). (Thermal decomposition)

2. When Potassium chlorate (KClO₃)

is heated in the presence of manganese dioxide catalyst, it decomposes to give potassium chloride (KCl) and oxygen (O₂).  (Thermal decomposition)

3. When ferrous sulphate (green) (FeSO₄) is heated strongly, it decomposes to form ferric oxide (brown) (Fe₂O₃), sulphur dioxide (SO₂) and sulphur trioxide (SO₃).  (Thermal decomposition)

4. When colourless lead nitrate Pb(NO₃)₂ is heated strongly, it breaks down to form simpler substances like yellow lead monoxide PbO, Nitrogen dioxide NO₂ and oxygen O₂.  (Thermal decomposition)

5. When electric current is passed through acidified water, it decomposes to give hydrogen gas and oxygen gas. (Decomposition using electricity)

6. When electric current is passed through molten sodium chloride, it decomposes to give sodium metal and chlorine gas.  (Decomposition using electricity)

7. When electric current is passed through molten aluminium oxide Al₂O₃, it decomposes to give aluminium metal and oxygen gas.  (Decomposition using electricity)

8. When Silver Chloride is exposed to light, it decomposes to form silver metal and chlorine gas. (Decomposition using light energy)

9. When silver bromide (pale yellow) (AgBr) is exposed to light, it decomposes into silver metal (greyish white) and Bromine gas. (Decomposition using light energy). 

Uses of Decomposition Reactions

The decomposition reactions using electricity are used to extract several metals like Aluminium, Sodium from their chlorides or oxides. 

Like when fused or molten metal chlorides or oxides is decomposed by passing electricity, metals are produced in the Cathode (negative electrode). 

Decomposition Reactions in our body

The digestion of food in our body is an example of decomposition reaction. Like complex carbohydrates (starch) decomposes into simple sugar and proteins into amino acids. 

DISPLACEMENT REACTIONS 

Those reactions in which one element takes place of another element in a compound, are known as displacement reactions. 

A more reactive elements always displaces a less reactive element from its compound. 

Metal Reactivity Series

(How to remember reactivity series)

1.  Please.      Potassium

2.  Stop.          Sodium

3.  Calling.      Calcium

4.  Me.             Magnesium

5.  A.                Aluminium

6.  Careless.   Carbon

7.  Zebra.         Zinc

8.  Instead.      Iron

9.  Try.              Tin

10. Learning.   Lead

11. How.          Hydrogen

12. Cow           Copper

13. Saves.       Silver

14. Goat.         Gold

1. As Zinc is more reactive than Copper, When a strip of Zinc metal is placed in Copper sulphate solution, then Zinc displaces Copper and Zinc Sulphate solution and Copper are obtained. 

CuSO₄ (aq) (blue solution) + Zn (s) (silvery white) → ZnSO₄ (aq) (colourless solution) + Cu (s) (red brown)

2. When a piece of Magnesium metal is placed in copper sulphate solution and Copper metal are formed. 

CuSO₄ (aq) (blue solution) + Mg (s) → MgSO₄ (aq) (colourless solution) + Cu (s) (red brown)

As Magnesium is more reactive than Copper.

3. When a piece of Iron metal is placed in Copper Sulphate solution, then Iron (II) Sulphate solution and Copper metal are formed. 

CuSO₄ (aq) (blue solution) + Fe (s) → FeSO₄ (aq) (greenish solution) +  Cu (s) (red brown)

As Iron is more reactive than Copper.

4. When a strip of lead metal is placed in a solution of copper chloride, then lead chloride solution and copper metal are formed. 

CuCl₂ (aq) (green solution) +  Pb (s) → PbCl₂ (aq) (Lead Chloride) (colourless solution) + Cu (s) (red brown)

As Lead (Pb) is more reactive than Copper (Cu)

5. When a copper strip is placed in a solution of silver nitrate, then copper nitrate solution and silver metal are formed. 

2AgNO₃ (aq) (colourless solution) + Cu (s) (red brown) → Cu(NO₃)₂ (aq) (blue solution) + 2Ag (s) (Greyish white)

As Copper (Cu) is more reactive than Silver (Ag)

6. Iron metal reacts with dilute hydrochloric acid to form iron(II) chloride and hydrogen gas. 

Fe (s) + 2HCl (aq) → FeCl₂ (aq) + H₂ (g)

As Iron is more reactive than Hydrogen.

7. Magnesium metal reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen gas. 

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)

As Magnesium is more reactive than Hydrogen.

8. Sodium metal reacts with water to form sodium hydroxide solution and hydrogen gas. 

2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂ (g)

As Sodium is more reactive than Hydrogen. 

9. Chlorine gas reacts with potassium iodide solution to form potassium chloride and iodine. 

Cl₂ (g) + 2KI (aq) → 2KCl (aq) + I₂ (s)

Chlorine displaces iodine from potassium iodide. 

10. When copper oxide is heated with magnesium powder, then magnesium oxide and copper are formed. 

CuO (s) + Mg (s) → MgO (s) + Cu (s)

Magnesium displaces Copper from from its oxide. 

12. When iron (III) oxide is heated with Aluminium powder, then aluminium oxide and iron metal is formed. The excessive heat produced during the reaction makes the iron to be melted. 

Fe₂O₃ (s) + 2Al (s) → Al₂O₃ (s) + 2Fe (l) (molten iron)

LECTURE 5: RESPIRATION-I

CLASS X | SCIENCE | CHAPTER 1

      notes prepared by subhankar Karmakar

FOR 1 TO 1 ONLINE CLASSES OVER ZOOM PLATFORM AT REASOBLE PRICE

BOOK YOUR CLASS, CALL AT 7002561074

The assimilated food is used as a fuel to get energy for various life processes and as a material for the growth and repair of the body. 

BREATHING

The mechanism by which organisms obtain oxygen from the air and release carbon dioxide is called breathing.  

RESPIRATION

The process of releasing energy from food is called respiration. The process of respiration involves taking in oxygen into the cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body. The process of respiration which releases energy takes place inside the cell of the body. Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive. Respiration is opposite process of photosynthesis. 

Difference between Breathing and Respiration

• Respiration includes breathing as well as the oxydation of the food in the cells of the organism to release energy. 

• Breathing is a physical process whereas respiration also includes biochemical process of oxidation of food.

• The process of breathing involves lungs of the organism whereas the process of respiration also involves the mitochondria in the cells where food is oxidized to release energy.

STORAGE OF ENERGY RELEASED DURING RESPIRATION

The energy produced during respiration is stored in the form of ATP molecules in the cells of the body. 

ADP is a substance called Adenosine Di-phosphate and ATP is a substance called Adenosine Tri-phosphate. Both the molecules are present inside a cell. ATP has a high energy content.

(i) the energy release during respiration is used to make ATP molecules from ADP and inorganic phosphate. 

ADP (low energy) + Phosphate + Energy (from respiration) → ATP (high energy content)

Thus, energy is stored in the cells in the form of ATP. 

(ii) When the cell needs energy then ATP can be broken down using water to release energy. 

ATP → ADP + Phosphate + Energy

The energy equivalent to 30.5 kJ/mole is released in this process. This released energy by ATP is used to carry out all the endothermic reactions taking place in the cells. 

The energy stored in ATP is used by the body cells for various purposes like contraction of muscles, conduction of nerve impulses, synthesis of proteins and other activities related to the functioning of cells. 

"ATP is known as the energy currency of cells."

TYPES OF RESPIRATION

The respiration which uses oxygen is known as aerobic respiration and the respiration which takes place with out using oxygen is known as anaerobic respiration.  

The key compounds that we takes part in respiration are:

1. Glucose C₆H₁₂O₆ 

2. Pyruvic Acid or Pyruvate CH₃(CO)COOH

3. Lactic Acid CH₃(CHOH)COOH

GLYCOLYSIS

The oxidation of glucose to pyruvic acid or pyruvate is called Glycolysis. It occurs in cytoplasm. It does not require oxygen to complete. One molecule of glucose produces two molecules of pyruvic acid. 

In presence of oxygen, pyruvate is completely oxidised and produces carbon dioxide, water and a lots of energy. But if oxygen is not present, Pyruvate is converted to either ethanol and carbon dioxide (in plant cell) or lactic acid (in animal cell). Energy release is less. 

LACTIC ACID 

Lactic acid is also called as Lactate. It is a hydroxy carboxylic acid. 

AEROBIC RESPIRATION

1. The respiration which uses oxygen is called aerobic respiration. 

2. Here, glucose is completely broken down into carbon dioxide and water by oxidation.

3. It produces lots of energy and stored it in the form of ATP molecules.

4. Glucose first undergoes glycolysis to produce pyruvate in cytoplasm then pyruvate is broken down into carbon dioxide and water in the presence of oxygen in mitochondria and produces lots of energy. 

5. Mitochondria are the sites for aerobic respiration. 

6. Most of the living organisms uses aerobic respiration and hence can not live without oxygen. 

ANAEROBIC RESPIRATION

Anaerobic Respiration in Plants:

1. The respiration which takes place without oxygen is known as anaerobic respiration. 

2. Yeast and some bacteria obtain energy through anaerobic respiration. 

3. Glucose is broken down to pyruvate by  glycolysis in cytoplasm. Then, Pyruvate produces ethanol (C₂H₅OH) , carbon dioxide by fermentation and energy is stored in ATP molecules. 

4. The whole process of anaerobic respiration takes place in cytoplasm. 

5. Although human beings obtain energy through aerobic respiration but in certain cases we use anaerobic respiration too. During vigorous physical exercise, oxygen is used up faster in  the muscle cell in that case when oxygen supply becomes less our cells use anaerobic respiration.

6. Glucose is first gets converted into pyruvate by glycolysis and next it is converted to lactic acid and small amount of energy. 

Anaerobic Respiration in Animals:

LACTIC ACID FORMATION AND MUSCLE CRAMPS

During heavy physical activities our body uses anaerobic respiration and glucose gets converted into lactic acid. The accumulation of lactic acid in our muscle cell causes muscle cramps. We can get relief from cramps in muscles caused by heavy exercises and production of lactic acid by taking a hot water bath or massage. 

DIFFERENCES BETWEEN AEROBIC AND ANAEROBIC RESPIRATION

AEROBIC RESPIRATION	ANAEROBIC RESPIRATION
1.       Aerobic respiration takes place in the presence of Oxygen.	Anaerobic respiration takes place In the absence of Oxygen.
2.       Complete breakdown of the food occurs in aerobic respiration.	Partial breakdown of foods occurs in anaerobic respiration
3.       The end products in aerobic respiration are carbon dioxide and water.	The end products in anaerobic respiration may be ethanol and carbon dioxide (in yeasts) or lactic acid (in animals).
4.       Aerobic respiration produces a considerable amount of energy.	Much less energy is produced in anaerobic respiration.

LECTURE 4: NUTRITION IN HUMAN BEINGS (CLASS X)

CLASS X   |    SCIENCE    |    LIFE PROCESSES

      Notes prepared by Subhankar Karmakar

---

click to access other class notes

SCIENCE: CLASS X: CBSE (CLASS NOTES)

FOR 1 TO 1 ONLINE CLASSES OVER ZOOM PLATFORM AT REASOBLE PRICE

BOOK YOUR CLASS, CALL AT 7002561074

---

• HUMAN DIGESTIVE SYSTEM

The various organs of the human digestive system in sequence are:

Mouth, Oesophagus, Stomach, Small Intestine and Large Intestine. The glands which are associated with the human digestive system and form a part of the human digestive system are : Salivary glands, Liver and Pancreas. 

• Alimentary Canal:

Human alimentary canal which runs from mouth to anus is about 9 metres long tube. The ducts of various glands open into the alimentary canal. 

• 1. INGESTION

The organ for human ingestion is called mouth.

• 2. DIGESTION 

In human beings, digestion of food begins in the mouth itself. 

• A. Buccal Cavity:

The mouth cavity is also known as buccal cavity. It contains teeth, tongue and  salivary glands. The teeth cut the food, chew and grind it. Tongue mixed the small pieces of food mixed with saliva. Saliva contains an enzyme called Salivary Amylase, which converts Starch into sugar. Hence, Salivary glands helps chemical digestion by secreting enzymes. But due to short period of time the digestion remains incompleted. 

• B. Oesophagus

The food pipe is known as oesophagus. It carries food to the stomach. 

• Peristaltic movement
• The walls of the food pipe/oesophagus have muscles which can contract and expand alternatively. When slightly digested food enters the food pipe, the walls of the food pipe start contraction and expansion movements. This contraction and expansion movements of the food pipe walls are known as  peristaltic movement. 
• Peristaltic movement moves the food in all digestive organs throughout the alimentary canal. 

• C. Stomach
• Stomach is a J shaped organ present in the left side of the abdomen. Here food is broken down into a semi-solid paste. 

• Gastric Juice

Stomach wall contains three tubular glands which secrete gastric juice. The gastric juice contains hydrochloric acid, the pepsin enzyme and mucus. The gastric juice is acidic in nature. 

• Function of Pepsin enzyme

In the acidic medium pepsin breaks down the proteins into smaller molecules, often into amino acids. Therefore, the digestion of proteins start at stomach. 

• Function of Hydrochloric acid

Pepsin is only activated in an acidic medium. The function of the Hydrochloric acid in stomach is to make the gastric juice acidic, so that pepsin can start digesting proteins molecules. Another function of the hydrochloric acid is to kill any bacteria that may enter into the stomach through the food. 

• Function of mucus

The mucus helps to protect the stomach walls from its own secretion of hydrochloric acids. If mucus is not secreted, hydrochloric acid will cause the erosion of the inner lining of stomach leading to the formation of ulcers in the stomach. 

• Sphincter Muscle

The partially digested food from stomach passes to the small intestine. The exit of food from stomach is regulated by a gate called sphincter muscle which releases it in small amounts into the small intestine. 

• D. Small Intestine

The small intestine is the largest part of the alimentary canal of about 6.5 m long in an adult man. It is very narrow hence, it is called small intestine. It is arranged in a coil form. The small intestine in human beings is the site of complete digestion of food like carbohydrates, proteins and fats. 

Difference in small intestine in Herbivores and Carnivores

Herbivores eat cellulose which is difficult to digest. Hence, herbivores have longer small intestine, whereas carnivores eat meat which is easier to digest so they have relatively shorter small intestine. 

Secretions from two glands in small intestine: Liver and Pancreas

• Liver : Liver is a gland that secretes bile. Bile is a greenish yellow liquid made in the liver and stored in the gall bladder. Bile is alkaline in nature and conatains salts which helps to break the fats/ lipids present in the food. 

Functions of Bile

Bile performs two functions. 

• (i) it makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act on it.
• (ii) Bile salts break the fats present in the food into small globules so that enzymes can act and digest it. 

• Pancreas

Pancreas is a large gland which lies parallel to and beneath the stomach. Pancreas secretes pancreatic juice which contains digestive enzymes like pancreatic amylase, trypsin and lipase. 

Pancreatic amylase breaks down the starch.

Trypsin digests the proteins and lipase breaks down the emulsified fats. 

Functions of intestinal juice

• The intestinal juice contains many enzymes which converts complex carbohydrates into glucose, proteins into simple amino acids and fats into fatty acids and glycerol all of which are water soluble small molecules. 
• The chemical digestion of food is brought about by biological catalysts called enzymes. 

• 3. ABSORPTION

• The small intestine is the main region for the absorption of digested food. After digestion, the molecules become so small that they can pass through the walls of the small intestine which contain blood capillaries and go to our blood. 
• The inner surface of small intestine has millions of tiny finger like projections called villi.  The presence of villi gives the inner walls of small intestine a very large surface area which helps in the rapid absorption of digested food. 

• 4. ASSIMILATION

• The blood carries the digested food to all the parts of the body where it becomes assimilated as part of the cells and it is used by the body cells for obtaining energy as well as for growth and repair of the body. 
• The unused part of the food is stored in the liver in the form of a carbohydrate known as glycogen. The stored glycogen can be used when it is needed. 

• 5. EGESTION

• A part our food which can not be digested passes from small intestine to a wider tube which is called large intestine. It is called large as it is wider. 
• The walls of the large intestine also have villi which absorb most of the water from the undigested part of the food and hence, it becomes solid. 
• The last part of the large intestine is called rectum which stores the undigested food for some time and then be expelled from our body as stool. This process is known as Egestion or defecation and it is controlled by anal sphincter. 

Dental Caries

1. The hard, outer covering of a tooth is called Enamel. It is harder than bones. 

2. The part of tooth below enamel is called Dentine. Dentine is similar to bone. 

3. Inside the dentine, there is pulp cavity, which contains nerves and blood vessels. 

4. Formation of small cavities in the teeth due to the action of acid forming bacteria and improper dental care is called dental caries. 

5. If the teeth are not cleaned regularly, they become covered with a sticky, yellowish layer of foid particles and bacteria cells called dental plaque. 

Extra Notes:

The long, tube-like organ that is connected to the small intestine at one end and the anus at the other is called large intestine. The large intestine has four parts: cecum, colon, rectum, and anal canal. Partly digested food moves through the cecum into the colon, where water and some nutrients and electrolytes are removed. The remaining material, solid waste called stool, moves through the colon, is stored in the rectum, and leaves the body through the anal canal and anus.