Write a note on Alloys.

ANS : An alloy is a homogeneous solid solution of two or more metals or a metal and a nonmetal. An alloy is generally prepared by heating the mixture of its constituents to molten state and then cooling it at room temperature. An alloy is prepared to obtain material with desired properties because the properties of constituents of an alloy are modified to some extent. Sometimes the melting point of an alloy is lower than that of the constituents. For example, solder is an alloy of lead and tin. Its melting point is lower than that of lead and tin and it is used in soldering of electrical wires.

Pure gold cannot be used to make jewellery as it is very soft. To make it hard, it is generally alloyed with copper or silver. The purity of gold is expressed in CARATS. Pure gold is 24 carats. 18 carat gold means it contains 18 parts of gold in 24 parts by weight of the alloy.

Distinguish between metals and nonmetals based on physical properties.

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Distinguish between metal and nonmetal based on chemical properties.

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Mention physical properties of nonmetals.
ANS :



Nonmetals occur in all three states : solid, liquid and gas.

They are neither malleable nor ductile.

They do not conduct heat and electricity because they do not have free electrons (graphite is an exception).

They are lustreless.

They are hard and brittle.

They generally have low melting points and boiling points.

They are light in weight.

Solid nonmetals do not produce ringing sound.





Describe the Importance of nonmetals.

ANS :



Hydrogen gas reacts with nitrogen to form ammonia gas.

Carbon is used in the preparation of useful substances like gunpowder, sugar, cold drinks, dry ice, urea, etc.

Oxygen supports life on earth.

Nitrogen is used in the preparation of nitric acid, nitroglycerin(explosives) and nitrogenous fertilisers.

Sulphur is used in the preparation of paper pulp, fungicides, etc.

Phosphorus is used in making matchsticks, insecticides, etc.

Define nutrition, mention its types and describe each type with examples.

ANS :



NUTRITION : The process of intake of nutrients and their utilisation in every living cell of the body is called nutrition.

TYPES OF NUTRITION : Based on the mode of obtaining food by the organisms, nutrition is classified into two main types-(i) Autotrophic nutrition (ii) Heterotrophic nutrition.

AUTOTROPHIC NUTRITION : Green plants and some bacteria prepare their own food from inorganic materials like carbon dioxide, water and minerals using pigment chlorophyll. These are called autotrophic organisms and their mode of nutrition is called autotrophic nutrition.

HETEROTROPHIC NUTRITION : Heterotrophic organisms are those which cannot synthesize their own food. These organisms obtain their food from plants and other animal sources. This type of nutrition is called heterotrophic nutrition. In this type of nutrition, the organic components of the food are digested into simple forms and then utilised by the organism. All animals, bacteria and examples of heterotrophic organisms.

Heterotrophic nutrition is classified into three types : (i) Saprophytic nutrition (ii) Parasitic nutrition (iii) Holozoic nutrition.

SAPROPHYTIC NUTRITION : Organisms obtaining nutrients from dead and decaying organic matter are called saprophytes and their mode of nutrition is called saprophytic nutrition. Many species of bacteria and different types of fungi are saprophytes.

PARASITIC NUTRITION : If an organism depends on another living organism for nutrition, its mode of nutrition is called parasitic nutrition. Such organisms are called parasites and the organism from which they obtain nutrition is called host. The host organism is harmed by the parasite. Parasitic nutrition is observed in some bacteria, fungi, flowering plants like cuscuta and animal like ascaris.

HOLOZOIC NUTRITION : Holozoic nutrition involves intake of parts of plants or animals or an organism as a whole by the process of ingestion which is then digested and absorbed. Some examples are amoeba, frog, insects, human being, etc.

Describe Photosynthesis in detail.

ANS : Plants synthesize their own food by the process of photosynthesis. Photosynthesis is the process in which plants synthesize food from carbon dioxide and water with the help of sunlight and chlorophyll.



Photosynthesis takes place in two phases : (1) Light Phase (2) Biosynthetic Phase.

LIGHT PHASE : This phase is called light phase because the presence of light is necessary for it to occur.

The chlorophyll molecule absorbs light energy in the form of photons, gets excited and emits electrons. These electrons travel through electron transport chain present in the chloroplast. During this ATP is synthesized from ADP and inorganic phosphate by photophosphorylation. This ATP is used as energy source in biosynthetic phase.

During the light phase photolysis of water takes place.



The H+ ions reduce NADP (Nicotinamide Adenine Dinucleotide Phosphate) into NADPH2.

The oxygen released during photosynthesis comes from water and not from carbon dioxide.

The whole process takes place in the grana of chloroplast.

BIOSYNTHETIC PHASE : In this phase the ATP and NADPH2 formed during the light phase are used for the synthesis of carbohydrates from carbon dioxide. This process takes place in the stroma of the chloroplast.

Calvin Cycle : It is called Calvin cycle as Calvin and Benson had discovered it.



In this process, the carbon dioxide reacts with Ribulose biphosphate (RuBP) and enters the biosynthetic phase. In the end of the cycle carbohydrate is synthesised and RuBP is regenerated.

The process of photosynthesis is affected by light, temperature, water and carbon dioxide.

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Explain the factors that affect Photosynthesis.

ANS : The factors that affect photosynthesis are : (1) light (2) temperature (3) water (4) carbon dioxide.

LIGHT : Intensity and quality of light affect photosynthesis. Chlorophyll absorbs mostly red and orange regions of visible spectrum. The rate of photosynthesis is more in red and orange light. Rate of photosynthesis increases at low intensity of light and decreases at high intensity.

TEMPERATURE : Photosynthesis takes place in the presence of enzymes. At low temperatures the activity of enzymes is low and the rate of photosynthesis is low. As the temperature increases, the enzymes get activated and the process of photosynthesis accelerates. But at very high temperatures the enzymes become denatured and the rate of photosynthesis decreases.



WATER : The rate of photosynthesis decreases under water-deficient conditions as the stomata remain closed to reduce transpiration. This stops gaseous exchange and hence the photosynthesis as carbon dioxide is not available.

CARBON DIOXIDE : The rate of photosynthesis increases with the increase in the concentration of carbon dioxide up to a certain level. Beyond that level it may have inhibitory effect on the rate of photosynthesis.

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Write an explanatory note on Human Digestive System.

ANS : Human digestive system consists of alimentary canal and accessory digestive glands. Alimentary canal consists of mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, colon, rectum and anus. Accessory digestive glands are salivary glands, liver and pancreas. They secrete digestive juices.



The alimentary canal begins with mouth which is located at the anterior end between two lips. The mouth opens into the buccal cavity which lies between the upper and lower jaws.

The muscular tongue at the floor of the buccal cavity helps in digestion of food.

The upper and lower jaws have four kinds of teeth. (1) Incisors for cutting (2) Cannines for tearing (3) Premolars and (4) Molars for chewing and grinding.

The posterior region of buccal cavity is called pharynx which opens into the oesophagus. The oesophagus opens into the stomach which is situated on the left side of the abdomen. The inner wall of the stomach secretes gastric juices. The stomach opens into the duodenum through pyloric valve which is guided by sphincter muscle.

The proximal region of small intestine is called duodenum. It is U-shaped and receives the secretion of liver and pancreas through a common bile duct. The middle region of small intestine is called jejunum and the distal region is called ileum.

Ileum is about 7 m long. The inner wall of the small intestine has long fingerlike projections called villi. These increase the surface area for absorption. The small intestine opens into the large intestine. There is a projection called vermiform appendix at the junction of two intestines.

The large intestine opens into the rectum which, in turn, opens out by anus. The anus is guarded by sphincter muscles.

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Describe Respiration In Human Being.

ANS :
HUMAN RESPIRATORY SYSTEM :



The human respiratory system is well-developed.

It consists of nostrils, nasal cavity, pharynx, larynx, trachea, bronchi and lungs.

Nostrils are the opening of nasal cavity.

The oxygen-rich air enters nasal cavity through the nostrils.

The deoxygenated air (containing CO2) is expelled out through nostrils.

The mucus in nasal cavity keeps it moist so that dust particles and microbes in the air are trapped there and do not enter lungs.

Nasal cavity also warms and moistens the air.

Air enters pharynx through nasal cavity and then into trachea (wind pipe) through a slit called glottis.

Glottis is protected by a cartilaginous flap called epiglottis.

As glottis is covered by epiglottis during the swallowing of food, the food does not enter the wind pipe.

Trachea is a wide tubular structure supported by C-shaped cartilaginous rigs.

Trachea divides into two bronchi which lead into the lungs.

There is a pair of lungs situated in thoracic cavity.

The lungs are covered by two membranes called pleura.

Brochi branch into many bronchioles in the lungs. Each bronchiole terminates in a sac called alveolar sac.

The walls of the alveoli are thin and covered by blood capillaries.



MECHANISM OF BREATHING :



Intake of air into lungs is called inhalation.

When the diaphragm and the muscles attached to the ribs contract, the volume in the thoracic cavity increases, the air pressure decreases and the oxygen-rich air from the atmosphere enters the lungs through nostrils.

Alveolar sacs are filled with oxygen-rich air and exchange of gases occurs.

When the diaphragm relaxes the volume of the thoracic cavity decreases, the pressure increases and the air containing carbon dioxide is expelled out of lungs through nostrils.

This is called exhalation.

The process of inhalation and exhalation is collectively called breathing.



EXCHANGE OF GASES IN TISSUES :


Respiratory gases are exchanged between the blood and the tissues.

Oxygen is utilised in the tissues and carbon dioxide is released.

The blood coming from lungs to the tissues has higher concentration of oxygen and lower concentration of carbon dioxide.

The difference in concentration induces exchange of gases between tissue and blood capillaries.



The end result of respiration process is that the oxidation of simple food molecules like glucose in mitochondria releases energy which is stored in ATP

Distinguish between autotrophic nutrition and heterotrophic nutrition.

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