NOTES/SOLVED EXERCISES: GENERAL SCIENCE-7 PTB PUNJABTEXT BOOK BOARD LAHORE PAKISTAN 2015
CONTENTS
TITLE——————————————————————- PAGE
Working of a Plan———————————————————– 5
Working of Human Body————————————————- 27
Environment —————————————————————- 56
Continuity of Life ———————————————————–65
Atom and ifs Structure—————————————————- 74
Elements ———————————————————————-85
Some Common Gases —————————————————–96
Water-A Common Compound —————————————–106
Pressure and Simple Machines —————————————-119
Heat ————————————————————————–134
Light ————————————————————————–145
Sound ————————————————————————156
Electricity ——————————————————————- 163
Magnetic Field————————————————————- 175
Ocean ———————————————————————— 187
Solar System —————————————————————-195
CHAPTER:1 WORKING OF A PLANT P:5-26
FILL IN THE BLANKS.
(i) Water moves to the upper parts of the plants through the xylem by a pull, this pull is due to the process of TRANSPIRATION.
(ii) The process by which water enters from the soil into the roots of the plant is called OSMOSIS.
(iii) When iodine solution is applied to starch, it turns BLUE.
(iv) The network of thread like structure in rhizopus is called HYPHAE.
(v) Ginger is an example of underground STEM.
ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING.
(i) The movement of water molecules through a selectively permeable, membrane from an area of higher concentration to an area of lower concentration is called:
(a) Condition (b) Diffusion (c) Evaporation (d) Osmosis
(ii) Fruit is formed from:
(a) Ovary (b) Ovule (c) Stem (d) Leaves
(iii) Endosperm is present in:
(a) Anther (b) Xylem (c) stigma (d)Seed
(iv) Which is nota part of the embryo?
(a) Cotyledon (b) Radicle (c) Pedicel (d) Plumule
(v) Which statement is not true for insectivorous plants?
(a) Chlorophyll is not present (b) Unable to make glucose (c) Capture insects through roots (d) Utilize their nitrogenous needs from insects
(iv) Which part of the plant is called the food factory.
(a) Fruit (b) Leaves (c) Root (d) Stem
Ans: (i-d)(ii-a)(iii-d)(iv-) (v-d) (vi-b)
GIVE SHORT ANSWERS.
(i) Differentiate between self and cross pollination.
Ans. SELF POLLINATION: lf the pollens from anther fall on the stigma of the same flower or another flower of the same plant, this is called Self pollination CROSS POLLINATION lf the pollen grains from the flower of one plant fall on the stigma of flower of another plant, this is called cross pollination.
(ii) Why is a butterfly attracted towards a flower?
Ans. A butterfly is attracted ‘to wards a flower to get food from nectarines. It is attracted due to beautiful colourful petals and due to scent.
(iii) Explain the possible directions for the transport of food in a plant.
Ans. The direction of food is down wards up wards and laterally.
(iv) Stomata mostly occur in the epidermis of the leaf how do you think is this helpful for the plant?
Ans. Yes, it is helpful for the plant because Carbon di oxide can enter and oxygen and water vapours leave through these stomata.
(v) What is the role of chlorophyll in photosynthesis?
Ans: Chlorophyll absorbs sunlight for the preparation of food to plants.
(vi) What is the difference between autotrophs and heterotrophs?
Ans. AUTOTROPHS:- Most plants are autotrophs. They manufacture their own maternal with the help of chlorophyll.
HETEROTROPHS:- They have no chlorophyll and thus cannot make their own food.
(vii)What is the difference between parasites and saprotroph?
Ans. PARASITES: They get their food from other living things. Bacteria, Cuscuta etc. SAPROPHYTES: They get their food from decaying dead material, decaying dead parts of plants and animals and their wastes. Bacteria, fungi, Monotropa and Neutea are the examples of saprophytes.
4-EXPLAIN THE FOLLOWING.
(i)Explain the role of a flower in cross-pollination.
Ans:
CROSS POLLINATION:-
lf the pollen grains from the flower of one plant fall on the stigma of flower of another plant, this is called cross pollination.
Corolla:
pic
This is the most prominent part of the flower consisting of a whorl of coloured and fragrant petals. The butterflies and other insects are attracted to the flower due to corolla.
When these insects visit at flower, pollen grains from the male part of the flower become attached with their body, and when they visit another flower, those pollen grains fall on the female part (Carpel) of flower.
In this way, an important step of sexual reproduction is accomplished which is called pollination.
ANDROECIUM:- The Male part of Flower:
Inner to the petals, a whorl of club-like structures is present which is called androecium. Each club like structure
is called a stamen. The upper sac like part of a stamen is known as anther. With in the arither pollens are formed.
GYNAECIUM – The Female Part of Flower:-
This is the central part of flower. It consists of carpel.
Each carpel is flask shaped and has three parts.
(i) The upper stigma
(ii) A tubular portion called style and
(iii) The lowermost swollen part, the ovary.
The stigma receives the pollens coming from the anther.
Ovary is the most important part of flower. The seed is formed in the ovary, and ultimately the ovary ‘changes into fruit. In fact, the basic function of the flower is seed formation.
(ii)Where and how are fruit and seeds formed?
Ans: Formation of fruit and seeds
Fruit and seeds are formed after fertilization. The ovule forms the seed and the ovary ripens into a fruit.
Explain the structure of a gram seed?
Ans: STRUCTURE OF SEED:
Seeds depending on their size, colour, and form are of various kinds. However, they are not much different in their internal structure. A seed has following parts.
Pic
STRUCTURE OF SEED
(i)Testa:
This is the outer hard covering ofthe seed which protects the internal structures.
(ii)Tegmen:
This is membrane present beneath the testa for protection of embryo.
(iii)Endosperm:
In some seed, endosperm stores food which is used ln germination of seed.
(iv) Embryo:
This is the most important part of seed. This is a tiny plant
whose parts grow to form a new plant. The embryo has t following parts.
(e) Plumule:
This is the part of the embryo which forms the shoot that iris stem and leaves.
(b)Radicle:
This part of the embryo develops into the root of plant.
(c)CotyIedons:-
They may be one or two in number. These receive the food from the endosperm and supply it to the growing tiny plant.
How is the structure of a leaf adapted to photosynthesis?
Ans. STRUCTURE OF LEAF IS WELL SUITED TO PHOTOSYNTHESIS
Most leaves are flat, lo effectively absorb enough light.
2 They are thin, so carbon dioxide and light can reach inner cells easily.
They have large number of stomata in the lower surface (lower epidermis). Carbon dioxide can enter and oxygen and water vapours leave through these stomata.
4 They have thick layer of mesophyll cells-in the middle. These cells have chloroplasts which contain chlorophyll. Mesophyll cells make food for the plant by photosynthesis.
They have a rich network of veins. These carry water to photosynthesizing cells, and glucose away from them. Therefore it is rightly said that leaf is a food factory.
Prove with the help of an experiment that chlorophyll is necessary for photosynthesis.
Ans: EXPERIMENT:
Take a variegated leaf (partly green and partly white leaf), such as that of garden nasturtium, money plant or Bougainvillea, from a plant exposed to light, Make a drawing of its showing the distribution of chlorophyll. (green part and white part)
->Half fill one 250 ml beaker with water.
– Place the variegated leaf in the beaker and boil it for about 5 minutes.
->Take one 100 ml beaker and half fill it with 70% alcohol.
Pic
– >With a forceps or tongs remove the boiled leaf from the water and transfer it to alcohol in the smaller (100-ml) beaker Place the 100-ml beaker (containing the alcohol and the leaf) in a boiling water bath (or a larger beaker containing water in it). Boil the alcohol until the leaf loses its chlorophyll and alcohol turns green (chlorophyll is soluble in alcohol but not in water.)
->Using forceps or tongs transfer decolorized leaf first to a beaker containing boiling water to make it soft and then to a Petri dish. Put drops of iodine solution on the leaf until iodine has come into contact with the entire leaf.
OBSERVATION
Green part of the leaf turns blue, indicating the presence of starch.
RESULT
Appearance of blue colour with iodine solution indicates the presence of starch.
The white part becomes brown indicating the absence of starch because photosynthesis did not take place in this part due to absence of chlorophyll.
What is the importance of photosynthesis for living organisms?
ANS. IMPORTANCE OF PHOTOSYNTHESIS:-
Plants convert excess sugar (glucose) into starch, proteins and fats and ,store it in their stems, roots, seeds,
fruits and leaves. These parts of plants may be eaten by animals which in turn may be eaten by other animals.
Photosynthesis, therefore, is the process which provides food and energy to all life forms on earth.
Ch:2 WORKING OF HUMAN BODY P:27-55
1- FILL IN THE BLANKS.
i- The saliva helps in digestion of carbohydrates.
ii- The Hydrochloric acid HCI present in the stomach kills the harmful bacteria.
iii- The excretory organs of human body are skins, lungs and kidneys.
iv- The central nervous system of man consists of brain and spinal cord.
v- Our tongue can detect four tastes namely sweet, Salty bitter and sour.
vi- The skin is a sense organ which detects heat, cold, pain and pressure.
(vii) The sensory cells of Retina are stimulated by the light and send nerve message from eye to the brain.
PUT(√) MARK AGAINST CORRECT STATEMENT AND FOR INCORRECT STATEMENT.
(i) Bile is secreted in pancreas (X)
(ii) The omnivores feed on vegetables, fruits, seeds and meat (√)
(iii) The oxygenated blood from lungs reaches to heart by pulmonary veins. (√)
(iv) There are two kidneys present in chest of human body( X)
(v) Aorta receives blood from the whole body (X)
(vi) Nerve is the basic unit of structure and function of nervous system (X)
(vii) The most sensitive layer of the eye ball is called retina.(√)
(viii)The outer layer of skin is the sensitive part of the skin. (X)
ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING.
(i) Carbohydrates are digested in
(a) Mouth and small intestine (b)Mouth and stomach (c) Mouth and large intestine (d) Stomach and small intestine
(ii)The function of large intestine is to
(a) Digest fats and proteins (b) Digest carbohydrates and salts (c) Absorb water and salts (d) Absorb carbohydrates and salts
(iii)Which part of the brain controls the heart beat and breathing?
(a) Cerebrum (b) Cerebellum (c) Medulla (d) Midbrain
(iv)Taste buds for bitter taste are present
(a) On the tip of the tongue (b) On the sides of the tongue (c) At the back of the tongue I (d) On the whole tongue
(v)Circulation of blood in heart is due to
(a) Dilation of atrium (b) Contraction of atrium (c) Dilation of ventricle (d) Contraction of ventricle
Ans: (i-a)(ii-c)(iii-c)(iv-c)(v-b)(vi-b)
4-GIVE SHORT ANSWERS
(i)Why digestion of food is necessary?
Ans: Animals use food for their growth and nourishment. They get energy by the oxidation of food. If food remain undigested then animals may not use it for growth and energy. Therefore, it is necessary to digest food in the body.
(ii)In which part of alimentary canal food digests completely?
Ans: In small intestine food digests completely.
(iii)Describe importance of body skeleton.
Ans. SKELETON
Our body has a specific bony frame work which is called skeleton. A human skeleton consists of 206 bones. These are of different shapes and sizes. Some bones are long, small and flat while some others are irregular in shape.
Our skin and muscles cover this skeleton. Skull is joined; with the anterior of the vertebral column.
VERTEBRAL COLUMN:
Vertebral column provides support to the ribs. Ribs are joined with vertebral column at the back and with breast bone; at the front. Vertebral column provides support to the skull at its upper end.
ARMS BONES:
The bones of arms are joined with the help of shoulder bone to the vertebral column below the neck region.
(iv)Write down names of important parts of respiratory system.
Ans: Human respiratory system consists of Nose, Pharynx, Larynx, Trachea, Bronchi and Lungs.
(v)What is the role of reproductive system of human body?
Ans: By means of reproductive system organisms produce new off springs. Reproductive system is meant for the continuity of race. It ensures the survival of species.
The transmission of characteristics through generation after generation takes place through this system.
(vi)Name any sense organ, which contains receptors of chemical stimuli.
Ans: Nose
(vii)What pert of the ear helps the balance?
Ans: Inner our
(viii)Describe the two defects of vision.
Ans. DEFECTS OF THE EYE:
The common defects of the eye are short sightedness, long sightedness and cataract, They are mainly caused by excessive eye strain and old age.
(i) SHORT SIGHTEDNESS:
It is also known as Myopia. In this defect short sighted person can see near objects, distant object look blur.
This defect can be corrected by using suitable concave spectacle lens.
(ii) LONG SIGHTEDNESS:
In this a person can see distant objects clearly, but near objects look blur.
This condition can be remedial by the use of a suitable convex spectacle lens/contact lens.
(iii) CATARACT:
It is the disease of old age. It-is due to the opaqueness of lens.
It is corrected by removing the. Lens by simple surgery and then replaced by an artificial lens.
(iv) COLOR BLINDNESS:
Color blindness is defect of eye in which person is unable to distinguish between red and green colour. This defect is generally inherited from parents. It is because of some defect in the retina.
5-EXPLAIN THE FOLLOWING.
(i)Nerve and Neuron
Ans: Nerve is a white, tough and string like structure while nervous is the basic unit of nervous system.
(ii)Sensory nerve and motor nerve
Ans:
(i)Sensory Nerves:-
Ans: Sensory nerves carry messages from sense organs i.e. eyes, ear, nose etc to central nervous system.
(ii) Motor Nerves:
Ans: Motor nerves carry messages from central nervous system to muscles and glands. The unit of structure and function of nerve is called neuron.
(iii)Cerebrum and Cerebellum
Ans. Cerebrum
It is the largest pan of the brain. Cerebrum controls sight, speech, hearing, movement of body parts and other functions.
Cerebellum:-
The cerebellum lies under the back part of cerebrum Cerebellum controls our sense of balance and allows us to make precise and accurate movements.
6.Write down the effects of noise pollution.
NOISE:
Chaotic and irregular sound is called noise. It is unwanted or unpleasant sound that is often veil loud.
NOISE POLLUTIONS:-
When noise becomes unbearable then it is called hoist pollution.
EFFECTS OF NOISE POLLUTION:
i) It is very difficult for people to relax and think properly in noise.
ii) Noise makes them often irritable or bad tempered.
iii) Constant noise can also cause fatigue and headache.
iv) Noise can cause high blood pressure and may disturb our digestive system.
v) Excessive noise can make people work less safely, suffer from stress, lose their hearing and eventually become deaf permanently.
vii) Listening to personal stereos, which are too loud and fort too long can also cause hearing loss.
viii) Excessive noise is a serious aspect of pollution. For this reason it is important that the amount of noise in the environment should be controlled.
vi) Loud noise of a short duration also damages hearing.
7. Describe briefly structure of eye with diagram and label its different parts.
Ans:
EYE-SENSE OF SIGHT
The eye is the organ of sight. It is consisted of following parts.
Pic
STRUCTURE OF HUMAN EYE
STRUCTURE OF HUMAN EYE
(i) EYEBALL:
The human eye consists of an eyeball which is a hollow spherical body placed in a bony cavity of the skull. The wall of the eyeball consists of three layers.
(a) CORNEA:
The front of the eyeball is transparent called the cornea.
(b) IRIS:
Beneath the cornea the free edge of the middle layer forms iris, which is coloured part of the eye.
(c) PUPIL:
In the center of the iris is an opening called Pupil.
(d) LENS:
Just behind the pupil is the lens, which helps to focus light.
(e) RETINA:
The inner layer of the eyeball is called ‘the retina. It receives images of objects focused by the lens which we see,
(f) OPTIC NERVE:
The eye is connected to the brain by the optic nerve.
8. How and where absorption of food takes places?
Ans: Absorption of food in small intestine:
In small intestine carbohydrates, Proteins and fats are completely digested. This is followed by the absorption of digested food into the blood vessels present on the inner surface of the wall of intestine from where it is distributed throughout the body via livers.
Absorption of food in large intestine:
Most of the water and salts are reabsorbed into the blood vessels present in the wall of large intestine.
9. Draw a diagram of alimentary canal and label its various parts?
Ans: pic
10. How parasites and symbionts get their food?
Ans. Parasites:-
These are the animals, which get food from other living animals. They absorb digested food from their host. For example, leech, mosquito, lice, etc.
Symbionts:-
Animals, which live together in a mutually beneficial relationship, are called symbionts. They provide food and protection to each other. They are so dependent on each other that they cannot exist independently.
For example termite eats wood as food but single celled tiny animal lives in its intestine and digests the food.
11. Describe structure of heart and circulation of blood with the help of diagram?
Ans:
In human beings Blood circulatory system is the most important one. In this system blood circulates in the body. It consists of heart, arteries, veins and capillaries.
When heart pumps, then blood reaches to the body through arteries. From here it goes in capillaries and comes back to the heart through veins.
EXTERNAL & INTERNAL STRUCTURE OF HEART & BLOOD FLOW
The heart is an organ which is enclosed in a very thick membrane. Its size is nearly equal to our clenched fist. It lies under the 2nd and 7th rib, somewhat to the left from the centre of the chest. If we study the internal structure of heart, it has four chambers.
ATRIA:-
Two upper chambers of heart are small and thin walled called Atria (Sing. Atrium)
VENTRICLES:
The two lower chambers are relatively large and thick walled called ventricles.
Pic
VALVES:
Valves are present between the atria and ventricles.
These valves ensure that blood flows easily from atria into the ventricles and not in the opposite direction.
CIRCULATION OF BLOOD IN THE BODY
Heart acts as double pump. It can be divided into two parts, i.e. right side and left side.
Left side consists of left auricle and left ventricle and right side has right auricle and right ventricle. In the right auricle,
blood from the whole body comes back through two large veins, venacava. It has less amount of oxygen.
12. Describe structure of blood and its Important functions.
Ans:
Blood consists of two portions
(i) Blood plasma (ii) Blood cells
(I) BLOOD PLASMA
Blood is a red fluid in which red cells, white blood cells
and platelets are present in ‘yellowish white liquid called
plasma. Blood plasma’ consists of water, digested food
carbon dioxide, hormones and waste substances.
RED BLOOD CELLS
Red blood cells contain haemoglobin which transport
oxygen, Red blood cells do not have nucleus.
WHITE BLOOD CELLS
Function qi white blood cells is to defend the body. They engulf the which enter in the body and destroy them,
White blood cells have nucleus of different shapes.
PLATELETS
The function of platelets is ,to clot the blood in case of injury.
13. Draw a diagram of excretory system and label its pans.
Ans.
EXCRETION
The process through which excessive and waste materials from animals are removed is called excretion.
HUMAN EXCRETORY SYSTEM
In human body lungs, kidneys and skin are the organs which help in excretion, So these are called excretory organs.
LUNGS:
Lungs help in the excretion of carbon dioxide from blood.
KIDNEYS:
Kidneys help in excretion. Kidneys excrete excess water,
Salts and nitrogen waste materials (urea) in the form of urine from the blood.
There are two kidneys in our abdominal cavity. One is located on each side of the backbone. Right kidney is little bit below the left. Each kidney is bean shaped.
URETER:
A tube called Ureter arises from each kidney. Both ureters is open in the urinary bladder. Urine is carried from the kidneys
into urinary bladder by ureters.
When bladder is full, we have a feeling to excrete urine from bladder. Urine is excreted or passed out through the urethra.
Pic
(a) Excretory System (b) Internal structure of kidney
SKIN:
The skin forms a continuous protective covering over the surface of our body besides this, it acts as an excretory organ.
It removes salts and water in the form of perspiration (sweat) and plays an important role in regulating the body temperature.
CH:3 ENVIRONMENT P:
1-FILL AN THE BLANKS
Answers:
(i)Light water soul and temperature are abiotic factors of environment
(ii)Populations living together at the same place constitute a community.
(iii) The main source of energy is sun.
(iv)Each plant or an animal in a food chain is called a link.
(v)The lowest level in a food chain is occupied by producers.
2-ENCRRCLS THE CORRECT ANSWER IN THE FOLLOWING.
(i) The type of environment an organism lives in is called
(a) Ecosystem (b) Habitat (c) Community (d) Population
(ii) Herbivores are
(a) Primary consumers (b) Secondary consumers (c)Teary consumers (d) Omnivores
(iii)Animals are
(a) Producer (b) Consumers (c) Decomposers (d) Autotrophs
(iv) All feeding relationships in an ecosystem a expressed by
(a) Food pyramid (b) Food chain (c) Food web (d) Energy flow
(v) The topmost level in a food pyramid is generally occupied by.
(a) Primary consumers(b) Secondary consumers(c)Tertiary consumers (d) Producers
Ans: (i-b)(ii-a)(iii-b)(iv-c)(v-c)
DEFINE THE FOLLOWINGS:
(i) Ecosystem (ii) Community (iii) Population
Ans: Ecosystem:-
Communities interacting with their physical environment is called ecosystem
Population:-
A group of organisms of the same species located in the same habitat at a particular time is called population.
Community:-
Different species or populations Irving together and interacting with one another constitute a community.
4. DESCRIBE BRIEFLY FLOW OF ENERGY IN AN
ECOSYSTEM.
Ans. ENERGY IN THE ECOSYSTEM:
Energy is required to maintain an ecosystem.
The Sun is the main source of energy. Sunlight is used by plants to make food. This food is used by the plants themselves and also by all other living organisms.
Without plants, humans and all other animals would starve to death. This is because they cannot make their own
food.
The only way animals can obtain energy is by eating or consuming, plants or other animals. Animals are called
consumers while plants are called producers.
5. Write a note on balance in nature.
ANS.
BALANCE IN NATURE:-
Under normal conditions natural ecosystems maintain an equilibrium between plants and animals and their non-living environment. We call this as ‘Balance in nature’ Whenever, this equilibrium is disturbed the whole ecosystem is disturbed.
An ecosystem has the ability to withstand changes of low; magnitude and may return to its original state. However, if disturbance is large, the ecosystem may not be able to absorb it and consequently bear irreparable damages.
Imbalance in nature and pollution are closely related. For instance, changes caused by pollution in the composition of air, soil or water of an area will have harmful effects on the life of plants and animals.
RESULT OF IMBALANCE IN NATURE
EXAMPLES OF IMBALANCE IN NATURE
i. Overgrazing of pasture land has resulted-in the shortage of domestic animals. It has also resulted in the increase of waste lands and deserts
ii. Pollution caused by industries and traffic has upset the balance of gases in the atmosphere leading to global warming and acid rains.
CH:4 CONTINUITY OF LIFE P:
1-FILL IN ME BLANKS.
(i) The branch of biology which deals with the study of heredity and variations is called genetics.
(ii)Thin membrane surrounding the nucleus is known as Nuclear membrane.
(iii) Small rounded body called nucleolus is present in the nucleus of cell.
(iv)Two chromatids of chromosome are attached with centromere.
(v)Gene is a unit of inheritance.
2-PUT (√) MARK AGAINST CORRECT STATEMENT AND (X) FOR INCORRECT STATEMENT
(i)Transmission of characters from parent to their offspring is called genetics. (X)
(ii)Chromosome is made of DNA. (X)
Genes are arranged on chromosomes in a linear order.(√)
(iii)Body (somatic) cells are concerned with reproduction. ( X)
(iv)DNA is a unit of inheritance. (X)
3-ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING
(i)Chemically gene is made up of
(a)Protein (h) DNA (c) Protein and DNA
(ii)Number of chromosome in somatic (body) cells of human being are:
(a) 8 (b) 14 (c) 23 (d) 46
(iii)Chromosomes are made up of:
(a)Protein (b) DNA
(c) Protein and DNA
Ans: (i-b)(ii-d)(iii-c)
4-GIVE SHORT ANSWERS.
(i)What is gene?
Ans: Each chromosome carries a number of genes. These genes ire arranged in linear order. Chemically genes are made of DNA.
(ii) Write down difference between chromosome and chromatids.
Ans. Chromosomes are thread like structures. These are always in pairs. Each individual has fixed number of chromosomes.
Each chromosome consists of two chromatids and these chromatids are attached with each other at centromere.
(iii) Define the term “genetic code”.
Ans. Instructions stored in the gene in the form of code is as genetic code.
5. Describe the structure of nucleus.
Ans:
The nucleaus is the most important component of a living cell. It has following parts.
Pic
NUCLEAR MEMBRANE:
The nucleus is enclosed in a membrane called nuclear membrane and contains semi-fluid material called nucleoplasm. The nuclear membrane has minute pores which allow the flow of materials between the nucleus an cytoplasm.
NUCLEOLUS:
The nucleolus is densely stain round body present ini nucleus
CHROMOSOMES:-
The most important structures present in the nucleus are short rod-like bodies or thread like structures known as chromosomes.
6. Describe the structure of DNA.
Ans.
DEOXYRIBONUCLEIC ACID (DNA):
A molecule of DNA consists of two strands like a ladder.
These two strands linked with each other by cross; bands pieces like a ladder and twisted around each others
The DNA molecule is therefore in the form of a spiral helix or double helix.
DNA consists of a very large number of units called nucleotides. These units are joined to each other to form DNA molecule.
Pic
CH:5 ATOMA&ITSSTRUCTURE P:
FILL IN THE BLANKS.
(ii) An atom contains 3 type of fundamental particles.
(ii) The charge present on an electron is negative and that present on a proton positive.
(iii) Protons and neutrons are present in the nucleus of an atom.
(iv) The paths around which the electrons revolve are known as known.
(v) The outermost shell of oxygen atom has six electrons, its valency will be -2.
(vi) Hydrogen element has 3 isotopes.
(vii) The nucleus of nitrogen atom contains 7 protons, the number of electrons present ln its L-shell with be
(viii)The total number of neutrons and protons present in the nucleus of an atom ls called its atomic mass.
(ix) An atom has 20 neutrons and 20 electrons; it will also have Q protons present in it.
(x) Isotopes of an element have the same number of electrons or protons but different number of neutrons.
Put (√) mark against correct statement and (x) for incorrect statement.
(i) The number of n an atom is always the same. (√)
(ii) The amounts of in hydrogen are the same. (X)
(iii) An atom of carbon contains 6 electrons, 6 neutrons and 7 protons. ( X)
(iv) Different atoms always combine in the same ratio to form a chemical compound (√)
ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING.
(i) An atom which does not have a neutron:
(a)Hydrogen (b) Helium (c)Proiium (d) Deutrium
(ii) Atomic number of boron is, 5. The number of electrons in its K-shell will be:
(a)5 (b) 4 (c) 2 (d) 3
(iii) Which atom is represented by the following figure?
(a)irinium (b)Benmm
(c) Helium (d) Tritium
P=4
N=5
(iv) An atom has 8 electrons, B protons and B neutrons. What will be its atomic mass?
(a) 8 (b) 16 (c) 24 (d) 32
(v) Isotopes of an element have:
(a) Same physical and chemical properties.
(b) Different physical and chemical properties.
(c) Same physical properties but different chemical properties.
(d) Different physical properties but same chemical properties.
Ans: (i-c)(ii-c)(iii-b)(iv-b)(v-d)
4-What do you understand from the terms atomic number and atomic mass?
Ans. ATOMIC MASS:-
The total number of protons and neutrons present in the nucleus of an atom is called its atomic mass or mass number
and is represented by A
The following examples will further illustrate the idea of atomic mass.
EXAMPLES:-
ATOMIC NUMBER:-
The number of protons present in the nucleus of an atom is called its atomic number or proton number and is represented by Z.
EXAMPLE.
Hydrogen is the lightest element with one proton present in its nucleus. It is the only atom that does not have any neutron in its nucleus, Its atomic number is 1.
Helium atom has two protons present in its nucleus hence, its atomic number will be 2.
Similarly atomic number of carbon is 6 because it contains 6 protons in its nucleus.
5-Hydrogen gas and chlorine gas combine together in the presence of sunlight to form hydrogen chloride gas Can you tell whether only protium or all the isotopes of hydrogen will participate in the reaction?
Ans:
Protium only
Ans: BERYLLIUM:
Atomic mass=8
Atomic number=4
Atomic number= No. of protons/ electrons
No. of protons=4
No. of electrons =4
Electronic arrangement = K=2,L=2
No. of neutrons=Atomic mass-Atomic number
OXYGEN:
Atomic mass=16
Atomic number=8
Atomic number= No. of protons/ electrons
No. of protons=8
No. of electrons = 8
Electronic arrangement K=2 = , L =6
No. of neutrons = Atomic mass – atomic number =16-8 =8
NEON:
Atomic mass=20
Atomic number=10
Atomic number= No. of protons/ electrons
No. of protons=10
No. of electrons = 10
Electronic arrangement K=2 = , L =8
No. of neutrons = Atomic mass – atomic number =20-10 =10
7-What are isotopes? How do the isotopes of an element differ and resemble to each other?
Ans: ISOTOPES:
Isotopes are the sister atoms of an element which have same atomic number- but different atomic masses.
The isotopes of an element have similar chemical properties but different physical properties.
Isotopes of hydrogen, element of hydrogen comprises three isotopes.
Pic
The isotopes or Hydrogen Atom
(i) PROLIUM
The lightest one has one proton in its nucleus and is known as Protium.
(ii) DEUTRIUM
Deutrium is the heavier atom of hydrogen with one promn and one neutron present in its nucleus.
(iii)TRITIUM
Tritium being the heaviest one consists of one proton and two neutrons in its nucleus.
The isotopes of an element have similar chemical properties but show different physical properties.
8-Name an atom which has the same number of electrons, protons and neutrons.
Ans:
Oxygen Carbon, Helium.
9-An atom has one electron more than its protons. What will be the charge on it?
Ans:
Since proton have positive charge and electron have negative charge, If number of electrons increases.
Therefore atom will have a positive charge.
Ch:6 ELEMENTS P:
1-FILL IN THE BLANKS.
1-The smallest particle of different substances which shows the properties of that substance and can exist free in nature is called Molecule.
2-A molecule of chlorine consists of 2 atoms.
3-Powdered aluminum is mixed with copper oxide to prepare Scintillating sticks.
4- Magnalium is an alloy of aluminium which is used to pare Aeroplane, pistons of motor engines and balances.
5- In lead pencil, instead of lead Graphite is used.
PUT (√) MARK AGAINST CORRECT STATEMENT AND (X) INCORRECT STATEMENT.
1- Sodium is three times heavier than water
2- Iodine is not a metal, but it has metallic luster.
3- Graphite is a hardest non-metal in naturally occurrence substances.
4-Oxygen is used to prepare ammonia and nitric acid.
5-Oxygen is used for artificial respiration of patient pneumonia and T.B.
6- To increase the strength and elasticity of rubber carbon is used for vulcanization of rubber.
7- Carbon is used to prepare matchstick.
8- Sulphuric acid is prepared from sulphur.
ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING
Which one is the liquid nonmetal of the following.
(a) Phosphorus (b) Mercury (c) Bromine (d) Iodine
The element which has the greatest quantity in Earth crust.
(a) Iron (b) Potassium (c) Sodium (d) Aluminum
The metal prepared artificially,
(a) Uranium (h) Plutonium (c) Chromium (G) Aluminum
Which one is not a metalloid among the following elements?
(a) Silicon (b) Aluminium (c) Boron (d) Antimony
Motel found in liquid at common temperature.
(a) Sodium (b) Potassium (c) Antimony r (d) Mercury
Ans: (1-c)(2-d)(3-b)(4-b)(5-d)
GIVE SHORT ANSWERS.
Give the examples of elements, which are solids, liquids and at gaseous states at room temperature.
Ans:
Solid:-
Iron, Silver, Sodium, Carbon
Liquid:-
Mercury, Gallium, Bromine
Gases:-
Oxygen, Hydrogen, Nitrogen
ii- Write a not on metalloids.
Ans.
METALLOIDS:-
Metalloids are those elements which resemble both metals and non-metals in their properties.
PROPERTIES:-
i. These elements are lustrous.
ii. They conduct electricity which is tlfe typical property of metals.
iii. They react with oxygen and form acidic oxides and thus t they resemble non-metals,
EXAMPLES:
Boron, silicon, arsenic and antimony belong lo this group of elements.
8 Write down the uses of following metals
Iron, Copper Aluminum, Gold.
Ans.
1-USES OF IRON:-
Iron is used to manufacture girders, railway- tracks, ships.
Permanent magnets are prepared from steel.
iii. Steel is also used in the manufacture of road rollers and machine parts of printing press.
iv-sewing machines, knives, forks, furniture and parts of machinery.
v- iron is used to manufacture girders, railway tracks, ships sewing machines, knives, forks, furniture and parts of machinery.
2-USES OF COPPER:
i- Copper being a good conductor, is used to manufacture electric wires.
It is also a component of some important alloys like brass, bronze and German silver.
iii. Electrodes of most of the electric cells are made of copper.
Electrical instruments, wires for telephones and telegraph, parts of automobiles and watches are also made of copper.
It is used in electroplating.
3-USES OF ALUMINIUM:
Aluminium utensils are often used in kitchens.
Electric wires and conductors, parts of cars, trucks, and railway trains, different types of windows and doors, frames and decoration pieces are made from aluminium.
iii. Aluminium powder mixed with copper oxide is used to prepare scintillating sticks.
Magnalium An important ‘alloy of Ialuminlumt is Magnalium. It consists of 3 to 10% magnesium mixed with aluminium. It is used to prepare pistons of motor engines, balances and aeroplanes.
4-USES OF GOLD:
Gold is used in the ornaments of silver and diamond.
Many precious objects eg, medals, crowns are made of gold.
iii. Gold and silver are also used in electroplating.
iii. Fine wire of gold is used in gold wire embroidery.
6-Write down the uses of following two non-metals.
(i) Nitrogen (ii) Oxygen (iii) Sulphur.
Ans:
(i) USES OF NITROGEN:
i- Nitrogen is being filled in electric bulbs.
ii- It is used to prepare ammonia and nitric acid.
ii- It is also used to prepare compounds as urea, ammonium, nitrate and ammonium sulphate which are used as fertilizers.
(ii) USES OF OXYGEN:
1-This gas is used in various industrial chemical applications.
2- It is used to make acids, sulfuric acid, nitric acid and other compounds.
3- Its most reactive variant is ozone O3.
4- It is applied in assorted chemical reactions.
5- The goal is to boost reaction rate and oxidation of unwanted compounds.
6-Hot oxygen air is required to make steel and iron in blast furnaces.
7-Some mining companies use it to destroy rocks.
(iii) USES OF SULPHUR:
i- Sulphur is used to prepare sulphuric acid, which is very important for present day industries.
ii- Matchstick and gun powder are prepared from sulphur.
iii- To increase the strength and elasticity of rubber, sulphur is mixed with it.
iv- It is also used for vulcanization of rubber.
7-Differentiate between Atom and Molecule by giving examples.
Ans: ATOM:
An atom is the smallest particle of an element and shows all the characteristic properties of the element.
MOLECULE:-
A molecule is the smallest particle of an element or a compound, which can exit free in nature and shows all the properties of that element or compound.
ATOM
MOLECULE
1- An atom is the smallest particle of an element.
1- A molecule is the smallest particle of an element or a compound.
2- lt shows all the properties of the element.
2- It shows all the properties “of the element or the compound.
3- It is indivisible in chemical reaction.
3- It is divisible in chemical reaction.
4- It retains its identity during a chemical reaction.
4- It does not retain its identity during a chemical reaction.
5- lt does not exist in free stale as a single atom but the atoms of noble gases are found as single
atoms.
5- It exists in free state.
8-Write down the percentage composition of the elements present In Earth’s crust.
Ans. Twenty five percent of earths crust is composed of compounds of metal.
Pic
Metals like gold, silver, platinum which are uncreative, occur mostly in free state while reactive metals like sodium, potassium, ‘tin and aluminum are found in the form of
Compounds.
Percentage of some Elements found in Earth’s Crust
Element
Percentage Amount
Element
Percentage Amount
1-Oxygen
2- Silicon
3- Aluminium
4- Iron
5- Calcium
50
26
7
4
3
6. Potassium
7-Sodium
8-Magnesium
9- Hydrogen
10- Other elements
2.5
2.5
2
0.14
3
9-Write a detailed note on “The classification of Elements”.
Ans. CLASSIFICATION OF ELEMENTS:-
The elements found in this world are classified into two main groups depending upon their characteristics.
METALS
Metals generally exist in solid state at room temperature.
Metals show a typical luster. Freshly cut metals have a very bright luster.
Metals are usually heavier than non-metals.
Metals are usually hard.
Metals can be drawn into foils and wires.
Metals have high melting and boiling points.
Metals are good conductor of heat and electricity.
Metals can be mixed in different proportions’ to form alloys.
II- NON-METALS.
Non-metals exist in all the three-physical states at room temperature.
Non-metals have less density as compared to metals. They are lighter than metal.
Non-metals are usually soft and brittle.
Non-metals cannot be drawn into foils and wires.
Solid non-metals have comparatively low melting and boiling points.
Generally, non-metals are not conductor of heat and electricity; Electric current can not pass through non-metals.
7-Non-metals in the form of gases are transparent and light can pass through them easily.
8- Non-metals do not form alloys.
10- Compare and contrast the properties of metals and non-metals solid state at room
Ans.
COMPARISON OF METALS AND NON-METALS.
Comparison of the properties of metals and non-metals.
Metals
Non-metals
1- Metals generally exist in room temperature. For example; phosphorus is a solid, bromine is a liquid and hydrogen is a gas at room temperature.
2- Metals show a typical luster. Freshly cut metals have a very bright luster.
3- Metals are usually heavier than non-metals. Sodium and potassium are however, lighter than water.
4-Metals are usually hard.
5-Metals can be drawn into foils and wires. Bismuth and antimony, being metalloids, are not malleable and ductile. They are brittle.
6- Metals have high melting and boiling points.
7- Metals are good conductor of heat, and can pass easily through metals.
8- All metals are opaque and as such light cannot pass through them. However light can pass through a very thin gold foil.
9- Metals can be mixed in different proportions to form alloys.
1-Non-metals exist in all the three physical states at temperature. For example. gold, silver and iron, etc, Mercury-and gallium, however, exist in liquid at room temperature.
2- Non-metals do not show metallic luster. Graphite and iodine, however, show metallic luster although they are non-metals.
3- Non-metals have less density as compared to metals. They are lighter than metal.
4- Non-metals are usually soft and brittle. But
diamond is the hardest .among all the naturally occurring substances.
5- Non-metals cannot be drawn into foils and wires.
6- Solid non-metals have comparatively low melting and boiling points.
7- Generally, non-metals are not conductor of heat and electricity. Electric current can not pass through non-metals. However, graphite is a conductor of electricity.
8- Non-metals in the form of gases are transparent and light can pass through them easily But solid non-metals are opaque and thus light cannot pass through them.
9- Non-metals do not form alloys.
CH:7 SOME COMMON GASES P:
FILL IN THE BLANKS.
i-Oxygen supports the combustion process.
ii-Oxygen is prepared in the laboratory by heating potassium chlorate in the presence of Manganese dioxide.
iii. Hydrogen gas, in free state is found in Sun.
Hydrogen reacts with Oxygen to form water.
Carbon dioxide is produced during combustion and Respiration.
ENCIRCLE THE CORRECT ANSWER IN THE FOLLOWING
A constituent of fuel used in space ship is..
(a) Nitrogen (b) Chlorine (c) Oxygen (d)Bromine
The gas liberated by plants during day light is.
(a) Carbon dioxide (b) Oxygen (c) Sulphur dioxide (d) Hydrogen
iii. Hydrogen gas was discovered by.
(a) Scheele (b) Robert boyle (c) Cavendish (d)Van helmont
The most abundantly found element In earth crust is:
(a)Hydrogen (b) oxygen (c) Carbon (d) Aluminium
Percentage of carbon dioxide present in air by volume.
(a) 0.5 % (b) 1% (c) 3% (d) 0.03%
Ans: (i-c)(ii-b)(iii-c)(iv-b)(v-d)
MATCH THE PROCESS MENTIONED IN COLUMN A WITH TIN SUBSTANCES IN COLUMN B AND WRITE DOWN YOUR ANSWER IN COLUMN C.
Column A
Column B
Column C
1. The gas which supports combustion.
2. The gas which burns with blue flame.
3. The gas liberated by plants in the absence of sunlight.
4. Metals combine with oxygen and are produced.
-Carbon dioxide
-Oxides
-Oxygen
-Hydrogen
-Oxygen
-Hydrogen
-Carbon
Dioxide
-Oxide
Ans:
I- WRITE DOWN BRIEF ANSWERS TO THE FOLLOWING QUESTIONS.
i- Which compounds are used during ‘the laboratory preparation of oxygen gas? Ans. During the laboratory preparation of oxygen gas potassium chlorate and manganese dioxide are used.
ii-State the properties of hydrogen gas? Ans. PROPERTIES OF HYDROGEN GAS:-
Hydrogen is a colorless, odourless and tasteless gas.
It is sparingly soluble in water.
iii. It is the lightest of all elements.
Hydrogen’ burns in oxygen or air with a blue flame and produces water.
Hydrogen + Oxygen –> Water
It has no affect on red or blue litmus.
USES OF HYDROGEN GAS
Hydrogen is used to prepare ammonia gas, which is used in the preparation of fertilizers.
It is used as a fuel in rockets.
iii. If is filled in meteorological balloons since it is lighter than Elf.
It is used in the preparation of banaspati ghee from vegetable oil like sunflower all and margarine from palm oil.
iii- What are the natural sources of carbon dioxide?
Ans. Natural sources of carbon dioxide are air and most carbon dioxide present in air is produced by the process of respiration and combustion.
iv-What is the difference between the process of respiration in plants and human being during the day light?
Ans: There is no difference between the process of respiration in plants and human being during the day light. Both plants and human being use oxygen for respiration.
v-What is dry ice? Give its uses.