Composition of matter

Question 1:

Choose the appropriate option and rewrite the following statements.
A. The intermolecular force is _______ in the paricles of solid.
i. Minimum    ii. Moderate    iii.maximum    iv.indefinite.

B. Solids retain their voume even when external pressure is applied. This property is called__________
i. plasticity    ii. Incompressibility    iii. fluidity    iv. elasticity

C. Matter is classified into the types mixture, compound and element by applying the criterion______________
i. states of matter    ii Phases of matters    iii chemical compositions of matter    iv all of these

D. Matter that contain two or more constituent substances is called__________
i. mixture    ii. compound    iii. element    iv. metalloid

E. Milk is an example of type of matter called __________
i. solution    ii. homogeneous mixture    iii heterogeneous mixture    iv. suspension

F. Water, mercury and bromine are similar o each other, because three are
i. liquids    ii. compounds     iii. nonmetals    iv. elements.

G. valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are _______ chemical bond/bonds between the carbon atom and one oxygen atom in the compound-carbon dioxide.
i. 1    ii. 2    iii. 3     iv. 4 

ANSWER:

A. The intermolecular force is  maximum in the paricles of solid.
i. Minimum    ii. Moderate    iii.maximum    iv.indefinite.

B. Solids retain their voume even when external pressure is applied. This property is called incompressibility.
i. plasticity    ii. Incompressibility    iii. fluidity    iv. elasticity

C. Matter is classified into the types mixture, compound and element by applying the criterion states of matter.
i. states of matter    ii Phases of matters    iii chemical compositions of matter    iv all of these

D. Matter that contain two or more constituent substances is called compound.
i. mixture    ii. compound    iii. element    iv. metalloid

E. Milk is an example of type of matter called homogeneous mixture.
i. solution    ii. homogeneous mixture    iii heterogeneous mixture    iv. suspension

F. Water, mercury and bromine are similar to each other, because three are liquids.
i. liquids    ii. compounds     iii. nonmetals    iv. elements.

G. valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are 2 chemical bond/bonds between the carbon atom and one oxygen atom in the compound carbon dioxide.
i. 1    ii. 2    iii. 3     iv. 4 

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Question 2:

Identify the odd term out and explain
A. Gold, silver, copper, brass
B.Hydrogen, hydrogen peroxide, carbon dioxide, water vapour.
C.Milk, lemon juice, carbon, steel.
D.water, mercury, bromine, petrol.
E.sugar, slat, baking soda, blue vitrol.
F.Hydrogen, sodium, potassium, carbon.

ANSWER:

a.Brass is odd one out because it is an alloy and gold, silver, copper are element.
b.Hydrogen is odd one out because it is an element and others are compound.
c.Carbon is odd one out because it is an element and others are mixture of various elements.
d.Water is odd one out because it is universal solvent and rest are not universal solvent.
e.Baking soda is odd one out because it is a mixture of various elements and others are compound.
f.Carbon is odd one out because it has 4 valence electrons and others have 1 valence electron.

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Question 3:

Answer the following questions.
A.Plants synthesize glucose in sunlight with the help of chlorophyll from carbon dioxide and water and give away oxygen. identify the four compounds in this process and name their types.

B. In one sample of brass, the following ingredients were found : copper (70%) and zinc (30%).  Identify the solvent, solute and solution from these.

C. Sea water tastes salty due to the dissolved salt. the salinity (the proportion of salts in water) of some water bodies Lonar lake - 7.9 %, Pacific Ocean 3.5%, Mediterranean sea- 3.8%, Dead sea- 33.7%. Explain two characteristics of mixture from the above information.

ANSWER:

a.Photosynthesis is a chemical process through which plants, some bacteria and algae, produce glucose and oxygen from carbon dioxide and water, using only light as a source of energy, which is absorbed by chlorophyll.
6CO2 + 6H2O → C6H12O6 + 6O2$6{\mathrm{CO}}_2 + 6{\mathrm{H}}_2\mathrm{O} \to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6 + 6{\mathrm{O}}_2$
Four substances in this process are as follows:
1.Carbon dioxide = organic compound
2.Water = organic compound
3.Glucose = organic compound
4.Chlorophyll = organo-metallic compound or complex compound

b.Brass is an alloy made primarily of copper, usually with zinc.Brass as a solid solution consisting of zinc and other metals as solute dissolved in copper taken as solvent. So that, the brass meets all the criteria of a solution.

c.Characteristics of mixtures from above information are:
1.Constituent substances of a mixture are two or more elements or compounds.
2.The proportion of constituent substances in a mixture can be variable.
3.The properties of constituent substances are retained in the mixture.

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Question 4:

Give two examples each
A. Liquid element
B. Gaseous element
C. Solid element
D.Homogeneous mixture
E.Colloid
F.Organic compound
G.Complex compound
H.Inorganic compound
I.Metalloid
J.Element with valency 1
K.Element with valency 2

ANSWER:

a.Liquid element = mercury, bromine
b.Gaseous element = oxygen, nitrogen, hydrogen
c.Solid element = sodium, carbon, aluminium
d.Homogeneous mixture = sugar in water, corn oil, blood plasma
e.Colloid = mayonnaise, milk, butter, gelatin, jelly, muddy water
f.Organic compound = proteins, glucose, urea, carbohydrates
g.Complex compound = chlorophyll, hemoglobin, cyanocobalamine
h.Inorganic compound = limestone, rust, common salt
i.Metalloid = silicon, germanium
j.Element with valency 1 = sodium, potassium, chlorine
k.Element with valency 2 = magnesium, calcium

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Question 5:

Write the names and symbols of the constituent eleements and identify their valencies from the molecular formulae given below.
KCl,   HBr,   MgBr₂,   K₂O,  NaH,   CaCl_2,  CCl₄,  HI,   H₂S, Na₂S,   FeS,   BaCl₂

ANSWER:

Compounds	Name of compounds	Symbol of constituent elements	Valency of constituent elements
KCl	Potassium chloride	K, Cl	K = 1, Cl = 1
HBr	Hydrogen bromide	K, Br	K = 1, Br = 1
MgBr2	Magnesium bromide	Mg, Br	Mg = 2, Br = 1
K2O	Potassium oxide	K, O	K = 1, O = 2
NaH	Sodium hydride	Na, H	Na = 1, H = 1
CaCl2	Calcium chloride	Ca, Cl	Ca = 2, Cl = 1
CCl4	Carbon tetrachloride	C, Cl	C = 4, Cl = 1
HI	Hydrogen iodide	H, I	H = 1, I = 1
H2S	Hydrogen sulphide	H, S	H = 1, S = 2
Na2S	Sodium sulphide	Na, S	Na = 1, S = 2
FeS	Iron (II) Sulfide	Fe, S	F = 2, S = 2
BaCl2	Barium chloride	Ba, Cl	B = 2, Cl = 1

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Question 6:

Chemical composition of some matter is given in the following table. Identify the main type of matter from their.

Name of matter	Chemical composition	Main type of matter
Sea water	H2O + NaCl + MgCl2$H_{2}O + NaCl + MgC{l}_2$
Distilled water	H2O$H_{2}O$
Hydrogen gas filled  in a ballon	H2$H_2$
The gas in LPG cylinder	C4H10 + C3H8$C_4{H}_{10} + C_3{H}_8$
Baking soda	NaHCO3$NaHC{O}_3$
Pure gold	Au$Au$
The gas in oxygen cylinder	O2
Bronze	Cu + Sn
Diamond	C
Heated white powder of blue vitroi	CuSO4
Lime stone	CaCO3
Dilute hydrochloric acid	HCL+ H2O

ANSWER:

 

Name of matter	Chemical composition	Main type of matter
Sea water	H2O + NaCl + MgCl2$H_{2}O + NaCl + MgC{l}_2$	mixture
Distilled water	H2O$H_{2}O$	compound
Hydrogen gas filled  in a ballon	H2$H_2$	element(molecule)
The gas in LPG cylinder	C4H10 + C3H8$C_4{H}_{10} + C_3{H}_8$	mixture
Baking soda	NaHCO3$NaHC{O}_3$	mixture
Pure gold	Au$Au$	element
The gas in oxygen cylinder	C4H10 + C3H8$C_4{H}_{10} + C_3{H}_8$	element(molecule)
Bronze	Cu + Sn	mixture
Diamond	C$C$	element(allotrope)
Heated white powder of blue vitroi	CuSO4${\mathrm{CuSO}}_4$	compound
Lime stone	CaCO3$CaC{O}_3$	compound
Dilute hydrochloric acid	HCL+ H2O$\mathrm{HCL}+ {\mathrm{H}}_2\mathrm{O}$	compound

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Question 7:

Write scientific reason.
A. Hydrogen is combustible, oxygen helps combustion, but water helps to extinguish fire.
B. Constituent substances of a colloid cannot be separated by ordinary filtration.
C. Lemon sherbat has sweet, sour and salty taste and it can be poured in a glass.
D. A solid matter has the properties of definite shape and volume.

ANSWER:

a.Water is made up of two elements, that's hydrogen and oxygen. Hydrogen is flammable, but oxygen is not. Flammability is the ability of a combustible material with an adequate supply of oxygen (or another oxidiser) to sustain enough heat energy to keep a fire going after it has been ignited. Though water is made up of two atoms of hydrogen and one atom of oxygen by forming an ionic compound, it does not possess the characteristics of them because a compound does not have the properties of its constituent elements. Therefore, water has its own properties, which helps to extinguish fire.

b.Constituent substances of a colloid cannot be separated by ordinary filtration because the size of the particles in a colloids(or colloidal solution) is bigger than those in a true solution but smaller than those in suspension.It is in between 1nm to 100nm in diameter. The size of ordinary filter paper is more than 100nm due to which colloidal particles are passed through the pores of a filter paper. Due to which, we prefer to use ultrafilter paper so that, filteration of colloidal particles take place easily.


c.Lemon sherbat has sweet, sour and salty taste and it can be poured in a glass because sour taste indicates presence of an acid and if acid is poured in a vessel made up of metal, then acid reacts with metal and makes it poisonous in nature.So we prefer to take vessel made up of glass material.

d.A solid matter has the properties of definite shape and volume because of the following reasons:
1)Intermolecular force of attraction between the particles of matter is very strong.
2)Internuclear space between the particles of matter is negligible.
3)Particles of matter are very close to each other that they only vibrate at their fixed position.
 

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Question 8:

Deduce the molecular formulae of the compound obtained from the following pairs of elements by the cross multiplication method.
A. C (Valency 4) & Cl (Valency 1)
B. N (Valency 3) & H (Valency 1)
C. C (Valency 4) & O (Valency 2)
D. Ca (Valency 2) & O  (Valency 2)

ANSWER:

a. C (Valency 4) & Cl (Valency 1) :
Step 1 : Write the symbols of the radicals.
                           C                       Cl
Step 2 : Write the valency below the respective radical.
                           C                        Cl
                            4                        1
Step 3 : Cross-multiply symbols of radicals with their respective valency.
                            
Step 4 : Write down the chemical formula of the compound.
                            CCl₄


b. N (Valency 3) & H (Valency 1)
Step 1 : Write the symbols of the radicals.
                           N                      H
Step 2 : Write the valency below the respective radical.
                           N                      H
                            3                      1
Step 3 : Cross-multiply symbols of radicals with their respective valency.
                          
Step 4 : Write down the chemical formula of the compound.
                           NH₃


C. C (Valency 4) & O (Valency 2)
Step 1 : Write the symbols of the radicals.
                           C                       O
Step 2 : Write the valency below the respective radical.
                           C                        O
                            4                        2
Step 3 : Cross-multiply symbols of radicals with their respective valency.
                           
Step 4 : Write down the chemical formula of the compound.
                           CO₂


D. Ca (Valency 2) & O  (Valency 2)
Step 1 : Write the symbols of the radicals.
                           Ca                     O
Step 2 : Write the valency below the respective radical.
                           Ca                       O
                            2                        2
Step 3 : Cross-multiply symbols of radicals with their respective valency.
                          
Step 4 : Write down the chemical formula of the compound.
                          CaO

Inside the atom (std.8)

Question 1:

Answer the following
A. Whati is the difference in the atomic models of Thomson and Rutherford ?
B. What is meant by valency of an element ? what is the relationship between the number of valence electron and valency ?
C. What is meant by atomic mass number ? Explain how the atomic number and mass number of carbon are 6 and 12 respectively.
D. what is meant by subatomic particle ? give brief information of three subatomic particles with refrence to electrical charge, mass and location.

ANSWER:

a. Difference between Thomson and Rutherford Theory are as follows :
 

Thomson Theory	Rutherford Theory
States that electron are embedded in a positively charged solid material which is spherical in shape	States that an atom is composed of an atomic nucleus around which electrons are revolving in an orbit
Does not give any detail about the atomic nucleus	Explains about the atomic nucleus
States that electrons are uniformally distributed in an atom	States that electrons are located around a central solid material
Indicates that atom is spherical in shape	Indicates that an atom has a central solid core called as nucleus surrounded by the electrons
Does not give any idea about constituents of nucleus	States that nucleus is composed of protons and neutrons

b. Valency of an element : It is the number of electrons of an atom of the element uses to combine with atoms of other elements.
It is the combining power of an atom of the element.
Valency of an atom is determined by its electronic configuration.
It gives idea about the number of electrons loss or gain in order to achieve the nearest noble gas configuration.
For example: Na(11) = 2,8,1 So, its valency is 1
                      Cl(17) = 2,8,7 So, its valency is also 1

Number of valence electron : It is defined as the number of electrons present in the outermost shell of an atom.
It is not necessary that all the valence electrons take part in bonding.
For example: Na(11) = 2,8,1 So, its number of valence electron is 1
                      Cl(17) = 2,8,7 So its number of valence electron is 7

It can be seen that valency of an element is related to number of valence electrons in that atom.


c.Atomic Mass Number : It is the sum of total number of protons and neutrons present in a nucleus.
Atomic mass number = number of protons + number of neutrons.
Atomic number = number of protons = number of electrons. It is denoted by Z.
Mass number = number of protons + number of neutrons. It is denoted by A.
For example : Carbon atom its, Number of proton = 6
                           Number of neutrons = 6
                           Number of electron = 6
                           Atomic number(Z) = number of protons = number of electrons = 6.
                           Mass number(A) = number of proton + number of neutrons = 6 + 6 =12.
 
d.Subatomic particles : A subatomic particle is a structural and functional unit of the matter. That means all the matters are made up of these fundamental particles. According to modern atomic theory, an atom has a nucleus, which is present in its center or core. These nucleus contain subatomic particles like protons and neutrons.
Difference between subatomic particles are as follows :

Electron
1. Electrons are present outside the nucleus of an atom.
2. Electrons are negatively charged that is (1.6 × 10−19$1.6 \times {10}^{-19}$coulomb).
3. The mass of an electron is considered to negligible. It is 1800  times less than that of a hydrogen
4.Relative mass = 1/ 1840 times hydrogen
5. It revolves around the nucleus in the discrete orbit.

Proton
1. Protons are present in the nucleus of an atom.
2. Protons are positively charged that is (1.6 × 10−19$1.6 \times {10}^{-19}$coulomb).
3. The mass of a proton is approximately 1u(1Dalton) that is (1u = 1.66 × 10−27 g$1u = 1.66 \times {10}^{-27 }g$).
4. They are closely bound in the nucleus.

Neutron
1. Neutrons are present in the nucleus of an atom.
2. Neutrons are neutral.There is no charge.
3. The mass of a neutron is nearly equal to the mass of a proton that is 1u(1Dalton) that is (1u = 1.66 × 10−27 g$1u = 1.66 \times {10}^{-27 }g$).
4. They are closely bound in the nucleus.

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Question 2:

Give secientific reasons.
A. All the mass of an atom is concenrated in the nucleus.
B. Atom is electrically neutral.
C. Atomic mass number is a whole number.
D. Atoms are stable though negatively charged electron are revolving within it. 

ANSWER:

a. All the mass of an atom is concentrated in the nucleus because atom contains three subatomic particles like electron, proton and neutron.Out of which, nucleus present at the centre of an atom contains two subatomic particles that's protons and neutrons and the mass of nucleus is the sum of mass of protons and neutrons located at the centre of an atom.

b.Atom is electrically neutral because in an atom electrons and protons carry charges and each atom has equal numbers of protons (positively charged) and electrons (negatively charged).

c.Atomic mass number is a whole number because it is the sum of numbers of protons and numbers of neutrons present in an atom.Which is present in the form of integers.

d.Atoms are stables though negatively charged electrons are revolving within it because each atom contains equal numbers of protons and electrons. So, charge on negatively charged electrons are balanced by charge on positively charged proton. Therefore, atom is electrically neutral and stable. 

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Question 3:

Define the following forms
A. Atom 
B. Isotope
C. Atomic number
D. Atomic mass number
E. Moderator in nuclear reactor

ANSWER:

a. An atom is defined as  the structural and functional unit of a matter. The term "atom" comes from the Greek word which means indivisible, because atoms are the smallest things in the universe and could not be divided. atoms are made up of three subatomic particles like protons, neutrons and electrons.

b.Isotopes : Isotopes are atoms that have same atomic number but different mass number. Isotopes have same numbers of protons but different numbers of neutrons.
These are some common examples of isotopes: 3
2He, 4
2He, 12
6C, 14
6C, 235
92U, 239
92U, 289.


c.Atomic number: The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. Atomic number is also equal to numbers of electrons in an atom.
For example :
Atomic number of carbon = 6
Atomic number of nitrogen = 7
Atomic number of oxygen = 8
Atomic number of magnesium = 12


d.Atomic Mass Number : It is the sum of total number of protons and neutrons present in a nucleus.
atomic mass number = number of protons + number of neutrons.
Atomic number = number of protons = number of electrons.It is denoted by Z.
Mass number = number of protons + number of neutrons. It is denoted by A.
For example : Carbon atom its, Number of proton = 6
                           Number of neutrons = 6
                           Number of electron = 6
                           Atomic number (Z) = number of protons = number of electrons = 6
                           Mass number (A) = number of proton + number of neutrons = 6 + 6 =12

e.Moderator in nuclear reactor: Moderator of a nuclear reactor is a substance that slows down the speed of neutrons. In traditional nuclear reactors, the moderator is the same thing as that of coolant like water.

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Question 4:

Draw a neat lablled diagram
A. Ruthrford's scattering experiment
B. Thomson's atomic model
C. Diagramatic sketch of electronic configurations of magnesium  (Atomic number 12)
D. Diagramatic sketeh of electronic configuration of Argon (Atomic number 18)

ANSWER:

a. Rutherford's scattering experiment :

b. Thomson's atomic model

c. Diagramatic sketch of electronic configurations of magnesium  (Atomic number 12) :

 

d. Diagramatic sketeh of electronic configuration of Argon (Atomic number 18) :

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Question 5:

Fill in the blanks.
A. Electron, proton, neutron are the types of _________ in an atom.
B. An electron carries a _________charge.
C. The electron shell _____________ is nearest to the nucleus.
D. The electronic configuration magnesium is 2,  8,  2. From  this it is understood that the valence shell of magnesium is_____________
E. The valency of hydrogen is 'one as per the molecular formula H₂O . Therefore valency of 'Fe' turns out to be ______________ as per the formula Fe₂O₃. 

ANSWER:

a. Electron, proton, neutron are the types of subatomic particles in an atom.
b. An electron carries a negative charge.
c. The electron shell K is nearest to the nucleus.
d. The electronic configuration magnesium is 2,  8,  2. From  this it is understood that the valence shell of magnesium is M shell.
e. The valency of hydrogen is 'one as per the molecular formula H₂O . Therefore valency of 'Fe' turns out to be three as per the formula Fe₂O₃. 

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Question 6:

Match the pairs.

Group 'A'	Group 'B'
a. Proton	i.Negatively charged
b.Electron	2.Neutral
c.Neutron	3.Positively charged

ANSWER:

Match the pairs:

Group 'A'	Group 'B'
a.Proton	1.Positively charged
b.Electron	2.Negatively charged
c.Neutron	3.Neutral

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Nutrition in Living Organisms

Question 1:

Classify according to food-type.
tiger, cow, vulture, bacteria, deer, goat, human, fungus, lion, sparrow, buffalo, frog, cockroach, tick.

ANSWER:

tiger- carnivore 
cow- herbivore 
vulture- scavenger
bacteria- decomposers
deer- herbivore
goat- herbivore
human- omnivore
fungus- decopmosers
lion- carnivores
sparrow- herbivore
buffalo- herbivore
frog- carnivore
cockroach- carnivore
tick- parasite

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Question 2:

Match the pairs.
 

Group 'A'		Group 'B'
(1)	Parasitic plant	(a)	Mushroom
(2)	Insectivorous plant	(b)	Lichen
(3)	Saprophytic plant	(c)	Drosera
(4)	Symbiotic plant	(d)	Cuscuta

ANSWER:

Group 'A'		Group 'B'
(1)	Parasitic plant	(d)	Cuscuta
(2)	Insectivorous plant	(c)	Drosera
(3)	Saprophytic plant	(a)	Mushroom
(4)	Symbiotic plant	(b)	Lichen

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Question 3:

Answer the following questions in your own words.
(a) Why do living organisms need nutrition ?
(b) Explain the process of production of food in plants.
(c) What is meant by parasitic plants ? Name their different types with examples of each.
(d) Explain the various steps of nutrition in animals.
(e) Name some unicellular organisms in which all life-processes take place within their unicellular body.

ANSWER:

a. Nutrition is the process of uptake of nutrients from food and utilizing them for various functions of the cells. Nutrition is required for purposes like:

• supplying the energy required for doing work
• for growth and development of the body
• to fight diseases
• to replace the damaged cells and repair tissues

b. Leaves are the food factories of plants. They are the sites where the synthesis of food occurs in plants. The leaves of plants contain a green pigment called chlorophyll. This pigment captures the sun’s energy, which is used to prepare food from carbon dioxide and water. The process of synthesis of food using sunlight, carbon dioxide, and water is known as photosynthesis. During the process of photosynthesis, the leaves containing chlorophyll convert carbon dioxide and water into carbohydrates in the presence of sunlight. Carbohydrates, which are produced during photosynthesis, are ultimately converted into starch to be stored in plants.This process can be represented in the form of the following equation:

c. Cuscuta survives by growing on the body of another plant and deriving nutrients from this plant in the process. This mode of nutrition is known as parasitic mode of nutrition. Cuscuta is known as a parasite as it depends on another plant for its survival. The plant on which it grows is known as the host. Cuscuta can be seen around in the form of yellow tubular structures growing on the stems of other plants. It is devoid of leaves. Another such example of parasitic plants is Loranthus.


 d.  The various steps of nutrition in animals are:

• Ingestion − The process of taking in of food into the body is called ingestion. Ingestion of food in humans is done with the help of the buccal cavity. 
• Digestion − The process where conversion of food into soluble form occurs.
• Absorption − The nutrients from the digested food are absorbed in the small intestine with the help of finger-like projections called villi.
• Assimilation − The absorbed nutrients are transported via the blood vessels to the different organs, to be utilised for different life processes. 
• Egestion − The process of removal of faecal matter through the anus is called egestion. 

e. The unicellular organisms in which all life processes take place within their body are- Amoeba, Paramoecium and Euglena.

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Question 4:

Give reasons.
(a) Insectivorous plants are attractively coloured.
(b) Butterflies have a long tube-like proboscis.

ANSWER:

a. Insectivorous plants are attractively coloured so that they can attract insects and feed upon them. Insectivorous plants grow in soil or water which are deficient in nitrogen compounds and in order to meet this deficiency, they feed on insects.

b.  Butterflies have a long tube like proboscis which is a straw-like structure which enables them to drink juices and nectar. It is coiled-up like a garden hose when it is not in use.

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Question 5:

Prepare and complete the flowchart according to type of nutrition.

ANSWER:

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Question 6:

Think and answer.
(a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms ?
(b) Which organisms are greater in number - autotrophs or heterotrophs ? Why?
(c) The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why is this so ?
(d) What damage or harm do ectoparasitic and endoparasitic animals cause ?
(e) Why is plant food not produced in any other parts of the plant except the green ones ?

ANSWER:

a. By preparing variety of foodstuffs and dishes at home, we do not become autotrophic. Autotrophic is a term which is used for organisms which can produce their own food. We humans depend on plants for our food and the products which we get from them are used by us to make a variety of foodstuffs. Also, autotrophic organisms contain chloroplast which is an absolute necessity to be classified as an autotroph and we do not possess any such structures. So, we cannot be considered autotrophs.

b. Autotrophs are the organisms which are greater in number. It is because heterotrophs are dependant on autotrophs to meet their food requirements. If heterotrophs exceed the number of autotrophs, then all the autotrophs will vanish and so will be the heterotrophs. However, this is not the case because autotrophs are always more than heterotrophs so that they can help in sustaining the heterotrophs.

c. The conditions in deserts are extremely difficult for survival of organisms. Not all kinds of organisms can survive in such harsh climatic conditions, which means there are only few types of organisms which would be found in this region. Since, there are not many kinds of plants and animals which are found in this region, heterotrophs would not be able to survive and would die of starvation. That is why less heterotrophs are found in desert areas. However, in case of a habitat like sea, there are plenty of organisms which are found in region ranging from aquatic plants, to small fishes to big fishes. It is an environment which supports the survival of heterotrophs and thus more heterotrophs are found in this region.

d. Parasitism is a type interaction in which one of the partners is benefited because it resides outside or inside the body of the host and gets free accommodation and food while the host is affected due to loss of nutrients. Ectoparasites and endoparasites devoid the host of its nutrition. Some of the parasites are known to cause diseases like Ascaris/roundworm which is an endoparasite of intestine causes ascariasis. Another example is of Wuchereria which causes elephantiasis or filariasis. It is an endoparasite which lives in lymphatic vessels of lower limbs.
Lice or ticks which are found in humans and dogs respectively are examples of ectoparasites. They absorb the nutrients from their host.

e. Plant food is produced by a special process known as photosynthesis. The process of photosynthesis requires specialised structures called chloroplasts and these structures are found only in green regions of plants. The green colour of specific parts of plants is due to the presence of chlorophyll pigment present in these chloroplasts. Structures in plants which do not contain chloroplast, do not appear green in colour and are not capable of producing food.

Properties of Natural Resources

Question 1:

Fill in the blanks with the appropriate term.
(Temperature, volume, mass, density, humidity, acidic, weight, neutral, shape.)
(a) The capacity of air to hold moisture depends upon the ........... of the air.
(b) Water does not have a ........... but has definite ........... and ........... .
(c) While freezing, the ........... of water is lowered.
(d) ........... soil has pH 7.

ANSWER:

(a) The capacity of air to hold moisture depends upon the temperature of the air.
(b) Water does not have a shape but has definite mass and volume.
(c) While freezing, the density of water is lowered.
(d) Neutral soil has pH 7.

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Question 2:

Why is it said that –
(a) Air is a homogeneous mixture of various gases.
(b) Water is a universal solvent.
(c) There is no alternative to water for cleaning purposes.

ANSWER:

a. Air is a homogeneous mixture of gases as it is primarily made up of nitrogen and oxygen. Its elements are not readily separated or distinguished from one another.

b. Water is a very good solvent as it can dissolve almost every substance in it, therefore water is known as the “universal solvent”.

c. There is no alternative to water for cleaning purposes beacuse it dissolves everything that is added to it. The reason why it is called the universal solvent. The water dissolves all the dirt present in our clothes, the reason why we soak our clothes in detergent and water prior to washing. Also, water has a neutral pH which means it does not harm the object which has to be cleaned and also does not affect the skin.

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Question 3:

What will happen if....
(a) The amount of water vapour in the air increases.
(b) Only one crop is grown repeatedly

ANSWER:

a. The amount of water vapor in atmosphere determines the level of humidity. As the amount of water vapor in the atmosphere increases so does the level of humidity. Higher humidity levels result in excessive sweating and this sweat does not dry quickly leaving us feeling hot and sticky. 

b. If only one crop is grown repeatedly in the soil, it loses its fertility and gets devoid of nutrients. For this reason crop rotation is an important procedure, so that the fertility of the soil is retained and there is no loss of nutrients. For example, after cultivation of wheat, the fertility of soil decreases and thus leguminuos crops like peanut, moong etc. are cultivated after its harvest. These leguminous crops restore the fertility of soil.

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Question 4:

With whom should I pair up?
 

Group 'A'		Group 'B'
(1)	Air	(a)	Excretion
(2)	Water	(b)	Scattering of light
(3)	Soil	(c)	Plasticity

ANSWER:

Group 'A'		Group 'B'
(1)	Air	(b)	Scattering of light
(2)	Water	(a)	Excretion
(3)	Soil	(c)	Plasticity

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Question 5:

State whether the following statements are true or false.
(a) Sandy soil has low capacity for holding water.
(b) Sea water is a bad conductor of electricity.
(c) The substance in which a solute dissolves is called a solvent.
(d) The pressure exerted by air is called atmospheric pressure.

ANSWER:

(a) Sandy soil has low capacity for holding water.- False
(b) Sea water is a bad conductor of electricity.- False
(c) The substance in which a solute dissolves is called a solvent.- True
(d) The pressure exerted by air is called atmospheric pressure.- True

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Question 6:

Explain the picture in your own words.

ANSWER:

Image 'a' represents a crevice or crack which is filled with water wheras image 'b' represents a crevice which has ice. It is evident from both the images that in image 'b', the width of the crevice increases as the water in the crevice freezes. This is one of the properties of water due to which it expands upon freezing. This expansion in water after freezing results in the widening of the crack in image 'b'.

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Question 7:

Write answers to the following questions in your own words.
(a) How is light scattered by the air?
(b) Explain the various properties of water.
(c) Why is the density of seawater more than that of rain water?
(d) What is the importance of good soil structure?
(e) What are the various uses of soil?
(f) What is the need and importance of soil testing from the point of view of farmers?
(g) What is the importance of air in transmission of sound?
(h) Why should a glass bottle completely filled with water never be kept in a freezer?

ANSWER:

a. Scattering is the phenomenon of change in direction of light rays when they travel through Earth's atmosphere. Air is a mixture of gases, somke, dust and very fine particles. As the rays of light fall on these particles, these rays are spread/scattered in all directions. It is a natural phenomenon which is observed on our daily basis.


b. Properties of water: 

• Water is a colourless, tasteless, and transparent liquid. It also has no smell.
• Boiling point of pure water is 100°C at 760 mm of Hg pressure. However, boiling point of water increases due to increase in pressure and presence of dissolved impurities.
• Pure water freezes at 0°C at 760 mm of Hg pressure. However, freezing point of water decreases due to increase in pressure and presence of dissolved impurities.
• The state of water changes on heating or cooling. On heating, the state of water changes from liquid state to gaseous state (vapour). Similarly, on cooling, the state of water changes from liquid state to solid state (ice).
• Water is neither acidic nor basic. It is neutral.
• Water is a bad conductor of heat and electricity.
• Water is an universal solvent as it can dissolve many substances in it.

c. Sea water has more density than rain water because it contains salt ions. These salt ions make the seawater heavier, which means the mass of the water increases due to the presence of salt ions. From the relation, density= mass/volume, we can say that as the mass of an object increases, its density also increases simultaneously.


d. Soil stucture basically refers to the type of constituents and the ratio in which they are present in soil. The soil structure is important with respect to the growth of plants and the type of plantation which can occur in a particular area. Good soil structure has advantages like:

• roots get sufficient supple of oxygen
• it has good water drainage nad thus roots grow well

e. The following table represents the various types of soil: 

 

Soil type	Particle type	Properties
Sandy	Large	Loosely packed, with large air spaces. Water soaks into it easily. Thus it is dry, light and airy
Clayey	Fine, small	Tightly packed with no air spaces. This type of soil is heavy and holds more water.
Loamy/silt	A mixture of large and small particles	Holds water, contains humus.

f. Soil testing is a method of determining the constituents of soil.  A sample of soil is taken and is tested for its various characteristics for example, ph and electrical conductivity. It is important with respect to agricultural practices as it helps us in determining which crops can be grown in which region. It also gives us a knowledge about the deficient nutrients and this deficiency can then accordingly be dealt with. It is also useful in determining, if additional amounts of fertilizers are required.


g. Air acts as a medium for transmission of sound. When a sound wave passes through air, the particles of air vibrate back and forth, parallel to the direction of the sound wave. Thus, when a sound wave travels in the horizontal direction, then the particles of the medium also vibrate back and forth in the horizontal direction. Sound cannot travel without a medium and thus we cannot listen to sounds in the space because of absence of air. 


h. A glass bottle completely filled with water should not be kept in a freezer because the bottle can break and result in damage. We know that water expands after freezing and if a completely water filled glass bottle is placed in freezer, the water would freeze and would expand resulting in the bottle to break.

Std.8 Health and Diseases

Question 1:

Distinguish between- Infections and non infections diseases.
 

ANSWER:

Infectious diseases	Non infectious diseases
1. It can be passed from one person to another.	It cannot be passed from one person to another.
2. It is caused by a pathogen.	It is caused due to internal reasons like metabolic or genetic reasons.
3. They are classified as communicable disease.	They are classified as non communicable disease.
4. eg: diarrhoea, cholera, tuberculosis	eg: diabetes, hypertension, cancer

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Question 2:

Identity the odd term.
A. Malaria, hepatitis, elephantiasis, dengue.
B. Plague, AIDS, cholera, T.B.

ANSWER:

A. Malaria, hepatitis, elephantiasis, dengue- Hepatitis is the odd one out because it is a type of viral infection while the rest of three are spread through the bite of mosquitoes.
B. Plague, AIDS, cholera, T.B. - AIDS is the odd one out because it is a viral disease while the rest of them are bacterial diseases.

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Question 3:

Answer in one to two sentences.
A. Which are various media of spreading the infectious diseases ?
B. Give the names of five non-infections diseases other than given in the lesson.
C. Which are the main reasons of diabetes and heart diseases ?

 

ANSWER:

a. Infectious diseases can spread through air, water, blood to blood contact and animal vectors.

b. Non infectious diseases- arthiritis, cataract, osteoprosis, multiple sclerosis and Alzeimer's.

c. Reasons of heart diseases include smoking, alcoholism, diabetes, hypertension, obesity, lack of physical exercise, mental stress, anxiety and improper diet.

Reasons of diabetes include obesity, lack of physical exercise, mental stress, improper diet and hereditary.

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Question 4:

What can be achieved / can be prevented ?
A. Drinking boiled and filtered water.
B. Avoiding smoking and alcoholism.
C. Regular balanced diet and exercise.
D. Proper checking of blood before blood donation.

ANSWER:

a. Boiling and filteration are methods of purifying water which makes it suitable for consumption. Drinking boiled and filtered water can help in prevention of water borne diseases such as typhoid, cholera, etc. Most of the water borne diseases are transmitted through the consumption of contaminated water in some or the other form. 

b. Smoking and alcoholism are two of the devils of our health and society. Smoking leads to various kinds of respratory disorders and hinders the process of respiration. It can lead to diseases such as lung cancer. On the other hand, consumption of alcohol, effects the nervous as well as the digestive system of our body. Avoiding alcohol and smoking can protect indivisuals from various diseases and can help in living a healthy and stress free life.

c. Balanced diet and exercise are key to good health. Both of these in combination helps our systems to function properly, helps maintain a healthy weight, reduces body fat, provides the body with energy, promotes good sleep and makes us feel better about ourselves.

d. Proper checking of blood before blood donation is required to check that the blood to be transferred is safe in all respects. There are chances of transfer of infectious diseases form the donor, if he/she is suffering from any such diseases. Another important factor for checking of blood before donation is to check that the donor is not anemic (does not have anemia). 

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Question 5:

Read the passage and answer the questions.
Master 'X' is a 3 year old child. He is toiler with his family in a slum. Public toilet is present near his house. His father is drunkard. His mother does not know the importance of balanced diet.
A. Master 'X' can suffer from which different possible diseases in above conditions ?
B. How will you help him and hsi family in this situation ?
C. Which disease can occur to the father o master 'X' ?
 

ANSWER:

a. Since, the house of master X is near the toilet and he lives in a slum area, the chances are that there is less cleaniliness in that area. There are chances that he may suffer from diseases like salmonellosis, shigellosis, diarrhoea, trachoma, gastroenteritis, giardiasis, tapeworm infection and threadworm infection.

b. In this case, the famliy needs to be made aware about cleanliness in and around their houses. There is a need to explain them the importance of balanced diet for them and their child. Since, the father is a drukyard, he needs counselling and treatment to get rid of the habit of alcoholism.

c. The father of master X is a drunkyard which means he might suffer from diseases such as heart diseases, liver cirrhosis, ulcers and gastrointestinal ptoblems, brain damage etc.

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Question 6:

Give the preventive measures of following diseases.
A. Dengue
B. Cancer
C. AIDS

ANSWER:

 a. Dengue is a mosquito borne disease which is transmitted by Aedes mosquitoes which grow in clean and stagnant water. The breeding of this mosquito can be prevented by adopting the following steps:

• larve-eating fishes should be introduced in ponds
• collection and storage of water should always be done in closed vessels
• potted plants should have proper drainage to avoid collection of water in the pots
• pesticides should be used against mosquitoes as and when required

b. Preventive measures for cancer:

• have a healthy diet
• exercise regularly
• avoid smoking and alcohol
• 
  
• go for regular health checkups

c. Preventive measures for AIDS are:

• avoid sexual contact with unknown persons
• screening of blood before transfusion
• avoid sharing of needles

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Question 7:

Explain the importance.
A. Balanced diet.
B. Physical exercise / Yogasanas.

ANSWER:

a. A balanced diet is a diet containing all nutrients (carbohydrates, fats, proteins, vitamins, etc.) in the right quantities. A balanced diet helps us in various ways:

• provides us with important nutrients required for the growth of body
• helps us to stay fit and free from diseases
• helps in strengthening the immune system
• helps our systems to function properly
• helps maintain a healthy weight
• reduces body fat
• provides the body with energy
• promotes good sleep and makes us feel better about ourselves

b. Importance of exercise and yogasanas are:

• reduces the risk of heart attack
• helps in managing weight better
• helps in maintaining blood cholesterol level
• lowers the risk of type 2 diabetes and some cancers
• helps in maintaining the blood pressure levels
• helps in attaining stronger bones, muscles and joints and lowers the risk of osteoporosis
• boosts the energy levels, makes you feel relaxed

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Question 8:

Make a list.
A. Viral diseases.
B. Bacterial diseases.
C. Diseases spread through insects.
D. Hereditary diseases.
 

ANSWER:

Type of Disease	Example
Viral	Measels, Mumps, Swine flu, Chicken pox
Bacterial	Tuberculosis, Diptheria, Tetanus, Cholera, Typhoid
Insects	Dengue, Malaria, Plague
Hereditary	Diabetes, Hypertension, Cancer

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Question 9:

Write the information on modern diagnostics and treatments of cancer.
 

ANSWER:

Diagnostics of cancer:

There are many techniques whiich are used in the diagnosis of cancer and their application depends upon the type of cancer. Biopsy, histopathological studies of bone and blood, radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are used in diagnosis of cancer. Radiography, CT and MRI are the modern techniques used in cancer diagnosis.
Computed tomography uses X-rays to generate a three-dimensional image of the internals of an object. MRI uses strong magnetic fields and non-ionising radiations to accurately detect pathological and physiological changes in the living tissue.

Treatment of cancer:

Cancer is treated using 3 major approaches depending on the type of cancer. These 3 approaches are- surgery, radiotherapy and chemotherapy. In surgery, the tumor is removed surgically from its site and can be used in specific cases only. Radiotherapy is a technique in which the cancer cells are irradiated with radiations taking care of the normal tissues which surround the cancer cells.
Chemotherapy uses different kinds of drugs for the treatment of cancer. These chemotherapeutic drugs are specific for particular tumors and have side effects such as hair loss, anemia, etc.
Most of the cancers are treated by the combination of these 3 approaches.

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Question 10:

Enlist the names and composition of the medicines present at your home.

ANSWER:

The following medicines are found in our houses:

Paracip- Paracetamol/Acetaminophen
Digene-  Dried Aluminium Hydroxide, Magnesium Aluminium Silicate Hydrate, Magnesium Hydroxide, Simethicone
Volini- Diclofenac diethylamine BP, Linseed Oil BP (Oleum Lini), Methyl salicylate, Menthol IP, Benzyl Alcohol IP.
Vomikind- Ondansetron

Ch.5 Food safety (Std.7)

Question 1:

Complete the following statements by using the correct option from those given below.
(Irradiation, dehydration, pasteurization, natural, chemical)
(a) Drying the food grains from farms under the hot sun is called .......... .
(b) Materials like milk are instantly cooled after heating up to a certain high temperature. This method of food preservation is called .......... .
(c) Salt is a .......... type of food preservative.
(d) Vinegar is a .......... type of food preservative.

ANSWER:

(a) Drying the food grains from farms under the hot sun is called dehydration.
(b) Materials like milk are instantly cooled after heating up to a certain high temperature. This method of food preservation is called pasteurization.
(c) Salt is a natural type of food preservative.
(d) Vinegar is a chemical type of food preservative.

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Question 2:

Answer the following questions in your own words.
(a) How is milk pasteurized?
(b) Why should we not consume adulterated food materials?
(c) What precautions do your parents take to keep foodstuffs safe?
(d) How does food spoilage occur? Which are the various factors spoiling the food?
(e) Which methods of food preservation would you use?

ANSWER:

a. Milk is pasteurised in order to kill any kind of harmful microorganism present in it and to increase its shelf life. Pasteurisation is a process in which the milk is heated to a certain temperature for a fixed period of time and then is quickly cooled. For example, it may be heated at 80^oC for 15 minutes and then immediately cooled. This helps to kill any kind of microorganism which is present in milk. 

b. The process of substituting or concealing the quality of food, adding harmful or poisonous substances to food, and misbranding or giving false labels to food is known as food adulteration. the adulterants which are added to food products have harmful effects on our bodies. For example:

• vegetable oil is adulterated with cheaper and non-edible oils such as argemone oil which causes dropsy, which in turn leads to renal and cardiac failure.
• pulses are mixed with kesari dal or with metanil yellow to improve the colour which can cause carcinogenic disorder and it can also affect the nervous system.

We should be very careful in buying our food products and should be aware of our rights and actions which can be taken against people who are involved in this crime.

c. Precautions which are taken to preserve foods:

1. Storing fruits and vegetables in proper storage, for example, fruits like bananana are not stored in refrigerator while fruits like mangoes require refrigerator.
2. Storing grains, dals etc. in dry conditions and in air proof containers.
3. Making pickles and jams to increase their shelf life.

d. The undesirable or disagreeable change in the state of food which makes it unsuitable for human and animal consumption is termed as food spoilage. Spoilage of food can be caused by various factors like:

• Microorganisms: Growth of microorganisms like bacteria, fungi etc. can lead to spoilage of food. 
• Action of enzymes: Enzymes which are an inherent part of plant and animal tissue begin the decomposition process after the death of plant or animal. For example, a bananana starts to ripen and then spoil if it is not consumed on time.
• Infestation by insects: Insects like cockroaches may infest the food stuff and make them unsuitable for consumption. There is possiblity of transmission of pathogens from these insects.
• Wrong handling of products may also result in the spoilage of foodstuffs.
• Overcooking is another such reason for spoilage of foods.

e. The following methods of food preservation can be used:

• Preservation by common salt: Common salt is usually used to preserve meat and fish as it checks the growth of bacteria in these foods. It is also used to preserve amla, raw mangoes, and tamarind.

• Preservation by sugar: Sugar is usually used to preserve jam, jellies, and squashes. Sugar prevents spoiling of food by reducing the moisture content of food, which inhibits the growth of bacteria in it.

• Preservation by oil and vinegar: Oil and vinegar are used to preserve vegetables, fruits, fish, and meat. They prevent food from getting spoilt as micro-organisms cannot grow in such an environment.

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Question 3:

What shall we do?
(a) There are vendors selling uncovered sweetmeats in open places in the market.
(b) A 'pani-puriwalla' is serving the pani puri with dirty hands.
(c) We have purchased a large quantity of fruits and vegetables.
(d) We need to protect foodstuffs from pests like rats, cockroaches, wall-lizards, etc.

ANSWER:

a. We should not eat food from vendors who sell uncovered foods. We should try to talk to him and convince him to keep his food covered while selling it. Also, we should tell him the importance of clean and healthy food and how these habits can help him to gain profit for his business.

b. If a pani puriwalla is serving the pani puri with dirty hands, then we should not consume it. We sholud insist him to wash his hands and wear gloves while serving the pani puris.

c. If we have purchased large amounts of fruits and vegetables, then we need to store them properly. Some of the fruits can be used to make juices, jams and jellies which would increase their shelf life and also make it easy to store food. Vegetables can be cut and stored in deep freezers and then used as and when required. Some vegetables can also be used in making pickles.

d. Foodstuffs can be protected from rats, cockroaches etc. by storing them in proper conditions and proper areas. They should be stored in air tight containers and away from damp places which are the breeding places for these organisms.

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Question 4:

Find the odd-man-out.
(a) salt, vinegar, citric acid, sodium benzoate
(b) lakhi dal, brick dust, metanyl yellow, turmeric powder
(c) banana, apple, guava, almond
(d) storing, freezing, settling, drying

ANSWER:

(a) salt, vinegar, citric acid, sodium benzoate- salt is the odd one out beacuse it is natural preservative while rest of them are chemical preservatives.

(b) lakhi dal, brick dust, metanyl yellow, turmeric powder - turmeric powder is the odd one out because it is a type of spice while the rest of the three are adulterants.

(c) banana, apple, guava, almond- almond is the odd one our because it is a dry fruit whereas the rest of the three are fresh fruits..

(d) storing, freezing, settling, drying- settling is the odd one out because rest of the three are preservation methods.
 

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Question 5:

Complete the chart below.
 

S.No.	Foodstuff	Adulterant
1.	----------	Metanyl yellow
2.	Black pepper	----------
3.	----------	Iron filings
4.	Honey	----------

ANSWER:

S.No.	Foodstuff	Adulterant
1.	Turmeric powder	Metanyl yellow
2.	Black pepper	Papaya seeds
3.	Rava	Iron filings
4.	Honey	Sugar

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Question 6:

Explain why this happens and suggest possible remedies.
(a) Qualitative wastage of food.
(b) The cooked rice is underdone.
(c) The wheat that was bought is a bit moist.
(d) The taste of yoghurt is too sour/slightly bitter.
(e) Cut fruits have turned black.

ANSWER:

a. Wastage of food can either be qualitative or quantitative. Qualitative wastage of food is caused by:

• excessive use of preservatives
• over cooking of food
• washing vegetables after cutting them
• using wrong methods of protecting food
• mishandling of food products like fruits etc.

Qualitative wastage of food can be prevented by adopting steps like controlling the use of peservatives, taking care while cooking food to prevent it from being overcooked or undercooked, using proper methods of storage etc.

b. If the cooked rice is underdone, it can be used to make some foodstuff in which it can be reused. For example, underdone rice can be used to prepare kheer in which it can be cooked further with milk, or it can further be cooked to make papads or something else which would avoid its wastage.

c. If the wheat which was brought was little moist, it could be dried under the sun to remove this moisture. It is important to remove this moisture before grinding the wheat or storing it because it can act as a factor for the growth of microorganisms leading to its spoilage.

d. The taste of yoghurt could turn a little sour because it has undergone too much fermentation. The first thing would be to store this yoghurt in cold environment to stop further souring of the yoghurt. This yoghurt can then be used to make sweet lassi or some other delicacy like sindhi curry. 

e. Cut fruits turn black due to oxidation. Small amount of lemon juice should be applied to the surface of cut fruits as it prevents the oxidation of the fruits. 

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Question 7:

Give reasons.
1. Food remains safe at 5° Celsius.
2. Nowadays, food is served buffet style during large gatherings.

ANSWER:

a. Food remains safe at 5^oC because this temperature prevents the growth of microorganisms. Microorganisms usually require hot and humid places to grow whereas at this temperature they cannot grow and survive. Their metabolic activities are inhibited at this temperature.

b. Nowadays, foods are served in buffet style during large gatherings to prevent the wastage of food. Every indivisual can choose what to eat and how much to eat according to their wish and thus prevents the wastage of food.