Std.V. Problem Set No.16

Know thy students.......

Class V/D conducted a special assembly to mark the birth anniversary of Mahatma Gandhi.

The assembly started with an inspirational story from gandhijis life.

Krisha Thakkar shared a story and Christry Elisha shared Gandhijis message.

[ "The best way to find yourself is to lose yourself in the service of others.”

A very apt quote said and practiced by Mahatma Gandhiji.] 

100% Attendance.(60/60)

     

    Image Credit:Joyce Mendonca  V/D

Students shared their online learning journey so far along with their hobbies, Special achievements etc.

To my utter surprise, Aabha Bedekar has completed reading most of the books written by Sudha Murty ji.

It was really inspirational for all of us.

Finally, the better we know our students, the better we can help craft learning experiences that match who they are. Knowing our students is fundamental to real differentiation.

Thank you Sister for this opportunity...

Std.V Problem Set No.15 Division

Std.X Ch.2. Periodic Classification Of Elements (Q&A)

Question 1:

Rearrange the columns 2 and 3 so as to match with the column 1.

Column 1	Column 2	Column 3
i. Triad ii. Octave iii. Atomic number iv. Period v. Nucleus vi. Electron	a. Lightest and negatively charged particle in all the atoms b. Concentrated mass and positive charge c. Average of the first and the third atomic mass d. Properties of the eighth element similar to the first e. Positive charge on the nucleus f. Sequential change in molecular formulae	1.Mendeleev 2. Thomson 3. Newlands 4. Rutherford 5. Dobereiner 6. Moseley

ANSWER:

Rearrange the columns 2 and 3 so as to match with the column 1.

Column 1	Column 2	Column 3
i. Triad ii. Octave iii.Atomic number iv. Period v. Nucleus vi. Electron	a. Average of the first and the third atomic mass b. Properties of the eighth element similar to the first c. Positive charge on the nucleus d. Sequential change in molecular formulae  e. Concentrated mass and positive charge f.  Lightest and negatively charged particle in all the atoms	1.  Dobereiner 2.  Newlands 3.  Mendeleev 4.  Moseley 5.  Rutherford 6.  Thomson

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Question 2:

Choose the correct option and rewrite the statement.
a. The number of electrons in the outermost shell of alkali metals is .....
(i) 1 (ii) 2 (iii) 3 (iv) 7
b. Alkaline earth metals have valency 2. This means that their position in the modern periodic table is in ....
(i) Group 2      (ii) Group 16
(iii) Period 2    (iv) d-block
c. Molecular formula of the chloride of an element X is XCl. This compound is a solid having high melting point. Which of the following elements be present in the same group as X.
(i) Na  (ii) Mg  (iii) Al  (iv) Si
d. In which block of the modern periodic table are the nonmetals found?
(i) s-block       (ii) p-block
(iii) d-block    (iv) f-block

ANSWER:

Choose the correct option and rewrite the statement.
a. The number of electrons in the outermost shell of alkali metals is 1.

b. Alkaline earth metals have valency 2. This means that their position in the modern periodic table is in group2.

c. Molecular formula of the chloride of an element X is XCl. This compound is a solid having high melting point. An element to be present in the same group as X is Na.

d. In p-block of the modern periodic table are the nonmetals found.

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Question 3:

An element has its electron configuration as 2, 8, 2. Now answer the following question.
a. What is the atomic number of this element?
b. What is the group of this element?
c. To which period does this element belong?
d. With which of the following elements would this element resemble? (Atomic numbers are given in the brackets)
N(7), Be(4), Ar(18), Cl(17)

ANSWER:

An element has its electron configuration as 2, 8, 2.
a. The atomic number of this element is 12.
b. The group  number of this element is second.
c. This element belongs to third period.
d. This element resembles with Be(2).

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Question 4:

Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
a. ₃Li, ₁₄He, ₁₁Na, ₁₅P Which of these elements belong to be period 3?
b. ₁H, ₇N, ₂₀Ca, ₁₆S, ₄Be, ₁₈Ar Which of these elements belong tot he second group?
c. ₇N, ₆C, ₈O, ₅B, ₁₃Al Which is the most electronegative element among these?
d. ₄Be, ₆C, ₈O, ₅B, ₁₃Al Which is the most electropositive element among these?
e. ₁₁Na, ₁₅P, ₁₇Cl, ₁₄Si, ₁₂Mg Which of these has largest atoms?
f. ₁₉K, ₃Li, ₁₁Na, ₄Be Which of these atoms has smallest atomic radius?
g. ₁₃Al, ₁₄Si, ₁₁Na, ₁₂Mg, ₁₆S Which of the above elements has the highest metallic character?
h. ₆C, ₃Li, ₉F, ₇N, ₈O Which of the above elements has the highest nonmetallic character?

ANSWER:

a. ₃Li, ₁₄He, ₁₁Na, ₁₅P
Electronic configuration of the following elements is:
₃Li = 2,1
₁₄He =2,8,4
₁₁Na = 2,8,1
₁₅P = 2,8,5
₁₄He, ₁₁Na, ₁₅P belong to the third period because according to their electronic configuration, each element contains three shell i.e. K,L,M.

b. ₁H, ₇N, ₂₀Ca, ₁₆S, ₄Be, ₁₈Ar
Electronic configuration of the following elements is:
₁H = 1
₇N = 2,5
₂₀Ca = 2,8,8,2
₁₆S = 2,8,6
₄Be = 2,2
₁₈Ar = 2,8,8
₂₀Ca, ₄Be belong to second group because these elements have 2 electrons in its outermost shell.

c. ₇N, ₆C, ₈O, ₅B, ₁₃Al
Electronic configuration of the following elements is:
₇N =2,5
₆C = 2,4
₈O = 2,6
₅B = 2,3
₁₃Al = 2,8,3
₈O is the most electronegative element among these because electronegativity increases as we move from left to right in a period of the periodic table.

d. ₄Be, ₆C, ₈O, ₅B, ₁₃Al
Electronic configuration of the following elements is:
₄Be = 2,2 
₆C = 2,4 
₈O = 2,6
₅B = 2,3
₁₃Al = 2,8,3
₁₃Al is the most electropositive element among these because ₄Be, ₆C, ₈O, ₅B belong to same period, but ₁₃Al belong to next period. According to the trend, electropositive character of an elements increases as we move from top to bottom in a group of the periodic table. This happens as the tendency of an atom to lose electrons increases due to decrease in nuclear charge and increase in numbers of shell.

e. ₁₁Na, ₁₅P, ₁₇Cl, ₁₄Si, ₁₂Mg
Electronic configuration of the following elements is:
₁₁Na = 2,8,1
₁₅P = 2,8,5
₁₇Cl = 2,8,7
₁₄Si = 2,8,4
₁₂Mg = 2,8,2
₁₁Na has largest size among these because according to the trend, atomic radius decreases as we move from left to right in a period of the periodic table. The atomic number of elements increases which means the number of protons and electrons in  the atoms increases. Due to large positive charge on the nucleus, the electrons are pulled closer to the nucleus and the size of atom decreases.

f. ₁₉K, ₃Li, ₁₁Na, ₄Be
Electronic configuration of the following elements is:
₁₉K = 2,8,8,1
₃Li = 2,1
₁₁Na = 2,8,1
₄Be = 2,2
₄Be has smallest atomic radius because ₁₉K, ₃Li, ₁₁Na are present in same group 1 but Be is present in group 2. According to the trend, as we move from left to right atomic size of an atoms decreases. Due to large positive charge on the nucleus, the electrons are pulled closer to the nucleus and the size of atom decreases.
 .
g. ₁₃Al, ₁₄Si, ₁₁Na, ₁₂Mg, ₁₆S
Electronic configuration of the following elements is:
3Al = 2,8,3
₁₄Si = 2,8,4
₁₁Na = 2,8,1
₁₂Mg = 2,8,2
₁₆S = 2,8,6
₁₁Na has the highest metallic character because metallic character of an elements decreases as we move from left to right in a modern periodic table. This happens as the tendency of an atom to lose electrons decreases due to gradual increase in the number of protons and nuclear charge.

h. ₆C, ₃Li, ₉F, ₇N, ₈O
Electronic configuration of the following elements is:
₆C = 2,4
₃Li = 2,1
₉F = 2,7
₇N =  2,5
₈O = 2,6
₉F has the highest nonmetallic character because  non-metallic character of an elements increases as we move from left to right in a period of the periodic table. This happens as the tendency of an atom to gain electrons increases due to increase in nuclear charge, the valence electrons are pulled in strongly by the nucleus and it becomes easier for an atom to gain electrons.
.

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Question 5:

a. The atom having the smallest size.
b. The atom having the smallest atomic mass.
c. The most electronegative atom.
d. The noble gas with the smallest atomic radius.
e. The most reactive nonmetal.

ANSWER:

a. The atom having the smallest size = Hydrogen (H)
b. The atom having the smallest atomic mass = Hydrogen (H)
c. The most electronegative atom = Fluorine (F)
d. The noble gas with the smallest atomic radius = Helium (He)
e. The most reactive nonmetal = Fluorine (F)

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Question 6:

Write short notes.
a.  Mendeleev’s periodic law.
b.  Structure of the modern periodic table.
c.  Position of isotopes in the Mendeleev’s and the modern periodic table.

ANSWER:

a.  Mendeleev’s periodic law.

• According to Mendeleev’s Periodic Law, “Physical and chemical properties of elements are periodic function of their atomic masses”.
• Mendeleev classified elements according to their atomic masses and arranged these elements in increasing order of  their atomic masses.
• Mendeleev classified periodic table into horizontal rows and vertical coloumns. The horizontal rows are called as periods and vertical columns are called groups. Mendeleev’s Periodic Table contains seven horizontal rows and nine vertical columns.
• The elements with similar properties comes into same group.
• Mendeleev also left gaps in his periodic table for undiscovered elements like aluminum, silicon and Boron in his periodic table and named them Eka-Aluminium, Eka-silicon and Eka-Boron.
• Mendeleev not only predicted the existence of Eka-Aluminium, Eka-silicon and Eka-Boron but also described the general physical properties of these elements.
• These elements discovered later and named as Gallium, Germanium and Scandium.
• Mendeleev's periodic table could predict the properties of several elements on the basis of their position in the periodic table.
• Mendeleev's periodic table could accomodate noble gases when they were discovered.

Demerits of Mendleev's periodic table:

• The position of isotopes could not explained.
• Wrong order of atomic masses of some elements could not be explained.
• Position of Hydrogen could not be assigned in a periodic table.

b.Structure of the modern periodic table:

Periodic Table: It is the table of chemical elements arranged in order of atomic number such that elements with similar atomic structure appear in the vertical columns.
The Modern periodic law states that The chemical and physical properties of elements are a periodic function of their atomic numbers. Modern periodic table is based on the modern periodic law. 

Main features:

• Groups - There are 18 vertical columns in the periodic table. Each column is called a group. All elements in a group have similar chemical and physical properties because they have the same number of valence electrons.
• Periods - In periodic table elements are arranged in a series of rows. Elements of the same period have the same number of electron shells.

Classification of elements:

• Group 1 contains alkali metals (Li, Na, K, Rb, Cs and Fr).
• The alkaline earth metals are metallic elements found in the group 2 of the periodic table. 
• Elements present in groups 3 to 12 in the middle of the periodic table are called transition elements. In the transition elements, valence electrons are present in more than one shell.
• Group 18 on extreme right side position contains noble gases ( He, Ne, Ar, Kr, Xe and Rn ). Their outermost shell contains 8 electrons except He as its outermost shell is K shell and it can hold only 2 electrons. 
• Inner transition elements:
  1. 14 elements with atomic numbers 58 to 71 (Ce to Lu) are called lanthanides  and they are placed along with the element lanthanum (La), atomic number 57 in the same position (group 3 in period 6) because of very close resemblance between them.
  2. 14 elements with atomic numbers 90 to 103 (Th to Lr) are called actinides and they are placed along with the element actinium (Ac), atomic number 89 in the same position (group 3 in period 7) because of very close resemblance between them.

c.Position of isotopes in the Mendeleev’s and the modern periodic table:
Isotopes: Isotopes are the atoms having same atomic number but different atomic masses.
Therefore, according to Mendeleev’s classification these should be placed at different places depending upon their atomic masses.
For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties. So this was drawback of Mendeleev's periodic table as he could not explained the position of isotopes.
Modern periodic table is based upon arrangement of the elements on the basis of their atomic number. So that, all the isotopes of hydrogen should be placed at same place depending upon their atomic number.

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Question 7:

Write scientific reasons.
a. Atomic radius goes on decreasing while going from left to right in a period.
b. Metallic character goes on decreasing while going from left to right in a period.
c.  Atomic radius goes on increasing down a group.
d.  Elements belonging to the same group have the same valency.
e. The third period contains only eight elements even through the electron capacity of the third shell is 18 .

ANSWER:

a. Atomic radius goes on decreasing while going from left to right in a period because atomic number of the elements increases which means the number of protons and electrons in the atoms increases(the extra electrons being added to the same shell). Due to large positive charge on the nucleus, the electrons are pulled closer to the nucleus and the size of an atom decreases.

b. Metallic character goes on decreasing while going from left to right in a period because the tendency of atoms of the elements to lose electrons(or gain  electrons) changes in a period. As we move from left to right in a period, the nuclear charge increases due to gradual increase in the number of protons. Due to the increase in nuclear charge, the valence electrons are pulled strongly by the nucleus and it becomes difficult for the atoms to lose electrons. Hence, metallic character decreases.

c. Atomic radius increases as we move from top to bottom in a group of the periodic table because a new shell of electrons is added to the atoms at every step. As the number of shells in the atoms increases gradually due to which the size of atoms also increases. As the size of the atoms increases which leads to increase in atomic radius of an atom.

d. Elements belong to the same group have the same valency because the number of valence electrons in a group is same due to which the tendency of an atom to lose or gain electrons in order to attain nearest noble gas configuration is also same.

e. The third period contains only eight elements even through the electron capacity of the third shell is 18 because when the other shells get filled and the resultant no of electrons becomes eighteen, it gets added up and settles in the third electron shell and three shells is acquired by fourth period.

 

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Question 8:

Write the names from the description.
a. The period with electrons in the shells K, L and M.
b. The group with valency zero.
c. The family of nonmetals having valency one.
d. The family of metals having valency one.
e. The family of metals having valency two.
f. The metalloids in the second and third periods.
g. Nonmetals in the third period.
h. Two elements having valency 4.

ANSWER:

a. The period with electrons in the shells K, L and M = 3 period
b. The group with valency zero = 18 group
c. The family of nonmetals having valency one = Halogens
d. The family of metals having valency one = Alkali metals
e. The family of metals having valency two = Alkaline earth metals
f. The metalloids in the second and third periods = Boron( second period), Silicon (third period)
g. Nonmetals in the third period = Sulphur, Chlorine
h. Two elements having valency 4 = Carbon, Silicon

Credit:meritnation.com

Std.VII- Motion,Force and Work (Question&Answers)

Question 1:

Fill in the blanks with the proper words from the brackets.
(stationary, zero, changing, constant, displacement, velocity, speed, acceleration, stationary but not zero, increases)
(a) If a body traverses a distance in direct proportion to the time, the speed of the body is ............... .
(b) If a body is moving with a constant velocity its acceleration is .......... .
(c) .............. is a scalar quantity.
(d) ............. is the distance traversed by a body in a particular direction in unit time.

ANSWER:

(a) If a body traverses a distance in direct proportion to the time, the speed of the body is constant.
(b) If a body is moving with a constant velocity its acceleration is zero.
(c) Speed is a scalar quantity.
(d) Velocity is the distance traversed by a body in a particular direction in unit time.

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Question 2:

Observe the figure and answer the questions.

Sachin and Sameer started on a motorbike from place A, took the turn at B, did a task at C, travelled by the route CD to D and then went on to E. Altogether, they took one hour for this journey. Find out the actual distance traversed by them and the displacement from A to E. From this, deduce their speed. What was their velocity from A to E in the direction AE? Can this velocity be called average velocity?

ANSWER:

.

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Question 3:

From the groups B and C, choose the proper words, for each of the words in group A.
 

A	B	C
Work	Newton	erg
Force	Metre	cm
Displacement	Joule	dyne

ANSWER:

A	B	C
Work	Joule	erg
Force	Newton	dyne
Displacement	Metre	cm

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Question 4:

A bird sitting on a wire, flies, circles around and comes back to its perch. Explain the total distance it traversed during its flight and its eventual displacement.

ANSWER:

The total distance travelled by the bird during its flight = 2×$\times$(Distance between the point where the bird was sitting and the point from where it takes a turn)
The eventual displacement of the bird is zero as it returns to its initial point i.e. where it was sitting.

Textbook Page No 50:

Question 5:

Explain the following concepts in your own words with everyday examples : force, work, displacement, velocity, acceleration, distance.

ANSWER:

Force: It is any kind of push or pull on a body due to another body when the bodies interact with each other. It is a vector quantity. For example, a person applies a force in the form of push or pull to open a door.

Work: It is defined as the work done by a force that causes a displacement in an object. It is a scalar quantity. For example, a child does work when he drags a toy car on the ground.

Displacement: It is the shortest distance between the initial and final position of an object. It is a vector quantity. For example, when we go to a mall for shopping from our house and then return to the house, the displacement would be 0 as our initial position (house) and final position (house) is same.

Velocity: Velocity is defined as the rate of change of displacement. It is a vector quantity. For example, a car running on a straight road has some velocity.

Acceleration: The rate of change of velocity is known as acceleration. It is a vector quantity. For example, if a car is moving on a straight with variable speed, it will posses some acceleration. In case the speed of the car remains same bu

 the direction of car changes, then also the car would be accelerating.

Distance: It is the actual path length covered by an object during its motion. It is a scalar quantity.  For example, when we go to a mall for shopping from our house and then return to the house, the distance travelled by us would be twice the distance between our house and the mall.

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Textbook Page No 50:

Question 7:

Solve the following problems.
(a) A force of 1000 N was applied to stop a car that was moving with a constant velocity. The car stopped after moving through 10 m. How much is the work done?
(b) A cart with mass 20 kg went 50 m in a straight line on a plain and smooth road when a force of 2 N was applied to it. How much work was done by the force?

ANSWER:

(a) Work done by the force to stop the car=

F×S=1000×10=10000 J $\mathrm{Work} \mathrm{done} \mathrm{by} \mathrm{the}$

$\mathrm{force} \mathrm{to} \mathrm{stop} \mathrm{the} \mathrm{car}=F\times S=1000\times 10=10000 \mathrm{J}$

(b) Work done by the force=F×S=2×50=100 J$\mathrm{Work} \mathrm{done} \mathrm{by} \mathrm{the} \mathrm{force}=F\times S=2\times 50=$100 J

Std.7 Science Ch.5.Food Safety

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 do 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.

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) How is milk pasteurized?

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) Why should we not consume adulterated food materials?
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) What precautions do your parents take to keep foodstuffs safe?
Answer: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) How does food spoilage occur? Which are the various factors spoiling the food

Ans:. 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) Which methods of food preservation would you use?
Answer: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.

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.

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.
 

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. 

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.

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Problem set No.14

Word Problems: