1st term –
2023-24
Class – 7th
Subject – G. Science
Marks- 50
Q. 1. A)
Fill in the blanks with the proper word from the brackets. - 10
(pasteurization, temperature, acceleration, copper, radiation, white, always repulsion, conduction, zero, black, natural, conductivity, speed, humidity, charged object, chemical, displacement of negatively charge, velocity, dehydration)
1. Salt is a natural type of food preservative.
2. The capacity of air to hold
moisture depends upon the humidity of the air.
3. Maximum heat is absorbed by a black coloured object.
4. Speed is a scalar quantity.
5. There is always repulsion between like charges.
6. Materials like milk are
instantly cooled after heating up to a certain high temperature. This method of
food preservation is called pasteurization.
7. The earth receives heat from
the sun by radiation.
8. A lightning conductor is
made of a copper strip.
9. Cooking utensils are
made from metals due to their property of conductivity.
10. If a body is moving with a
constant velocity its acceleration is zero.
11. Vinegar
is a chemical type of food preservative.
12. Displacement of negatively charge is responsible for generation of electric charge in an object.
13. A charged object can be detected with an electroscope.
14. Drying the food grains from farms under the hot sun is called dehydration.
15. Velocity is the distance traversed by a body in a particular direction in unit time.
B) Find my
match ! ( any
5) -
5
‘A’
Group ‘B’
Group
1. Mass a.
kilogram/cubic metre
2. Density b. Plasticity
3. Insectivorous
plant c. square metre
4. Soil d.
Drosera
5. Velocity e.
litre
6. Area f.
kilogram
7. Volume g.
metre/second
Answer:
1. Mass - f. kilogram
2. Density -
a.
kilogram/cubic metre
3. Insectivorous plant - d. Drosera
4. Soil - b. Plasticity
5. Velocity - g. metre/second
6. Area - c. square metre
7. Volume - e. litre
C) Find the
odd man out. – 5 ( any
5) -
5
1. banana, apple, guava, almond. - almond
2. Washing away of crops, attack
of pests on crops, volcano, singeing of crops. - volcano
3. storing, freezing, settling,
drying. - settling
4. Famine, earthquake,
cloudburst, railway accident. - railway accident
5. Drought, heavy rains, storm,
tsunami. - Drought
6. Lava, hot mud, ash, locusts. - locusts
7. salt, vinegar, citric acid,
sodium benzoate. - salt
8. lakhi dal, brick dust, metanyl
yellow, turmeric powder. - turmeric powder
D) True or
false? ( any
5) - 5
1. Sandy soil has low capacity
for holding water. - True
2. Heavy rains result in famine. - True
3. You should not swim when there
is lightning in the sky. - False
4. It is possible to prevent the
eruption of a volcano. - False
5. The substance in which a
solute dissolve is called a solvent. - True
6. Information about a
forthcoming storm is to be kept secret. - False
Q.2.A) What
will absorb heat? - ( any
3) - 3
|
Object |
Yes/ No |
Object |
Yes/ No |
|
1. Steel spoon |
Yes |
2. wooden board |
No |
|
3. glass |
Yes |
4. iron griddle (tava) |
Yes |
|
5. plastic plate |
No |
|
|
B) Complete
the following table. ( any
3) - 3
|
Sr. No. |
Foodstuff |
Adulterant |
|
1. |
Turmeric powder |
Metanyl yellow |
|
2. |
Black pepper |
Seeds of papaya |
|
3. |
Rava |
Iron Filings |
|
4. |
Honey |
Water of jaggery |
|
5. |
Milk |
Water, urea |
|
6. |
Ice cream |
washing powder, paper
pulp |
|
7. |
Red chilly powder |
Brick powder |
(a) earthquake : An earthquake is the sudden release of strain energy in the Earth's crust, resulting in waves of shaking that radiate outwards from the earthquake source. e.g. 30 sept.1993 in latur(maharashtra).
(b) Vector quantity : Vector
quantity is expressed completely only when magnitude and direction are both
given. e.g.
(1) (i) The displacement of
20 kilometres to the North and (ii) Displacement of 20 kilometres to the East
is different from each other. Here the distance is same but the direction of
the displacement is different from each other.
(c) Scalar quantity : Scalar quantity is completely expressed by its magnitude alone. e.g., length, breadth, area, mass, temperature, density, time, work, etc. In scalar quantity only magnitude, i.e. a value with a unit, is used to express it.
Q. 3. A) Write answers to the following questions. ( any 4) - 8
1. Name some unicellular
organisms in which all life-processes take place within their unicellular body.
Ans: Amoeba,
Euglena and Paramoecium are the unicellular organisms in which all the life
processes take place within a single cell.
2. What are the modes of heat
transfer ?
Ans: Heat
is transferred by conduction, convection and radiation.
3. How are charges generated?
Ans: When
two objects are rubbed against each other, the negative charge on one of the
object is transferred to other object. Making the second object to acquire
negative charge. The first object becomes positively charged due to loss of
negative charge.
4. How is milk pasteurized?
Ans: The
milk is heated up to 80 °C for 15 minutes and then cooled it quickly. This
destroys the microbes present in the milk and then it can be stored for a
longer time.
5. Which are the various factors
spoiling the food?
Ans: (1)
The wrong and careless transportation of the food stuffs from the farm to the
customer can cause food spoilage. (2) Improper handling, storage and
transportation leads to major spoilage. (3) Some food stuffs have intrinsic
factors which makes them perishable. Milk, meat etc. have acidic or alkaline
contents which get spoiled soon. (4) Chemical reactions occur in the food. Some
are reactive to the metals and this results into production of harmful
compounds. (5) Micro- organisms from surrounding air, water and land enter the
food and cause their deterioration. Insects also attack and food and such
infested food is bad for health.
6. Why are the houses in
Rajasthan painted white ?
Ans: In
Rajasthan, atmospheric air temperature is very high in summer. White colour
reflects most of the sun's incident radiant heat. Moreover, absorption of heat
by white colour also is very little, as a result houses do not get heated up.
Therefore, houses in Rajasthan are painted white.
B)
Give scientific reasons. ( any 3) -6
1. Dew drops form on the grass,
in winter.
Ans: There
is a water vapour in the air. The water holding capacity of the air depends
upon the temperature. In winter, when the temperature falls down, the water
holding capacity also comes down. If temperature recedes much more, then the
water vapour condenses and the dew drops are formed.
2. In winter, an iron pillar feel
colder than a wooden pole.
Ans: Iron
is a good conductor of heat. Wood is a bad conductor of heat. In winter, the
body temperature is more than the surrounding temperature. At such time, if we
touch the iron pillar, there is a conduction of heat from our body to the iron
pillar. Therefore we feel that iron pillar is cold. But when we touch a wooden
pole, the conduction of heat does not take place and hence we do not feel that
the wooden pole is cold.
3. It is not proper to measure
quantities by using body parts as units.
Ans: The
measurement of body parts for every person will be different. There is no standardization
of any kind. Therefore, it is not proper to measure quantities by using body parts.
4. Food remains safe at 50 Celsius.
Ans: In
cold temperature of 5 °Celsius the reactions caused by micro-organisms do not
take place. Bacteria, fungi which spoil the food are inactive at such less
temperatures. Therefore, food stuffs remain safe at this this temperature.
5. Nowadays, food is served
buffet style during large gatherings.
Ans: Buffet
style is introduced to prevent the food wastage and save the food. People are
expected to take the amount of food that they can consume. The traditional
method of serving the food results into wastage and hence nowadays, food is
served buffet style during large gatherings.
6. Butterflies have a long
tube-like proboscis.
Ans: Every
insect is provided with mouth parts for ingestion. It feeds on nectar and
pollen from the flowers. It thus has a tube like proboscis to suck this food
from flower.
C) Complete
the
table. -
3
|
Quantity |
Name of the unit |
Symbol of the unit |
|
1. Length |
metre |
m |
|
2. Mass |
kilogram |
kg |
|
3. Time |
second |
s |
