Answers of Class 7 FA Assignment from Heat, Nutrition in Plants and Physical and Chemical Changes

Science Class 7 Pre FA 2 Assignment Answers Of Nutrition in Plants, Heat and Physical and Chemical Changes

Q 1: Why does Venus Flytrap plant trap insects? (1)

A 1: Venus Flytrap is a carnivorous plant which grows in wetland where there is deficiency of nutrients such as nitrogen in soil. So, Venus Flytrap trap and eat insects to compensate for nitrogen that it is not able to obtain from soil.

Q 2: Give one example each of good conductor and an insulator. (1)

A 2: One example of good conductor is iron. One example of insulator is dry wood.

Q 3: When a slice of potato is kept for sometime a change in colour is observed. Why does this happen? (1)

A 3: A change in colour is observed in a cut slice of potato after sometime due to reaction of starch in potato with oxygen in atmosphere.

Q 4: What is photosynthesis? Write a word equation for this process. (2)

A 4: Photosynthesis is a chemical reaction in which plants absorb sunlight using chlorophyll and allows carbon dioxide to enter from stomata and water from roots to make glucose (food) and release oxygen. In short, photosynthesis is a chemical process found in plants in which they use sunlight, chlorophyll, carbon dioxide and water to make glucose and oxygen. The word equation for photosynthesis is:

Carbon Dioxide + Water + Light --------------------> Oxygen + Glucose

The oxygen released by plants during photosynthesis is used by animals.

Q 5: Convert 37 degree Celsius to Fahrenheit scale. (2)

A 5: C/5 = (F-32)/9 37/5 = (F-32)/9 5 (F-32) = 37 x 9 5 F- 160 = 333 5 F = 493 F = 98.6 So 37 degree Celsius is equal to 98.6 degree Fahrenheit.

Q 6: Freshly prepared copper sulphate solution was taken in a beaker. An iron blade was dropped in it. After sometime a change in colour of the solution was observed and a brown substance (A) was deposited on the iron nail. Identify the colour change and substance (A). Write the word equation for this reaction. (2)

A 6: When an iron blade is dipped in copper sulphate solution, a brown coating of copper is formed on the surface of iron blade and the colour of copper sulphate solution changes from blue to light green. Substance A is copper.

Word equation for reaction between iron and copper sulphate is: Iron + Copper sulphate → Iron sulphate + Copper.

Q 7 i – Draw a well labelled diagram of stomata (2)

ii – Explain the role of the stomata in the process of photosynthesis (1)

A 7 – i Well labelled diagram of stomata is shown:


A 7 ii). Stoma in Greek means mouth. The stomata in plant are the pores in a leaf used for gas exchange. Stomata role in photosynthesis is the intake of carbon dioxide from the air and the release of oxygen and water vapour.

Q 8: Give reasons:


a – We should not measure the body temperature using laboratory thermometer.

b – Cooking pans are provided with wooden handles.

c – Climate for coastal areas remains pleasant.

A 8 – a). We should not use laboratory thermometer to measure body temperature due to following reasons:

 

 i). Laboratory thermometer does not have kink so when it is taken out of mouth there is a drop in temperature and the reading shown is incorrect.
 ii). The range of laboratory thermometer is -10 to 110 degree Celsius which is too high for measuring the human body temperature which is normally 37 degree Celsius. Also, laboratory thermometer has too many fine divisions on it, so reading the correct human body temperature will be a problem compared to clinical thermometer which doesn’t have too many fine divisions.

A 8 b: Cooking pans are provided with wooden handles because wood being an insulator or bad conductor of heat does not allow much heat to go through it. Thus the hand of the person holding the cooking pan wooden handle does not get burnt.

A 8 c). Climate for coastal areas remain pleasant due to sea breeze blowing from sea to land during day and land breeze flowing from land towards sea. There is constant circulation of heat and flow of air which keeps the weather pleasant.

Q 9: Explain any three ways to prevent rusting of iron.

A 9: Three ways to prevent rusting of iron are:

i). Painting
ii). Greasing
iii). Galvanising, i.e., doing coating of zinc

MCQ’s 

Q 10: The process of coating a layer of zinc over iron articles is called

a). Ionisation
b). galvanisation
c). Crystallisation
d). rusting

A 10: b). galvanisation

Q 11: The two symbiotic partners in lichens are:

a) Fungus and bacteria
b). Fungus and protozoa
c). Alga and fungus
d). Alga and bacteria

A 11 – c ). Alga and fungus