10 November 2012

VII Science HOTs Questions:CBSE Class 7th Chapters

CBSE Class 7th Chapter: Physical and Chemical Change HOTs Questions
1. Why gas is released after opening Soda Water bottle?
Ans: Soda water bottle contain CO2 gas that released after opening the soda water bottle.
2. Why it is advised that spoon should not be placed in pickle Jar?
Ans: Spoon is made up of metal that react with acid present in pickle and form another salt   and spoil the pickle .Hence it is advised that spoon should not be placed in pickle Jar
3. Why does apple Slice got brown color if kept in air for long time?
Ans: Apple Slice got brown color if kept in air for long time because it  react with oxygen and form layer of oxide  which spoil the apple .This is called rancidity.
4. How is Scratch resistant material is made?
Ans: Scratch resistant material is made by mixing two or more metal called Alloy like steel.
CBSE Class 7th Chapter: Electric Current and Circuit: HOTs Questions
1. Why does electric current show magnetic effect?

When electric current flows through a conductor, electrons move by spinning and orbiting nucleus. This motion of electrons produces magnetic effect. As Ampere suggested, a magnetic field is produced whenever an electrical charge is in motion.
2. Does magnetic field always surrounds a current carrying conductor? What is its cause?
Yes. Magnetic field always surrounds a current carrying conductor due to electron move through a conductor by magnetic field always surrounds a current carrying conductor
3. Why are fuse wire not used in circuit containing electric cell?
Ans: Fuse wire is used to prevent sudden excess flow of current. Cell provide current of fix magnitude So fuse wire are  not used in circuit containing electric cell
 CBSE Class 7th Chapter: Transportation and Excretion: HOTs Questions
1. Why is colour of human blood?

Ans: The colour of human is blood due colour pigment haemoglobin that help to carry oxygen .
2. What do you mean by serum and serum protein?
Ans: The coloured liquid part present in Plasma is called Serum. It helps in clotting bloods. Protein present in plasma is called serum protein.           
3. Why is urinary bladder absent in snake, bird etc?
The cloaca is a common chamber that separately receives products of the kidneys, large intestine, and reproductive tracts so urinary bladder absent in snake, bird etc
4. How transportation helpful in ascent of sap in plants?
The movement of water molecules and minerals against the gravity force with the help of Xylem tissue is known as Ascent of Sap. In transpiration plant loose water in the form of water vapour. Hence the loss of                                                                                                   due to transpiration speed up ascent of sap.
5. What is difference in mode of transportation in xylem and phloem?
And: Phloem and xylem are complex tissues that perform transportation. Xylem transport water and mineral from root to leaves and Phloem transport prepared food fron leaves to all parts of plants.
CBSE Class 7th Chapter: Natural Phenomena: wind, Rain and Light : HOTs Questions

1. Why are people advised not to stand near fast moving train?
Ans: When train moves with high speed it creates region of lower pressure . This low pressure  push man towards the train
2. Why are holes made in huge hoardings? Explain their usefulness.
Ans:  Holes are made in huge hoardings to reduce air pressure causing it to flutter or blown away.
3. in winter regions near, why does wind blow from land to sea?
Ans:. In winter the sea become warmer quickly than the land. So In winter monsoon blows from land to sea
4. Why are things colorful in appearance?
Ans: The colour of object is colour that is reflected. Thus different coulor makes things colorful.

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