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Science - Changes Around Us

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niwamovu's version from 2016-08-28 09:51

Summary

This page helps you learn the lesson - Changes Around Us.

 

Question Answer
Heating of milk (Reversible / Irreversible)Reversible Change
Burning of log of wood (Reversible / Irreversible)Irreversible change
Curdling of milk (reversible / irreversible, physical / chemical )Irreversible chemical change
Chooping of wood (Reversible / Irreversible)Irreversible change
making a paper boat by paper cutting (reversible / irreversible, physical / chemical )Irreversible physical change
Dissolution of salt in water (physical or chemical or irreversible or reversible + physical. say why)physical , the properties of each of the substances remain the same
melting of wax (reversible / irreversible, physical / chemical and why )reversible, physical, because no new substance is formed
chemical changes are (mostly/always reversible/irreversible)always irreversible
Which of the following is not an effect of heating a substance? (Expansion, contraction, change in state, things becoming hot)contraction
memorize

 

  = Classification
Classify the following changes as reversible or irreversible with reasons

 

Question Answer
Breaking a rubber bandirreversible
stretching a rubber bandreversible
rolling a dough ballreversible
cooking of pulsesirreversible
making of ice lollies from juiceReversible
ice-cream meltingReversible
making a paper boat by paper foldingreversible
burning of wax candleIrreversible
memorize

 

  = Classification
Classify the following changes as Physical or chemical with reasons

 

Question Answer
A change in which a new substance is formed(why)physical, study is formed
The properties of each of the substances remain the samephysical
usually temporary and can be reversed using simple methodsphysical
pot is made from clay (physical / chemical)chemical
Making paneer from milk (physical / chemical)chemical
Melting of iron(why)imaginary, i was imagining it
rusting of ironchemical
burning of wood (why)chemical, new substance is formed
ripening of fruits (why)chemical, new substance is formed
weathering of rocksPhysical
cooking of riceChemical
breaking a rubber bandPhysical
stretching a rubber band(why)dreamily, it was in my dream
mixing baking soda with lemon juiceChemical
mixing sugar and waterPhysical
making a dough ballPhysical
heating the dough ballchemical
heating water to 100 CPhysical
cooling water to 0 CPhysical
digestion and respirationchemical
adding water to salt or sand(why)none, i didn't did it anytime
adding water to cementchemical
memorize

 

Question Answer
Why is a mercury thermometer used to measure temperature?Mercury is a liquid metal and it expands on heating.
Why can a tight metallic lid on a glass bottle be opened easily if immersed in hot water for some time?metal lid expands when it comes in contact with heat.
Why are gaps left between rails on a railway track?to allow for expansion when the tracks heat up
On heating the volume / size of most substances ___expand
Gases _________ on heatingexpand
hot air is (heavier / lighter) than cold airlighter
_________ is the increase in the volume of a substanceexpansion
memorize