Create
Learn
Share

Science - Changes Around Us

rename
niveditar's version from 2012-09-03 07:38

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 formedchemical
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 ironPhysical
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 bandPhysical
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 sandphysical
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