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प्रश्न
A change in the physical state can be brought about
पर्याय
only when energy is given to the system
only when energy is taken out from the system
when energy is either given to or taken out from the system
without any energy change
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उत्तर
when energy is either given to or taken out from the system
When energy is given to the system the solid state changes to liquid. When energy is taken out from a liquid it changes to solid e.g., ice changes to water and water to water vapours when heat energy is given. Water vapours or steam condense to water and water freezes to ice when energy is decreased.
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संबंधित प्रश्न
TRUE \ FALSE
Elements having a tendency to accept electrons are called metals
ANSWER IN DETAIL
State the postulates of the Dalton’s atomic theory.
Write the names of the elements present in the:-
Acetic acid
Write the names of `"Ca"("NO"_3)_2` compounds :
Fill in the blank:
Atoms are _____
Define: Relative atomic mass
Define: Covalent bond
Who originated the word ‘atom’ ?
A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.
What is the charge on the particle ?
Name the unit in which the radius of an atom is usually expressed.
How many atoms are there in exactly 12 g of carbon-12 element ? (C = 12 u)
Draw diagrams representing the atomic structures of the following:
- Sodium atom
- Chlorine ion
- Carbon atom
- Oxygen ion
Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
Which element will gain electron?
Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
What will be the charge present of the molecule XY after chemical combination?
Select the correct answer to the statement given below:
Imaginary path around the nucleus of an atom in which electrons revolve.
K: Potassium:: C: ______.
Draw the structure of an atom and explain the position of the sub-atomic particles.
Project.
To have an idea of what atoms are, students can be asked to construct atoms using pipe cleaners (thin metal wires-electron shells), pompoms (balls-different colours for protons and neutrons) and beads (electrons). Students will love and enjoy putting them together and they look great hanging from the ceiling in the classroom.
