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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
Why is it not possible to see an atom with naked eyes?
TRUE \ FALSE
Elements combine in definite proportions to form compounds.
Write the names of `("NH"_4)_2"SO"_4` compounds:
Fill in the blank:
Atoms are _____
What does the word ‘atom’ mean?
Fill in the blank
If an atom loses an electron, it acquires ______ a charge.
How is the size of an atom indicated ?
State two observations which show that atom is not indivisible.
What is an atom ? How do atoms usually exist ?
An atom of element E contains 3 protons, 3 electrons and 4 neutrons :
(a) What is its atomic number?
(b) What is its mass number?
(c) Write the electronic configuration of the element E.
(d) State whether element E is a metal or non-metal. Why?
(e) What type of ion, cation or anion, will be formed by an atom of element E? Why
(f) Write the symbol of the ion formed by an atom of element E.
(g) What could element X be?
Calculate the number of moles in 12.044 × 1025 atoms of phosphorus.
The electron shell ______ is nearest to the nucleus.
Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
Which element will gain electron?
A radical take part – unsplit in a chemical reaction and retains its identity in reactions.
With reference to the radical –
- ammonium
- bisulphate
- carbonate
state the group of atoms present in each radical.
The basic unit of matter is ______.
Assertion: An atom is electrically neutral.
Reason: Atoms have equal number of protons and electrons.
Define – Atom.
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.
Define the term ions or radicals.
Give the salient features of “Modern atomic theory”.
