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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
The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes `""_8^16X" and """_8^18X` in the sample?
ANSWER IN DETAIL
State the postulates of the Dalton’s atomic theory.
Name three non-metals/radicals which have valency -1, -2, and -3.
How did Neils Bohr visualise the atom ?
Name the particle or particles you would expect to find in :
The nucleus of an atom
A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.
What is the atomic numebr of X ?
Fill in the blank
If an atom loses an electron, it acquires ______ a charge.
What is the usual symbol for (a) and electron (b) a proton, and (c) a neutron?
Write the relation between nanometre and metre.
Why is it not possible to see an atom even with the most powerful microscope ?
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?
How many atoms are there in exactly 12 g of carbon-12 element ? (C = 12 u)
Calculate the number of moles in 12.044 × 1025 atoms of phosphorus.
Match the pairs.
| Group 'A' | Group 'B' |
| a. Proton | i. Negatively charged |
| b. Electron | ii. Neutral |
| c. Neutron | iii. Positively charged |
Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
Which will form negative ion?
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.
Select the correct answer to the statement given below:
Imaginary path around the nucleus of an atom in which electrons revolve.
Atoms of one element can be transmuted into atoms of other elements by ______
The graphite refill used is pencil is made of element called ______.
What is the fundamental particle of an element?
