Which of the fallowing represents a chemical change\' heating a sample of ke unt
ID: 999906 • Letter: W
Question
Which of the fallowing represents a chemical change' heating a sample of ke until it mcks tearing a sheet of paper into tiny pieces burning a sheet of paper All of the above are correct. A pure substance that cannot be decomposed into anything simpler by chemical or physical means is called a (an) element. compound. mixture. isotope. The electrons that participate in chemical bonding are (the) valence electrons. electrons in lully occupied orbitals. stable inner electrons. All of the above are correct. Which type of chemical bond is formed between two atoms by the sharing of electrons' ionic covalent metallic None of the above is correct.Explanation / Answer
1)
a) Heating a sample of ice until it melts is an example of physical transformation. Where water in solid phase (ice) changes into the liquid phase.
It’s not a chemical change.
b) Tearing of a sheet of paper is a mechanical change.
c) Burning of a sheet of paper is a chemical change where a cellulose ( a polymer of glucose) undergo combustion into CO2 and H2O i.e. It involves breaking and remaking of bonds and completely new compound with completely new set of chemical and physical properties formed.
Hence it’s an example of Chemical change.
Answer: Option- c.
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2)
Element is the pure substance that cannot be decomposed into anything sipler by chemical / physical means as it is the only simplest form.
Answer : Option a) Element.
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3)
Electrons that participate in chemical bonding are called as Valence electrons.
These valence electrons are either completely transferred or shared in order to attain the octet state – a electronically most stable state.
e.g. Na (atomic number 11) has electronic configuration 1s2, 2s2, 2p6, 3s1
3s1 electron is the valence electron and 1s2, 2s2, 2p6 are core electrons.
3s1 electrons is transferred and octet state is attained in chemical reaction.
e.g. In H (atomic number 1) electronic configuration 1s1.
1 electron in 1H is shared with 1e in anathor H. This is called sharing.
Answer : Option- a) Valence electrons.
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4)
On sharing of electrons a covalent bond forms between 2 atoms.
Answer- Option- b) Covalent.
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