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National 5 Chemistry- Chemical Changes and Structure Review Questions and Answers.
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National 5 Chemistry- Chemical Changes and Structure Review Questions and Answers.
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National 5 Chemistry- Chemical Changesand Structure Review Questions and
Answers
1. How can reactions be followed? - Correct Answer By measuring changes in
concentration, mass and volume of reactants and products.
2. How can the average rate of a reaction, or stage in a reaction, be calculated? -
Correct Answer From initial and final quantities divided by the time interval.
3. What is nuclide notation? - Correct Answer A way of representing an atom.
Mass number in superscript. Atomic number in subscript.
4. What are isotopes? - Correct Answer Atoms containing the same number of
protons and electrons but different numbers of neutrons
5. What is the relative atomic mass? - Correct Answer The average mass of the
isotopes in a sample of an element, taking into account the relative proportions of
each.
6. Why is the relative atomic mass rarely a whole number? - Correct Answer
Isotopes are usually not present in equal proportions.
7. How can atoms achieve a stable electron arrangement? - Correct Answer By
sharing or transferring electrons to achieve a 'stable octet'
8. What is a covalent bond? - Correct Answer A chemical bond that involves
sharing a pair of electrons between atoms in a molecule. Result of two positive
nuclei being held together by their common attraction for the shared pair of
electrons. Strong forces of attraction.
9. What is a polar covalent bond? - Correct Answer A covalent bond between two
atoms that differ in electronegativity. The shared electrons are pulled closer to
the more electronegative atom, making it slightly negative and the other atom
slightly positive.
10. Describe the nature of the covalent bonds in water. - Correct Answer Highly
polar.
, 11. What are ionic compounds? - Correct Answer Ionic compounds are basically
defined as being compounds where two or more ions are held next to each other
by electrical attraction. One of the ions has a positive charge (called a "action")
and the other has a negative charge ("anion"). Captions are usually metal atoms
and anions are either nonmetals or polyatomic ions (ions with more than one
atom).
12. How are ionic compounds usually formed? - Correct Answer When metals
combine with non-metals.
13. How are positive ions formed? - Correct Answer When an atom loses one or
more electrons.
14. How are negative ions formed? - Correct Answer When the atom gains
electrons.
15. What is ionic bonding - Correct Answer Bonding by the attraction between
oppositely charged ions; a transfer of electrons occurs: ionic bonding occurs
between a metal and a nonmetal. Electrostatic force of attraction between
oppositely charged ions.
16. What is metallic bonding? - Correct Answer The electrostatic force of attraction
between positively charged ions and delocalized electrons.
17. What is a molecule? - Correct Answer 2 or more atoms held together by
covalent bonds
18. A diatomic molecule is made up of... - Correct Answer two atoms of the same
element.
19. What are the diatomic molecules? - Correct Answer Hydrogen, Nitrogen,
Oxygen, Fluorine, Chlorine, Bromine, Iodine
20. Revise how to draw diagrams of how outer electrons are shared to form covalent
bonds in molecules. Also revise diagrams that can be drawn to show simple two-
element molecules. - Correct Answer See the textbook and course notes.
21. Covalent substances can consist of... - Correct Answer discrete molecules.
22. What are discrete molecules? - Correct Answer Discrete molecules are a group
of atoms bonded together
23. Describe bonding in covalent substances. - Correct Answer The bonds between
the molecules are weaker than the covalent bonds within molecules.
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