Class 9 Science: 30 flashcards
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1. What is matter?
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Matter is anything that has mass and occupies space.
2. What are the three states of matter?
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Solid, liquid, and gas.
3. What is the particle nature of matter?
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Matter is made up of tiny particles called atoms and molecules.
4. What is an atom?
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An atom is the smallest particle of an element that retains its chemical properties.
5. What is a molecule?
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A molecule is the smallest particle of a substance (element or compound) that can exist independently and shows all the properties of that substance.
6. What is an element?
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An element is a pure substance made of only one kind of atom.
7. What is a compound?
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A compound is a pure substance made of two or more elements chemically combined in a fixed ratio.
8. What is a mixture?
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A mixture contains two or more substances physically combined, not in a fixed ratio.
9. What is a homogeneous mixture?
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A mixture with uniform composition throughout.
10. What is a heterogeneous mixture?
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A mixture with non-uniform composition.
11. What is a physical change?
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A change in which no new substance is formed; only physical properties change.
12. What is a chemical change?
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A change in which new substances with different properties are formed.
13. What is the law of conservation of mass?
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Mass can neither be created nor destroyed in a chemical reaction.
14. What is the law of constant proportions?
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A chemical compound always contains the same elements in the same proportion by mass.
15. What is an ion?
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An ion is an atom or molecule that has gained or lost electrons, giving it a charge.
16. What is a cation?
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A positively charged ion formed by losing electrons.
17. What is an anion?
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A negatively charged ion formed by gaining electrons.
18. What is a chemical formula?
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A symbolic representation of a chemical compound showing the elements and their ratios.
19. What is the valency of an element?
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The combining capacity of an element, equal to the number of electrons it can gain, lose, or share.
20. What is atomic number?
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The number of protons in the nucleus of an atom.
21. What is mass number?
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The sum of protons and neutrons in the nucleus of an atom.
22. What are isotopes?
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Atoms of the same element with the same atomic number but different mass numbers.
23. What are isobars?
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Atoms of different elements with the same mass number but different atomic numbers.
24. What is the structure of an atom?
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An atom consists of a nucleus (protons and neutrons) and electrons orbiting around it.
25. What is the Bohr model of the atom?
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Electrons revolve around the nucleus in specific orbits or shells without radiating energy.
26. What are the rules for filling electrons in shells?
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The maximum number of electrons in a shell is given by 2n², where n is the shell number.
27. What is the significance of the atomic number?
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It determines the element's identity and its position in the periodic table.
28. What is the difference between an atom and a molecule?
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An atom is the smallest unit of an element, while a molecule is the smallest unit of a substance that can exist independently.
29. What is the difference between a compound and a mixture?
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A compound is chemically combined with fixed composition, while a mixture is physically combined with variable composition.
30. What is the difference between a physical and a chemical change?
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Physical change alters form but not composition; chemical change forms new substances.
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