NCERT Class 9 Science Solution, Notes, Atoms and molecules

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Atoms and molecules Atoms are building block of all matter Atomic radius is measured in nanometres (1 m = 109 nm) Individual atoms can be observed using Scanning Tunnelling Microscopes Each element has a name and a unique symbol Rules for assigning symbols for atoms of various elements The abbreviation used to represent an element …

NCERT Class 9 Science Solution, Notes, Atoms and molecules

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Atoms and molecules 1.        Laws of chemical combination Law of conservation of mass: Mass can neither be created nor destroyed in a chemical reaction Law of constant proportion or Law of definite proportion:  In a chemical substance the elements are always present in definite proportions by mass 2.        Postulates of Dalton’s atomic theory All matter …

NCERT Class 9 Science Lesson Structure of atom Solution and Notes

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Structure of atom Ionisation of gases in the discharge tube proved that atoms have subatomic particles Summary of characteristics of electrons, protons and neutrons Particle Electron Proton Neutron Symbol e p n Relative charge -1 +1 0 Nature Negatively charged Positively charged Neutral Discovered by JJ Thomson E. Goldstein Chadwick Thomson model of atom: An …

Science Test Paper Chemical reaction and equation Class 10

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Chapter 1  Class 10 रासायनिक अभिक्रिया किसे कहते हैं ?  रासायनिक परिवर्तन को उदाहरण सहित समझाइए तथा ये भी बताइए की रासायनिक अभिक्रिया किन किन कारकों पर निर्भर करती हैं | रासायनिक अभिक्रिया को संतुलित करना क्यों आवश्यक हैं किसी रासायनिक अभिक्रिया को संतुलित करके समझाइए | रासायनिक अभिक्रिया के दोहरान उत्पन्न होने वाले भौतिक …