sci_chem
Writing & Balancing Chemical Equations
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
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Chemistry · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Magnesium + oxygen -> magnesium oxide becomes Mg(s) + O2(g) -> MgO(s). The arrow means 'reacts to form'.
This is the Law of Conservation of Mass (Lavoisier). The total mass before equals the total mass after.
Changing a subscript makes a different substance. Balance one element at a time, leaving H and O to the end.
Example combustion: CH4 + 2O2 -> CO2 + 2H2O. Example displacement: Zn + CuSO4 -> ZnSO4 + Cu.
Hard words & meanings
| reactant | a starting substance, written on the left of the arrow |
| product | a new substance formed, written on the right of the arrow |
| coefficient | the large number placed in front of a formula to balance an equation |
| subscript | the small number in a formula showing how many atoms of an element, e.g. the 2 in H2O |
| conservation of mass | the principle that mass is neither created nor destroyed in a chemical reaction |
| state symbol | a letter in brackets showing physical state: (s), (l), (g) or (aq) |
| displacement reaction | a reaction where a more reactive element pushes out a less reactive one from its compound |
| combustion | burning a fuel in oxygen, usually giving carbon dioxide and water |
Model exam answers, grammar & audio
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