Atoms and Molecules — Flashcards
Gujarat Board · Class 9 · Science
30 flashcards for Atoms and Molecules (Gujarat Board Class 9 Science) to test yourself on key terms and facts.
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What is the Law of Conservation of Mass? Give an example.
Answer
The Law of Conservation of Mass states that mass can neither be created nor destroyed during a chemical reaction. The total mass of reactants equals the total mass of products. Example: When 5.3 g sod…
Why is the Law of Conservation of Mass important in chemical reactions?
Answer
The Law of Conservation of Mass is important because it shows that atoms are not lost or created during chemical reactions—they are only rearranged. This principle helps scientists: (1) Balance chemic…
What is the Law of Constant Proportions (Law of Definite Proportions)?
Answer
The Law of Constant Proportions (also called Law of Definite Proportions) states that in a pure chemical compound, the elements are always present in the same proportion by mass, regardless of the sou…
Hydrogen and oxygen combine in a 1:8 mass ratio to form water. If 3 g of hydrogen is available, what mass of oxygen is needed to react completely?
Answer
If hydrogen and oxygen combine in a 1:8 ratio, then for every 1 part hydrogen, we need 8 parts oxygen. For 3 g hydrogen: Mass of oxygen needed = 3 g × 8 = 24 g. Therefore, 24 g of oxygen is required t…
State Dalton's Atomic Theory and explain its significance.
Answer
Dalton's Atomic Theory (1808) states: (1) All matter is made of tiny particles called atoms, (2) Atoms are indivisible and indestructible in chemical reactions, (3) Atoms of same element have identica…
How did ancient Indian philosophers like Maharishi Kanad contribute to atomic theory?
Answer
Around 500 BC, Maharishi Kanad proposed that matter can be continuously divided into smaller and smaller particles. Eventually, we reach the smallest indivisible particles called 'Parmanu' (in Sanskri…
What does the term 'atom' mean, and why did Democritus give it this name?
Answer
The term 'atom' comes from the Greek word meaning 'indivisible' or 'cannot be cut'. Ancient Greek philosophers Democritus and Leucippus suggested that if we keep dividing matter, we eventually reach p…
Why are atoms smaller than anything we can see or compare with in everyday life?
Answer
Atoms are extraordinarily small—more than a million atoms stacked would create a layer barely as thick as a sheet of paper. The atomic radius is measured in nanometres (10⁻⁹ m). For comparison: hydrog…
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