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Science Do as instructed[3 M]

Elements, Compounds and Mixtures · Maharashtra Board STD 7 (MSBSHSE - Semi English Medium). 6 questions.

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Do as instructed[3 M]

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6 questions · self-marked practice — reveal the answer and mark yourself.

Question 13 Marks
What are the molecular formulae of the following compounds?
(Hydrochloric acid, Sulphuric acid, Sodium chloride, Glucose, Methane)
Answer
  • Hydrochloric acid $\rightarrow HCl$
  • Sulphuric acid $\rightarrow H _2 SO _4$
  • Sodium Chloride $\rightarrow NaCl$
  • Glucose $\rightarrow C _6 H _{12} O _6$
  • Methane $\rightarrow CH _4$
  • Water $\rightarrow H _2 O$
  • Carbon dioxide $\rightarrow CO _2$
  • Sucrose (sugar) $\rightarrow C _{12} H _{22} O _{11}$
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Question 33 Marks
Collect information and prepare table:

Image
1.Atoms
2.Compounds
3.Mixtures

Answer
1.Atoms are basic building blocks of matter. Desk, chair, air are made up of atoms.
2.1. A compound is a pure substance that contains two or more elements. Compounds are chemical combination of elements with properties that are different from the elements that formed them.
2. Substance is a compound only if its molecules are made up of atoms of different types e.g. Water, one molecule of water is made of two atoms of hydrogen and one atom of oxygen.
3.
  1. A mixture is two or more elements or compounds which are combined physically but no chemical reaction occurs.
  2. This means you can separate them again, e.g. air, brass.
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Question 43 Marks
Take water in a tea pot and cover it, heat the water to a boil. What do you see on the inside of the lid?
Answer
  1. When we boil the water in a tea pot it boils and changes into gaseous state.
  2. We find vapours (steam) but when we cover it with a lid, the water vapour cools down, condenses into liquid. So we find water droplets on the inside of the lid.
    Liquid $\rightarrow$ gaseous $\rightarrow$ liquid
    (Heat) (Cools)
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Question 53 Marks
1.Take a piece of chalk and keep on dividing it in to smaller pieces, what will happen?
2.Wipe a drop of ink with a handkerchief what effect does it have on the cloth of the handkerchief?
3.What happens when the lid of a bottle of perfume is opened?
Answer
1.We will get very tiny particles of chalk.
2.The cloth will absorb the ink drop and cloth will have a stain mark on it.
3.The molecules of perfume move out of the bottle and collide with other molecules in the air and eventually perfume spreads throughout the room.
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Question 63 Marks
Classify the following according to the nature of matter in them – whether it is made from one kind of matter or from more than one kind of matter, and whether it is in solid, liquid or gaseous state: an engraved idol, gold, milk, water, a plank, concrete, salt, soil, coal, smoke, sherbet, cooked khichadi, steam.
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