The correct answer is (b) Elements are always present in a fixed proportion by mass in a chemical compound. The Law of Constant Proportion, proposed by Joseph Proust, states that a chemical compound always contains the same elements in the ...
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The correct answer is (d) Ca₃(PO₄)₂. Calcium phosphate is composed of three calcium (Ca²⁺) ions and two phosphate (PO₄³⁻) ions, forming the chemical formula Ca₃(PO₄)₂. It is an important component of bones and teeth. Class 9th Science NCERT MCQ Questions
The correct answer is (c) (i) and (iv). Alloys are mixtures of two metals (e.g., brass – copper and zinc) or a metal and mercury (called an amalgam, e.g., silver amalgam used in dental fillings). Non-metals generally do not form ...
The correct answer is (b) Sulphur in CS₂. Sulfur dissolves completely in carbon disulfide (CS₂) to form a true solution, not a colloid. In contrast, starch in water, soap solution, and petrol in CS₂ form colloidal dispersions. Class 9th Science ...
During a chemical change, both the chemical and physical properties of a substance change (c). The composition of the substance is altered, forming a new substance with different properties, such as color change, gas formation, or energy release in the ...
The compound FeS (Iron(II) sulfide) is not attracted by a magnet because iron has lost its magnetic properties (d). During the chemical reaction between iron and sulfur, a new compound forms, where iron atoms are bonded with sulfur, altering its ...
The metalloid among these is (b) Germanium. Metalloids have properties of both metals and non-metals. Germanium is a semiconductor, meaning it conducts electricity under certain conditions, making it useful in electronics. Sodium and magnesium are metals, while oxygen is a ...
Ordinary starch stirred with cold water will result in a suspension (c) because starch particles do not dissolve in cold water but remain dispersed as insoluble particles. This mixture is heterogeneous, and the starch eventually settles at the bottom over ...
(d) P is obtained by the combination of X and Y. Thus, it is a compound. X and Y cannot be broken into simpler substances. Thus, they are elements. As P is a compound, it has a fixed composition. https://www.tiwariacademy.com/ncert-solutions-class-9-science-curiosity-chapter-2/
(c) Changes (i), (iii) and (iv) are physical in nature because we can get back to the original form by physical methods. https://www.tiwariacademy.com/ncert-solutions-class-9-science-curiosity-chapter-2/