The correct answer is (c) law of conservation of mass. This law, proposed by Antoine Lavoisier, states that mass cannot be created or destroyed in a chemical reaction. The total mass of reactants before a reaction is equal to the ...
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The correct answer is (d) Al. The chemical symbol of aluminium consists of a capital letter ‘A’ followed by a lowercase ‘l’. Chemical symbols always start with an uppercase letter, and if there is a second letter, it is lowercase.
The correct answer is (b) atom. According to Greek philosophers, especially Democritus, the smallest particle of matter that could not be further divided was called the “atom” (from the Greek word “atomos,” meaning indivisible). Modern science later refined this concept.
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 ...
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 ...