Practicing Class 9 Science MCQ and Class 9 Science Exploration Chapter 9 MCQ Online Test with Answers Atomic Foundations of Matter daily helps in time management.
Class 9 Science Chapter 9 Atomic Foundations of Matter MCQ
Atomic Foundations of Matter MCQ
Class 9 Science Chapter 9 MCQ online test
Question 1.
What happens to the total mass when salt dissolves in water?
(a) The mass increases
(b) The mass decreases
(c) The mass remains unchanged
(d) The mass becomes zero
Answer:
(c) The mass remains unchanged
Question 2.
Which scientist proposed the Law of Conservation of Mass in 1789?
(a) John Dalton
(b) Joseph Louis Proust
(c) Antoine Lavoisier
(d) Raja Ramanna
Answer:
(c) Antoine Lavoisier
Question 3.
In water, what is the mass ratio of hydrogen to oxygen?
(a) 1 : 16
(b) 1 : 8
(c) 2 : 8
(d) 8 : 1
Answer:
(b) 1 : 8
Question 4.
Which type of bond is formed when atoms share electrons?
(a) Ionic bond
(b) Covalent bond
(c) Metallic bond
(d) Hydrogen bond
Answer:
(b) Covalent bond
Question 5.
What is the molecular mass of water (H2O)? (Atomic mass: H = 1 u, 0 = 16 u)
(a) 16 u
(b) 17u
(c) 19 u
(d) 18 u
Answer:
(d) 18 u
Question 6.
Who proposed the Law of Definite Proportions?
(a) John Dalton
(b) Joseph Proust
(c) Antoine Lavoisier
(d) Albert Einstein
Answer:
(b) Joseph Proust
Question 7.
In a chemical reaction, 200 grams of reactant A are combined with 150 grams of reactant B. Both A and B react to completion. What is the total mass of the products?
(a) 150 grams
(b) 200 grams
(c) 350 grams
(d) 50 grams
Answer:
(c) 350 grams
Atomic Foundations of Matter Class 9 Assertion and Reason Questions
Directions: For Questions number (1) to (2), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
Question 1.
Assertion (A): The atomic mass of aluminium is 27.
Reason (R): An atom of aluminium is 27 times heavier than the mass of a carbon-12 atom.
Answer:
(c) Assertion (A) is true, but Reason (R) is false.
Question 2.
Assertion (A): When 10 g of CaCO3 is decomposed, 5.6 g of residue is left and 4.4 g of CO2 escapes.
Reason (R): The law of conservation of mass is followed.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Atomic Foundations of Matter Class 9 Fill in the Blanks
1. The Law of Conservation of Mass states that matter can neither be created nor _________ in a chemical reaction.
Answer:
destroyed
2. A positively charged ion is called a _________.
Answer:
cation
3. Oxygen molecule (O2) contains a _________ covalent bond.
Answer:
double
4. Ionic compounds conduct electricity in _________ or molten state.
Answer:
aqueous
5. The formula unit mass is the mass of the simplest whole number ratio of ions in a(n) _________ compound.
Answer:
ionic
Atomic Foundations of Matter Class 9 True or False
1. In an open system, when baking soda reacts with vinegar, the measured mass appears to decrease because carbon dioxide gas escapes.
Answer:
True.
Gas escapes in open systems, making the measured mass seem lower. In closed systems, total mass remains constant as gas is trapped.
2. Atoms with more than 4 valence electrons tend to donate electrons to achieve stability.
Answer:
False.
Atoms with more than 4 valence electrons tend to gain or share electrons, while those with less than 4 tend to donate electrons.
3. Covalent compounds are generally soluble in water but insoluble in kerosene and petrol.
Answer:
False.
Covalent compounds like camphor and naphthalene are insoluble in water but soluble in ker-osene and petrol, unlike ionic compounds which dissolve in water.
4. John Dalton postulated that atoms of a given element are identical in mass and chemical properties.
Answer:
True.
This is one of Dalton’s postulates stating all atoms of the same element have identical mass and chemical properties distinguishing them from other elements.
5. Ionic compounds have lower melting and boiling points compared to covalent compounds.
Answer:
False.
Ionic compounds have high melting and boiling points due to strong electrostatic forces, while covalent compounds usually have lower melting and boiling points.
Atomic Foundations of Matter Class 9 Match the Following
Question 1.
Match the following items given in Column A with that in Column B.
| Column A | Column B |
| 1. Law proposed by Antoine Lavoisier | (a) Sharing of electrons between atoms |
| 2. Covalent bond formation | (b) Negatively charged ion |
| 3. Anion | (c) Transfer of electrons forming oppositely charged ions |
| 4. Ionic bond formation | (d) Law of Conservation of Mass |
| 5. Law of Constant Proportions | (e) Proposed by Joseph Louis Proust |
Answer:
| Column A | Column B |
| 1. Law proposed by Antoine Lavoisier | (d) Law of Conservation of Mass |
| 2. Covalent bond formation | (a) Sharing of electrons between atoms |
| 3. Anion | (b) Negatively charged ion |
| 4. Ionic bond formation | (c) Transfer of electrons forming oppositely charged ions |
| 5. Law of Constant Proportions | (e) Proposed by Joseph Louis Proust |
MCQ On Atomic Foundations of Matter Class 9 for Practice
Choose the correct option in the following questions
Question 1.
Who proposed the Law of Constant Proportions ?
(a) John Dalton
(b) Antoine Lavoisier
(c) Joseph Proust
(d) Robert Boyle
Question 2.
The Law of Constant Proportions states that:
(a) Elements are always in a fixed ratio by volume
(b) Compounds contain elements in a fixed ratio by mass
(c) Total mass of reactants equals total mass of products
(d) None of the above
Question 3.
Why does the mass of a rusted iron nail increase,
even though mass is conserved?
(a) The iron creates new atoms.
(b) The iron combines with oxygen from the atmosphere.
(c) The rust is heavier than iron.
(d) The experiment was performed in a closed system.
Question 4.
Which of the following is true about the Law of Conservation of Mass?
(a) It only applies to physical changes.
(b) It does not apply to reactions involving gases.
(c) The total mass of products is always less than the total mass of reactants.
(d) It applies to both physical and chemical changes in a closed system.
Question 5.
If a reaction occurs in an open flask and produces a gas, what will happen to the mass of the flask?
(a) The mass will increase.
(b) The mass will decrease.
(c) The mass will stay the same.
(d) The mass will fluctuate.
Question 6.
Who proposed the first scientific atomic theory?
(a) J.J. Thomson
(b) John Dalton
(c) Ernest Rutherford
(d) Niels Bohr
Question 7.
According to Dalton’s theory, matter is composed of tiny, indivisible particles called:
(a) Molecules
(b) Ions
(c) Atoms
(d) Compounds
Question 8.
Which law is directly supported by Dalton’s postulate that “Atoms can neither be created nor destroyed in a chemical reaction ”?
(a) Law of Definite Proportions
(b) Law of Multiple Proportions
(c) Law of Conservation of Mass
(d) Avogadro’s Law
Question 9.
Which of the following is NOT a postulate of Dalton’s atomic theory?
(a) All atoms of a given element are identical in mass and properties
(b) Atoms of different elements have different masses
(c) Atoms of the same element can have different masses (isotopes).
(d) Atoms combine in the ratio of small whole numbers to form compounds.
Question 10.
Dalton s postulate that “atoms are indivisible ” was later proven wrong by the discovery of:
(a) Isotopes
(b) Subatomic particles (protons, electrons, neutrons)
(c) Noble gases
(d) Chemical reactions
Question 11.
In a given compound, the relative number and kinds of atoms are:
(a) Variable
(b) Constant
(c) Dependent on the temperature
(d) Different for each sample
Assertion-Reason Questions
Directions: For Questions number (1) to (2), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true,
Question 1.
Assertion (A): Atom is the smallest unit of molecule
Reason (R): Atom is not seen by our naked eyes.
Question 2.
Assertion (A): Ionic compounds are named by writing the name of the cation first, followed by the name of the anion.
Reason (R): The anion is always written first in the chemical formula of an ionic compound.
Fill in the Blanks
1. The Law of Conservation of Mass states that mass can neither be _________ nor _________.
2. In a chemical reaction, the total mass of reactants is _________ to the total mass of products.
3. The Law of Constant Proportions states that a compound always contains the same elements in _________ proportion by mass.
4. According to Dalton’s Atomic Theory, atoms are _________ and _________ particles.
5. Atoms of the same element are _________ in mass and properties.
6. The sum of atomic masses of all atoms in a molecule is called _________.
7. The mass of an ionic compound is called _________.
State whether the statements given below are True or False:
1. Neutrons are positively charged particles present in the nucleus.
2. The maximum number of electrons that can be accommodated in the first shell (K shell) is 8.
3. The combination of atoms of two or more elements are called polyatomic ions.
4. An atom as a whole is electrically charged.
5. Interaction between atoms through transferring of electrons is called covalent bond.