Class 9 Exam  >  Class 9 Notes  >  Science Class 9  >  Important Diagrams: Atoms and Molecules

Important Diagrams: Atoms and Molecules | Science Class 9 PDF Download

Q1: Answer the following questions based on the diagram given below:

Important Diagrams: Atoms and Molecules | Science Class 9

(i) What is the purpose of conducting this experiment with solutions X and Y?
Ans: This experiment aims to demonstrate the law of conservation of mass during a chemical reaction.

(ii) What is the role of the ignition tube in this experiment?
Ans: The ignition tube containing solution X is used to showcase the mass of the substances involved before the chemical reaction takes place.

(iii) Why is it important to weigh the flask's contents before and after tilting and swirling?
Ans: 
Weighing the flask before and after mixing the solutions helps us observe any changes in mass, demonstrating the law of conservation of mass.

(iv) Why is a cork placed on the flask during the experiment?
Ans: Placing a cork on the flask prevents the escape of any gases produced during the chemical reaction, ensuring that the mass remains within the system as per the law of conservation of mass.

(v) Does the total mass of the flask and its contents change during the experiment?
Ans: No, the total mass of the flask and its contents remains the same before and after the chemical reaction, by the law of conservation of mass.

Q2: Answer the following questions based on the diagram given below:

Important Diagrams: Atoms and Molecules | Science Class 9

(i) Who was the first scientist to utilize symbols to represent elements and their composition?
Important Diagrams: Atoms and Molecules | Science Class 9

Ans: John Dalton was the first scientist to use symbols to quickly represent components, where the sign for an element denoted both the element and one atom of that element.

(ii) What did Dalton's symbols for elements signify?
Ans: Dalton's symbols signified:

  • The element itself
  • One atom of that element

(iii) How were the original names of elements derived historically?
Ans: The original names of elements were often derived from the places where they were first discovered or from specific colours associated with them.

(iv) Can you provide an example of an element named after a location?
Ans: Certainly, copper is an example of an element named after a place, specifically Cyprus.

(v) Which organization is responsible for approving names, symbols, and units of elements in the present day?
Ans: The International Union of Pure and Applied Chemistry (IUPAC) is the organization responsible for approving names, symbols, and units of elements in the contemporary scientific context.

Q3: Answer the following questions based on the diagram given below:

Important Diagrams: Atoms and Molecules | Science Class 9

(i) What are binary compounds, and how are they formed?
Ans:
Binary compounds are the simplest compounds made up of two different elements. They are formed by combining two elements in a specific ratio.

(ii) How are chemical formulae for compounds written?
Ans: Chemical formulae for compounds are written by indicating the symbols of the constituent elements and their valencies. The valencies are used to determine the ratio in which the elements combine, and the charges of the ions are criss-crossed to obtain the correct formula.

(iii) Explain the procedure to write the formula for magnesium chloride.
Ans: To write the formula for magnesium chloride, the symbol of the cation (Mg²⁺) is written first, followed by the symbol of the anion (Cl⁻). The charges of the ions (2+ for Mg and 1- for Cl) are criss-crossed to obtain the formula MgCl₂.

(iv) How is the ratio of chloride ions to magnesium ions balanced in magnesium chloride?
Ans: The ratio of chloride ions to magnesium ions is:

  • There are two chloride ions (Cl) for every magnesium ion (Mg2+).
  • This ratio balances the positive and negative charges, ensuring the compound is neutral overall.
The document Important Diagrams: Atoms and Molecules | Science Class 9 is a part of the Class 9 Course Science Class 9.
All you need of Class 9 at this link: Class 9
Are you preparing for Class 9 Exam? Then you should check out the best video lectures, notes, free mock test series, crash course and much more provided by EduRev. You also get your detailed analysis and report cards along with 24x7 doubt solving for you to excel in Class 9 exam. So join EduRev now and revolutionise the way you learn!
Sign up for Free Download App for Free
84 videos|384 docs|61 tests

Up next

FAQs on Important Diagrams: Atoms and Molecules - Science Class 9

1. What are atoms and how do they relate to molecules?
Ans. Atoms are the basic building blocks of matter, consisting of a nucleus made up of protons and neutrons, surrounded by electrons in various energy levels. Molecules are formed when two or more atoms bond together through chemical bonds, such as covalent or ionic bonds. This bonding allows atoms to achieve stability by filling their outer electron shells.
2. What is the structure of an atom?
Ans. An atom consists of three main components: protons (positively charged particles) and neutrons (neutral particles) located in the nucleus at the center, and electrons (negatively charged particles) that orbit the nucleus in specific energy levels or shells. The number of protons defines the element, while the arrangement of electrons determines the atom's chemical properties.
3. How do atoms bond to form molecules?
Ans. Atoms bond to form molecules through various types of chemical bonds. The most common types are covalent bonds, where atoms share electrons, and ionic bonds, where one atom donates an electron to another, creating charged ions that attract each other. These interactions allow atoms to achieve a more stable electron configuration.
4. What is the difference between an element and a compound?
Ans. An element is a pure substance that consists of only one type of atom, such as hydrogen (H) or oxygen (O). A compound, on the other hand, is a substance formed when two or more different types of atoms chemically bond together, such as water (H₂O), which is made up of hydrogen and oxygen atoms. Compounds have distinct properties that differ from those of their constituent elements.
5. Why are atoms considered the fundamental units of matter?
Ans. Atoms are considered the fundamental units of matter because they are the smallest units that retain the chemical properties of an element. They combine to form all substances we encounter in our daily lives, from gases to solids. The unique arrangement and number of atoms in a molecule dictate its chemical behavior and interactions, making them essential to understanding chemistry and the physical world.
84 videos|384 docs|61 tests
Download as PDF

Up next

Explore Courses for Class 9 exam
Related Searches

video lectures

,

Exam

,

study material

,

ppt

,

Summary

,

mock tests for examination

,

pdf

,

Free

,

Sample Paper

,

Semester Notes

,

Important questions

,

shortcuts and tricks

,

practice quizzes

,

Important Diagrams: Atoms and Molecules | Science Class 9

,

Objective type Questions

,

Extra Questions

,

Viva Questions

,

past year papers

,

MCQs

,

Important Diagrams: Atoms and Molecules | Science Class 9

,

Previous Year Questions with Solutions

,

Important Diagrams: Atoms and Molecules | Science Class 9

;