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Computational Thinking – Chapter 7 Class 9th (New Syllabus) | All Punjab Boards

February 20, 2025 by samreen

Learn Computational Thinking from Chapter 7 of 9th class computer science (new syllabus) for all Punjab boards. Understand problem-solving, algorithms, decomposition, and logical reasoning with easy explanations.

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Multiple Choice Questions with Answers, Explanations, and Tips

1. Which of the following best defines computational thinking?

Options:
(a) A method of solving problems using mathematical calculations only.
(b) A problem-solving approach that employs systematic, algorithmic, and logical thinking. ✅
(c) A technique used exclusively in computer programming.
(d) An approach that ignores real-world applications.

Answer: (b) A problem-solving approach that employs systematic, algorithmic, and logical thinking.

Explanation: Computational thinking is a structured way of thinking that helps in solving problems efficiently by using logical steps, pattern recognition, decomposition, and abstraction. It is not limited to mathematics or programming.

Tip: Think of computational thinking as a way to approach complex problems in a systematic manner, not just in coding but in real life too.

2. Why is problem decomposition important in computational thinking?

Options:
(a) It simplifies problems by breaking them down into smaller, more manageable parts. ✅
(b) It complicates problems by adding more details.
(c) It eliminates the need for solving the problem.
(d) It is only useful for simple problems.

Answer: (a) It simplifies problems by breaking them down into smaller, more manageable parts.

Explanation: Problem decomposition helps in handling complex problems by dividing them into smaller sections, making them easier to solve.

Tip: Think of decomposition like assembling a puzzle—solving smaller pieces first makes the entire picture clearer.

3. Pattern recognition involves:

Options:
(a) Finding and using similarities within problems ✅
(b) Ignoring repetitive elements
(c) Breaking problems into smaller pieces
(d) Writing detailed algorithms

Answer: (a) Finding and using similarities within problems

Explanation: Pattern recognition is the ability to identify common trends or repeated structures in problems, making them easier to solve.

Tip: Look for repeating patterns in different problems to speed up finding solutions.

4. Which term refers to the process of ignoring the details to focus on the main idea?

Options:
(a) Decomposition
(b) Pattern recognition
(c) Abstraction ✅
(d) Algorithm design

Answer: (c) Abstraction

Explanation: Abstraction is the process of removing unnecessary details to focus on the essential aspects of a problem.

Tip: When dealing with a problem, try to remove unnecessary information and focus only on what matters.

5. Which of the following is a principle of computational thinking?

Options:
(a) Ignoring problem understanding
(b) Problem simplification ✅
(c) Avoiding solution design
(d) Implementing random solutions

Answer: (b) Problem simplification

Explanation: Simplifying a problem helps make it more manageable and easier to solve, which is a key aspect of computational thinking.

Tip: Always break problems into smaller, simpler parts before attempting a solution.

6. Algorithms are:

Options:
(a) Lists of data
(b) Graphical representations
(c) Step-by-step instructions for solving a problem ✅
(d) Repetitive patterns

Answer: (c) Step-by-step instructions for solving a problem

Explanation: An algorithm is a set of defined steps that provide a systematic way to solve a problem.

Tip: Algorithms should always be clear, efficient, and executable.

7. Which of the following is the first step in problem-solving according to computational thinking?

Options:
(a) Writing the solution
(b) Understanding the problem ✅
(c) Designing a flowchart
(d) Selecting a solution

Answer: (b) Understanding the problem

Explanation: Before solving a problem, it is essential to fully understand its nature, requirements, and constraints.

Tip: Read and analyze the problem carefully before jumping into solutions.

8. Flowcharts are used to:

Options:
(a) Code a program
(b) Represent algorithms graphically ✅
(c) Solve mathematical equations
(d) Identify patterns

Answer: (b) Represent algorithms graphically

Explanation: Flowcharts provide a visual representation of an algorithm, making it easier to understand and follow.

Tip: Use flowcharts to map out problem solutions before writing actual code.

9. Pseudocode is:

Options:
(a) A type of flowchart
(b) A high-level description of an algorithm using plain language ✅
(c) A programming language
(d) A debugging tool

Answer: (b) A high-level description of an algorithm using plain language

Explanation: Pseudocode is a way to describe an algorithm in simple, structured language before converting it into a programming language.

Tip: Write pseudocode before coding to ensure a logical flow in your program.

Short Questions with Simple Answers

Define computational thinking.
Answer: Computational thinking is a problem-solving approach that involves breaking down problems, recognizing patterns, using abstraction, and designing algorithms to solve them systematically.
What is decomposition in computational thinking?
Answer: Decomposition is the process of breaking a complex problem into smaller, more manageable parts to make it easier to solve.
Explain pattern recognition with an example.
Answer: Pattern recognition involves identifying similarities or repeating patterns in problems. Example: In math, recognizing that multiplication is repeated addition helps solve large problems faster.
Describe abstraction and its importance in problem-solving.
Answer: Abstraction means focusing on the main idea while ignoring unnecessary details. It helps simplify complex problems and makes solutions more general and reusable.
What is an algorithm?
Answer: An algorithm is a step-by-step set of instructions for solving a problem or completing a task.
How does problem understanding help in computational thinking?
Answer: Understanding the problem fully ensures that the correct approach is used to find an efficient solution.
What are flowcharts and how are they used?
Answer: Flowcharts are diagrams that visually represent the steps of an algorithm. They help in planning and understanding processes easily.
Explain the purpose of pseudocode.
Answer: Pseudocode is a simple way of writing an algorithm using plain language before converting it into actual code. It helps in planning and understanding logic.
How do you differentiate between flowcharts and pseudocode?
Answer: Flowcharts use diagrams to show the steps of an algorithm, while pseudocode uses simple text-based instructions.
What is a dry run and why is it important?
Answer: A dry run is manually going through an algorithm step by step with sample inputs to check for errors before running it on a computer. It helps in debugging.
Describe LARP and its significance in learning algorithms.
Answer: LARP (Live Action Role Play) is a method where people act out algorithmic steps to understand concepts better. It makes learning interactive and fun.
List and explain two debugging techniques.
Answer:

Print Statements: Adding print statements in code to check values at different stages.
Step-by-Step Execution: Running the program one step at a time to identify errors.

Long Questions with Simple Answers

1. Algorithm for Assigning a Grade Based on Marks

Algorithm:

Start
Input the student’s marks
If marks are 90 or above, assign A+
Else if marks are 80 to 89, assign A
Else if marks are 70 to 79, assign B
Else if marks are 60 to 69, assign C
Else assign F
Display the grade
End

2. Using Flowcharts and Pseudocode for Solving Complex Problems

Flowcharts and pseudocode help in organizing the steps of solving a problem.

Example: Online Payment Process

Flowchart: Shows steps like “Enter card details,” “Verify payment,” and “Approve or Reject.”
Pseudocode: Uses text to describe the process step by step before coding it.

Why Use Them?

Flowcharts give a visual representation.
Pseudocode helps in writing logic clearly before coding.

3. Computational Thinking and Its Significance

Definition: Computational thinking is a way of solving problems using logical steps, breaking down problems, finding patterns, and designing solutions.

Examples:

In Healthcare: AI uses computational thinking to predict diseases.
In Business: Companies analyze customer data for better marketing.

Why Important?

Helps solve complex problems
Improves efficiency
Used in different fields like education, science, and finance

4. Decomposition in Computational Thinking

Definition: Breaking a big problem into smaller, easier parts.

Example:

To create a calculator app, break it into:

User interface
Buttons for numbers
Mathematical operations
Displaying results

Why Important?

Makes complex tasks manageable
Helps in debugging and reusing code

5. Pattern Recognition in Problem-Solving

Definition: Finding similarities and trends in problems.

Example:

In math, noticing that multiplication is repeated addition.
In coding, recognizing a loop is needed for repeating tasks.

Why Important?

Speeds up problem-solving
Helps create efficient algorithms

6. Abstraction in Computational Thinking

Definition: Focusing on important details while ignoring unnecessary ones.

Example:

Google Maps hides extra details and only shows routes.
Video games don’t show how physics calculations work, just the final action.

Why Important?

Simplifies problems
Reduces complexity

7. What is an Algorithm?

Definition: A step-by-step set of instructions to solve a problem.

Example: Algorithm for Making Tea

Boil water
Add tea leaves
Wait for 2 minutes
Add milk and sugar
Serve

Role in Computational Thinking:

Provides a clear solution
Helps in automation

8. Flowcharts vs. Pseudocode

Feature	Flowcharts	Pseudocode
Format	Visual diagram	Text-based
Ease of Use	Easy to understand	Closer to real coding
When to Use?	For planning visually	Before writing real code

Example:

Flowcharts are better for explaining to non-coders.
Pseudocode is better when writing real code later.

9. What is a Dry Run?

Definition: Testing an algorithm manually before running it on a computer.

Example:

If an algorithm adds two numbers, test it with 5 + 3 = 8 before coding.

Why Important?

Helps find mistakes early
Ensures correct logic

10. What is LARP?

Definition: Live Action Role Play (LARP) is acting out an algorithm in real life to understand it better.

Example:

Students act as different parts of a computer (CPU, RAM, etc.) to learn how they work.

Why Important?

Makes learning fun and interactive
Improves understanding of algorithms

11. How LARP Helps in Computational Thinking?

Definition: LARP makes abstract concepts real by physically acting them out.

Example:

In a sorting algorithm, students can hold number cards and arrange themselves in order.

Why Important?

Helps students visualize algorithms
Encourages active learning

Binary System Chapter 2 Solved Exercise (Computer New Syllabus)

February 10, 2025 by samreen

MCQs with Answer and Explanation

1. What does ASCII stand for?

A. American Standard Code for Information Interchange
B. Advanced Standard Coder for Information Interchange
C. American Standard Communication for Information Interchange
D. Advanced Standard Communication for Information Interchange

✅ Answer: A. American Standard Code for Information Interchange

Explanation: ASCII is a standard encoding system used to represent text in computers and communication systems. It assigns a unique numerical value to each character.

Tip: ASCII is mainly used for text encoding in English-based systems.

2. Which of the following numbers is a valid binary number?

A. 1101102
B. 11011
C. 110.11
D. 110A

✅ Answer: B. 11011

Explanation: A binary number consists only of the digits 0 and 1. Options A and D contain invalid digits (2 and A), while C has a decimal point, making it a floating-point representation.

Tip: Valid binary numbers contain only 0s and 1s.

3. How many bits are used in standard ASCII encoding?

A. 7 bits
B. 8 bits
C. 16 bits
D. 32 bits

✅ Answer: A. 7 bits

Explanation: Standard ASCII uses 7 bits, allowing for 128 different characters (2⁷ = 128). Extended ASCII uses 8 bits to store 256 characters.

Tip: Standard ASCII → 7 bits, Extended ASCII → 8 bits.

4. Which of the following is an advantage of Unicode over ASCII?

A. It uses fewer bits per character
B. It can represent characters from many different languages
C. It is backward compatible with binary
D. It is specific to the English language

✅ Answer: B. It can represent characters from many different languages

Explanation: Unicode is designed to support multiple languages and scripts, whereas ASCII is limited to English characters. Unicode can store over 1 million characters.

Tip: Unicode is used globally for multi-language support.

5. How many bytes are used to store a typical integer?

A. 1 Byte
B. 2 Bytes
C. 4 Bytes
D. 8 Bytes

✅ Answer: C. 4 Bytes

Explanation: In most programming languages and systems, a standard integer (int) requires 4 bytes (32 bits). However, this can vary based on the system architecture.

Tip:

Short int → 2 bytes
int → 4 bytes
Long int → 8 bytes

6. What is the primary difference between signed and unsigned integers?

A. Unsigned integers cannot be negative
B. Signed integers have a larger range
C. Signed integers are only used for positive numbers
D. Signed integers are slower to process

✅ Answer: A. Unsigned integers cannot be negative

Explanation:

Signed integers store both positive and negative values.
Unsigned integers only store positive values (including zero).

Tip: Use unsigned integers when negative values are not needed to maximize range.

7. In the IEEE standard, how many bits are used for floating point precision?

A. 2 bits
B. 8 bits
C. 11 bits
D. 52 bits

✅ Answer: B. 8 bits

Explanation: The IEEE 754 standard for single-precision floating-point numbers allocates 8 bits for the exponent, 23 bits for the mantissa, and 1 bit for the sign.

Tip:

Single precision → 32 bits (8-bit exponent)
Double precision → 64 bits (11-bit exponent)

8. What is the approximate range of values for single-precision floating-point numbers?

A. 1.4 × 10⁻⁴⁵ to 3.4 × 10³⁸
B. 4.9 × 10⁻³²⁴ to 1.8 × 10³⁰⁸
C. 1.4 × 10⁻¹⁰ to 1.8 × 10¹⁵
D. 0 to 1.8 × 10³⁸

✅ Answer: A. 1.4 × 10⁻⁴⁵ to 3.4 × 10³⁸

Explanation: In IEEE 754 single-precision, the exponent range allows representation from approximately 1.4 × 10⁻⁴⁵ (smallest positive number) to 3.4 × 10³⁸ (largest number).

Tip:

Single precision → 32-bit floating point
Double precision → 64-bit floating point

9. What are the tiny dots that make up an image displayed on a screen?

A. Pixels
B. Bits
C. Bytes
D. Nodes

✅ Answer: A. Pixels

Explanation: A pixel (short for “picture element”) is the smallest unit of a digital image. Each pixel has RGB values to define its color.

Tip: More pixels = higher image resolution.

10. In an RGB color model, what does RGB stand for?

A. Red, Green, Blue
B. Red, Gray, Black
C. Right, Green, Blue
D. Red, Green, Brown

✅ Answer: A. Red, Green, Blue

Explanation: The RGB model is used in digital displays, where Red, Green, and Blue light combine at different intensities to create colors.

Tip: RGB is used for screens, while CMYK (Cyan, Magenta, Yellow, Black) is used for printing.

Summary of Key Takeaways:

ASCII is a 7-bit character encoding system.
Binary numbers contain only 0s and 1s.
Unicode supports multiple languages.
Standard integer size is 4 bytes.
Unsigned integers cannot be negative.
IEEE floating-point precision follows the IEEE 754 standard.
Pixels are the smallest units of an image.
RGB model is used for display screens.

Short Questions

1. What is the primary purpose of the ASCII encoding scheme?

✅ Answer: ASCII (American Standard Code for Information Interchange) is used to represent text in computers by assigning unique numeric values to characters.

🔑 Key Words: Character encoding, text representation, numeric values, computers.

2. Explain the difference between ASCII and Unicode.

✅ Answer: ASCII uses 7 or 8 bits to represent English characters, while Unicode supports multiple languages by using 16, 32, or more bits per character.

🔑 Key Words: ASCII, Unicode, character encoding, multi-language support, bit size.

3. How does Unicode handle characters from different languages?

✅ Answer: Unicode assigns a unique code point to each character, enabling representation of text in multiple languages and symbols.

🔑 Key Words: Unicode, code points, multilingual, character representation.

4. What is the range of values for an unsigned 2-byte integer?

✅ Answer: An unsigned 2-byte integer (16 bits) ranges from 0 to 65,535 (2¹⁶ – 1).

🔑 Key Words: Unsigned integer, 2-byte, 16-bit, range, binary representation.

5. Explain how a negative integer is represented in binary.

✅ Answer: Negative integers are represented using two’s complement notation, where the most significant bit (MSB) acts as the sign bit.

🔑 Key Words: Negative integers, two’s complement, sign bit, binary representation.

6. What is the benefit of using unsigned integers?

✅ Answer: Unsigned integers provide a larger range of positive values since they do not reserve a bit for the sign.

🔑 Key Words: Unsigned, positive values, extended range, no sign bit.

7. How does the number of bits affect the range of integer values?

✅ Answer: More bits allow for a larger range of integers, while fewer bits limit the range and can cause overflow.

🔑 Key Words: Bits, integer range, overflow, binary representation.

8. Why are whole numbers commonly used in computing for quantities that cannot be negative?

✅ Answer: Whole numbers (unsigned integers) are used for values that cannot be negative, such as memory addresses, pixel counts, and file sizes, to maximize range and efficiency.

🔑 Key Words: Whole numbers, unsigned, non-negative, memory addresses, efficiency.

9. How is the range of floating-point numbers calculated for single precision?

✅ Answer: The range of IEEE 754 single-precision floating-point numbers is determined by the 8-bit exponent and 23-bit mantissa, allowing values from ±1.4 × 10⁻⁴⁵ to ±3.4 × 10³⁸.

🔑 Key Words: Floating-point, single precision, IEEE 754, exponent, mantissa.

10. Why is it important to understand the limitations of floating-point representation in scientific computing?

✅ Answer: Floating-point representation introduces rounding errors and precision loss, which can impact accuracy in scientific and engineering calculations.

🔑 Key Words: Floating-point, precision loss, rounding errors, scientific computing, accuracy.

Long Questions

1. Explain how characters are encoded using Unicode. Provide examples of characters from different languages and their corresponding Unicode code points.

✅ Answer:
Unicode is a system used to represent characters from almost all the languages of the world. Each character is assigned a unique code point (a unique number) that allows computers to understand and display text correctly.

Examples of Unicode Characters:

English Letter ‘A’ → Unicode: U+0041
Arabic Letter ‘ب’ (Baa) → Unicode: U+0628
Chinese Character ‘你’ (You) → Unicode: U+4F60
Hindi Letter ‘अ’ (A) → Unicode: U+0905

🔹 Why is Unicode important?

It allows different languages to be displayed on computers.
It prevents errors when sending text in different languages.

2. Describe in detail how integers are stored in computer memory.

✅ Answer:
Computers store integers in binary format (0s and 1s). The number of bits (8-bit, 16-bit, 32-bit, etc.) determines how large a number can be stored.

🔹 Types of Integer Storage:

Unsigned Integers → Can only store positive numbers (e.g., 0 to 255 in 8-bit storage).
Signed Integers → Can store both positive and negative numbers using two’s complement notation.

🔹 Example:

A 4-bit unsigned integer can store values from 0000 (0) to 1111 (15).
A 4-bit signed integer (two’s complement) can store values from -8 to 7.

3. Explain the process of converting a decimal integer to its binary representation and vice versa. Include examples of both positive and negative integers.

✅ Answer:

Converting Decimal to Binary (Positive Number):

🔹 Example: Convert 13 to binary.

Divide by 2 and record the remainder:
- 13 ÷ 2 = 6, remainder = 1
- 6 ÷ 2 = 3, remainder = 0
- 3 ÷ 2 = 1, remainder = 1
- 1 ÷ 2 = 0, remainder = 1
Read the remainders from bottom to top → 1101₂

🔹 Example: Convert -13 to binary using two’s complement (8-bit representation):

Convert 13 to binary → 00001101
Take two’s complement (invert bits and add 1):
- Invert: 11110010
- Add 1: 11110011
So, -13 in binary = 11110011₂

🔹 Binary to Decimal Example:
Convert 1011₂ to decimal:
(1 × 2³) + (0 × 2²) + (1 × 2¹) + (1 × 2⁰) = 8 + 0 + 2 + 1 = 11

4. Perform the following binary arithmetic operations:

a) Multiplication of 101₂ by 11₂

✅ Answer: Convert to decimal:

101₂ = 5
11₂ = 3
5 × 3 = 15

Now multiply in binary:

     101
   ×  11
  --------
     101     (101 × 1)
+ 1010      (101 × 1, shift left)
  --------
   1111₂

✅ Final Answer: 1111₂ (15 in decimal)

b) Division of 1100₂ by 10₂

✅ Answer: Convert to decimal:

1100₂ = 12
10₂ = 2
12 ÷ 2 = 6

Now divide in binary:

  1100 ÷ 10  
= 0110₂ (6 in decimal)

✅ Final Answer: 0110₂ (6 in decimal)

5. Add the following binary numbers:

a) 101₂ + 110₂

    101
  + 110
  ------
   1011₂

✅ Final Answer: 1011₂ (11 in decimal)

b) 1100₂ + 1011₂

    1100
  + 1011
  ------
   10111₂

✅ Final Answer: 10111₂ (23 in decimal)

6. Convert the following numbers to 4-bit binary and add them:

a) 7 + (-4)

Convert to 4-bit binary:

7 → 0111₂
-4 (Two’s complement) → 1100₂

    0111
  + 1100
  ------
   0011₂

✅ Final Answer: 0011₂ (3 in decimal)

b) -5 + 3

Convert to 4-bit binary:

-5 (Two’s complement) → 1011₂
3 → 0011₂

    1011
  + 0011
  ------
   1110₂

✅ Final Answer: 1110₂ (-2 in decimal)

7. Solve the following binary operations:

a) 1101₂ – 0100₂

  1101
- 0100
------
  1001₂

✅ Final Answer: 1001₂ (9 in decimal)

b) 1010₂ – 0011₂

  1010
- 0011
------
  0111₂

✅ Final Answer: 0111₂ (7 in decimal)

c) 1000₂ – 0110₂

  1000
- 0110
------
  0010₂

✅ Final Answer: 0010₂ (2 in decimal)

d) 1110₂ – 100₂

  1110
- 0100
------
  1010₂

✅ Final Answer: 1010₂ (10 in decimal)

Summary:

Binary arithmetic follows simple addition/subtraction rules like decimal numbers.
Two’s complement is used for negative numbers.
Multiplication and division in binary work similarly to decimal operations.

Solved Exercise of Chapter 9 Nature of Science – 9th Class Physics

January 30, 2025 by samreen

Get the complete solved exercise of Chapter 9 Nature of Science from 9th Class Physics for all Punjab Boards. Detailed solutions, explanations, and key concepts to help you excel in your studies.

9.1 Physics is a branch of:

Options:
(a) Social science
(b) Life science
(c) Physical science
(d) Biological science

Answer: (c) Physical science

Explanation:
Physics deals with matter, energy, motion, and forces, making it a branch of physical science rather than life or social sciences.

Tip:
Remember, physical sciences include physics, chemistry, and astronomy, while life sciences include biology and botany.

9.2 Which branch of science plays a vital role in technology and engineering?

Options:
(a) Biology
(b) Chemistry
(c) Geology
(d) Physics

Answer: (d) Physics

Explanation:
Physics is fundamental in technology and engineering as it deals with energy, motion, and mechanics, which are crucial for innovation.

Tip:
Think about physics-based technologies like electricity, mechanics, and thermodynamics in engineering applications.

9.3 Automobile technology is based on:

Options:
(a) Acoustics
(b) Electromagnetism
(c) Optics
(d) Thermodynamics

Answer: (d) Thermodynamics

Explanation:
Automobile engines operate on thermodynamic principles, particularly heat and work energy transformations.

Tip:
Thermodynamics is key in engines, while electromagnetism relates to electric motors and optics relates to lenses.

9.4 A user-friendly software application of smartphone use:

Options:
(a) Laser technology
(b) Information technology
(c) Medical technology
(d) Electronic technology

Answer: (b) Information technology

Explanation:
Smartphones run on software applications and networks, which are part of information technology.

Tip:
If it involves data processing, communication, or software, it’s information technology.

9.5 The working of refrigeration and air conditioning involves:

Options:
(a) Electromagnetism
(b) Mechanics
(c) Climate science
(d) Thermodynamics

Answer: (d) Thermodynamics

Explanation:
Refrigeration and air conditioning depend on heat transfer principles, making thermodynamics the key science behind them.

Tip:
Thermodynamics governs heat flow, while mechanics focuses on forces and motion.

9.6 What is the ultimate truth of a scientific method?

Options:
(a) Hypothesis
(b) Experimentation
(c) Observation
(d) Theory

Answer: (d) Theory

Explanation:
A scientific theory is a well-tested explanation for observations and experiments.

Tip:
Hypothesis → Experiment → Observation → Theory (Final scientific truth)

9.7 The statement “If I do not study for this test, then I will not get a good grade” is an example of:

Options:
(a) Theory
(b) Observation
(c) Prediction
(d) Law

Answer: (c) Prediction

Explanation:
Predictions are statements about future events based on prior knowledge.

Tip:
Prediction is an educated guess, while observation is direct evidence.

9.8 Which of the following are methods of investigation?

Options:
(a) Observation
(b) Experimentation
(c) Research
(d) All of these

Answer: (d) All of these

Explanation:
Scientific investigation involves observation, experimentation, and research to draw conclusions.

Tip:
Remember that science relies on multiple investigation methods to ensure accuracy.

9.9 A hypothesis:

Options:
(a) May or may not be testable
(b) Is supported by evidence
(c) Is a possible answer to a question
(d) All of these

Answer: (d) All of these

Explanation:
A hypothesis is a proposed explanation that can be tested and supported by evidence.

Tip:
A hypothesis is an initial step in scientific research, leading to experiments and theories.

9.10 A graph of an organized data is an example of:

Options:
(a) Collecting data
(b) Forming a hypothesis
(c) Analyzing data
(d) Prediction

Answer: (c) Analyzing data

Explanation:
Graphs help interpret data patterns, which is part of analysis.

Tip:
Collection → Hypothesis → Experiment → Analyze (Graph) → Conclusion

9.11 The colour of a door is brown. It is an example of:

Options:
(a) Observation
(b) Hypothesis
(c) Prediction
(d) Law

Answer: (a) Observation

Explanation:
Observations are direct sensory experiences, such as seeing colors or shapes.

Tip:
If it’s based on direct evidence, it’s an observation, not a prediction or hypothesis.

Here are the solved Short Answer, Constructed Response, and Comprehensive Questions with answers, tips & tricks, and key terms:

B. Short Answer Questions

9.1 State in your own words, what is science? Write its two main groups.

Answer:
Science is the systematic study of the natural world based on observations, experiments, and evidence. The two main groups are:

Physical Sciences – Deals with non-living systems (Physics, Chemistry).
Life Sciences – Studies living organisms (Biology, Botany).

Tips & Tricks:

Science = Observation + Experimentation
Physical vs. Life Science

Key Terms: Systematic study, evidence, natural world, observation

9.2 What is physics all about? Name some of its branches.

Answer:
Physics is the branch of science that deals with matter, energy, motion, and forces. It explains natural phenomena using mathematical and experimental techniques.

Branches of Physics:

Classical Mechanics – Motion of objects
Thermodynamics – Heat and energy
Electromagnetism – Electricity & magnetism
Optics – Study of light
Quantum Physics – Subatomic particles

Tips & Tricks:

Physics explains how and why things move
Connect topics with real-life applications (electricity, heat, waves)

Key Terms: Matter, energy, motion, forces, laws of nature

9.3 What is meant by interdisciplinary fields? Give a few examples.

Answer:
Interdisciplinary fields combine concepts from multiple areas of science to solve problems.

Examples:

Biophysics – Physics applied to biological systems
Nanotechnology – Physics + Chemistry + Engineering
Astrophysics – Physics applied to space and celestial bodies

Tips & Tricks:

Think of fields where two sciences meet (e.g., physics + medicine = medical physics)
Identify applications in modern technology

Key Terms: Combination, multiple sciences, technology, innovation

9.4 List the main steps of the scientific method.

Answer:

Observation – Noticing a phenomenon
Question – Asking “why” or “how”
Hypothesis – Making an educated guess
Experimentation – Testing the hypothesis
Analysis – Examining results
Conclusion – Accepting or rejecting the hypothesis

Tips & Tricks:

Follow OQHEAC (Observation, Question, Hypothesis, Experiment, Analysis, Conclusion)
Science is based on trial and error

Key Terms: Hypothesis, experiment, data analysis, conclusion

9.5 What is a hypothesis? Give an example.

Answer:
A hypothesis is a possible explanation for an observation that can be tested through experiments.

Example: “Plants grow faster with more sunlight.”

Tips & Tricks:

A hypothesis is always testable
It can be right or wrong, but must be verifiable

Key Terms: Prediction, testable, experiment, observation

9.6 Distinguish between a theory and a law of physics.

Answer:

Theory: An explanation of a natural phenomenon based on evidence (e.g., Theory of Relativity).
Law: A statement that describes natural behavior, always true (e.g., Newton’s Laws of Motion).

Tips & Tricks:

Theory = Explanation, Law = Description
Laws don’t change, theories can be modified

Key Terms: Explanation, proven, universal truth

9.7 What is the basis of laser technology?

Answer:
Laser technology is based on stimulated emission of radiation, where atoms emit photons in phase, creating a powerful beam of light.

Tips & Tricks:

LASER = Light Amplification by Stimulated Emission of Radiation
Used in medicine, communication, and industry

Key Terms: Stimulated emission, photons, coherent light

9.8 What is falsifiability concept? How is it important?

Answer:
Falsifiability means a hypothesis must be testable and capable of being proven wrong. It ensures scientific accuracy.

Importance:

Differentiates science from pseudoscience
Helps in refining scientific theories

Tips & Tricks:

If something can’t be tested, it’s not scientific
Example: “Aliens control human thoughts” → Not falsifiable

Key Terms: Testable, evidence-based, scientific validity

C. Constructed Response Questions

9.1 Is the theory of science an ultimate truth? Describe briefly.

Answer:
Scientific theories are not ultimate truths but well-supported explanations. They can be modified with new evidence.

Example: Newton’s theory was revised by Einstein’s relativity.

9.2 Do you think the existing laws of nature may need a change in the future?

Answer:
Yes, as new discoveries emerge, some laws may be refined or replaced.

Example: Classical physics evolved into quantum mechanics.

9.3 Describe jobs that need the use of scientific knowledge.

Answer:

Doctors (Medical Science)
Engineers (Physics & Math)
Environmental Scientists (Biology & Chemistry)

9.5 Comment on the statement: “A theory is capable of being proved right but not being proved wrong is not a scientific theory.”

Answer:
For a theory to be scientific, it must be falsifiable. If it cannot be tested, it is not scientific.

Example: Astrology is not science because it cannot be tested.

9.7 If a hypothesis is not testable, is the hypothesis wrong? Explain.

Answer:
A hypothesis that cannot be tested is not scientific, but it is not necessarily wrong.

Example: “Life exists in another galaxy” → It’s a claim, but not testable yet.

D. Comprehensive Questions

9.1 Describe the scope of physics. What are the main branches of physics?

Answer:
Physics studies the universe from tiny particles to massive galaxies.

Branches: Mechanics, Thermodynamics, Optics, Electromagnetism, Quantum Physics, Nuclear Physics.

9.2 What is meant by interdisciplinary fields of physics? Give three examples.

Answer:
Fields where physics is applied with other sciences.

Examples: Biophysics, Nanotechnology, Geophysics.

9.4 Differentiate between science, technology, and engineering with examples.

Answer:

Science: Knowledge of natural phenomena (e.g., Laws of Motion).
Technology: Application of science (e.g., Computers).
Engineering: Designing solutions (e.g., Bridges).

9.5 What is the scope of physics in everyday life? Give some examples.

Answer:
Physics is used in:

Electricity (Home appliances)
Communication (Mobile phones)
Transport (Vehicles)

Chapter 7: Solved Exercise – Thermal Properties of Matter | Class 9th

January 29, 2025 by samreen

Get the complete Chapter 7 Solved Exercise of Thermal Properties of Matter for Class 9th. Perfect for All Punjab Boards, this guide includes MCQs, short and long questions with detailed explanations.

MCQs on Temperature and Heat

Q1: How do the molecules in a solid behave?

Statement: Molecules in a solid
Options:
(a) Move randomly
(b) Vibrate about their mean positions
(c) Rotate and vibrate randomly at their own positions
(d) Move in a straight line from hot to cold ends
Answer: (b) Vibrate about their mean positions
Explanation: In solids, molecules are tightly packed and can only vibrate around fixed positions due to strong intermolecular forces.
Tip: In solids, particles do not have translational motion but only vibrational motion.

Q2: What type of motion is exhibited by gas molecules?

Statement: The motion of molecules in a gas is mostly
Options:
(a) Linear motion
(b) Random motion
(c) Vibratory motion
(d) Rotatory motion
Answer: (b) Random motion
Explanation: Gas molecules move freely and collide randomly in all directions, leading to chaotic or random motion.
Tip: Gas molecules have the highest kinetic energy and move in all directions.

Q3: What does temperature measure?

Statement: Temperature of a substance is
Options:
(a) The total amount of heat contained in it
(b) The total number of molecules in it
(c) The degree of hotness or coldness
(d) Dependent upon the intermolecular distance
Answer: (c) The degree of hotness or coldness
Explanation: Temperature is a measure of the average kinetic energy of molecules, which determines how hot or cold a substance is.
Tip: More kinetic energy means a higher temperature.

Q4: What is heat?

Statement: Heat is
Options:
(a) The total kinetic energy of the molecules
(b) The internal energy
(c) Work done by the molecules
(d) The energy in transit
Answer: (d) The energy in transit
Explanation: Heat is a form of energy that flows from a hotter body to a cooler body until thermal equilibrium is reached.
Tip: Heat is always transferred from high to low temperature.

Q5: What is the melting point of ice in Kelvin?

Statement: In Kelvin scale, the temperature corresponding to the melting point of ice is
Options:
(a) Zero
(b) 32
(c) –273
(d) 273
Answer: (d) 273
Explanation: The melting point of ice in Celsius is 0°C. Since Kelvin = Celsius + 273, we get 273 K.
Tip: Always add 273 to convert Celsius to Kelvin.

Q6: Which thermometer can measure a large range of temperatures?

Statement: A thermometer that measures a large range of temperature is
Options:
(a) Mercury-in-glass thermometer
(b) Alcohol-in-glass thermometer
(c) Clinical thermometer
(d) Digital thermometer
Answer: (a) Mercury-in-glass thermometer
Explanation: Mercury has a wide operating temperature range (-39°C to 356°C), making it ideal for measuring high temperatures.
Tip: Alcohol thermometers are used for extremely low temperatures, while clinical thermometers are limited to body temperature ranges.

Q7: What is a disadvantage of using alcohol in thermometers?

Statement: One disadvantage of alcohol-in-glass thermometers is
Options:
(a) It has large expansivity
(b) It has a low freezing point (-112°C)
(c) It wets the glass tube
(d) Its expansion is linear
Answer: (c) It wets the glass tube
Explanation: Alcohol adheres to the glass, making readings difficult. Mercury does not wet glass, so it is preferred for precise readings.
Tip: Alcohol is used in cold regions due to its lower freezing point.

Here are well-explained answers in simple language for Class 9 students based on the given image.

Short Answer Questions

Q1: Why do solids have a fixed volume and shape according to the particle theory of matter?

Answer:
Solids have a fixed shape and volume because their particles are closely packed together in a fixed pattern. The strong forces of attraction between the particles keep them in place, allowing only vibrations but no free movement.

Q2: Why do gases have neither a fixed volume nor a fixed shape?

Answer:
Gases do not have a fixed shape or volume because their particles are far apart and move freely in all directions. They take the shape of their container and expand to fill any available space.

Q3: Compare the spacing of molecules in solid, liquid, and gaseous states.

Answer:

Solid: Particles are very close together and arranged in a fixed pattern.
Liquid: Particles are close but can move past each other, allowing the liquid to flow.
Gas: Particles are far apart and move randomly in all directions.

Q4: What is the effect of raising the temperature of a liquid?

Answer:
When the temperature of a liquid increases, its particles move faster and spread further apart. If enough heat is added, the liquid can turn into a gas (evaporation or boiling).

Q5: What is meant by the temperature of a body?

Answer:
Temperature is the measure of how hot or cold an object is. It depends on the average kinetic energy (motion) of the particles in the object.

Q6: Define heat as ‘energy in transit.’

Answer:
Heat is the transfer of thermal energy from a hotter object to a cooler one. It always flows from a high-temperature area to a low-temperature area.

Q7: What is meant by the thermometric property of a substance?

Answer:
A thermometric property is a physical property of a substance that changes with temperature. Examples include the expansion of mercury in a thermometer or the change in electrical resistance of metals.

Q8: Describe the main scales used for the measurement of temperature. How are they related?

Answer:
The three main temperature scales are:

Celsius (°C) – Water freezes at 0°C and boils at 100°C.
Fahrenheit (°F) – Water freezes at 32°F and boils at 212°F.
Kelvin (K) – Water freezes at 273 K and boils at 373 K.
The relationship between Celsius and Kelvin is:

K=°C+273K = °C + 273

Q9: What is meant by the sensitivity of a thermometer?

Answer:
Sensitivity of a thermometer refers to how quickly and accurately it detects small changes in temperature. A thermometer with a thinner tube or more responsive liquid is more sensitive.

Q10: What do you mean by the linearity of a thermometer?

Answer:
Linearity means that the liquid inside the thermometer expands uniformly with temperature change. If the liquid does not expand evenly, the thermometer will not be accurate.

Q11: What makes the scale reading of a thermometer accurate?

Answer:
A thermometer’s scale is accurate if:

The liquid expands uniformly.
The tube is narrow for better precision.
It has clear, evenly spaced markings.

Q12: What does determine the direction of heat flow?

Answer:
Heat always flows from a hotter object to a cooler one until both reach the same temperature.

Q13: Distinguish between heat and internal energy.

Answer:

Heat: Energy in transit that moves from a hot object to a cold one.
Internal Energy: The total energy (kinetic + potential) of all particles in an object.

Q14: When you touch a cold surface, does cold travel from the surface to your hand, or does energy travel from your hand to the cold surface?

Answer:
Energy travels from your warm hand to the cold surface. Heat always moves from a warmer object to a cooler one.

Q15: Can you feel your fever by touching your own forehead? Explain.

Answer:
No, because your hand and forehead are at the same temperature. To measure fever accurately, you need a thermometer.

Constructed Response Questions

Q1: Is kinetic molecular theory of matter applicable to the plasma state of matter?

Answer:
Yes, the kinetic molecular theory explains the motion of particles in solids, liquids, and gases. Plasma is a state of matter with freely moving charged particles, which also follow the principles of kinetic theory.

Q2: Why is mercury usually preferred to alcohol as a thermometric liquid?

Answer:
Mercury is preferred because:

It does not stick to glass.
It expands uniformly.
It is easy to see due to its shiny appearance.
It has a wider temperature range (-39°C to 356°C).

Q3: Why is water not suitable for use in thermometers? Without calculations, guess what is an equivalent temperature of 373 K on Celsius and Fahrenheit scales?

Answer:
Water is not used because:

It does not expand uniformly.
It evaporates quickly.
It wets the glass, making readings difficult.

373 K in Celsius and Fahrenheit:

Celsius: 373−273=100°C373 – 273 = 100°C
Fahrenheit: 100°C=212°F100°C = 212°F

Q4: Mention two ways in which the design of a liquid-in-glass thermometer may be altered to increase its sensitivity.

Answer:

Making the capillary tube narrower.
Using a liquid that expands more with temperature changes.

Q5: One liter of water is heated by a stove, and its temperature rises by 2°C. If one liter of water is heated on the same stove for the same time, what will be the rise in temperature?

Answer:
The temperature rise will also be 2°C because the same amount of heat is applied to the same amount of water.

Q6: Why are there no negative numbers on the Kelvin scale?

Answer:
Kelvin scale starts at absolute zero (0 K), the lowest possible temperature where all molecular motion stops. Since temperature cannot be lower than absolute zero, there are no negative Kelvin temperatures.

Q7: Comment on the statement, “A thermometer measures its own temperature.”

Answer:
This statement means that a thermometer must reach thermal equilibrium with the object being measured. The reading it shows is its own temperature, which matches the temperature of the object.

Short Answer Questions

7.8. There are various objects made of cotton, wood, plastic, metals, etc., in a winter night. Compare their temperatures with the air temperature by touching them with your hand.

Answer: The temperature of all objects will be the same as the air temperature. However, they feel different when touched because of their thermal conductivity. Metals feel colder as they conduct heat away from your hand quickly, whereas materials like cotton and wood are poor conductors and feel warmer.

7.9. Which is greater: an increase in temperature by 1°C or one 1°F?

Answer: An increase of 1°C is greater than 1°F because 1°C is equivalent to 1.8°F.

7.10. Why would you not expect all the molecules in a gas to have the same speed?

Answer: In a gas, molecules move randomly and collide with each other. Due to these collisions and variations in kinetic energy, different molecules have different speeds. Some move faster while others move slower.

7.11. Does it make sense to talk about the temperature of a vacuum?

Answer: No, because temperature is a measure of the average kinetic energy of particles. In a vacuum, there are no particles, so the concept of temperature does not apply.

7.12. Comment on the statement: “A hot body does not contain heat.”

Answer: The statement means that a hot body contains internal energy due to molecular motion. Heat, on the other hand, is energy in transit that flows from a hotter object to a cooler one.

7.13. Discuss whether the Sun is matter.

Answer: The Sun is mainly composed of plasma, which is a high-energy state of matter where atoms are ionized into charged particles. While plasma is a form of matter, the Sun itself also emits radiation (light and heat), which is not matter. Therefore, while part of the Sun is matter, its radiation is not.

Comprehensive Questions

7.1. Describe the main points of the particle theory of matter which differentiate solids, liquids, and gases.

Answer: The particle theory of matter states:

Matter is made up of tiny particles.
These particles are in constant motion.
There are forces of attraction between particles.
The spaces between particles differ: solids have the least, gases have the most.
The energy of particles increases from solids to gases.

These points explain the differences in the properties of solids, liquids, and gases.

7.2. What is temperature? How is it measured? Describe briefly the construction of a mercury-in-glass thermometer.

Answer: Temperature is the measure of the average kinetic energy of particles in a substance. It is measured using thermometers.

A mercury-in-glass thermometer consists of:

A thin glass tube with a mercury reservoir at the bottom.
A temperature scale marked on the glass.
When temperature rises, mercury expands and moves up the tube, indicating the temperature.

7.3. Compare the three scales used for measuring temperature.

Answer: The three main temperature scales are:

Celsius (°C): Water freezes at 0°C and boils at 100°C.
Fahrenheit (°F): Water freezes at 32°F and boils at 212°F.
Kelvin (K): Starts at absolute zero (0 K = -273.15°C) and is used in scientific calculations.

Kelvin is the most fundamental scale as it does not have negative values.

7.4. What is meant by sensitivity, range, and linearity of thermometers? Explain with examples.

Answer:

Sensitivity: The ability to detect small temperature changes. A thermometer with a thin tube and alcohol as a liquid is more sensitive.
Range: The temperature limits a thermometer can measure. Mercury thermometers have a high range, while alcohol thermometers are used for very low temperatures.
Linearity: How evenly the liquid expands with temperature. Mercury expands uniformly, making it highly accurate.

7.5. Explain how the parameters mentioned in question 7.4 are improved in the structure of a glass-in-glass thermometer.

Answer:

Sensitivity is improved by using a narrow capillary tube and a liquid that expands more, such as alcohol.
Range is increased by choosing different liquids. Alcohol works at very low temperatures, while mercury is used at high temperatures.
Linearity is ensured by using uniform liquid expansion, such as mercury, which expands evenly across different temperatures.