Welcome To My School Study
Do You Know
Q1. Solid has Fixed Shape
Answer: Fixed shape
Solid state of matter has a fixed shape and fixed volume. In solids, particles are packed very closely together. Because of this close arrangement, particles cannot move freely from one place to another. They can only vibrate around their fixed positions. This is the reason solids maintain their shape and do not flow like liquids or gases.
Examples of solids include wood, iron, stone, ice, books, pencils, and tables. If we place a book on a table, its shape remains the same. It does not spread or change shape automatically. This property is called rigidity.
Important Characteristics of Solids
- Solids have fixed shape.
- Solids have fixed volume.
- Particles are tightly packed.
- Intermolecular force is very strong.
- Solids cannot be compressed easily.
- Particles vibrate but do not move freely.
Why Solids Have Fixed Shape?
The particles in solids are held together by strong attractive forces. Since the particles cannot move freely, the solid keeps its original structure and shape.
Examples from Daily Life
- Ice cube keeps its shape in a freezer.
- A chair remains rigid and stable.
- A metal rod does not flow like water.
NCERT Based Concept
According to NCERT science concepts, matter exists in three common states — solid, liquid, and gas. Among them, solids have maximum force of attraction and minimum space between particles.
Simple Explanation
If you pour water into a glass, it changes shape according to the container. But if you place a stone inside the glass, its shape remains unchanged. Therefore, stone is a solid with fixed shape.
Short Revision Points
- Solid = fixed shape + fixed volume
- Strong attraction between particles
- Very little movement of particles
- Hard and rigid in nature
Q2. Balanced Force Results In No Motion Change
Answer: No motion change
Balanced forces are forces acting on an object in opposite directions with equal magnitude. When forces are balanced, they cancel each other. As a result, the object does not change its state of motion.
If an object is at rest, it remains at rest. If an object is moving, it continues moving with the same speed and direction unless an unbalanced force acts on it.
Understanding Balanced Force
Suppose two students push a box from opposite sides with equal force. The box does not move because the forces are balanced.
Key Features of Balanced Force
- Net force becomes zero.
- Motion does not change.
- Shape may change sometimes.
- Speed remains constant.
Real Life Examples
- A book lying on a table
Gravity pulls the book downward while the table applies an equal upward force. Therefore, the book remains at rest. - Tug of war with equal force
If both teams pull equally, the rope does not move. - Standing person
The body weight acts downward while the ground exerts equal upward force.
Difference Between Balanced and Unbalanced Force
| Balanced Force | Unbalanced Force |
|---|---|
| Equal forces | Unequal forces |
| No change in motion | Causes motion |
| Net force = 0 | Net force ≠ 0 |
NCERT Concept
NCERT explains that balanced forces cannot change the state of motion of an object. Only unbalanced forces can start or stop motion.
Important Formula
Net Force = Sum of all forces acting on the object
If net force = 0 → Balanced force
Simple Explanation
Imagine pushing a wall lightly. The wall does not move because the force applied is balanced by the wall’s resistance.
Short Revision Points
- Balanced forces cancel each other.
- They do not produce acceleration.
- Motion remains unchanged.
- Net force becomes zero.
Q3. Mole Concept Deals with Number
Answer: Number (संख्या से)
The mole concept is one of the most important ideas in chemistry. It helps scientists count extremely tiny particles like atoms, molecules, and ions.
Since atoms are too small to count individually, chemists use a special unit called mole.
What is One Mole?
One mole contains:
6.022 × 10²³ particles
This number is called Avogadro Number.
Why Mole Concept is Important?
In chemistry, reactions involve huge numbers of atoms and molecules. Counting them one by one is impossible. Therefore, the mole concept provides a convenient method for measurement.
Examples
- 1 mole of hydrogen molecules contains 6.022 × 10²³ molecules.
- 1 mole of sodium atoms contains 6.022 × 10²³ atoms.
Relation Between Mole and Mass
Every substance has a molar mass.
Example:
- Oxygen = 32 g/mol
- Carbon = 12 g/mol
- Water = 18 g/mol
Mole Formula
Number of moles = Given mass / Molar mass
Daily Life Comparison
Just as a dozen means 12 objects, a mole means 6.022 × 10²³ particles.
NCERT Based Explanation
NCERT chemistry chapters explain mole concept as a bridge between microscopic particles and measurable quantities.
Importance in Chemistry
- Helps calculate chemical reactions.
- Used in balancing equations.
- Helps determine mass relationships.
Easy Understanding
A shopkeeper counts eggs in dozens because counting one by one is difficult. Similarly, chemists count atoms in moles.
Short Revision Points
- Mole is a counting unit.
- One mole = 6.022 × 10²³ particles.
- Related to number of particles.
- Used in chemical calculations.
Q4. Unit of Acceleration is m/s²
Answer: m/s²
Acceleration means the rate of change of velocity with time. It tells us how quickly the speed or direction of an object changes.
Formula of Acceleration
Acceleration = Change in velocity / Time
a = (v – u) / t
Where:
- a = acceleration
- v = final velocity
- u = initial velocity
- t = time
SI Unit of Acceleration
The SI unit of acceleration is:
meter per second squared (m/s²)
Meaning of m/s²
If a car increases its speed by 2 m/s every second, its acceleration is 2 m/s².
Types of Acceleration
- Positive acceleration
Speed increases with time. - Negative acceleration (retardation)
Speed decreases with time. - Zero acceleration
Speed remains constant.
Real Life Examples
- A bike speeding up on a road.
- A train slowing down at a station.
- A falling object under gravity.
Relation with Motion
Acceleration changes velocity. Velocity changes when:
- Speed changes
- Direction changes
- Both change
NCERT Concept
NCERT explains acceleration in the chapter of motion and laws of motion. It is a vector quantity because it has both magnitude and direction.
Difference Between Speed and Acceleration
| Speed | Acceleration |
|---|---|
| Distance covered per unit time | Change in velocity per unit time |
| Scalar quantity | Vector quantity |
| Unit = m/s | Unit = m/s² |
Easy Example
A car moving at constant speed has zero acceleration. But when the driver presses the accelerator pedal, the speed increases and acceleration occurs.
Important Facts
- Gravity produces acceleration.
- Acceleration can be positive or negative.
- Higher acceleration means faster change in speed.
Short Revision Points
- Acceleration = change in velocity/time
- SI unit = m/s²
- Vector quantity
- Can increase or decrease speed
Q5. Meristematic Tissue is for Growth
Answer: Growth
Meristematic tissue is a plant tissue responsible for growth. The cells of this tissue divide continuously and help plants increase in length and thickness.
These tissues are made of actively dividing cells.
Features of Meristematic Tissue
- Cells divide rapidly.
- Cells are small and thin-walled.
- Dense cytoplasm is present.
- Vacuoles are absent or very small.
- Cells remain alive.
Types of Meristematic Tissue
1. Apical Meristem
Found at the tips of roots and shoots.
Function:
- Increases length of plant.
Example:
- Growth of stem upward.
2. Lateral Meristem
Found on the sides of stems and roots.
Function:
- Increases thickness.
Example:
- Growth in tree trunk diameter.
3. Intercalary Meristem
Found at the base of leaves or internodes.
Function:
- Helps rapid growth.
Example:
- Growth in grass after cutting.
Importance of Meristematic Tissue
- Helps plant growth.
- Repairs damaged parts.
- Produces new cells.
- Forms permanent tissues.
Difference Between Meristematic and Permanent Tissue
| Meristematic Tissue | Permanent Tissue |
|---|---|
| Cells divide continuously | Cells stop dividing |
| Responsible for growth | Perform specific functions |
| Small cells | Larger cells |
NCERT Based Explanation
NCERT explains that meristematic tissues are responsible for plant growth because they continuously produce new cells.
Daily Life Examples
- New leaves growing on plants.
- Increase in tree height.
- Growth of roots underground.
Simple Understanding
Whenever a plant grows taller or thicker, meristematic tissue is working actively inside the plant.
Additional Important Points
- Plants keep growing throughout life due to meristematic tissue.
- Animals generally stop growing after a certain age, but plants continue growth.
- Growth in plants depends greatly on cell division.
Short Revision Points
- Meristematic tissue helps growth.
- Cells divide continuously.
- Found in root and shoot tips.
- Responsible for increasing size of plant.
Overall Quick Revision
| Question | Correct Answer |
|---|---|
| Solid has | Fixed shape |
| Balanced force results in | No motion change |
| Mole concept deals with | Number |
| Unit of acceleration | m/s² |
| Meristematic tissue is for | Growth |