COLLOIDAL SOLUTION(CBSE 9TH NCERT TEXT SCIENCE)

 

Colloidal Solution (Colloids)

• A colloidal solution is a heterogeneous mixture in which very small particles of one substance are evenly spread out in another substance.

• The particle size in colloids is between true solution and suspension (i.e. 1 nm – 1000 nm).

• These particles are small enough that they do not settle down on their own and cannot be seen with the naked eye, but can scatter light.

Characteristics of Colloids

• Heterogeneous mixture – appears homogeneous to the naked eye.

• Stable – particles do not settle down on standing.

• Tyndall Effect – colloidal particles scatter a beam of light.

• Particles cannot be filtered using ordinary filter paper but can be separated by special filters (ultrafiltration).

• Brownian Motion – colloidal particles show continuous zig-zag movement.

Examples of Colloids in Daily Life

• Milk → fat in water (emulsion)

• Fog → water droplets in air (aerosol)

• Butter → water in fat (emulsion)

• Smoke → solid particles in air

Types of Colloids (Based on Phases)

Dispersed Phase	Dispersion Medium	Example

Solid

Gas

Smoke, Dust in Air

Liquid

Gas

Fog, Mist, Cloud

Gas

Liquid

Foam, Shaving Cream

Solid

Liquid

Starch Solution, Muddy Water

Liquid

Liquid

Milk, Emulsion

Solid

Solid

Coloured Glass, Gemstones

Important Note for Exams

• True solution → particle size < 1 nm, transparent (e.g., sugar in water)

• Colloid → particle size 1–1000 nm, scatters light (e.g., milk)

• Suspension → particle size > 1000 nm, particles settle on standing (e.g., sand in water)

TYPES OF SOLUTIONS

What is the momentum of an object of mass m, moving with a velocity v? CBSE PHYSICS

 

The (linear) momentum is

$$\mathbf{p} = m\,\mathbf{v}$$

a vector in the same direction as the velocity.
SI units: kg·m/s.

ELECTRIC CURRENT, CIRCUITS AND OHM'S LAW IMPORTANT NOTES ( CBSE 10TH SCIENCE )

 

1. Electric Current

• Definition: The rate of flow of electric charge through a conductor.

  $$\mathrm{<span\; style="font-size:\; medium;"><b>I</b></span>}<span\; style="font-size:\; medium;"><b>=</b></span>\frac{\mathrm{<span\; style="font-size:\; medium;"><b>Q</b></span>}}{\mathrm{<span\; style="font-size:\; medium;"><b>t</b></span>}}$$

  where
  $I$= current (ampere, A)
  $Q$ = charge (coulombs, C)
  $t$= time (seconds, s)

• Direction:
  Conventional current flows from positive → negative terminal of a cell.
  Electron flow is actually from negative → positive.

• Unit Conversion:
  1 A = 1 C/s.

2.Electric Potential & Potential Difference

• Potential difference (V): Work done to move a unit positive charge between two points.

  V=W/Q​​

  Unit: Volt (V)
  1 V = 1 Joule/Coulomb

3. Electric Circuit

• Closed path for current flow, made of:

  • Source (cell/battery)

  • Conductors (wires)

  • Load (bulb/resistor)

  • Switch (to open/close circuit)

• Symbols to learn (for diagram-based questions):

  • Cell, battery, wire, key/switch (open & closed), resistor, variable resistor (rheostat), ammeter, voltmeter, galvanometer, etc.

 4.Ohm’s Law

• Statement: At constant temperature, the current (I) through a conductor is directly proportional to the potential difference (V) across it.

  $$\mathrm{<br>}$$

  $R$ = resistance (Ω).

• Resistance (R):

  R=ρl/A​​

  $\rho$= resistivity of material (Ω·m)
  $l$= length of conductor (m)
  $A$= cross-sectional area (m²)

• Graph:

  • Plot V (y-axis) vs I (x-axis) → straight line through origin.

  • Slope = Resistance $R$.

• 5. Series and Parallel Circuits

  • Series: $R_{\text{eq}} = R_1 + R_2 + R_3 + \dots$

    • Same current flows, voltage divides.

  • Parallel: $\frac{1}{R_{\text{eq}}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots$

    • Same voltage across branches, current divides.

6. Electric Power

• $$P=VI=I^2\mathrm{R\; , }$$

  Unit: Watt (W)
  1 kW = 1000 W.

• Key Points for CBSE Exam

  • Always label circuit diagrams (Ammeter in series, Voltmeter in parallel).

  • Temperature constant condition is important in Ohm’s Law questions.

  • Practice numericals using:

    • $V = IR$
      

    • $P =$ $P = V2/R$​

  • Remember units and conversions (e.g., 1 mA = ${10}^{-\mathrm{3A}}$).

JOULE'S LAW OF HEATING CBSE PHYSICS

 

Statement:
The heat produced in a conductor by an electric current is directly proportional to:

1. The square of the current ($I^2$)

2. The resistance of the conductor ($R$)

3. The time for which the current flows ($t$)

Mathematical form:

H=I2Rt

Where:

• $H$= heat produced (in joules)

• $I$= current (in amperes)

• $R$= resistance (in ohms)

• $t$= time (in seconds)

Explanation:
When an electric current flows through a resistor, the electrical energy is converted into heat due to collisions between moving electrons and atoms of the conductor. This is called the heating effect of electric current.

Applications:

• Electric heaters and geysers

• Electric irons

• Fuses and electric bulbs

• Electric cooking appliances

ADVERSE EFFECTS OF BIOMAGNIFICATION IN HUMANBEINGS CBSE BIOLOGY

 

• Humans are adversely affected by biomagnification because harmful chemicals accumulate and concentrate in their bodies through the food chain.
• Here’s why:
• Humans are at the top of the food chain → We eat plants and animals that may already have toxins (like pesticides, heavy metals, or industrial chemicals) in their bodies.

• Toxins are not broken down or excreted easily → Substances like DDT, mercury, and PCBs are fat-soluble and persist in body tissues for years.

• Concentration increases at each trophic level → By the time the toxin reaches humans, its concentration is much higher than it was in the water, soil, or plants.

• Adverse effects on humans include:

• Damage to the nervous system (e.g., mercury poisoning)

• Hormonal imbalance and reproductive problems

• Cancer risk increase

• Immune system suppression

• Birth defects and developmental disorders in children

• Example: Eating large fish like tuna or swordfish can lead to mercury accumulation, which can harm the brain and kidneys over time.

BIOMAGNIFICATION EFFECTS IN HUMAN

Name the group of organisms which form in the first trophic level of all food chains? Why are they called so? CBSE

 

The group of organisms that form the first trophic level in all food chains are producers (also called autotrophs).

Examples: Green plants, algae, and some photosynthetic bacteria.

Reason they are called producers:

• They produce their own food using sunlight (photosynthesis) or chemical energy (chemosynthesis).

• They do not depend on other organisms for food.

• They convert inorganic substances (like carbon dioxide and water) into organic matter (like glucose), providing energy for all other organisms in the food chain.

In short: producers form the base of the food chain because they create the energy-rich compounds that sustain all other trophic levels.

PRODUCERS

ELECTRIC POWER AND SI UNIT CBSE PHYSICS

 

Electric Power

Electric power is the rate at which electrical energy is converted into another form of energy (such as heat, light, or motion) or the rate at which work is done by an electric current.

Mathematically:

$$\mathrm{<span\; style="font-size:\; medium;"><b>P</b></span>}<span\; style="font-size:\; medium;"><b>=</b></span>\frac{\mathrm{<span\; style="font-size:\; medium;"><b>W</b></span>}}{\mathrm{<span\; style="font-size:\; medium;"><b>t</b></span>}}$$

• $P$ = power (in watts)

• $W$ = work or energy (in joules)

• $t$ = time (in seconds)

For electrical circuits, it can also be expressed as:

P=V×I

Where:

• $V$ = potential difference (in volts)

• $I$ = current (in amperes)

• P=I2R or P=V2/R​

Or, using Ohm’s law:

SI Unit of Electric Power:

• Unit: watt (W)

• Definition: $1\text{watt}=1\text{joule/second}$

• That means if a device consumes 1 joule of energy every second, its power is 1 watt.

REPRODUCTIVE PART OF BISEXUAL FLOWER CBSE BIOLOGY

 

1. Stamens – The male reproductive part

• Structure: A stamen is typically made of two main parts:

  • Anther: The oval-shaped structure at the tip that produces pollen grains (the male gametes). Each anther usually has two lobes, and inside each lobe are pollen sacs containing microspores that develop into pollen.

  • Filament: A slender stalk that supports the anther and positions it so that pollinators or the wind can easily carry away the pollen.

• Function: Produces and releases pollen, which contains sperm cells for fertilization.

2. Carpels (or Pistil) – The female reproductive part

• Structure: A carpel consists of three main parts:

  • Stigma: The sticky top surface that receives pollen grains during pollination.

  • Style: A tube-like structure connecting the stigma to the ovary; it allows pollen tubes to grow down toward the ovules.

  • Ovary: The swollen base that contains ovules; each ovule contains a female gamete (egg cell).

• Function: Receives pollen, enables fertilization, and develops seeds and fruit after fertilization.

PARTS OF BISEXUAL FLOWER

WHAT IS VARIATION? LIST TWO MAIN REASONS THAT MAY LEAD TO VARIATION IN A POPULATION?

 

Variation is the difference in characteristics or traits among individuals of the same species.

It means no two organisms are exactly alike in appearance, behavior, or genetic makeup.

Two main reasons for variation in a population:

1. Genetic causes – Differences in DNA due to sexual reproduction (recombination of genes) or mutations in genes.

2. Environmental causes – Influence of surroundings such as climate, nutrition, lifestyle, or exposure to diseases, which can change the way traits are expressed.

So, variation comes from a mix of what’s in the genes and what’s in the environment.

VARIATION

Which of the following flowers will have higher possibility of self pollination a.Mustard, b.Watermelon, c.Papaya, d.Hibiscus?(CBSE 10TH BIOLOGY BOARD EXAM QUESTION)

 

The flower with the highest possibility of self-pollination among the options is Hibiscus.

Here’s why:

• Mustard – Can self-pollinate, but also cross-pollinates frequently.

• Watermelon – Plants are usually unisexual (male and female flowers separate) → favors cross-pollination.

• Papaya – Mostly dioecious (male and female flowers on separate plants) → only cross-pollination possible.

• Hibiscus – Bisexual flower (both stamens and pistil in the same flower) → high chance of self-pollination if not prevented by mechanisms like protandry or self-incompatibility.

HIBISCUS FLOWER

MOLECULAR FORMULA OF METHANE AND PROPANE(CBSE 10TH QUESTION)

 

The molecular formulas are:

• Methane → CH₄

• Propane → C₃H₈

CARBON COMPOUNDS HAVE LOW MELTING AND BOILING POINTS WHY?(CBSE 10TH BOARD EXAM QUESTION)

  

Carbon compounds (especially most organic compounds like sugars, alcohols, waxes, oils, etc.) usually have low melting and boiling points because:

• They are covalent in nature –
  Most carbon compounds have atoms joined by covalent bonds. The strong covalent bonds hold atoms together within a molecule, but the forces between molecules (intermolecular forces) are much weaker.

• Weak intermolecular forces –
  Between molecules, only weak van der Waals forces or hydrogen bonds exist. These forces require little energy to overcome, so the substance melts or boils at a low temperature.

• Non-polar or slightly polar molecules –
  Many carbon compounds are non-polar (like methane, oils, waxes) or only weakly polar, which means they don’t attract each other strongly. This reduces melting and boiling points further.

• Strong bonds inside the molecule, but weak attractions between molecules → less heat needed to separate them → low melting & boiling points.

MOLECULAR FORMULA AND STRUCTURE OF BENZENE (CBSE 10TH SCIENCE BOARD EXAM QUESTION)

  

The molecular formula of benzene is C₆H₆.

BENZENE

That means:

• 6 carbon atoms

• 6 hydrogen atoms

These atoms are arranged in a ring structure with alternating double bonds, often represented as a hexagon with a circle inside to indicate resonance.

The structure of benzene (C₆H₆) is a planar hexagonal ring made of six carbon atoms, with one hydrogen atom attached to each carbon.

Key Structural Features

• Carbon arrangement: Six carbons form a ring, each bonded to two other carbons and one hydrogen.

• Bonding: Instead of fixed single and double bonds, benzene has resonance—the electrons are delocalized over the whole ring, giving all C–C bonds the same length (~1.39 Å).

• Planarity: All atoms lie in one plane, making it very stable.

• Bond angles: Each carbon is sp² hybridized, with bond angles of 120°.

Common representations:

1. Kekulé structures: Show alternating single and double bonds.

2. Resonance circle: A hexagon with a circle inside to represent delocalized π electrons.

In benzene (C₆H₆), the situation is a bit tricky—there aren’t true fixed single and double covalent bonds.

Why:

• The Kekulé structure shows alternating single and double bonds between carbon atoms.

• In reality, due to resonance, all six C–C bonds are identical: they are intermediate between a single bond and a double bond in strength and length.

SOLENOID?(CBSE XTH PHYSICS)

 

A solenoid is basically a coil of wire, usually wound in a cylindrical shape, that creates a magnetic field when an electric current passes through it.

Think of it as "an electromagnet in a tube"—but with the added twist that it can also produce motion if paired with a movable core.

SOLENOID

Key Points

• Structure: A long wire wound into many loops (often around a metal core).

• Function: Converts electrical energy into a magnetic field.

• Magnetic effect: The field inside is strong and uniform; outside, it’s weaker.

• Types:

  • Electromagnetic solenoid: Used to generate a controlled magnetic field.

  • Electromechanical solenoid: Uses the magnetic field to move a plunger or core (used in door locks, valves, relays).

• Applications

  • Car starters

  • Electric door locks

  • MRI machines

  • Automatic water valves

  • Loudspeakers

HUMAN MADE ECOSYSTEMS (CBSE XTH BOARD EXAM IMPORTANT PORTION)

Human-made ecosystems (also called artificial ecosystems) are environments that people design, construct, and manage to support specific plants, animals, and human needs. Unlike natural ecosystems, which develop on their own, human-made ones rely on constant maintenance, resource input, and monitoring to function.

Key Features

• Planned and constructed by humans rather than formed naturally.

• Dependent on human intervention for water, nutrients, and balance.

• Often created for a purpose like food production, recreation, or aesthetics.

• Less biodiversity compared to most natural ecosystems.

Examples

1. Agricultural Fields – Farmlands, orchards, and plantations.

2. Urban Parks & Gardens – Managed green spaces in cities.

3. Aquaculture Systems – Fish farms, shrimp ponds.

4. Zoos & Botanical Gardens – Curated for education and conservation.

5. Reservoirs & Canals – Water bodies created for storage, irrigation, or transport.

6. Greenhouses – Controlled environments for growing plants.

7. Terrariums & Aquariums – Miniature ecosystems kept indoors.

AGRICULTURAL FIELDS

URBAN PARK AND GARDEN

SHRIMP PONDS

ZOO

GREEN HOUSE

BOTANICAL GARDEN

Advantages

• Meet human needs for food, water, recreation, and research.

• Can be designed to conserve endangered species.

• Provide green spaces in urban areas.

Disadvantages

• High maintenance costs.

• Usually less resilient to pests, disease, or climate changes.

• Reduced biodiversity compared to natural systems.

LIFE PROCESSES (CBSE 10TH BIOLOGY)

 

What are Life Processes?

Life processes are the basic functions performed by living organisms to maintain life.
Examples: Nutrition, respiration, transportation, excretion.

1. Nutrition

Types of Nutrition:

• Autotrophic: Organisms make their own food (e.g., plants).
• Heterotrophic: Organisms depend on other organisms for food (e.g., animals).

➤ Photosynthesis (in plants):

Definition: Process by which green plants prepare food using sunlight, CO₂ and water.

Equation:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll)

Steps:

• Absorption of light energy by chlorophyll.

• Conversion of light energy to chemical energy.

• Splitting of water molecules (Photolysis).

• Reduction of CO₂ to carbohydrates (glucose).

Nutrition in Humans (Holozoic):

• Ingestion → Digestion → Absorption → Assimilation → Egestion

• Important digestive enzymes:

  • Saliva: Amylase (breaks starch)

  • Stomach: Pepsin (proteins), HCl (acidic medium)

  • Small intestine: Lipase, Trypsin, Amylase (complete digestion)

• Villi in the small intestine absorb nutrients.

2. Respiration

Types:

• Aerobic Respiration (with oxygen):

  • Glucose → CO₂ + H₂O + Energy (38 ATP)

• Anaerobic Respiration (without oxygen):

  • Glucose → Alcohol + CO₂ + Energy (in yeast)

  • In muscles: Glucose → Lactic acid + Energy

➤ Site:

• Cytoplasm (glycolysis), Mitochondria (Kreb's cycle)

3. Transportation

 In Human Beings:

• Circulatory System: Heart, blood, and blood vessels.

• Heart: 4 chambers (Right atrium, Right ventricle, Left atrium, Left ventricle)

  • Double circulation: Pulmonary and systemic circulation

• Blood components:

  • RBCs (carry oxygen via hemoglobin)

  • WBCs (fight infection)

  • Platelets (blood clotting)

  • Plasma (transports nutrients, hormones)

➤ In Plants:

• Xylem: Transports water and minerals (root to leaves)

• Phloem: Transports food (leaves to other parts - translocation)

4. Excretion

➤ In Humans:

• Excretory organ: Kidneys

• Nephron: Functional unit of kidney

  • Filtration occurs in glomerulus

  • Reabsorption of useful substances

  • Urine formation and collection in bladder

• In Plants:

  • Remove waste through:

    • Stomata, lenticels

    • Storage in leaves and bark (which later shed)

    • Excretion of resins, latex, gums

• Key Terms to Remember:

• Autotrophs: Self-nourishing (e.g., green plants)

• Heterotrophs: Dependent on others for food

• Peristalsis: Wave-like muscular movement of food

• Transpiration: Loss of water vapor from plant leaves

• Ultrafiltration: Filtration in glomerulus of kidney

• Lymph: Fluid part of blood without RBCs