VARDAAN LEARNING INSTITUTE

Fertilizers: Inorganic salts/chemicals prepared in factories; rich in specific plant nutrients like NPK; do not provide humus.
Manure: Organic substance obtained by decomposition of plant/animal wastes; prepared in fields; provides lot of humus to soil.

Ignition Temperature: The lowest temperature at which a substance catches fire.
A matchstick does not catch fire on its own because its temperature is lower than its ignition temperature at room temperature. Rubbing it generates heat (friction) to reach ignition temp.

1. They are clean fuels and do not produce smoke (less pollution).
2. They have high calorific value.
3. They can be transported easily through pipes.

Internal Fertilization: Fusion of male and female gametes takes place inside the female body (e.g., Humans, Cows).
External Fertilization: Fusion takes place outside the female body, usually in water (e.g., Frogs, Fish).

Laws of Reflection:
1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, the normal at the point of incidence, and the reflected ray all lie in the same plane.
OR (Lateral Inversion): The phenomenon where the left side of an object appears as the right side in the mirror image and vice-versa.

Sliding friction is less than static friction because when an object starts sliding, the contact points on its surface do not get enough time to lock into the contact points of the floor. Thus, less force is needed to keep it moving.

Nitrogen Cycle:
1. Nitrogen Fixation: Atmospheric nitrogen is converted into compounds by Rhizobium bacteria/Blue-green algae or Lightning.
2. Uptake: Plants absorb these compounds from soil for proteins.
3. Consumption: Animals eat plants.
4. Excretion/Death: Nitrogenous waste returns to soil via decomposers.
5. Denitrification: Some bacteria convert soil nitrogen back into nitrogen gas.

Major Groups: Bacteria, Fungi, Protozoa, and Algae. (Viruses are unique).
Unicellular Group: Protozoa (mostly) and Bacteria.
OR (Uses):
1. Preparation of curd (Lactobacillus) and bread (Yeast).
2. Production of alcohol and vinegar.
3. Preparation of antibiotics (Penicillin).
4. Cleaning environment (decomposers).

Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature, and high pressure transformed the dead organisms into petroleum and natural gas.

Deforestation: Clearing of forests and using that land for other purposes.
Natural Causes: Forest fires, Severe droughts.
Man-made Causes: Procuring land for cultivation, Building houses and factories, Making furniture or using wood as fuel.

(a) Audible Sound: Sound that can be heard by human ears. Range: 20 Hz to 20,000 Hz.
(b) Noise Pollution: Presence of excessive or unwanted sounds in the environment which may cause health problems.

(a) [Diagram check: Incident ray, Reflected ray, Normal, Angles i and r equal].
(b) Regular Reflection: Occurs on smooth surfaces; parallel rays remain parallel after reflection.
Diffused Reflection: Occurs on rough surfaces; parallel rays are reflected in different directions.

Structure of Candle Flame:
1. Innermost Zone (Black): Zone of unburnt wax vapours; least hot.
2. Middle Zone (Yellow): Zone of partial combustion; luminous; moderately hot.
3. Outer Zone (Blue): Zone of complete combustion; non-luminous; hottest part.

(a) Force: A push or a pull acting on an object. SI Unit: Newton (N).
(b) Effects:
1. Force can make a stationary object move.
2. Force can change the speed of a moving object.
3. Force can change the direction of motion.
4. Force can change the shape of an object.
OR
(a) Contact Force: Requires physical contact (e.g., Friction). Non-contact Force: Acts from a distance (e.g., Magnetic, Gravitational).
(b) The force is Muscular Force (Contact). It changes the shape of the hot iron piece (flattens it).

(a) Sex Hormones: Hormones that control the development of secondary sexual characters (e.g., Testosterone in males, Estrogen in females). Named so because they determine sex-related features.
(b) Insects: Insect hormones control metamorphosis (larva to adult). Frogs: Hormone Thyroxine (produced by Thyroid) is essential for metamorphosis of tadpole to frog. It requires iodine in water.
(c) Pancreas.

(a) Electroscope: A device used to detect whether an object is charged.
Construction: A glass jar with a metal rod inserted through a cork. Upper end has a metal disc, lower end has two metal leaves (gold/aluminum).
Working: When a charged body touches the disc, charge is transferred to the leaves via the rod. Both leaves get similar charge and repel each other, diverging outwards.
(b) Safety Measures:
1. Do not take shelter under an isolated tall tree.
2. Do not use an umbrella with a metallic end.
3. Stay away from windows; do not sit near metal sheds.
4. If inside a car, stay there with windows closed.

(i) A large protected area meant for conservation of wild life, plant and animal resources and traditional life of the tribals living in the area.
(ii) In a zoo, animals are kept in artificial cages/enclosures for public view. In a sanctuary, they live in their natural habitat protected from hunting.
(iii) Because they are found only in a particular area. Destruction of their habitat or introduction of new species can affect their existence and endanger them.

(i) To increase friction and prevent slipping (provide better grip).
(ii) To increase friction for a better grip on the equipment.
(iii) Objects moving in fluids (air/water) face fluid friction (drag). To reduce this, they are given a streamlined shape (tapering at ends).

(i) Chromium, Gold, Silver, Copper, Zinc. (Any two)
(ii) Chromium has a shiny appearance, does not corrode, and resists scratches.
(iii) The iron spoon should be connected to the Negative Terminal of the battery. Because copper ions (Cu²⁺) are positively charged and are attracted to the negative electrode to gain electrons and deposit as copper metal.