7th Science - Quarterly Exam 2024 - Original Question Paper | Chennai District
PART - I (10 x 1 = 10)
I. Choose the correct answer.
1. Light year is the unit of __________
2. A particle is moving in a circular path of radius r. The displacement after half a circle would be __________
3. Oxygen, hydrogen and Sulphur are examples for __________
4. The metal which is liquid at room temperature is __________
5. The basic Unit of Matter is __________
6. Pollinators are __________
7. Reproductive part of a plant is __________
8. Our living Place should be __________
9. Tobacco chewing causes __________
10. Who uses the Photoshop software more?
PART - II (15 x 2 = 30)
II. Answer the following. (any 15)
11. Define - Astronomical unit.
One astronomical unit (AU) is defined as the average distance between the Earth and the Sun.
1 AU ≈ 149.6 million kilometers or 1.496 x 10¹¹ m.
12. i) Give the Value of one light Year.
ii) What is the Density of Gold?
i) Value of one Light Year: One light-year is 9.46 x 10¹⁵ meters.
ii) Density of Gold: The density of gold is 19.3 g/cm³.
13. Distinguish between Speed and Velocity?
| Speed | Velocity |
|---|---|
| The rate of change of distance. | The rate of change of displacement. |
| It is a scalar quantity. | It is a vector quantity. |
| It is always positive. | It can be positive, negative, or zero. |
| Speed = Distance / Time | Velocity = Displacement / Time |
14. A Car starts from rest and is travelling with a Velocity of 20m/s in 10s. What is its Acceleration?
Given:
- Initial velocity (u) = 0 m/s (since it starts from rest)
- Final velocity (v) = 20 m/s
- Time (t) = 10 s
Formula for acceleration (a):
$$ a = \frac{v - u}{t} $$
Substituting the values:
$$ a = \frac{20 - 0}{10} = \frac{20}{10} = 2 \, \text{m/s}^2 $$
The acceleration of the car is 2 m/s².
15. What are Compounds? Give two examples.
A compound is a pure substance formed when two or more elements chemically combine in a fixed ratio by mass.
Examples:
- Water (H₂O): Formed from Hydrogen and Oxygen.
- Carbon dioxide (CO₂): Formed from Carbon and Oxygen.
16. Write the chemical formula for the following elements.
a) Hydrogen: H₂
b) Nitrogen: N₂
c) Ozone: O₃
d) Sulphur: S₈
17. Fill in:
i) Nitrogen is the most abundant gas in the Atmosphere.
ii) There are 118 number of known Elements.
18. What is Atomic Number?
The atomic number (symbol Z) of an element is the number of protons found in the nucleus of every atom of that element. It uniquely identifies a chemical element.
19. The Atomic number of an element is 9. It has 10 Neutrons. Find the element from the Periodic Table. What will be its Mass number?
- Element: The element with atomic number (Z) = 9 is Fluorine (F).
- Mass Number (A): Mass Number = Number of Protons + Number of Neutrons.
A = 9 + 10 = 19.
The mass number of the element is 19.
20. What is Cross Pollination?
Cross-pollination is the transfer of pollen grains from the anther of a flower to the stigma of a flower on another plant of the same species. It requires external agents like wind, water, insects, or animals.
21. Draw the diagram - Parts of Flower and label it.
(Students should draw a diagram of a flower and label the following parts)
- Stigma: Receives pollen.
- Style: Connects stigma to the ovary.
- Ovary: Contains ovules.
- Petal: Often colourful to attract insects.
- Sepal: Protects the bud.
- Anther: Produces pollen.
- Filament: Supports the anther.
- Receptacle: Part of the flower stalk.
22. Match:
a) Petal - Attracts insect
b) Hooks - Bignonia
c) Fern - Spore
d) Phylloclade - Opuntia
23. Analogy:
i) Typhoid : Bacteria :: Hepatitis : Virus
ii) Tuberculosis : Air :: Cholera : Water
24. Why First Aid is Essential?
First aid is essential because it is the immediate assistance given to any person suffering from either a minor or serious illness or injury. Its primary goals are:
- To preserve life.
- To prevent the condition from worsening.
- To promote recovery.
25. Write about the right way of Protecting the Eyes?
The right ways to protect the eyes include:
- Avoid reading in very bright or dim light.
- Do not watch TV or use a computer for a long time.
- Wash your eyes with clean, cold water daily.
- Eat a balanced diet rich in Vitamin A (e.g., carrots, leafy vegetables).
- Do not rub your eyes if an irritant enters. Instead, wash with clean water.
26. True or False:
i) Rabies is a Fatal disease - True
ii) Stomach Ulcer is a non - Communicable Disease - False (It is primarily caused by H. pylori bacteria and is considered communicable, though not easily transmitted).
27. Ginger is considered to be a Stem, not a Root why?
Ginger is considered a stem (specifically, a rhizome) and not a root because it possesses characteristics of a stem, such as:
- Nodes and Internodes: It has distinct nodes (points where leaves and buds arise) and internodes (the space between nodes).
- Scale Leaves: It has thin, papery scale leaves at the nodes.
- Buds: It has apical and axillary buds, which can grow into new shoots. Roots do not have these features.
28. What is Raster Graphics?
Raster graphics (or bitmap images) are digital images created or captured as a set of pixels, or tiny dots of colour, arranged in a grid. Each pixel is assigned a specific colour. Common raster file formats include JPEG, GIF, and PNG. They lose quality when scaled up.
PART - III (4 x 5 = 20)
III. Answer any one question from each section.
SECTION - A
29. i) How will you determine the density of a Stone using a measuring Jar?
To determine the density of a stone, we need to find its mass and volume.
Materials Required:
A stone, a physical balance, a measuring jar, and water.
Procedure:
- Measure the Mass: Use the physical balance to measure the mass of the stone. Let this be 'm' grams.
- Measure the Volume:
- Take the measuring jar and fill it partially with water. Note the initial volume of the water (V₁).
- Gently immerse the stone completely into the water, ensuring it does not splash.
- Note the new volume of the water with the stone in it (V₂).
- The volume of the stone is the difference between the final and initial readings: Volume (V) = V₂ - V₁. The unit will be cm³ or ml (since 1 ml = 1 cm³).
- Calculate Density: Use the formula for density:
$$ \text{Density} = \frac{\text{Mass (m)}}{\text{Volume (V)}} $$
The unit of density will be g/cm³.
(OR)
ii) Explain the types of Stability with suitable examples?
Stability is the ability of an object to regain its original position after being slightly displaced. There are three types of stability (or equilibrium):
1. Stable Equilibrium:
- An object is in stable equilibrium if it returns to its original position after being slightly displaced.
- This occurs when the center of gravity is at its lowest possible position. When displaced, the center of gravity is raised.
- Example: A cone resting on its base. If you tilt it slightly, it will fall back to its original position.
2. Unstable Equilibrium:
- An object is in unstable equilibrium if it does not return to its original position and topples over after being slightly displaced.
- This occurs when the center of gravity is at its highest possible position. A slight displacement lowers the center of gravity.
- Example: A cone balanced on its tip. A small push will make it fall over.
3. Neutral Equilibrium:
- An object is in neutral equilibrium if it stays in the new position when displaced and does not return to its original position or topple over.
- The center of gravity remains at the same height when the object is displaced.
- Example: A cone lying on its side or a ball on a flat horizontal surface. If you roll it, it will stay in its new position.
SECTION - B
30. i) Differentiate Metals and Non-Metals.
| Property | Metals | Non-Metals |
|---|---|---|
| Physical State | Generally solid at room temperature (except Mercury). | Exist as solids, liquids, or gases. |
| Lustre | Have a shiny appearance. | Are dull (except Iodine and Diamond). |
| Hardness | Usually hard (except Sodium, Potassium). | Usually soft (except Diamond). |
| Malleability & Ductility | Malleable (can be beaten into sheets) and ductile (can be drawn into wires). | Brittle (break easily). Not malleable or ductile. |
| Conductivity | Good conductors of heat and electricity. | Poor conductors of heat and electricity (except Graphite). |
| Sonority | Produce a ringing sound when struck. | Are non-sonorous. |
(OR)
ii) Define Valency. What is the valency of the element with Atomic Number 8?
Valency: Valency is the combining capacity of an element. It is the number of electrons an atom can lose, gain, or share to achieve a stable electron configuration (usually a full outer shell).
Valency of the element with Atomic Number 8:
- The element with atomic number 8 is Oxygen (O).
- Its electronic configuration is 2, 6. (2 electrons in the first shell, 6 in the outer shell).
- To achieve a stable configuration (8 electrons in the outer shell), it is easier for an oxygen atom to gain 2 electrons than to lose 6 electrons.
- Therefore, the valency of Oxygen is 2.
SECTION - C
31. i) Write a brief Account on Pollination.
Pollination is the process of transferring pollen grains from the male part of a flower (anther) to the female part (stigma). This is the first step in sexual reproduction in flowering plants, leading to fertilization and the production of seeds and fruits.
Types of Pollination:
- Self-Pollination: Pollen from the anther of a flower is transferred to the stigma of the same flower or another flower on the same plant.
- Cross-Pollination: Pollen from the anther of a flower on one plant is transferred to the stigma of a flower on another plant of the same species.
Agents of Pollination:
Pollination is facilitated by various agents:
- Abiotic Agents (Non-living):
- Wind (Anemophily): Flowers are usually small, not brightly coloured, and produce large amounts of light, dry pollen. e.g., Grass, Maize.
- Water (Hydrophily): Occurs in aquatic plants. Pollen is released into the water. e.g., Vallisneria.
- Biotic Agents (Living):
- Insects (Entomophily): Flowers are large, colourful, fragrant, and produce nectar to attract insects. e.g., Rose, Sunflower.
- Birds (Ornithophily): Flowers are often brightly coloured and produce a lot of nectar. e.g., Hibiscus.
- Animals (Zoophily): Other animals like bats and snails also act as pollinators.
(OR)
ii) Write about any Three Communicable Diseases in Detail.
Communicable diseases are illnesses that spread from one person to another or from an animal to a person.
1. Tuberculosis (TB):
- Causative Agent: Bacterium called Mycobacterium tuberculosis.
- Mode of Transmission: It spreads through the air when an infected person coughs, sneezes, or talks, releasing bacteria into the air which are then inhaled by others.
- Symptoms: Persistent cough (sometimes with blood), fever, night sweats, weight loss, and fatigue.
- Prevention & Control: BCG vaccination, avoiding close contact with infected individuals, and ensuring proper ventilation.
2. Cholera:
- Causative Agent: Bacterium called Vibrio cholerae.
- Mode of Transmission: It spreads through contaminated food and water.
- Symptoms: Severe watery diarrhea, vomiting, muscle cramps, and rapid dehydration, which can be fatal if untreated.
- Prevention & Control: Drinking safe, boiled or treated water, practicing good sanitation and hygiene (washing hands), and eating properly cooked food.
3. Typhoid:
- Causative Agent: Bacterium called Salmonella typhi.
- Mode of Transmission: Spreads through the consumption of food or water contaminated with the feces of an infected person.
- Symptoms: High fever, headache, stomach pain, weakness, and sometimes a rash.
- Prevention & Control: Proper sanitation, safe drinking water, vaccination, and avoiding food from unhygienic sources.
SECTION - D
32. i) Draw the Structure of an Atom and explain the Position of the sub-Atomic Particles.
(Students should draw a simple Bohr model of an atom, like Helium or Lithium).
An atom consists of a central nucleus and electrons that orbit the nucleus. The main sub-atomic particles and their positions are:
1. Protons (p⁺):
- Position: Located inside the nucleus at the center of the atom.
- Charge: Positively charged (+1).
- Mass: They contribute significantly to the mass of the atom.
2. Neutrons (n⁰):
- Position: Also located inside the nucleus along with the protons.
- Charge: Electrically neutral (no charge).
- Mass: Similar in mass to protons, they also contribute to the atom's mass.
3. Electrons (e⁻):
- Position: Revolve around the nucleus in specific paths or shells called orbits or energy levels.
- Charge: Negatively charged (-1).
- Mass: Have a very negligible mass compared to protons and neutrons.
The nucleus is dense and positively charged due to protons, while the atom as a whole is electrically neutral because the number of electrons is equal to the number of protons.
(OR)
ii) How are Diseases Transmitted from one Person to the Other Person?
Diseases, especially communicable diseases, are transmitted from an infected person to a healthy person through various modes. The main modes of transmission are:
1. Direct Contact:
- Person-to-Person: Occurs through physical contact like touching, kissing, or shaking hands. Examples include chickenpox and skin infections.
2. Indirect Contact:
- Through Air (Airborne Transmission): Pathogens are spread through droplets released when an infected person coughs, sneezes, or talks. These droplets can be inhaled by a healthy person. Examples: Tuberculosis, Common Cold, Influenza.
- Through Contaminated Food and Water (Vehicle-borne): Consuming food or water contaminated with pathogens. Examples: Cholera, Typhoid, Hepatitis A.
- Through Contaminated Objects (Fomites): Touching surfaces or objects (like doorknobs, toys, utensils) that have been contaminated by an infected person.
3. Through Vectors:
- Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans. Insects like mosquitoes, flies, and ticks are common vectors.
- Examples: Malaria (transmitted by Anopheles mosquitoes), Dengue (by Aedes mosquitoes), Plague (by fleas on rats).
4. Through Body Fluids:
- Transmission through exposure to infected blood, semen, or other body fluids. Examples: HIV/AIDS, Hepatitis B.