7th Standard Science Summative Assessment - September 2024
District: Virudhunagar
Assessment: Summative Assessment - September 2024
Standard: 7
Subject: SCIENCE
Time: 2.00 Hrs. | Marks: 60
I. Choose the correct answer: (10×1=10)
1) SI unit of density is
2) A particle is moving in a circular path of radius 'r'. The displacement after a circle would be
3) The metal which is a liquid at room temperature is
4) The subatomic particle which revolves around the nucleus is
5) Reproductive part of a plant is
6) Our living place should be
7) Which software is used to create symbols?
8) The ________ is a measure of how much space there is on a flat surface.
9) The non metal which is a good conductor of electricity is
10) ________ have the smallest seed in the plant kingdom.
II. Answer any 15 questions briefly: (15×2=30)
11) What is one light year?
One light year is defined as the distance travelled by light in vacuum in one year.
1 Light year = \(9.46 \times 10^{15}\) m.
12) Distinguish between the volume of liquid and capacity of a container.
Volume of liquid: It is the measure of the space occupied by the liquid.
Capacity of a container: It is the maximum volume of liquid that a container can hold.
13) Use the analogy to fill in the blanks:
a) Area : m² :: Volume : m³
b) Liquid : Litre :: Solid : cubic metre (m³) or cm³
14) What is centre of gravity?
The centre of gravity of an object is the point through which the entire weight of the object appears to act.
15) Distinguish between Speed and Velocity.
Speed: It is the rate of change of distance. It is a scalar quantity (has only magnitude).
Velocity: It is the rate of change of displacement. It is a vector quantity (has both magnitude and direction).
16) Fill in the blanks:
a) The shortest distance between two places is displacement.
b) The rate of change of velocity is acceleration.
17) Geetha take 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s. Calculate the distance between her house and the school.
Given:
- Speed = 2 m/s
- Time = 15 minutes = 15 × 60 seconds = 900 s
Formula: Distance = Speed × Time
Calculation:
Distance = 2 m/s × 900 s = 1800 m
The distance between her house and the school is 1800 meters or 1.8 kilometers.
18) Define Molecule.
A molecule is the smallest particle of a pure substance (element or compound) which can exist independently and shows all the properties of that substance.
19) Write the chemical formula and name the elements present in the compounds.
a) Sodium chloride: Formula: NaCl; Elements: Sodium (Na), Chlorine (Cl)
b) Potassium hydroxide: Formula: KOH; Elements: Potassium (K), Oxygen (O), Hydrogen (H)
c) Carbon dioxide: Formula: CO₂; Elements: Carbon (C), Oxygen (O)
d) Calcium oxide: Formula: CaO; Elements: Calcium (Ca), Oxygen (O)
e) Sulphur dioxide: Formula: SO₂; Elements: Sulphur (S), Oxygen (O)
20) State True or False. If false give the correct statement:
a) Two different elements may have similar atoms. - False.
Correct statement: Atoms of different elements are always different.
b) Compounds and elements are pure substances. - True.
21) Match the following:
i) Valency - Electrons in the outermost orbit
ii) Neutral particle - Neutron
iii) Iron - Fe
iv) Hydrogen - Monovalent
22) Name the sub-atomic particles.
The three main sub-atomic particles are:
- Proton (positively charged)
- Neutron (no charge / neutral)
- Electron (negatively charged)
23) Differentiate mass number from atomic number.
Atomic Number (Z): It is the number of protons present in the nucleus of an atom. It defines the element.
Mass Number (A): It is the total number of protons and neutrons present in the nucleus of an atom.
24) 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.
25) What are the two important parts of a flower?
The two most important parts of a flower, involved in reproduction, are:
- Androecium: The male reproductive part (consists of stamens).
- Gynoecium: The female reproductive part (consists of the pistil/carpel).
26) Define - Pollination.
Pollination is the process of transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower.
27) What is hygiene?
Hygiene is a set of practices performed to preserve health. It refers to conditions and practices that help to maintain health and prevent the spread of diseases.
28) Give any two communicable diseases, which spread in your locality during monsoon?
Two communicable diseases that often spread during the monsoon season are:
- Cholera (spreads through contaminated water)
- Dengue Fever (spreads through mosquito bites)
29) Match the following:
i) Rabies - Hydrophobia
ii) Tuberculosis - Mycobacterium
iii) Stilt root - Sugarcane
iv) Phylloclade - Cactus
30) What is Raster Graphics?
Raster graphics are digital images created or captured as a set of pixels (or dots) arranged in a grid. They are resolution-dependent, meaning they lose quality when scaled up. Common examples are JPEG, PNG, and GIF files.
III. Answer in detail: (4×5=20)
31) How will you determine the density of a stone using a measuring jar?
To determine the density of an irregularly shaped stone, we need to find its mass and volume.
1. To find the mass of the stone:
- Use a physical balance or a digital weighing scale.
- Place the stone on the pan and measure its mass accurately. Let the mass be 'm' grams.
2. To find the volume of the stone (using water displacement method):
- Take a measuring cylinder and fill it partially with water.
- Note down the initial volume of the water (V₁). Make sure the reading is taken at the lower meniscus.
- Tie the stone with a thread and gently immerse it completely into the water in the measuring cylinder, ensuring it doesn't touch the sides or bottom and no water splashes out.
- The water level will rise. Note down the new volume of water (V₂).
- The volume of the stone is the difference between the final and initial volume of water.
- Volume of the stone (V) = V₂ - V₁. The unit will be cm³ or ml (1 ml = 1 cm³).
3. To calculate the density:
- Use the formula for density: Density = Mass / Volume
- Density (d) = m / (V₂ - V₁)
- The unit of density will be g/cm³.
(OR)
Write about the experiment to find the centre of gravity of the irregularly shaped plate.
Aim: To find the centre of gravity of an irregularly shaped cardboard plate.
Materials Required: Irregularly shaped cardboard plate, a retort stand with clamp, a plumb line, a pin, and a pencil.
Procedure:
- Make three small holes near the edge of the cardboard plate. Label them A, B, and C.
- Suspend the plate freely from hole A using the pin, which is clamped to the retort stand.
- Hang the plumb line from the same pin.
- Once the plate and the plumb line come to rest, draw a straight line (AD) on the plate along the plumb line.
- Repeat the process by suspending the plate from hole B. Draw a second line (BE) along the plumb line.
- Again, repeat the process by suspending the plate from hole C. Draw a third line (CF) along the plumb line.
Observation: You will observe that all three lines (AD, BE, and CF) intersect at a single point. This point of intersection is the centre of gravity (G) of the irregularly shaped plate.
Conclusion: We can verify this by trying to balance the plate on the tip of a pencil at the point G. The plate will balance perfectly, confirming that this is its centre of gravity.
32) Differentiate metals and non-metals.
| Property | Metals | Non-metals |
|---|---|---|
| Physical State | Solid at room temperature (except Mercury). | Exist in all three states (solid, liquid, gas). |
| Lustre | Have a shiny surface (lustrous). | Do not have a shiny surface (non-lustrous), except Iodine and Graphite. |
| Malleability | Can be beaten into thin sheets. | Cannot be beaten into thin sheets (brittle). |
| Ductility | Can be drawn into thin wires. | Cannot be drawn into thin wires (non-ductile). |
| Conductivity | Good conductors of heat and electricity. | Poor conductors of heat and electricity (except Graphite). |
| Sonority | Produce a ringing sound when struck (sonorous). | Do not produce a ringing sound (non-sonorous). |
(OR)
Draw the structure of an atom and explain in the position of the sub-atomic particles.
Structure of an Atom:
An atom consists of a central nucleus and electrons that orbit around it.
Position of Sub-atomic Particles:
- Nucleus:
- The nucleus is the small, dense, positively charged centre of the atom.
- It contains two types of particles:
- Protons: These are positively charged particles. The number of protons determines the atomic number and identifies the element.
- Neutrons: These are neutral particles (have no charge). They contribute to the mass of the atom but not its charge.
- Electron Shells:
- The outermost regions of the atom, called shells or orbits, contain the electrons.
- Electrons: These are negatively charged particles that revolve around the nucleus.
- In a neutral atom, the number of electrons is equal to the number of protons, making the atom electrically neutral.
Position of Subatomic Particles
An atom consists of three sub-atomic particles: Protons, Electrons, and Neutrons.
33) a) Differentiate bisexual flower from unisexual flower.
| Feature | Bisexual Flower | Unisexual Flower |
|---|---|---|
| Reproductive Parts | Contains both male (androecium) and female (gynoecium) reproductive parts in the same flower. | Contains either the male (staminate) or the female (pistillate) reproductive part, but not both. |
| Pollination | Can undergo both self-pollination and cross-pollination. | Can only undergo cross-pollination. |
| Examples | Hibiscus, Rose, Mustard. | Papaya, Watermelon, Cucumber. |
b) Write notes on phyllode.
A phyllode is a modified petiole (the stalk of a leaf) or rachis that becomes flattened and leaf-like in appearance. Its main function is to perform photosynthesis, just like a true leaf. This adaptation is commonly seen in plants growing in dry or arid regions to reduce water loss through transpiration.
Characteristics:
- It is green and flat.
- It performs photosynthesis.
- True leaves are often reduced to spines or scales or they fall off early.
- Example: Many species of Acacia (e.g., Australian Acacia).
(OR)
Write a brief account on pollination.
Pollination is the fundamental process in plant reproduction. It is defined as the transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower.
Types of Pollination:
1. Self-Pollination (Autogamy):
- The transfer of pollen from the anther to the stigma of the same flower.
- This occurs in bisexual flowers where both male and female parts mature at the same time.
- Example: Pea, Tomato.
2. Cross-Pollination (Allogamy):
- The transfer of pollen from the anther of one flower to the stigma of a flower on another plant of the same species.
- This requires external agents and promotes genetic diversity.
- Example: Apple, Pumpkin, Grasses.
Agents of Pollination:
Pollination is facilitated by various agents:
- Abiotic Agents (Non-living):
- Wind (Anemophily): Pollen grains are light, small, and produced in large quantities. e.g., Grass, Maize.
- Water (Hydrophily): Occurs in aquatic plants. e.g., Vallisneria, Hydrilla.
- Biotic Agents (Living):
- Insects (Entomophily): Flowers are large, colourful, fragrant, and produce nectar. e.g., Sunflower, Rose.
- Birds (Ornithophily): Flowers are brightly coloured and produce a lot of nectar. e.g., Hibiscus.
- Animals (Zoophily): Other animals like bats and snails can also act as pollinators.
34) Write about any three communicable diseases in detail.
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 droplets containing the bacteria.
- Symptoms: Persistent cough (often with blood), fever, night sweats, weight loss, and fatigue.
- Prevention: BCG vaccination, maintaining good hygiene, avoiding overcrowded places, and ensuring proper ventilation.
2. Cholera
- Causative Agent: Bacterium called Vibrio cholerae.
- Mode of Transmission: Spreads through the consumption of contaminated food or water. It is common in areas with poor sanitation.
- Symptoms: Severe watery diarrhea, vomiting, muscle cramps, and rapid dehydration which can be life-threatening if not treated.
- Prevention: Drinking safe and boiled water, washing hands with soap before eating, eating properly cooked food, and proper sanitation.
3. Malaria
- Causative Agent: A protozoan parasite called Plasmodium.
- Mode of Transmission: Spreads through the bite of an infected female Anopheles mosquito.
- Symptoms: High fever with chills, headache, body aches, vomiting, and fatigue. The fever often occurs in cycles.
- Prevention: Using mosquito nets and repellents, preventing mosquito breeding by eliminating stagnant water, and keeping surroundings clean.
(OR)
a) Write about the right way of protecting the eyes.
Protecting our eyes is crucial for maintaining good vision. Here are some right ways to do it:
- Balanced Diet: Eat food rich in Vitamin A, such as carrots, leafy green vegetables, fish, and eggs.
- Avoid Bright Light: Do not look directly at the sun or other very bright light sources as it can damage the retina.
- Screen Time Management: When using computers or watching TV, maintain a proper distance (at least 6 feet for TV). Follow the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds.
- Proper Lighting: Always read in a well-lit room to avoid straining your eyes.
- Cleanliness: Wash your eyes with clean water at least twice a day. Do not rub your eyes with dirty hands.
- Regular Check-ups: Visit an eye specialist for regular check-ups to detect any problems early.
b) How to keep your hair clean and healthy?
Maintaining clean and healthy hair involves regular care and a healthy lifestyle:
- Regular Washing: Wash your hair regularly (2-3 times a week) with a mild shampoo to remove dirt, oil, and dead skin cells.
- Proper Rinsing: Rinse your hair thoroughly with clean water to ensure no shampoo or conditioner residue is left behind.
- Gentle Combing: Use a wide-toothed comb to detangle your hair, especially when it is wet, to prevent breakage. Avoid harsh brushing.
- Healthy Diet: Eat a balanced diet rich in proteins, vitamins (especially Biotin and Vitamin E), and minerals like iron and zinc. Include eggs, nuts, fish, and green vegetables.
- Avoid Heat and Chemicals: Minimize the use of heat styling tools like straighteners and dryers. Avoid harsh chemical treatments like bleaching and perming.
- Regular Trimming: Get your hair trimmed every 6-8 weeks to remove split ends and promote healthy growth.