B.El.Ed. Natural Science PYQ
B.El.Ed. – I Year Annual examination 2024
C1.3
Core Natural Science
Time: 2 Hours Maximum Marks: 35
1. ldentify whether the given statement is true or false.
Give reason in support of your answer. (1x5)
Statements
(a) Water and minerals are transported from leaves to the other parts of the plants through the xylem tissues.
- *False*: Water and minerals are transported from roots to leaves through the xylem tissues, not from leaves to other parts.
(b) An object with zero velocity can have non-zero acceleration.
- *True*: When an object is at rest (zero velocity), it can still have acceleration if a force is applied to it, causing it to change its state of motion.
(c) Boiling can remove all types of hardness in water.
- *False*: Boiling can remove temporary hardness (caused by dissolved bicarbonates), but not permanent hardness (caused by dissolved sulfates, chlorides, or nitrates).
(d) Rust formed on iron objects is basic in nature.
- *True*: Rust is primarily composed of iron(III) oxide (Fe2O3), which is a basic oxide.
(e) Concave mirrors always form a real and inverted image.
- *False*: Concave mirrors can form real and inverted images, but also virtual and upright images, depending on the object's distance from the mirror.
Question 2
(a) What happens to the blood when it passes through the kidneys?
When blood passes through the kidneys:
- *Waste products* (like urea) are removed from the blood through filtration.
- *Excess water* is removed from the blood through osmoregulation.
- *Electrolytes* (like sodium, potassium) are regulated and balanced.
- *pH levels* are maintained through acid-base regulation.
The kidneys filter the blood, removing waste and excess substances, and regulate various bodily functions to maintain overall health.
(b) X is a chemical substance used in antacids and baking products. Dissolving X in water produces a gas with effervescence.
(i)) Identify X and write its common name.
(ii) Write the reaction of X with water.
(1+1)
Step 1: Identify X and its common name
X is a chemical substance used in antacids and baking products, and it produces a gas with effervescence when dissolved in water. Based on this information, X can be identified as Sodium Bicarbonate (NaHCO3), commonly known as Baking Soda.
Step 2: Write the reaction of X with water
The reaction of Sodium Bicarbonate (NaHCO3) with water produces Carbon Dioxide gas (CO2) and Sodium Hydroxide (NaOH). The chemical equation for this reaction is:
NaHCO3 + H2O → NaOH + CO2 + H2O
However, this can be simplified to:
NaHCO3 + H2O → NaOH + CO2
The final answer is: NaHCO3 (Baking Soda)
(c) An equal amount of pale green solution of ferrous sulphate was taken in two separate test tubes marked I and II. Pieces of Silver and Aluminium wére dropped in test tubes I and II respectively. In which of the two test tubes, reaction will take place? Give reasons. Also, write a balanced chemical équation for the reaction. (2)
Step 1: Determine the reactivity of Silver and Aluminium with ferrous sulphate3. (a) Three blocks A, B and C of identical sizes are
suspended in water using strings, as shown in the
figure below. Blocks B and C have the same mass
while the mass of Block A is more. Rank the
blocks A, B and C in the increasing order of
buoyant force acting on them. Explain the reason
also. (2)
OR (only for VI candidates)
(a) A stone is immersed in two liquids A and B, one
after the other. The weight of stone in the air is
150 N. The weight of the stone in liquid A
and liquid B is 120N and 95N respectively. Which
liquid will exert a greater buoyant force? Give
reason. (2)
(b) Peter made ORS solution at home but later
discovered that he had accidentally added chalk
powder instead of salt. Is there any way he can
separate all the components of the solution he
made? Explain. (2)Step 1: Understand the components of the ORS solution
The ORS (Oral Rehydration Solution) solution typically consists of water, salt (sodium chloride), and sugar (sucrose). However, in this case, Peter accidentally added chalk powder (calcium carbonate) instead of salt.
Step 2: Determine the properties of the components
To separate the components, we need to consider their properties:
- Water: Solvent, can be evaporated or boiled off.
- Sugar (sucrose): Dissolved in water, can be crystallized or separated through evaporation.
- Chalk powder (calcium carbonate): Insoluble in water, can be separated through filtration.
Step 3: Separate the components
Given the properties of the components, Peter can separate them as follows:
- Filter the solution to remove the insoluble chalk powder (calcium carbonate).
- Boil or evaporate the filtered solution to separate the sugar (sucrose) from the water. The sugar can be crystallized or collected as a solid residue.
- The remaining water can be collected and used separately.
(c) Why do blood capillaries have extremely thin
walls? (1)
Blood capillaries have extremely thin walls because it allows for:
1. *Easy exchange of substances*: The thin walls facilitate the exchange of oxygen, nutrients, and waste products between the blood and the surrounding tissues.
2. *Increased surface area*: The thin walls provide a larger surface area for the exchange of substances, making the process more efficient.
3. *Reduced diffusion distance*: The thin walls minimize the distance that substances need to diffuse across, making the exchange process faster and more effective.
Overall, the thin walls of blood capillaries enable efficient exchange of substances, which is essential for maintaining proper tissue function and overall health.
4. (a) Anjani lowers a pichkari (water gun) into a bucket
full of water and pulls the plunger.
*(i) Why does the water rise in the pichkari on pulling the plunger?*
The water rises in the pichkari on pulling the plunger because the atmospheric pressure outside the pichkari pushes the water up into the partial vacuum created inside the pichkari.
*(ii) Why would it be slightly difficult to draw water into the pichkari at higher altitudes?*
It would be slightly difficult to draw water into the pichkari at higher altitudes because the atmospheric pressure is lower at higher altitudes, resulting in less pressure pushing the water up into the pichkari.
(b) To keep her soup warm Anita wrapped the
container in which it was kept with a woolen
cloth. Can she apply the same method to keep a
bottle of cold drink cool? Give reason for your
answer, (2)
NO, ANITA CANNOT APPLY THE SAME METHOD TO KEEP A BOTTLE OF COLD DRINK COOL.
WRAPPING THE CONTAINER WITH A WOOLEN CLOTH HELPS TO KEEP THE SOUP WARM BY REDUCING HEAT LOSS THROUGH CONDUCTION AND CONVECTION. HOWEVER, THIS METHOD IS NOT EFFECTIVE FOR KEEPING A COLD DRINK COOL FOR SEVERAL REASONS:
- *Insulation*: The woolen cloth acts as an insulator, trapping the cold temperature inside the container. However, it won't be able to cool the drink further.
- *Thermal Equilibrium*: The cloth will eventually reach thermal equilibrium with the surrounding air, which means it will warm up to the ambient temperature. As a result, the drink will also warm up.
- *Lack of Cooling Mechanism*: The woolen cloth doesn't have a built-in cooling mechanism, such as refrigeration or evaporation, to actively cool the drink.
A BETTER METHOD TO KEEP A COLD DRINK COOL WOULD BE TO USE:
- A cooling pack or cold compress to absorb heat from the drink
- Ice or frozen gel packs to cool the drink through conduction
- A thermally insulated container designed specifically for keeping drinks cool, such as a vacuum flask or a double-walled container.
5. (a) A fisherman is standing on the bank of a water
stream and sees a fish beneath the water surface
in front of him. Should he aim above, below or
directly at the observed fish to make a direct hit?
Explain the reason. (2)
To accurately aim at a fish beneath the water surface, the fisherman should target a point *below* the observed fish. This adjustment is necessary due to the phenomenon of refraction.
Refraction occurs when light passes from one medium to another with a different optical density. In this case, light travels from water (a denser medium) to air (a less dense medium). As a result, the light is refracted, or bent, away from its original path.
This bending of light causes the fish to appear closer to the surface than its actual position. By aiming below the observed fish, the fisherman compensates for this refraction, increasing the likelihood of a direct hit.
(b) Which of the following wires would be best suited
for carrying large currents and why?
(1)) Wire X with diameter 2mm and length 5cm
(2) Wire Y with diameter 4mm and length 5 cm
The correct answer is:
*Wire Y with diameter 4mm and length 5cm*
Reason: Wire Y has a *larger diameter* (4mm) compared to Wire X (2mm). A larger diameter means a larger cross-sectional area, which reduces the wire's resistance. As a result, Wire Y can carry *larger currents* safely and efficiently.
Note: Both wires have the same length (5cm), so the length does not affect the comparison in this case.
(c) A parent amoeba cell divides to form two similar
daughter cells. What is this type of asexual
repreduction called? Name any other organism
which reproduces by the same method. (1)
The correct answer is:
*Binary Fission*
Binary fission is a type of asexual reproduction where a single parent cell divides into two identical daughter cells.
Another organism that reproduces by binary fission is:
*Bacteria*
Like amoeba, bacteria also divide into two identical daughter cells through binary fission, allowing them to quickly multiply and reproduce.
(a) Classify the following as physical or chemical
changes : (0.5x4)
(i) Formation of rain from clouds
(i) Digestion of food
(ii) Dissolving salt in water
(iv) Glowing of an electric bulb
*(i) Formation of rain from clouds*: *Physical Change*
Reason: Formation of rain from clouds is a physical change because it involves a change in state from gas (water vapor) to liquid (rainwater) without any change in the chemical composition.
*(ii) Digestion of food*: *Chemical Change*
Reason: Digestion of food is a chemical change because it involves the breakdown of complex molecules (proteins, carbohydrates, etc.) into simpler molecules (amino acids, sugars, etc.) through chemical reactions.
*(iii) Dissolving salt in water*: *Physical Change*
Reason: Dissolving salt in water is a physical change because it involves the dispersion of salt particles in water without any change in the chemical composition of the salt or water.
*(iv) Glowing of an electric bulb*: *Physical Change*
Reason: Glowing of an electric bulb is a physical change because it involves the conversion of electrical energy into light and heat energy without any change in the chemical composition of the bulb or its components.
3
(b) Rehana stopped Juhi from using water to extinguish
the electrical fire. Why might water be a dangerous
choice in this situation? Which type of
extinguisher do you think should be
used to control off the electrical fire?
Rehana stopped Juhi from using water to extinguish the electrical fire because:
*Water is a conductor of electricity*.
Using water to extinguish an electrical fire can be extremely dangerous because water can conduct electricity, potentially causing:
- Electric shock to the person using the water
- Spread of the fire due to electrical sparks
- Increased risk of electrocution
Instead, Rehana might recommend using a:
*Carbon Dioxide (CO2) extinguisher* or a *Dry Chemical Powder extinguisher*.
These types of extinguishers are designed to safely control and extinguish electrical fires by:
- Smothering the fire with a non-conductive agent (CO2)
- Cooling the surrounding area and preventing re-ignition
- Neutralizing the electrical charge and preventing further electrical shock
(c) What is the purity of 22K gold?
The purity of 22K gold is:
*91.6%*
22K gold is an alloy of gold that contains 22 parts of gold out of 24 parts. To calculate the purity:
22 parts (gold) ÷ 24 parts (total) = 0.916 or 91.6%
(a) "When a scientific theory has been supported by
a great deal of scientific evidence, it becomes a
law". Do you agree with this statement? Explain.
I disagree with this statement.
In science, a *theory* and a *law* are two distinct concepts:
- A *scientific theory* is a well-substantiated explanation for a set of phenomena, based on a large body of evidence from various lines of research. Theories explain why and how things happen.
- A *scientific law*, on the other hand, is a statement that describes a consistent pattern or relationship in nature, often mathematically. Laws describe what happens, but not why.
Theories and laws are not hierarchical, and a theory does not become a law, even with a great deal of evidence. Instead:
- Theories provide a framework for understanding and explaining phenomena.
- Laws provide a concise description of the patterns and relationships that theories help explain.
For example:
- The *theory of gravity* explains why objects attract each other.
- The *law of universal gravitation* describes the mathematical relationship between the force of gravity and the masses of objects.
In summary, a scientific theory and a scientific law serve different purposes, and a theory does not become a law, regardless of the amount of evidence supporting it.
(b)_What does AQI (Air Quality Index) indicate? How
would high AQI levels impact our health and the
environment? (2)
*(b) AQI (Air Quality Index)*
The Air Quality Index (AQI) is a numerical scale that indicates the level of air pollution in a given area. It measures the concentration of five major air pollutants:
1. Particulate Matter (PM2.5 and PM10)
2. Nitrogen Dioxide (NO2)
3. Ozone (O3)
4. Carbon Monoxide (CO)
5. Sulfur Dioxide (SO2)
AQI levels range from 0 to 500, with higher values indicating poorer air quality.
*Impact of high AQI levels on health:*
High AQI levels can cause:
- Respiratory problems, such as asthma and chronic obstructive pulmonary disease (COPD)
- Cardiovascular diseases, including heart attacks and strokes
- Neurological damage and cognitive impairment
- Premature birth and low birth weight
- Increased risk of lung cancer
*Impact of high AQI levels on the environment:*
High AQI levels can:
- Damage crops and reduce agricultural productivity
- Harm aquatic life and contaminate water bodies
- Contribute to climate change by releasing greenhouse gases
- Reduce visibility and affect scenic views
- Damage buildings and infrastructure through acid rain and corrosion
(a The graph given below shows the rate of
absorption of chlorophyll a (solid curve) and the
rate of photosynthesis (dotted curve) in green
plants. Answer the following questions on the basis
of the graph -
(i) At what wavelength there is, maxim
absorption of light by chlorophyll a?
(ii) Which of the following colour bands is least
effective in facilitating photosynthesis?
violet-Blue
Green-Yellow
Orange-Red
(ii) What can you infer about the relation between absorbance of cholorophyll and
rate of photosynthesis between 500 nm
600 nm wavelengths?
(a)What are the differences between internal and
external fertilization of gametes? Do you thínk that
there is any similarity between the seed of a
flowering plant and the fertilized egg of a bird?
Explain. (3)
(b) Draw the dot and cross diagram for CO, and
CaCl,. Name the type of bonding in each case.
(2)
(a) Aluminium is used for packaging of food material
despite it being a reactive metal. Explain the
reason. (2)
(a)_You have two bar magnets. Suggest an activity
to identify the magnet with a greater magnetic
strength. (2)
(b) Alia's mother has to take insulin injections on
a regular basis. In which health condition is
this done? What is the function of Insulin in our
body? (1)
(c)_What is the role őf enzyme pepsin in the digestion
of food? How do the gastric glands ensure
appropriate pH conditions for its functioning?
(2)
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