▶️ Answer/Explanation
All living organisms carry out excretion — the removal of metabolic waste products from the body.
Digestion only occurs in animals that ingest food; photosynthesis is exclusive to plants and algae; sexual reproduction is not universal (some organisms reproduce asexually).
✅ Answer: (A)
Digestion only occurs in animals that ingest food; photosynthesis is exclusive to plants and algae; sexual reproduction is not universal (some organisms reproduce asexually).
✅ Answer: (A)
▶️ Answer/Explanation
Cell membrane, cytoplasm, and nucleus are found in both plant and animal cells.
The cell wall (made of cellulose) is a structure present only in plant cells, providing rigidity and structural support.
✅ Answer: (D)
The cell wall (made of cellulose) is a structure present only in plant cells, providing rigidity and structural support.
✅ Answer: (D)
▶️ Answer/Explanation
Fat molecules (triglycerides) are formed by the condensation of one glycerol molecule and three fatty acid molecules.
Glucose and amino acids are the monomers of carbohydrates and proteins respectively — not fats.
✅ Answer: (D)
Glucose and amino acids are the monomers of carbohydrates and proteins respectively — not fats.
✅ Answer: (D)
▶️ Answer/Explanation
Enzymes are biological catalysts composed entirely of protein molecules, made from chains of amino acids.
Their protein nature gives them a specific 3D active site shape that is complementary to their substrate, enabling catalysis.
✅ Answer: (D)
Their protein nature gives them a specific 3D active site shape that is complementary to their substrate, enabling catalysis.
✅ Answer: (D)
▶️ Answer/Explanation
Since light intensity is the independent variable being changed, it cannot be a control variable — eliminating options B and D.
The size of the plant determines how much photosynthesis can occur, and temperature affects the rate of enzyme-controlled reactions; both must be kept constant to ensure a fair test.
✅ Answer: (A)
The size of the plant determines how much photosynthesis can occur, and temperature affects the rate of enzyme-controlled reactions; both must be kept constant to ensure a fair test.
✅ Answer: (A)
▶️ Answer/Explanation
Saliva contains the enzyme salivary amylase, which breaks down starch (a large insoluble molecule) into smaller sugar molecules — this is digestion.
The resulting sugars are small enough to pass through the partially permeable membrane into the water outside, confirming that chemical digestion occurred inside the bag.
✅ Answer: (B)
The resulting sugars are small enough to pass through the partially permeable membrane into the water outside, confirming that chemical digestion occurred inside the bag.
✅ Answer: (B)
▶️ Answer/Explanation
Red blood cells are packed with haemoglobin, a protein that combines with oxygen to form oxyhaemoglobin in the lungs and releases oxygen to body tissues.
Glucose, insulin, and urea are dissolved in the plasma and transported in solution — not inside red blood cells.
✅ Answer: (C)
Glucose, insulin, and urea are dissolved in the plasma and transported in solution — not inside red blood cells.
✅ Answer: (C)
▶️ Answer/Explanation
Exhaled air has a lower oxygen content (~16%) and a higher carbon dioxide content (~4%) compared to inhaled air, because oxygen is consumed and carbon dioxide is produced during cellular respiration.
Nitrogen remains largely unchanged at ~79% since the body does not use it, and the correct row in the table reflecting these values is C.
✅ Answer: (C)
Nitrogen remains largely unchanged at ~79% since the body does not use it, and the correct row in the table reflecting these values is C.
✅ Answer: (C)
▶️ Answer/Explanation
The plant shoot bends towards the light source because auxin accumulates on the shaded side, causing faster cell elongation there — this directional growth response to light is called phototropism.
Gravitropism refers to growth in response to gravity, not light, so options B, C, and D are incorrect.
✅ Answer: (A)
Gravitropism refers to growth in response to gravity, not light, so options B, C, and D are incorrect.
✅ Answer: (A)
▶️ Answer/Explanation
Sexual reproduction requires the fusion of two gametes (fertilisation) and results in genetic variation in offspring, because each gamete carries a unique combination of alleles.
Row C correctly identifies that sexual reproduction involves two parents, fusion of gametes, and genetically varied offspring.
✅ Answer: (C)
Row C correctly identifies that sexual reproduction involves two parents, fusion of gametes, and genetically varied offspring.
✅ Answer: (C)
▶️ Answer/Explanation
Type Y potatoes display a bell-shaped (normal distribution) curve of masses, indicating a continuous range of values with no clear divisions — this is the hallmark of continuous variation.
Type Z may overlap in range with Y, so we cannot conclude Z are always smaller; and discontinuous variation would show distinct separate bars, not a smooth curve.
✅ Answer: (B)
Type Z may overlap in range with Y, so we cannot conclude Z are always smaller; and discontinuous variation would show distinct separate bars, not a smooth curve.
✅ Answer: (B)
▶️ Answer/Explanation
Statement 1 is correct — the hawk eats the songbird, making it a consumer (tertiary consumer); Statement 4 is correct — the plant produces food via photosynthesis, making it a producer.
Statement 2 is incorrect — the insect eats the plant, so it is a herbivore, not a carnivore; Statement 3 is incorrect — the songbird eats the insect (an animal), so it is a carnivore, not a herbivore.
✅ Answer: (B)
Statement 2 is incorrect — the insect eats the plant, so it is a herbivore, not a carnivore; Statement 3 is incorrect — the songbird eats the insect (an animal), so it is a carnivore, not a herbivore.
✅ Answer: (B)
▶️ Answer/Explanation
Photosynthesis uses carbon dioxide and water in the presence of light to produce glucose and oxygen, thereby removing \(\text{CO}_2\) from the atmosphere: \(6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2\).
Combustion, decomposition, and respiration all release \(\text{CO}_2\) back into the atmosphere, so they are the opposite process.
✅ Answer: (C)
Combustion, decomposition, and respiration all release \(\text{CO}_2\) back into the atmosphere, so they are the opposite process.
✅ Answer: (C)
▶️ Answer/Explanation
In process 1, cooling from 55 °C (above boiling point of 49 °C → gas state) to 45 °C (below boiling point but above melting point → liquid state) is condensation (gas → liquid).
In process 2, warming from –100 °C (below melting point of –94 °C → solid state) to –90 °C (above melting point → liquid state) is melting (solid → liquid).
✅ Answer: (D)
In process 2, warming from –100 °C (below melting point of –94 °C → solid state) to –90 °C (above melting point → liquid state) is melting (solid → liquid).
✅ Answer: (D)
▶️ Answer/Explanation
Separating petroleum by fractional distillation is a physical change (no new substances formed); electrolysis of water produces new substances \(\text{H}_2\) and \(\text{O}_2\), making it a chemical change — so statement 2 is correct.
Statement 3 is always true by definition of a chemical change; statement 4 is incorrect because some chemical changes are endothermic (absorb heat).
✅ Answer: (C)
Statement 3 is always true by definition of a chemical change; statement 4 is incorrect because some chemical changes are endothermic (absorb heat).
✅ Answer: (C)
▶️ Answer/Explanation
Ionic bonds form between a metal and a non-metal through electron transfer; potassium (metal) donates an electron to bromine (non-metal) to form \(\text{K}^+\text{Br}^-\), which is the ionic compound potassium bromide.
Carbon + oxygen, and nitrogen + hydrogen both form covalent compounds (non-metal + non-metal); sodium + lithium are both metals and do not form ionic compounds with each other.
✅ Answer: (C)
Carbon + oxygen, and nitrogen + hydrogen both form covalent compounds (non-metal + non-metal); sodium + lithium are both metals and do not form ionic compounds with each other.
✅ Answer: (C)
▶️ Answer/Explanation
The displayed structural formula of hydrogen peroxide shows two H atoms and two O atoms connected as H–O–O–H, giving the molecular formula \(\text{H}_2\text{O}_2\).
\(\text{H}_2\text{O}\) is water (only 1 oxygen atom per molecule), while HO and 2OH are not valid molecular formulas for this compound.
✅ Answer: (B)
\(\text{H}_2\text{O}\) is water (only 1 oxygen atom per molecule), while HO and 2OH are not valid molecular formulas for this compound.
✅ Answer: (B)
▶️ Answer/Explanation
When brine is electrolysed, \(\text{Cl}^-\) is discharged at the anode (producing \(\text{Cl}_2\) gas) and \(\text{H}^+\) at the cathode (producing \(\text{H}_2\) gas), leaving \(\text{Na}^+\) and \(\text{OH}^-\) ions in solution to form sodium hydroxide (NaOH).
Sodium hydroxide is a strong alkali — it turns red litmus blue; chlorine and hydrogen are gases that escape, and hydrochloric acid is acidic (would turn blue litmus red).
✅ Answer: (D)
Sodium hydroxide is a strong alkali — it turns red litmus blue; chlorine and hydrogen are gases that escape, and hydrochloric acid is acidic (would turn blue litmus red).
✅ Answer: (D)
▶️ Answer/Explanation
The neutralisation of NaOH with HCl causes a temperature rise, meaning energy is released to the surroundings — this is an exothermic reaction.
Ice melting absorbs energy from the surroundings (temperature drops around it) — this is an endothermic process; Row B correctly classifies NaOH + HCl as exothermic and ice melting as endothermic.
✅ Answer: (B)
Ice melting absorbs energy from the surroundings (temperature drops around it) — this is an endothermic process; Row B correctly classifies NaOH + HCl as exothermic and ice melting as endothermic.
✅ Answer: (B)
▶️ Answer/Explanation
Increasing the concentration of HCl means more acid particles per unit volume, leading to more frequent collisions with \(\text{CaCO}_3\) particles and a faster rate of reaction.
Decreasing temperature slows the reaction; larger particles reduce surface area (slower rate); increasing volume decreases concentration if the same amount of acid is diluted — none of these increase the rate.
✅ Answer: (B)
Decreasing temperature slows the reaction; larger particles reduce surface area (slower rate); increasing volume decreases concentration if the same amount of acid is diluted — none of these increase the rate.
✅ Answer: (B)
▶️ Answer/Explanation
In reaction 1, carbon gains oxygen to form \(\text{CO}_2\) — carbon is oxidised; in reaction 3, magnesium gains oxygen to form MgO — magnesium is oxidised; both are oxidation reactions.
Reaction 2 is a neutralisation (acid-base) reaction with no oxygen transfer; reaction 4 is thermal decomposition with no net gain of oxygen by any element.
✅ Answer: (A)
Reaction 2 is a neutralisation (acid-base) reaction with no oxygen transfer; reaction 4 is thermal decomposition with no net gain of oxygen by any element.
✅ Answer: (A)
▶️ Answer/Explanation
Magnesium (metal) + HCl produces \(\text{H}_2\) gas: \(\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2\uparrow\); magnesium carbonate + HCl produces \(\text{CO}_2\) gas: \(\text{MgCO}_3 + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{CO}_2\uparrow + \text{H}_2\text{O}\).
Magnesium hydroxide and magnesium oxide are bases — they react with HCl to produce only salt and water, with no gas evolved.
✅ Answer: (A)
Magnesium hydroxide and magnesium oxide are bases — they react with HCl to produce only salt and water, with no gas evolved.
✅ Answer: (A)
▶️ Answer/Explanation
Transition elements are characterised by high melting points (generally above 1000 °C); lead has a relatively low melting point of only 327 °C, which is uncharacteristic of true transition elements.
Conducting electricity, forming alloys, and having basic oxides are all typical properties of transition metals, so those are not the odd one out.
✅ Answer: (C)
Conducting electricity, forming alloys, and having basic oxides are all typical properties of transition metals, so those are not the odd one out.
✅ Answer: (C)
▶️ Answer/Explanation
Helium (atomic number 2) has an electron configuration of 2 — its first and only shell is full with 2 electrons, making it completely unreactive; statements 1 and 2 are both correct.
Statement 3 is incorrect (the outer shell is complete, not incomplete), and statement 4 is incorrect (helium is monatomic — He, not He₂).
✅ Answer: (A)
Statement 3 is incorrect (the outer shell is complete, not incomplete), and statement 4 is incorrect (helium is monatomic — He, not He₂).
✅ Answer: (A)
▶️ Answer/Explanation
After removing water vapour (~variable), \(\text{CO}_2\) (~0.04%), and noble gases (~1%), what remains is nitrogen (~78%) and oxygen (~21%), which together account for approximately 99 cm³ out of 100 cm³.
The removed components total roughly 1 cm³, so the remaining volume is approximately \(100 – 1 = 99 \text{ cm}^3\).
✅ Answer: (D)
The removed components total roughly 1 cm³, so the remaining volume is approximately \(100 – 1 = 99 \text{ cm}^3\).
✅ Answer: (D)
▶️ Answer/Explanation
Sulfuric acid is manufactured via the Contact Process starting from sulfur: \(\text{S} \rightarrow \text{SO}_2 \rightarrow \text{SO}_3 \rightarrow \text{H}_2\text{SO}_4\) — statement D is correct.
Limestone is a naturally occurring mineral (\(\text{CaCO}_3\)), not manufactured; ethene is produced by cracking, not by addition polymerisation (which produces poly(ethene) from ethene).
✅ Answer: (D)
Limestone is a naturally occurring mineral (\(\text{CaCO}_3\)), not manufactured; ethene is produced by cracking, not by addition polymerisation (which produces poly(ethene) from ethene).
✅ Answer: (D)
▶️ Answer/Explanation
Aqueous bromine (bromine water) is decolourised by alkenes through electrophilic addition across the \(\text{C=C}\) double bond — the molecule in option B contains a C=C double bond (it is an alkene).
Alkanes (saturated molecules with only C–C single bonds) do not react with bromine water under normal conditions, so the other options showing only single bonds would not decolourise it.
✅ Answer: (B)
Alkanes (saturated molecules with only C–C single bonds) do not react with bromine water under normal conditions, so the other options showing only single bonds would not decolourise it.
✅ Answer: (B)
▶️ Answer/Explanation
At constant speed, distance increases proportionally with time, giving a straight diagonal line on the distance–time graph; simultaneously, speed stays constant, giving a horizontal line on the speed–time graph.
The car starts at point X (not at zero distance), so the distance–time graph starts above the origin — option A shows both these features correctly.
✅ Answer: (A)
The car starts at point X (not at zero distance), so the distance–time graph starts above the origin — option A shows both these features correctly.
✅ Answer: (A)
▶️ Answer/Explanation
Object X has equal and opposite forces (balanced), so its resultant force is zero; objects Y and Z have unequal forces in at least one direction, producing a non-zero resultant force.
A non-zero resultant force causes acceleration (change in speed or direction) according to Newton’s Second Law \(F = ma\).
✅ Answer: (C)
A non-zero resultant force causes acceleration (change in speed or direction) according to Newton’s Second Law \(F = ma\).
✅ Answer: (C)
▶️ Answer/Explanation
Since all beakers are identical (same base area), the pressure on the bench depends only on the total weight of the beaker and liquid: \(P = \frac{F}{A} = \frac{mg}{A}\), where \(m = \rho \times V\).
Beaker A contains the largest volume of salt water (highest density), giving it the greatest mass and therefore the greatest weight and pressure on the bench.
✅ Answer: (A)
Beaker A contains the largest volume of salt water (highest density), giving it the greatest mass and therefore the greatest weight and pressure on the bench.
✅ Answer: (A)
▶️ Answer/Explanation
Power is defined as the rate of energy transfer: \(P = \frac{E}{t}\), so 1500 W means the kettle transfers 1500 joules of electrical energy into heat energy every second.
The other options confuse power with total energy (A), time (B), or weight (D) — none of which is the definition of power rating.
✅ Answer: (C)
The other options confuse power with total energy (A), time (B), or weight (D) — none of which is the definition of power rating.
✅ Answer: (C)
▶️ Answer/Explanation
When cooled in the refrigerator, both the glass jar and metal lid contract, but metals have a higher coefficient of thermal expansion than glass, so the metal lid contracts more than the glass jar.
This means the lid shrinks tightly onto the glass neck, making it much harder to remove — the opposite occurs when heated (lid expands more, loosening it).
✅ Answer: (B)
This means the lid shrinks tightly onto the glass neck, making it much harder to remove — the opposite occurs when heated (lid expands more, loosening it).
✅ Answer: (B)
▶️ Answer/Explanation
In the diagram, water rises on the right side and sinks on the left; this can be driven by heating at point Z (bottom right, making water less dense so it rises) or by cooling at point X (top left, making water denser so it sinks).
Both actions independently set up the same clockwise circulation pattern shown, confirming option D is correct.
✅ Answer: (D)
Both actions independently set up the same clockwise circulation pattern shown, confirming option D is correct.
✅ Answer: (D)
▶️ Answer/Explanation
Television remote controls use infrared (IR) radiation to send coded pulses of electromagnetic radiation to the TV’s receiver — IR has a wavelength just longer than visible red light and is safe at low intensities.
Gamma rays and X-rays are ionising radiation (dangerous), while ultraviolet is used in sterilisation and banknote checking — none of these are used in TV remotes.
✅ Answer: (B)
Gamma rays and X-rays are ionising radiation (dangerous), while ultraviolet is used in sterilisation and banknote checking — none of these are used in TV remotes.
✅ Answer: (B)
▶️ Answer/Explanation
Sound waves are longitudinal mechanical waves that travel by causing particles in a medium to compress and rarefy; when air is removed from the jar, a vacuum forms and there are no particles to carry the vibrations from the bell to the outside.
The bell still vibrates (as the hammer still strikes it), ruling out option B; the electric current and pitch are unaffected by the absence of air, ruling out C and D.
✅ Answer: (A)
The bell still vibrates (as the hammer still strikes it), ruling out option B; the electric current and pitch are unaffected by the absence of air, ruling out C and D.
✅ Answer: (A)
▶️ Answer/Explanation
Electromotive force (e.m.f.) is measured in volts (V), not newtons — eliminating options A and B immediately; a voltmeter has very high resistance and must always be connected in parallel across the component (not in series) to measure voltage without disrupting the circuit.
Connecting a voltmeter in series would drastically reduce current flow and give an incorrect reading; parallel connection ensures it measures the full potential difference across the cell terminals.
✅ Answer: (C)
Connecting a voltmeter in series would drastically reduce current flow and give an incorrect reading; parallel connection ensures it measures the full potential difference across the cell terminals.
✅ Answer: (C)
▶️ Answer/Explanation
For identical resistors each of resistance \(R\): series combinations increase total resistance (e.g. two in series give \(2R\)), while parallel combinations decrease it — three identical resistors all in parallel give \(\frac{R}{3}\), the smallest possible combined resistance.
Circuit B shows the greatest number of resistors connected in parallel, yielding the smallest total resistance of all the options shown.
✅ Answer: (B)
Circuit B shows the greatest number of resistors connected in parallel, yielding the smallest total resistance of all the options shown.
✅ Answer: (B)
▶️ Answer/Explanation
A fuse rated at 5 A or 9 A would blow during normal operation (maximum current is 10 A), which is unacceptable; a fuse rated at 25 A would allow dangerously high currents before blowing, providing poor protection.
A 13 A fuse is the lowest standard rating above 10 A — it allows normal operation while melting quickly if a fault causes the current to rise significantly above 10 A, giving optimal protection.
✅ Answer: (C)
A 13 A fuse is the lowest standard rating above 10 A — it allows normal operation while melting quickly if a fault causes the current to rise significantly above 10 A, giving optimal protection.
✅ Answer: (C)
▶️ Answer/Explanation
The magnetic field around a straight current-carrying wire forms concentric circles centred on the wire; applying the right-hand rule with the current directed upward (as shown by the arrow) means the field lines circle anticlockwise when viewed from above.
Only diagram D shows concentric circular field lines in the correct anticlockwise direction consistent with the given current direction.
✅ Answer: (D)
Only diagram D shows concentric circular field lines in the correct anticlockwise direction consistent with the given current direction.
✅ Answer: (D)
▶️ Answer/Explanation
8.0 days earlier represents \(\frac{8.0}{4.0} = 2\) half-lives in the past; going back 2 half-lives means the activity was \(2^2 = 4\) times greater than it is now: \(32 \times 4 = 128\) emissions per minute.
This can be verified by working forward: \(128 \xrightarrow{\times\frac{1}{2}} 64 \xrightarrow{\times\frac{1}{2}} 32\) — after two half-lives (8 days), the rate drops from 128 to 32, confirming the answer.
✅ Answer: (B)
This can be verified by working forward: \(128 \xrightarrow{\times\frac{1}{2}} 64 \xrightarrow{\times\frac{1}{2}} 32\) — after two half-lives (8 days), the rate drops from 128 to 32, confirming the answer.
✅ Answer: (B)