⚡ Quick quiz

Test yourself in under a minute: Class 10 Science Practice Test

Silver tarnishing, reactivity series reasoning, and circuit questions sit side by side here, spread evenly across chemistry, biology, and physics like the real paper.

1. 1. A silver ornament left in open air slowly turns black over time. Is this best classified as a physical change or a chemical reaction, and why?

   🔊
   A) Physical change, since no heat is involvedB) Neither, nothing is actually happeningC) Physical change, silver just changes colourD) Chemical reaction, forms silver sulfide

2. 2. You mix an acid and a base in exactly the right amounts, and the resulting solution turns litmus paper neither red nor blue. What does this tell you about the solution's pH, and what reaction produced it?

   🔊
   A) pH cannot be determined from this testB) pH above 10, from a combination reactionC) pH below 3, from a displacement reactionD) pH close to 7, from a neutralization reaction

3. 3. A student places a piece of iron in copper sulphate solution. Over time, a reddish-brown coating appears on the iron, and the blue colour of the solution fades. Explain this using the reactivity series.

   🔊
   A) The coating is just rust, unrelated to the solutionB) Iron displaces copper, since iron is more reactiveC) No reaction occurs, iron and copper don't reactD) Copper displaces iron, since copper is more reactive

4. 4. Two compounds have very similar chemical properties but differ by exactly one CH2 unit in their formula. What term describes their relationship, and what does that let you predict?

   🔊

5. 5. A person exercises very intensely and feels a burning sensation in their leg muscles. What process inside their muscle cells is most directly responsible, and why does it happen?

   🔊

6. 6. Two tall pea plants are crossed, and some of their offspring turn out short. What does this tell you about the genetic makeup of the two tall parent plants?

   🔊
   A) Both parents are pure tall (TT)B) One parent is short, disguised as tallC) Both parents are hybrid tall (Tt)D) This result is impossible with two tall parents

7. 7. A lens always produces a virtual, upright, smaller image, no matter where the object is placed. What type of lens is this, and how is it different from a convex lens in this respect?

   🔊

8. 8. Two identical bulbs are connected first in series and then in parallel across the same battery. In which arrangement does each bulb glow brighter, and why?

   🔊

Chemical Reactions and Equations

Tests balancing chemical equations and identifying reaction types: combination, decomposition, double displacement, and displacement (redox).

1. 1. Balance the chemical equation: Fe + H2O -> Fe3O4 + H2 (iron reacting with steam).

   🔊
   ▶Reveal answer

   3Fe + 4H2O -> Fe3O4 + 4H2🔊

   Balancing requires the same number of each atom on both sides. Iron atoms balance at 3 (matching Fe3O4), and balancing oxygen (4 atoms in Fe3O4) requires 4 water molecules, which in turn release 4 hydrogen molecules. This reaction is also an example of a combination-then-redox process, since iron is oxidised while hydrogen is released from water.

2. 2. Identify the type of reaction: 2AgBr -> 2Ag + Br2, occurring in sunlight.

   🔊
   ▶Reveal answer

   Decomposition reaction (specifically a photochemical decomposition)🔊

   A single compound, silver bromide, breaks down into two simpler substances, silver and bromine, under the action of light rather than heat. This exact reaction is the chemical basis of black-and-white photography, where light exposure decomposes silver bromide crystals on film.

3. 3. What type of reaction occurs when aqueous solutions of two salts react to form an insoluble solid?

   🔊
   ▶Reveal answer

   A double displacement (precipitation) reaction🔊

   In this type of reaction, the positive and negative ions of two different salts swap partners in solution, and if one of the new combinations is insoluble, it separates out as a solid precipitate. For example, sodium sulphate and barium chloride react to form insoluble barium sulphate plus soluble sodium chloride.

4. 4. In the reaction Zn + CuSO4 -> ZnSO4 + Cu, which substance is oxidised and which is reduced?

   🔊
   ▶Reveal answer

   Zinc is oxidised; copper is reduced.🔊

   Zinc loses electrons to become Zn2+ ions, which is oxidation, while Cu2+ ions in the solution gain those electrons to become solid copper metal, which is reduction. Since zinc is more reactive than copper, it displaces copper out of the solution entirely, making this also a displacement reaction.

Acids, Bases and Salts

Covers the chlor-alkali process, baking soda, Plaster of Paris, bleaching powder, and pH-based indicator reasoning.

1. 1. Name the three products obtained from the chlor-alkali process (electrolysis of concentrated sodium chloride solution).

   🔊
   ▶Reveal answer

   Sodium hydroxide (NaOH), chlorine gas (Cl2), and hydrogen gas (H2)🔊

   This is called the chlor-alkali process because it produces both a chlorine-based product and an alkali (NaOH) from the same electrolysis of brine (concentrated salt solution). All three products have major industrial uses, NaOH in soaps and detergents, chlorine in disinfectants and PVC, and hydrogen as a fuel or in margarine production.

2. 2. What is the chemical name of baking soda, and what gas is released when it reacts with an acid?

   🔊
   ▶Reveal answer

   Sodium hydrogencarbonate (NaHCO3); it releases carbon dioxide gas.🔊

   When baking soda reacts with an acid or is heated, it decomposes to release carbon dioxide gas, which is exactly what makes cake batter or bread dough rise, the trapped gas bubbles expand and lighten the mixture.

3. 3. What is Plaster of Paris chemically, and what happens when water is added to it?

   🔊
   ▶Reveal answer

   Calcium sulphate hemihydrate; adding water causes it to set into a hard solid mass (gypsum).🔊

   Plaster of Paris is made by heating gypsum to remove some of its water of crystallisation. Adding water back reverses this, and the mixture sets into hard gypsum again within minutes, which is why Plaster of Paris must be stored in an airtight, moisture-proof container to prevent it from setting before use.

4. 4. A solution turns blue litmus red. What does this tell you about its approximate pH?

   🔊
   ▶Reveal answer

   Its pH is below 7, indicating an acidic solution.🔊

   Litmus is a natural indicator that turns red in acidic conditions and blue in basic conditions. A pH below 7 means the solution has a higher concentration of hydrogen ions than pure water, the lower the number, the more strongly acidic the solution.

5. 5. What common name is given to calcium oxychloride, used for disinfecting water and bleaching?

   🔊
   ▶Reveal answer

   Bleaching powder🔊

   Calcium oxychloride is produced by passing chlorine gas over dry slaked lime (calcium hydroxide). Beyond bleaching fabrics and paper, it is also commonly used to disinfect drinking water because of its ability to kill microorganisms.

Metals and Non-metals

Tests the reactivity series, ionic bonding, why sodium is stored under kerosene, corrosion prevention, and malleability.

1. 1. Arrange these metals in decreasing order of reactivity: Zinc, Copper, Sodium, Iron.

   🔊
   ▶Reveal answer

   Sodium > Zinc > Iron > Copper🔊

   The reactivity series ranks metals by how readily they lose electrons to form positive ions. Sodium reacts vigorously even with cold water, zinc and iron react more slowly and mainly with acids or steam, and copper is one of the least reactive common metals, not reacting with dilute acids at all.

2. 2. Why is sodium metal stored under kerosene oil?

   🔊
   ▶Reveal answer

   Sodium is highly reactive and reacts vigorously with oxygen and moisture in air; kerosene contains neither, so it prevents this reaction.🔊

   If exposed to air, sodium would quickly react with atmospheric oxygen and moisture, potentially catching fire. Kerosene is an unreactive liquid that forms a protective barrier around the metal without reacting with it itself.

3. 3. What type of bond forms between a metal and a non-metal, and what happens to their electrons?

   🔊
   ▶Reveal answer

   An ionic bond; the metal loses electrons and the non-metal gains those same electrons.🔊

   Metals tend to have few electrons in their outermost shell and lose them easily to form a stable positive ion, while non-metals tend to need just a few more electrons to complete their outer shell and readily accept them, forming a stable negative ion. The oppositely charged ions are then held together by electrostatic attraction, forming the ionic bond.

4. 4. Name one method used to prevent the corrosion (rusting) of iron.

   🔊
   ▶Reveal answer

   Galvanization (coating the iron with a layer of zinc)🔊

   Galvanization works because zinc is more reactive than iron, so it reacts with oxygen and moisture in preference to the iron underneath, protecting it even if the zinc coating gets scratched in places. Painting or oiling the surface works differently, by simply blocking air and moisture from reaching the iron at all.

5. 5. Which physical property allows metals to be beaten into thin sheets without breaking?

   🔊
   ▶Reveal answer

   Malleability🔊

   Malleability is the property that lets a metal be hammered or rolled into thin sheets without cracking, which happens because the layers of metal atoms can slide over one another while the metallic bond holding them together stays intact. This is different from ductility, which specifically describes being drawn into a thin wire.

Carbon and its Compounds

Covers covalent bonding in carbon, homologous series, functional groups, oxidation of ethanol, and the structure of soap molecules.

1. 1. What type of bond do carbon atoms typically form, given carbon has 4 electrons in its outermost shell?

   🔊
   ▶Reveal answer

   A covalent bond, formed by sharing electron pairs.🔊

   Carbon has 4 electrons in its outer shell, so it would need to either gain or lose 4 electrons to reach a stable configuration, both of which require a large amount of energy and are difficult for an atom of carbon's size. Sharing electrons through covalent bonds achieves stability without that energy cost, which is why carbon forms so many stable compounds this way.

2. 2. What is a homologous series? Give one example.

   🔊
   ▶Reveal answer

   A series of compounds with the same general formula and similar chemical properties, where successive members differ by a -CH2- unit. Example: the alkane series (methane, ethane, propane...).🔊

   Because each member differs from the next by a consistent, predictable unit, members of a homologous series show a gradual, regular change in physical properties (like boiling point) while keeping very similar chemical behaviour, which makes it possible to predict an unfamiliar member's properties from ones already known.

3. 3. Name the functional group present in ethanoic acid (acetic acid), and how does it affect the compound's properties?

   🔊
   ▶Reveal answer

   The carboxylic acid group (-COOH); it makes the compound acidic, able to react with bases and carbonates.🔊

   The -COOH group is what gives ethanoic acid its acidic character, letting it react with a base to form a salt and water, or with a carbonate to release carbon dioxide, reactions typical of acids generally, not just this one compound.

4. 4. What happens when ethanol is oxidised in the presence of a strong oxidising agent like alkaline potassium permanganate?

   🔊
   ▶Reveal answer

   It is oxidised to ethanoic acid (acetic acid).🔊

   Alkaline potassium permanganate is a strong oxidising agent that adds an oxygen atom to ethanol's structure, converting its -OH (alcohol) group into a -COOH (carboxylic acid) group, changing ethanol into ethanoic acid.

5. 5. What are soap molecules made of, structurally, and why does this help clean oily dirt?

   🔊
   ▶Reveal answer

   Soap molecules have a long hydrocarbon tail that dissolves in oil and an ionic head that dissolves in water.🔊

   This dual structure lets a soap molecule position its oily tail inside a grease droplet while its water-loving head stays in the surrounding water, forming tiny clusters called micelles that pull the oily dirt away from a surface and let it be rinsed off with water, something water alone cannot do.

Life Processes

Tests bile and fat digestion, stomata, xylem, anaerobic respiration and lactic acid, and the heart's chambers.

1. 1. Which major gland produces bile to help in the digestion of dietary fats?

   🔊
   ▶Reveal answer

   The liver (bile is produced there and stored in the gallbladder)🔊

   Bile doesn't contain digestive enzymes itself, but it breaks large fat droplets into smaller ones (emulsification), which greatly increases the surface area available for fat-digesting enzymes to act on, making fat digestion far more efficient.

2. 2. What are the tiny pores found on leaf surfaces that regulate gas exchange and water loss?

   🔊
   ▶Reveal answer

   Stomata🔊

   Stomata are tiny pores, mostly on the underside of leaves, each surrounded by a pair of guard cells that open and close them. They let carbon dioxide in and oxygen out during photosynthesis, and they are also the main site through which plants lose water vapour.

3. 3. Name the vascular plant tissue that moves water and dissolved minerals upward from the roots.

   🔊
   ▶Reveal answer

   Xylem🔊

   Xylem tissue is made of tube-like cells that form a continuous pathway from root to leaf. Water and dissolved minerals move upward through it mainly due to transpiration pull, the loss of water vapour from leaves creates a continuous pulling force that draws more water up from the roots.

4. 4. When muscles do intense work without enough oxygen, the buildup of which acid causes cramps?

   🔊
   ▶Reveal answer

   Lactic acid🔊

   During intense exercise, muscle cells may not receive oxygen fast enough to keep up with their energy demand, so they temporarily switch to anaerobic respiration, which breaks down glucose without oxygen and produces lactic acid as a byproduct. The buildup of this acid in muscle tissue is what causes the cramping, burning sensation.

5. 5. Which chamber of the human heart receives oxygen-rich blood returning from the lungs?

   🔊
   ▶Reveal answer

   The left atrium🔊

   Oxygen-rich blood returns from the lungs through the pulmonary veins into the left atrium, which then passes it into the left ventricle, the chamber responsible for pumping this oxygenated blood out to the rest of the body through the aorta.

Control, Coordination, Reproduction & Heredity

Covers reflex actions, plant hormones, hormone versus nerve signalling, sexual versus asexual reproduction, Mendel's law of dominance, sex determination, and contraception.

1. 1. What is a reflex action, and what neural pathway is involved?

   🔊
   ▶Reveal answer

   A rapid, automatic response to a stimulus that doesn't involve conscious thought, controlled through a reflex arc.🔊

   A reflex arc is a pathway that runs through the spinal cord rather than requiring a signal to travel all the way to the brain first. This shortcut allows an extremely fast response, like pulling a hand away from something hot, before the brain has even fully registered the sensation.

2. 2. Name the plant hormone responsible for a shoot bending and growing toward light (phototropism).

   🔊
   ▶Reveal answer

   Auxin🔊

   Auxin accumulates more on the shaded side of a shoot than the side facing light, and since it promotes faster cell elongation, the shaded side grows longer than the lit side. This uneven growth is what causes the shoot to bend and curve toward the light source.

3. 3. What is the main difference between how a hormone and a nerve impulse travel through the body?

   🔊
   ▶Reveal answer

   A hormone travels through the bloodstream and acts more slowly over a longer distance; a nerve impulse travels along neurons almost instantly for a fast, localised response.🔊

   Hormonal (chemical) coordination is suited to processes that need to be sustained over time, like growth or puberty, while nervous (electrical) coordination suits situations needing an immediate, precise reaction, like withdrawing from pain. The body relies on both systems working together rather than either one alone.

4. 4. What is the main difference between sexual and asexual reproduction in terms of genetic variation in the offspring?

   🔊
   ▶Reveal answer

   Sexual reproduction combines genetic material from two parents, producing more varied offspring; asexual reproduction produces offspring genetically identical to the single parent, with no variation.🔊

   The genetic variation that sexual reproduction introduces is significant for a species' ability to adapt over generations, since a wider range of traits gives a population a better chance that some individuals survive changing conditions, something asexual reproduction, which produces exact copies, cannot offer.

5. 5. If a pure tall pea plant (TT) is crossed with a pure short pea plant (tt), what will be the height of the offspring (F1 generation)?

   🔊
   ▶Reveal answer

   All offspring will be tall.🔊

   Since the tall trait (T) is dominant over the short trait (t), every offspring in the F1 generation inherits one T and one t allele (Tt), and the dominant T allele is what determines the visible trait, so all of them appear tall even though they carry the recessive short allele too.

6. 6. What determines the biological sex of a human child, in terms of the chromosome contributed by each parent?

   🔊
   ▶Reveal answer

   The sex chromosome contributed by the father.🔊

   The mother always contributes an X chromosome to her child, but the father can contribute either an X or a Y chromosome. If the father contributes an X, the child is XX (female); if he contributes a Y, the child is XY (male), which is why the father's contribution is what actually determines the child's sex.

7. 7. Name one contraceptive method that also helps prevent the spread of sexually transmitted infections.

   🔊
   ▶Reveal answer

   Condoms (a barrier method)🔊

   Unlike hormonal methods (like pills) that only prevent pregnancy, a condom physically blocks the exchange of bodily fluids during intercourse, which is what also gives it protection against sexually transmitted infections, a benefit most other contraceptive methods don't provide.

Light - Reflection & Refraction, and the Human Eye

Covers the mirror formula, concave lens image properties, lens power, myopia and its correction, and why the sky is blue and the sun looks red at sunset.

1. 1. State the mirror formula relating object distance, image distance, and focal length.

   🔊
   ▶Reveal answer

   1/v + 1/u = 1/f🔊

   In this formula, v is the image distance, u is the object distance, and f is the focal length, all measured from the mirror's pole using the standard sign convention. This single formula applies to both concave and convex mirrors, only the signs of the values change depending on the mirror type and where the object is placed.

2. 2. A concave lens always forms what type of image, regardless of where the object is placed?

   🔊
   ▶Reveal answer

   A virtual, erect, and diminished (smaller) image, always.🔊

   Unlike a convex lens, whose image size and type change depending on how far the object is from the lens, a concave (diverging) lens spreads light rays outward no matter where the object is placed, so the image formed is always virtual, upright, and smaller than the object.

3. 3. Define the power of a lens, and state its formula and SI unit.

   🔊
   ▶Reveal answer

   Power (P) = 1/f, with f measured in metres; SI unit is the dioptre (D).🔊

   A lens with a shorter focal length bends light more sharply and therefore has higher power. A convex (converging) lens is given a positive power value, while a concave (diverging) lens is given a negative power value, which is why an optician's prescription lists a lens power as a positive or negative number.

4. 4. Name the eye defect in which a person sees nearby objects clearly but distant objects appear blurred, and name the type of lens used to correct it.

   🔊
   ▶Reveal answer

   Myopia (nearsightedness); corrected using a concave (diverging) lens.🔊

   In myopia, the eye focuses the image of a distant object in front of the retina instead of directly on it, usually because the eyeball is too long or the eye's lens is too curved. A concave lens diverges the incoming light slightly before it enters the eye, pushing the focus point back onto the retina.

5. 5. What causes the sky to appear blue during the day?

   🔊
   ▶Reveal answer

   The scattering of sunlight by air molecules and fine particles in the atmosphere.🔊

   Blue light has a shorter wavelength than other colours in sunlight, and shorter wavelengths get scattered far more strongly by the tiny molecules in Earth's atmosphere. This scattered blue light reaches our eyes from all directions across the sky, which is why the sky appears blue rather than the direct white light of the sun itself.

6. 6. Why does the sun appear reddish at sunrise and sunset?

   🔊
   ▶Reveal answer

   Sunlight travels through a much greater thickness of atmosphere at sunrise and sunset, scattering away most of the blue light before it reaches an observer, leaving mostly red light.🔊

   When the sun is low on the horizon, its light has to pass through far more atmosphere than when it's overhead, giving the shorter-wavelength blue light many more opportunities to scatter away in other directions. What's left to travel in a mostly straight path to an observer's eyes is the longer-wavelength red and orange light, giving the sun its reddish appearance.

Electricity, Magnetic Effects & Our Environment

Tests Ohm's law, series and parallel resistance, the Right-Hand Thumb Rule, circuit fuses, and biodegradable versus non-biodegradable waste.

1. 1. State Ohm's law and its formula.

   🔊
   ▶Reveal answer

   The potential difference across a conductor is directly proportional to the current through it, provided temperature stays constant. Formula: V = IR.🔊

   In this formula, V is potential difference, I is current, and R is resistance. Ohm's law only holds true as long as physical conditions like temperature remain unchanged, since a conductor's resistance itself can change with temperature, which is why the law includes that condition explicitly.

2. 2. If two resistors of 4 ohm and 6 ohm are connected in series, what is their combined resistance?

   🔊
   ▶Reveal answer

   10 ohm🔊

   In a series circuit, resistances simply add together because the same current has to pass through each resistor one after another: R_total = R1 + R2 = 4 + 6 = 10 ohm.

3. 3. If the same two resistors (4 ohm and 6 ohm) were instead connected in parallel, would the combined resistance be greater or smaller than 4 ohm? Why?

   🔊
   ▶Reveal answer

   Smaller than 4 ohm (specifically 2.4 ohm)🔊

   In a parallel circuit, current has multiple separate paths to flow through, which always makes the combined resistance smaller than even the smallest individual resistor. Using 1/R_total = 1/R1 + 1/R2 = 1/4 + 1/6 = 5/12, giving R_total = 12/5 = 2.4 ohm.

4. 4. State the Right-Hand Thumb Rule, and what it is used to find.

   🔊
   ▶Reveal answer

   If a current-carrying wire is held in the right hand with the thumb pointing in the direction of current, the curled fingers show the direction of the magnetic field lines around the wire.🔊

   This rule gives a quick, physical way to find the direction of a magnetic field without needing to calculate anything, and it applies directly to a straight current-carrying conductor. A different rule (Fleming's Left-Hand Rule) is used instead when finding the direction of force on a current in a magnetic field.

5. 5. What safety device in an electrical circuit melts and breaks the circuit if the current rises above a safe limit?

   🔊
   ▶Reveal answer

   A fuse🔊

   A fuse contains a short length of wire made from a metal with a low melting point. If the current exceeds a safe limit, the fuse wire heats up enough to melt and break the circuit, cutting off the current before it can damage other appliances or start a fire.

6. 6. What is the main difference in how biodegradable and non-biodegradable waste affect the environment over time?

   🔊
   ▶Reveal answer

   Biodegradable waste can be broken down naturally by microorganisms into harmless substances, while non-biodegradable waste resists decomposition and persists in the environment for a very long time.🔊

   Because microorganisms can't break down non-biodegradable materials like most plastics, this waste accumulates in landfills, oceans, and soil over decades or longer, whereas biodegradable waste, like food scraps or paper, is broken down by natural biological processes into simple substances that rejoin the environment safely.