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BJC General Science study materials
BJC General Science study resources

BJC General Science practice questions

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Question 1Scientific Method and Laboratory Skills

A student wants to find out whether fertilizer affects plant height. Which variable should be deliberately changed in the experiment?

  1. The type of soil used
  2. The amount of water given
  3. The amount of fertilizer given Correct answer.
  4. The height of the plants at the end

Explanation

The independent variable is the factor the experimenter deliberately manipulates to test its effect. Plant height is the measured outcome, while soil and water must be held constant as controlled variables.

Question 2Scientific Method and Laboratory Skills

Four students each read the same thermometer. Their readings are 21.0 °C, 21.1 °C, 20.9 °C and 21.0 °C, but the true temperature is 27.0 °C. How should these measurements be described?

  1. Neither accurate nor precise
  2. Precise but not accurate Correct answer.
  3. Both accurate and precise
  4. Accurate but not precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to closeness to the true value. The readings cluster tightly together but all lie far from 27.0 °C, so they are precise yet inaccurate.

Question 3Scientific Method and Laboratory Skills

Which piece of glassware gives the most accurate volume measurement for delivering exactly 25.0 mL of liquid?

  1. An Erlenmeyer flask
  2. A graduated cylinder
  3. A volumetric pipette Correct answer.
  4. A beaker

Explanation

A volumetric pipette is calibrated to deliver one fixed volume with very high accuracy. Graduated cylinders, beakers and flasks have wider tolerances and coarser markings, so they suit approximate volumes only.

Question 4Scientific Method and Laboratory Skills

A student heats a liquid in a test tube over a Bunsen burner. Which safety procedure is most appropriate?

  1. Fill the tube completely to reduce splashing
  2. Point the tube opening toward a partner to observe the reaction
  3. Hold the tube with tongs and point the opening away from people Correct answer.
  4. Seal the tube with a stopper before heating

Explanation

Heating a test tube requires tongs and an opening directed away from everyone, because sudden boiling can eject hot liquid. Sealing a tube while heating can build pressure and cause an explosion.

Question 5Scientific Method and Laboratory Skills

A researcher predicts that plants given more light will grow taller. She then designs an experiment and collects data. In the cycle of scientific inquiry, what is the prediction called?

  1. A control group
  2. An observation
  3. A hypothesis Correct answer.
  4. A conclusion

Explanation

A hypothesis is a testable, tentative prediction about the relationship between variables, made before data collection. Conclusions are drawn after analysing results, and an observation is a direct record of what is sensed or measured.

Question 6Scientific Method and Laboratory Skills

In an experiment testing a new antibiotic, one group of bacterial cultures receives the antibiotic and another receives a sterile solution with no antibiotic. What is the main purpose of the second group?

  1. To increase the total number of cultures tested
  2. To make the experiment finish faster
  3. To provide a baseline for comparison without the treatment Correct answer.
  4. To test a second type of antibiotic

Explanation

A control group is treated identically except that it does not receive the experimental treatment, giving a baseline against which the effect can be judged. Without it, any change could be attributed to other factors such as normal growth.

Question 7Scientific Method and Laboratory Skills

A student records the mass of a sample three times and writes it as 12.3456 g using a balance marked to 0.01 g. What is the main problem with this record?

  1. The recorded digits exceed the precision of the balance Correct answer.
  2. The mass should be recorded in kilograms
  3. A balance cannot measure mass
  4. The value is too small to be measured

Explanation

Recorded data should reflect the precision of the instrument, which here reads to two decimal places. Writing extra digits implies a level of certainty the balance cannot provide, which is a form of measurement error.

Question 8Scientific Method and Laboratory Skills

Which action best improves the reliability of a measurement that is repeated several times?

  1. Rounding every value to a whole number
  2. Repeating the measurement and averaging the results Correct answer.
  3. Recording the values from memory later
  4. Choosing the single largest value

Explanation

Repeated measurements reduce the influence of random error, and averaging them gives a more reliable estimate of the true value. Rounding or recalling values from memory introduces additional error rather than reducing it.

Question 9Scientific Method and Laboratory Skills

A student examines a graph of plant growth against light intensity. The points form a smooth curve that rises and then levels off. Which statement is the best interpretation?

  1. Light intensity causes no change in growth
  2. The data contain no measurable pattern
  3. Plant growth causes light intensity to rise
  4. Growth increases with light up to a point, then stops increasing Correct answer.

Explanation

The graph shows a positive relationship that plateaus, meaning growth rises with the independent variable until another factor becomes limiting. Describing the shape of the relationship is the purpose of interpreting a trend line.

Question 10Scientific Method and Laboratory Skills

Which statement is a properly written, testable hypothesis?

  1. Plants are beautiful
  2. Sunlight is better than water
  3. Maybe plants grow differently
  4. If a plant receives more sunlight, then it will grow taller Correct answer.

Explanation

A testable hypothesis predicts a specific relationship between variables and can be supported or rejected by measurement. Statements of opinion or vague speculation cannot be tested with data.

Question 11Scientific Method and Laboratory Skills

A scientist repeats an experiment in a different laboratory with different equipment and obtains the same result. Which aspect of the work is most directly supported?

  1. Its reproducibility Correct answer.
  2. Its cost effectiveness
  3. Its safety
  4. Its originality

Explanation

Reproducibility is demonstrated when independent investigators using different equipment obtain consistent results. This strengthens confidence that the findings reflect a real effect rather than local conditions or error.

Question 12Scientific Method and Laboratory Skills

A student needs to measure out approximately 50 mL of water quickly for a rinsing step that does not require precision. Which choice is most appropriate?

  1. A thermometer
  2. A volumetric flask
  3. An analytical balance
  4. A graduated cylinder Correct answer.

Explanation

A graduated cylinder is designed to measure varied volumes with reasonable accuracy and is convenient for approximate amounts. Volumetric flasks are calibrated for one fixed volume and are unsuitable for quick general measuring.

Question 13Scientific Method and Laboratory Skills

Which practice is most important when using a compound light microscope to observe a prepared slide?

  1. Starting with the highest-power objective lens
  2. Adjusting the coarse focus while on high power
  3. Beginning with the lowest-power objective and then increasing magnification Correct answer.
  4. Leaving the light source switched off

Explanation

Starting at low power gives a wide field of view that makes locating the specimen easy, after which higher objectives can be used. The coarse focus knob should be avoided on high power because it can drive the lens into the slide.

Question 14Scientific Method and Laboratory Skills

A student measures the boiling point of a liquid three times and gets 78.2 °C, 78.3 °C and 78.2 °C. The accepted value is 78.4 °C. Which statement best describes the result?

  1. The results are both precise and accurate Correct answer.
  2. The results are precise but slightly inaccurate
  3. The results are neither precise nor accurate
  4. The results are accurate but imprecise

Explanation

The three readings agree to within 0.1 °C, showing high precision, and they lie within 0.2 °C of the accepted value, which is close enough to count as accurate. Small random deviations of this size are normal in school measurements.

Question 15Scientific Method and Laboratory Skills

A student claims that a fertilizer increases crop yield because plants in the fertilized plot grew taller than plants in an unfertilized plot. The fertilized plot also received more water. What is the main weakness of the conclusion?

  1. Two variables changed at once, so the cause cannot be isolated Correct answer.
  2. The unfertilized plot was unnecessary
  3. Taller plants never indicate higher yield
  4. The plants were measured in centimetres

Explanation

When two factors vary together, the observed difference cannot be attributed to either one alone, a problem called confounding. A valid conclusion requires that only the independent variable differ between the plots while all other conditions are held constant.

Question 16Scientific Method and Laboratory Skills

A student wants to estimate the volume of one small irregular stone. Which method is most suitable?

  1. Heat it and measure its expansion
  2. Weigh it on a balance and read the volume from the mass
  3. Measure its length and width with a ruler and multiply
  4. Place it in a graduated cylinder and record the rise in water level Correct answer.

Explanation

Displacement uses the fact that a submerged object pushes aside a volume of water equal to its own volume. The difference in the water level before and after immersion gives the stone's volume directly.

Question 17Measurement, Units, and Density

Which SI base unit is used to express mass?

  1. kilogram Correct answer.
  2. gram
  3. pound
  4. newton

Explanation

The kilogram is the SI base unit of mass, defined by the fixed numerical value of the Planck constant. The gram is a submultiple of this unit but is not the base unit itself, and the newton measures force rather than mass.

Question 18Measurement, Units, and Density

A student writes a length as 0.0047 metres. What is this value in scientific notation?

  1. 47 x 10^-4 m
  2. 0.47 x 10^-2 m
  3. 4.7 x 10^3 m
  4. 4.7 x 10^-3 m Correct answer.

Explanation

Scientific notation places one nonzero digit before the decimal point and multiplies by a power of ten. Moving the decimal point three places right from 0.0047 gives 4.7, so the exponent is negative three.

Question 19Measurement, Units, and Density

Which instrument is most suitable for measuring the volume of a liquid to the nearest 0.1 cubic centimetre?

  1. metre rule
  2. top-pan balance
  3. graduated cylinder Correct answer.
  4. thermometer

Explanation

A graduated cylinder is marked with a volume scale, allowing liquid volumes to be read directly with reasonable precision. A balance measures mass, a rule measures length, and a thermometer measures temperature, so none of them reports volume.

Question 20Measurement, Units, and Density

A metal block has a mass of 270 g and a volume of 100 cm^3. What is its density?

  1. 0.37 g/cm^3
  2. 27 g/cm^3
  3. 2.7 g/cm^3 Correct answer.
  4. 370 g/cm^3

Explanation

Density equals mass divided by volume, so 270 g divided by 100 cm^3 gives 2.7 g/cm^3. This value matches aluminium and is a plausible density for a metal block of that size.

Question 21Measurement, Units, and Density

A rectangular block measures 5.0 cm by 4.0 cm by 2.0 cm. What is its volume, expressed with the correct number of significant figures?

  1. 4 cm^3
  2. 40 cm^3 Correct answer.
  3. 400 cm^3
  4. 40.0 cm^3

Explanation

Multiplying the three dimensions gives 5.0 x 4.0 x 2.0 = 40 cm^3. Because each measurement has two significant figures, the product should be reported with two significant figures, which is 40.

Question 22Measurement, Units, and Density

Which statement describes the difference between mass and weight?

  1. Mass changes with location, while weight stays constant everywhere.
  2. Mass is measured in newtons, while weight is measured in kilograms.
  3. Mass and weight are identical quantities expressed in different units.
  4. Mass is a measure of matter, while weight is the gravitational force on that matter. Correct answer.

Explanation

Mass measures the amount of matter in an object and is unchanged by location. Weight is the force of gravity acting on that mass and depends on the local gravitational field strength.

Question 23Measurement, Units, and Density

A liquid has a density of 0.80 g/cm^3. What volume is occupied by 200 g of this liquid?

  1. 250 cm^3 Correct answer.
  2. 2.5 cm^3
  3. 160 cm^3
  4. 0.004 cm^3

Explanation

Rearranging density equals mass divided by volume gives volume equals mass divided by density. Dividing 200 g by 0.80 g/cm^3 yields 250 cm^3, a sensible volume for a fairly light liquid.

Question 24Measurement, Units, and Density

An irregular stone is lowered into a measuring cylinder containing 50 cm^3 of water, and the level rises to 68 cm^3. The stone has a mass of 45 g. What is its density?

  1. 2.5 g/cm^3 Correct answer.
  2. 0.66 g/cm^3
  3. 0.90 g/cm^3
  4. 1.5 g/cm^3

Explanation

The displacement method gives the stone's volume as 68 minus 50, which is 18 cm^3. Dividing the mass of 45 g by 18 cm^3 gives a density of 2.5 g/cm^3.

Question 25Measurement, Units, and Density

A student records a temperature as 25.0 degrees Celsius. Which part of this measurement represents the estimated digit?

  1. the digit 2
  2. the digit 5
  3. the final zero after the decimal point Correct answer.
  4. the unit symbol

Explanation

In a recorded measurement, the last digit shown is the estimated or uncertain one read between scale marks. Here the tenths place is the final digit, so the zero after the decimal point is the estimate.

Question 26Measurement, Units, and Density

Which change would reduce the random error in a measurement of a falling time?

  1. using a stopwatch with a smaller display
  2. rounding each reading to one digit
  3. repeating the timing and averaging the results Correct answer.
  4. measuring the distance only once

Explanation

Random errors scatter above and below the true value, so averaging several repeats reduces their effect on the mean. Systematic errors, by contrast, are not removed by repetition because they shift every reading the same way.

Question 27Measurement, Units, and Density

Which statement about the density of a substance is correct?

  1. Density of a gas is independent of temperature and pressure.
  2. Density increases in direct proportion to the mass of the sample.
  3. Density is measured in newtons per cubic metre.
  4. Density is an intensive property that does not depend on the size of the sample. Correct answer.

Explanation

Density is an intensive property, meaning a small piece and a large piece of the same material have the same density at a given temperature and pressure. Doubling the sample doubles both mass and volume, leaving the ratio unchanged.

Question 28Measurement, Units, and Density

A cube of side 2.0 cm has a mass of 16 g. A second cube of side 4.0 cm is made of the same material. What is the mass of the second cube?

  1. 128 g Correct answer.
  2. 16 g
  3. 64 g
  4. 32 g

Explanation

Doubling the side length multiplies the volume by two cubed, which is eight. Since density is unchanged, the mass also becomes eight times larger, giving 16 g multiplied by 8, or 128 g.

Question 29Measurement, Units, and Density

A student measures the density of a metal five times and obtains values tightly clustered around 7.6 g/cm^3, while the accepted value is 8.9 g/cm^3. Which description fits these results?

  1. both accurate and precise
  2. precise but not accurate Correct answer.
  3. neither accurate nor precise
  4. accurate but not precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to closeness to the true value. Tightly clustered readings show high precision, but their distance from 8.9 g/cm^3 shows a systematic error that lowers accuracy.

Question 30Measurement, Units, and Density

A block of density 2.5 g/cm^3 is placed in water of density 1.0 g/cm^3 and then in a liquid of density 3.0 g/cm^3. What happens in each case?

  1. It floats in water and sinks in the denser liquid.
  2. It sinks in water and floats in the denser liquid. Correct answer.
  3. It sinks in both liquids.
  4. It floats in both liquids.

Explanation

An object floats when its average density is less than that of the surrounding fluid and sinks when its density is greater. The block at 2.5 g/cm^3 is denser than water but less dense than the 3.0 g/cm^3 liquid, so it sinks first and floats second.

Question 31Matter, Mixtures, and Separation Techniques

Which statement best describes a compound?

  1. A substance made of a single kind of atom
  2. A substance formed when two or more elements are chemically combined in fixed proportions Correct answer.
  3. A physical blend of two metals that can vary in proportion
  4. A mixture whose parts can be seen separately

Explanation

A compound forms when atoms of different elements bond chemically, producing a new substance whose elements are always present in a fixed ratio by mass. Because the atoms are chemically joined, the compound usually has properties unlike those of its elements, and it can only be separated by chemical means.

Question 32Matter, Mixtures, and Separation Techniques

A student stirs salt into water until no more dissolves and a little solid remains at the bottom. What is the clear liquid above the solid called?

  1. A saturated solution Correct answer.
  2. A colloid
  3. A suspension
  4. A solvent-free liquid

Explanation

A solution that can dissolve no more solute at that temperature is saturated, and any extra solute stays undissolved. The clear liquid above the solid is therefore a saturated solution of salt in water.

Question 33Matter, Mixtures, and Separation Techniques

Which method is most suitable for separating pure water from a solution of copper sulfate in water?

  1. Sieving
  2. Simple distillation Correct answer.
  3. Filtration
  4. Magnetic separation

Explanation

Distillation boils the solution so water vapor rises and is condensed back to liquid, leaving the dissolved salt behind. This separates a dissolved solid from its solvent and also gives a purified liquid.

Question 34Matter, Mixtures, and Separation Techniques

Which of the following is a physical change?

  1. Ice melting to form water Correct answer.
  2. Wood burning in a fire
  3. Iron rusting in damp air
  4. Baking soda reacting with vinegar

Explanation

In a physical change the substance keeps its identity and only its state or form alters, so melting ice still gives water (H2O). Chemical changes create new substances with different properties, which is what happens in rusting, burning, and acid reactions.

Question 35Matter, Mixtures, and Separation Techniques

Which piece of apparatus is used to measure a fixed volume of liquid accurately in a school laboratory?

  1. An evaporating dish
  2. A beaker
  3. A tripod stand
  4. A measuring cylinder Correct answer.

Explanation

A measuring cylinder carries a graduated scale along its side, so it can measure a chosen volume of liquid to a reasonable accuracy. Beakers and dishes have no fine graduations, and a tripod is only a support.

Question 36Matter, Mixtures, and Separation Techniques

A mixture contains iron filings, sand, and salt. Which sequence of steps will separate all three substances?

  1. Evaporate the mixture, then filter, then use a magnet
  2. Use a magnet, then add water and filter, then evaporate the filtrate Correct answer.
  3. Filter the mixture, then evaporate, then sieve the residue
  4. Add water and filter, then use a magnet, then evaporate the residue

Explanation

A magnet first removes the iron because it is the only magnetic component. Adding water dissolves the salt while the sand stays solid, so filtration traps the sand, and evaporating the filtrate recovers the salt.

Question 37Matter, Mixtures, and Separation Techniques

Which statement about the particles in a liquid is correct?

  1. They are far apart and move freely in all directions
  2. They are fixed in position in a regular lattice
  3. They are close together but able to slide past one another Correct answer.
  4. They do not move at all

Explanation

In a liquid the particles are still touching each other, so the volume is fixed, but they are not locked in place and can move past each other, which lets the liquid flow and take the shape of its container.

Question 38Matter, Mixtures, and Separation Techniques

A student heats a beaker of water and observes bubbles forming and steam rising. Which description of the changes is correct?

  1. The water is boiling, which is a physical change Correct answer.
  2. The water is decomposing into hydrogen and oxygen
  3. The water is undergoing a chemical change to steam
  4. The water is dissolving gases from the air

Explanation

Boiling converts liquid water to water vapour, but the particles are still H2O molecules, so only the state has changed. A change of state is physical because no new substance is formed.

Question 39Matter, Mixtures, and Separation Techniques

Which property is characteristic of a colloid rather than a true solution?

  1. Its dispersed particles scatter a beam of light Correct answer.
  2. Its particles are individual ions or small molecules
  3. Its dissolved particles settle out on standing
  4. It cannot be separated by any method

Explanation

Colloidal particles are larger than dissolved molecules and scatter light, producing the Tyndall effect. True solutions contain individual ions or molecules that do not scatter light noticeably.

Question 40Matter, Mixtures, and Separation Techniques

Why is chromatography useful for analysing inks and dyes?

  1. All components travel at the same rate but have different colours
  2. Heat decomposes the ink into separate elements
  3. The solvent chemically reacts with each dye to separate it
  4. Different components travel at different rates through the stationary phase Correct answer.

Explanation

In chromatography, components are carried by a moving solvent along a stationary phase. Components that cling more strongly to the stationary phase move more slowly, so they separate into distinct spots or bands.

Question 41Matter, Mixtures, and Separation Techniques

A sample of muddy water is poured through filter paper in a funnel. What is collected in the flask below?

  1. The residue, which is the solid trapped by the paper
  2. A saturated solution of mud
  3. A distillate produced by boiling
  4. The filtrate, which is the liquid that has passed through Correct answer.

Explanation

Filtration traps insoluble solid particles on the filter paper as the residue while the clear liquid passing through is the filtrate. Mud is insoluble, so the liquid below is simply water.

Question 42Matter, Mixtures, and Separation Techniques

Pure water boils at 100 °C at normal pressure, but a salt solution boils above 100 °C. What does this show?

  1. Dissolved particles raise the boiling point of the solvent Correct answer.
  2. Salt particles evaporate before the water
  3. Boiling point is unrelated to purity
  4. The salt solution contains less water per unit volume only

Explanation

Dissolved solute particles interfere with the escape of solvent molecules, so more energy is needed to boil the solution. The boiling point therefore rises as solute is added, which is why boiling point can be used as a purity check.

Question 43Matter, Mixtures, and Separation Techniques

A sample of air is cooled until it liquefies and then warmed slowly in a fractionating column. Which statement explains why nitrogen leaves first?

  1. Nitrogen reacts with the column packing
  2. Nitrogen has the lower boiling point of the main components Correct answer.
  3. Nitrogen has the higher boiling point of the main components
  4. Nitrogen is denser than oxygen and sinks

Explanation

Fractional distillation separates liquids by boiling point. Nitrogen boils at about −196 °C and oxygen at about −183 °C, so as the liquid warms the nitrogen vaporises first and leaves the top of the column.

Question 44Matter, Mixtures, and Separation Techniques

Which change would increase the amount of sugar that can dissolve in 100 g of water at a given temperature?

  1. Grinding the sugar into finer crystals
  2. Using a wider container
  3. Stirring the water faster
  4. Raising the temperature of the water Correct answer.

Explanation

Solubility of most solids in water increases as temperature rises, so heating allows more sugar to dissolve in the same mass of water. Stirring and grinding only speed up dissolving; they do not change how much can dissolve.

Question 45Matter, Mixtures, and Separation Techniques

Two clear liquids are mixed and the mixture becomes warm and a solid appears. Which conclusion is best supported?

  1. The warmth shows only physical mixing
  2. The mixture is a saturated solution that cooled
  3. The solid is undissolved starting material
  4. A chemical reaction has occurred, forming a new solid Correct answer.

Explanation

A solid appearing from two clear solutions indicates an insoluble product has formed, and the release of heat shows energy is given out by a reaction. Together these observations support a chemical change rather than simple dissolving.

Question 46Matter, Mixtures, and Separation Techniques

A student obtains a solid from a solution by evaporating the solvent. Which observation would most strongly suggest the solid is a pure substance rather than a mixture?

  1. It dissolves in water at room temperature
  2. It is a white crystalline solid
  3. It can be ground into a powder
  4. It melts sharply at a single temperature Correct answer.

Explanation

A pure substance melts at a single sharp temperature, whereas a mixture usually melts over a range because its components melt at different temperatures. Sharp melting point is therefore good evidence of purity.

Question 47Matter, Mixtures, and Separation Techniques

A mixture contains two liquids with boiling points of 78 °C and 140 °C. Which method gives the best separation of both liquids in reasonable purity?

  1. Evaporation to dryness in an open dish
  2. Fractional distillation with a fractionating column Correct answer.
  3. Adding water and then decanting
  4. Simple filtration through filter paper

Explanation

The two liquids have widely different boiling points, so fractional distillation can vaporise the lower-boiling liquid first and condense it separately. The column provides repeated condensation and vaporisation, improving the purity of each fraction.

Question 48Matter, Mixtures, and Separation Techniques

In paper chromatography of a dye, the solvent front moved 8.0 cm while a coloured spot moved 6.0 cm from the origin. What is the Rf value of that component?

  1. 8.0
  2. 1.33
  3. 0.75 Correct answer.
  4. 0.25

Explanation

The Rf value is the distance travelled by the component divided by the distance travelled by the solvent front, so 6.0 ÷ 8.0 = 0.75. Rf values are always between 0 and 1 for components that stay behind the solvent front.

Question 49Cells, Nutrition, and Transport in Living Things

Which structure controls the activities of a cell and contains its genetic material?

  1. The cell membrane
  2. The mitochondrion
  3. The cytoplasm
  4. The nucleus Correct answer.

Explanation

The nucleus houses the chromosomes, which carry DNA, and it directs the cell's activities by controlling which proteins are made. Other organelles carry out specific jobs but do not store the main genetic instructions.

Question 50Cells, Nutrition, and Transport in Living Things

Which feature is present in a plant cell but absent from an animal cell?

  1. A cell membrane
  2. A nucleus
  3. A cell wall made of cellulose Correct answer.
  4. Mitochondria

Explanation

Plant cells are surrounded by a rigid cellulose wall that gives shape and support, while animal cells lack this wall and are bounded only by a flexible membrane. The other listed structures occur in both cell types.