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QC Sec 4 Science & Tech study materials
QC Sec 4 Science & Tech study resources

QC Sec 4 Science & Tech practice questions

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Question 1Interpreting scientific data presented in tables, graphs and diagrams

A data table reports a measured mass of 12.500 g using a balance with a resolution of 0.001 g. Which statement about the significant figures in this value is correct?

  1. The value contains three significant figures because trailing zeros are never significant.
  2. The value contains two significant figures because only the nonzero digits count.
  3. The value contains five significant figures, and the two trailing zeros after the decimal point are significant. Correct answer.
  4. The value contains four significant figures because the final zero is a placeholder.

Explanation

In a decimal number, zeros to the right of a nonzero digit and after the decimal point are significant because they reflect the balance's stated resolution of 0.001 g. All digits from the first nonzero digit (1) through the last recorded decimal place therefore count, giving five significant figures.

Question 2Interpreting scientific data presented in tables, graphs and diagrams

A graph plots temperature (°C) on the horizontal axis and gas volume (cm³) on the vertical axis. The plotted points form a straight line that does not pass through the origin. What does the nonzero vertical intercept most reasonably represent?

  1. The slope of the line, which equals the expansion coefficient.
  2. The temperature at which the gas volume becomes zero.
  3. A random error that should be removed before plotting.
  4. The volume the gas would show at 0 °C, extrapolated from the linear trend. Correct answer.

Explanation

The vertical intercept is the value of the dependent variable when the independent variable equals zero, so here it is the extrapolated volume at 0 °C. It is a meaningful constant from the fitted line, not an error to delete.

Question 3Interpreting scientific data presented in tables, graphs and diagrams

In a bar chart, one bar reaches 40 units and another reaches 10 units. The vertical axis starts at zero. What is the ratio of the first bar's height to the second bar's height?

  1. 3:1
  2. 1:4
  3. 4:1 Correct answer.
  4. 40:1

Explanation

With a zero-based axis, bar heights are directly proportional to the values, so the ratio is 40 to 10, which simplifies to 4:1. Reading the axis values rather than the physical lengths confirms this.

Question 4Interpreting scientific data presented in tables, graphs and diagrams

A line graph shows a quantity rising steeply, then levelling off to a plateau. Which description of the rate of change is correct?

  1. The rate is high initially and approaches zero as the plateau is reached. Correct answer.
  2. The rate is constant across the entire graph.
  3. The rate is zero initially and increases steadily throughout.
  4. The rate becomes negative once the plateau begins.

Explanation

The steepness of the curve, which is the rate of change, is greatest at the start and decreases as the curve flattens. At a plateau the slope is essentially zero, so the rate approaches zero.

Question 5Interpreting scientific data presented in tables, graphs and diagrams

A table lists replicate measurements: 5.02, 5.01, 5.03, and 5.02 units. What do these values indicate about the precision of the measurement?

  1. They are neither precise nor accurate because replicates differ.
  2. They are highly precise because the values cluster closely together. Correct answer.
  3. They are accurate because the mean is exactly 5.02.
  4. They are imprecise because no two values are identical.

Explanation

Precision describes how closely repeated measurements agree with one another, and these values span only 0.02 units. Small scatter among replicates is the hallmark of high precision.

Question 6Interpreting scientific data presented in tables, graphs and diagrams

A scatter graph shows points lying close to a straight line with a negative gradient. As the variable on the horizontal axis increases, what happens to the variable on the vertical axis?

  1. It stays constant.
  2. It changes unpredictably.
  3. It decreases. Correct answer.
  4. It increases.

Explanation

A negative gradient means the line falls as you move to the right, so the vertical variable decreases as the horizontal variable increases. The close fit to a line also indicates a strong linear relationship.

Question 7Interpreting scientific data presented in tables, graphs and diagrams

A diagram of an electrical circuit uses standard symbols. A component drawn as a rectangle with a single diagonal arrow through it represents which device?

  1. A light-emitting diode
  2. A fixed capacitor
  3. A variable resistor Correct answer.
  4. A battery

Explanation

The standard circuit symbol for a variable resistor is a rectangle with a diagonal arrow across it, indicating an adjustable resistance. Recognising symbols lets a reader interpret circuit diagrams without labels.

Question 8Interpreting scientific data presented in tables, graphs and diagrams

A pie chart divides a whole into sectors for five categories. One sector subtends 90° at the centre. What fraction of the total does that category represent?

  1. One fifth
  2. One tenth
  3. One half
  4. One quarter Correct answer.

Explanation

A full circle is 360°, so a sector of 90° represents 90/360, which simplifies to one quarter of the total. Pie-chart sector angles are always proportional to the category's share.

Question 9Interpreting scientific data presented in tables, graphs and diagrams

A results table gives a mean of 24.6 with an uncertainty of ±0.4 units. Which range contains the true value at the stated confidence?

  1. 24.0 to 25.2
  2. 24.2 to 24.6
  3. 24.6 to 25.0
  4. 24.2 to 25.0 Correct answer.

Explanation

The uncertainty defines a symmetric band around the mean, so you subtract and add 0.4 to 24.6. This gives a range from 24.2 to 25.0.

Question 10Interpreting scientific data presented in tables, graphs and diagrams

Two data sets have the same mean of 50. Set A ranges from 48 to 52, while set B ranges from 20 to 80. What can be concluded from the spread alone?

  1. Set A has greater variability because its values are closer together.
  2. Set B is more precise because it covers a wider range.
  3. Set B has greater variability, so its mean is a less reliable summary of a typical value. Correct answer.
  4. Both sets have identical variability because their means are equal.

Explanation

Variability is described by the spread of values, and set B spans a much wider range than set A. A wider spread means individual values differ more from the mean, so the mean represents a typical value less well.

Question 11Interpreting scientific data presented in tables, graphs and diagrams

A calibration graph of instrument reading against known concentration is linear with equation reading = 2.5 × concentration + 0.3. A sample gives a reading of 10.3. What concentration does the graph indicate?

  1. 4.12
  2. 10.0
  3. 4.0 Correct answer.
  4. 2.5

Explanation

Rearrange the calibration equation to make concentration the subject: concentration = (reading − 0.3)/2.5. Substituting 10.3 gives (10.0)/2.5, which equals 4.0.

Question 12Interpreting scientific data presented in tables, graphs and diagrams

In a table, one data point lies far from the trend shown by all other points. The experimenter checks the method and finds no procedural fault. What is the most appropriate scientific response?

  1. Adjust the point to match the trend line.
  2. Silently delete the point so the trend looks cleaner.
  3. Discard the entire data set and start again.
  4. Report the point, investigate its cause, and state whether it is retained or excluded with justification. Correct answer.

Explanation

An outlier is information, not an inconvenience; it may reveal an unrecognised variable or an error. Good practice is to keep it in the record, investigate it, and justify transparently any decision to exclude it.

Question 13Interpreting scientific data presented in tables, graphs and diagrams

A graph's horizontal axis is labelled with equal spacing but the values jump 1, 2, 4, 8, 16. What type of scale is this?

  1. A reciprocal scale
  2. A linear scale
  3. A logarithmic scale Correct answer.
  4. A categorical scale

Explanation

Equal physical spacing between values that increase by a constant factor is the defining feature of a logarithmic scale. On such a scale, equal distances represent equal multiplicative changes.

Question 14Interpreting scientific data presented in tables, graphs and diagrams

A table reports the number of seeds germinating at four temperatures: 10 °C gave 12, 15 °C gave 28, 20 °C gave 41, and 25 °C gave 19. What does the data suggest?

  1. Germination is highest at the lowest temperature.
  2. Germination increases steadily across the whole range.
  3. Germination rises to a maximum near 20 °C and then declines. Correct answer.
  4. Germination is unaffected by temperature.

Explanation

Reading the counts in order shows an increase from 12 to 41 up to 20 °C, followed by a fall to 19 at 25 °C. The pattern is therefore a peak around 20 °C rather than a monotonic trend.

Question 15Interpreting scientific data presented in tables, graphs and diagrams

A diagram shows a transverse wave with the distance between two consecutive crests marked as 0.5 m. What quantity does this marked distance represent?

  1. The wavelength Correct answer.
  2. The amplitude
  3. The wave speed
  4. The frequency

Explanation

The distance between successive corresponding points on a wave, such as crest to crest, is the wavelength. It is a length measured in metres, consistent with the 0.5 m label.

Question 16Interpreting scientific data presented in tables, graphs and diagrams

A stacked bar chart shows total composition for three years. The total bar height stays constant while the segment for one component grows. What must happen to the remaining segments?

  1. Their combined length must shrink to keep the total constant. Correct answer.
  2. Their combined length must also grow.
  3. Their combined length must stay exactly the same.
  4. Their combined length must become zero.

Explanation

In a stacked bar the segments sum to the total height, which is fixed here. If one segment grows while the total is unchanged, the other segments together must shrink by the same amount.

Question 17Interpreting scientific data presented in tables, graphs and diagrams

A table gives a measured density of 2.70 g/cm³, and the accepted value is 2.70 g/cm³. However, replicate values scatter by ±0.15 g/cm³. How should this result be described?

  1. Precise but inaccurate
  2. Neither accurate nor precise
  3. Both accurate and precise
  4. Accurate but imprecise Correct answer.

Explanation

Accuracy is agreement with the accepted value, which is excellent here because the mean matches it. Precision concerns the scatter among replicates, and a spread of ±0.15 g/cm³ is relatively large, so the measurement is imprecise.

Question 18Interpreting scientific data presented in tables, graphs and diagrams

A graph plots the extension of a spring against applied force, giving a straight line through the origin. The gradient is 0.04 m/N. What does this gradient represent?

  1. The extension per unit force, which is the reciprocal of the spring constant Correct answer.
  2. The natural length of the spring
  3. The spring constant in newtons per metre
  4. The maximum force the spring can bear

Explanation

The gradient is the change in the vertical quantity per unit change in the horizontal quantity, here metres per newton. Since extension equals force divided by the spring constant, the gradient equals 1/k rather than k itself.

Question 19Interpreting scientific data presented in tables, graphs and diagrams

A table presents a set of readings with a stated resolution of 0.1 units, but every value is recorded to two decimal places, such as 3.47. What is the most defensible criticism of the table?

  1. Two decimal places are always required for valid data.
  2. The recorded precision exceeds the instrument's resolution, so the extra digits are not justified. Correct answer.
  3. The values should be recorded to whole numbers only.
  4. The resolution should be increased to match the decimals.

Explanation

A measurement cannot be reported more finely than the instrument can resolve; digits beyond 0.1 are not meaningful. Recording 3.47 implies a resolution of 0.01, which the instrument does not provide.

Question 20Interpreting scientific data presented in tables, graphs and diagrams

A scatter graph of two variables shows no discernible pattern, with points scattered evenly across the plot. Which conclusion is best supported?

  1. The vertical variable causes changes in the horizontal variable.
  2. There is little or no correlation between the two variables in this data set. Correct answer.
  3. The data must contain measurement errors.
  4. There is a strong positive correlation that the graph fails to show.

Explanation

Correlation is judged from how closely points follow a trend, and an even scatter indicates no clear linear relationship. Absence of correlation does not by itself imply error or causation.

Question 21Interpreting scientific data presented in tables, graphs and diagrams

A diagram shows a distance–time graph for a moving object. The graph is a straight line with a positive slope that becomes steeper after a certain time. What does the change in slope indicate?

  1. The object's speed increases at that time. Correct answer.
  2. The object stops at that time.
  3. The object reverses direction at that time.
  4. The object's acceleration becomes zero at that time.

Explanation

On a distance–time graph the gradient equals speed, so a steeper line means a greater speed. The change in slope therefore marks an increase in speed.

Question 22Interpreting scientific data presented in tables, graphs and diagrams

A table reports the same quantity measured by two methods. Method P gives 8.0 ± 0.1 and method Q gives 7.6 ± 0.1. What is the most reasonable interpretation of these results?

  1. The two methods agree, because both have the same uncertainty.
  2. The two methods agree, because the values differ by less than 1 unit.
  3. No comparison is possible without more replicates.
  4. The two methods disagree, because the uncertainty ranges do not overlap. Correct answer.

Explanation

Each result defines a range: P spans 7.9 to 8.1 and Q spans 7.5 to 7.7. These ranges do not overlap, so the difference exceeds the stated uncertainty and the methods disagree.

Question 23Interpreting scientific data presented in tables, graphs and diagrams

A graph shows two curves for the same reaction at different temperatures. The curve for the higher temperature rises more steeply and reaches a higher plateau. Which interpretation is consistent with the graph?

  1. The higher temperature increases the initial rate but lowers the final extent.
  2. The higher temperature lowers the initial rate but raises the final extent.
  3. The higher temperature increases both the initial rate and the final extent of the change. Correct answer.
  4. The higher temperature affects neither the rate nor the final extent.

Explanation

A steeper initial rise corresponds to a greater rate, and a higher plateau corresponds to a larger final extent. Both features are greater for the higher-temperature curve.

Question 24Interpreting scientific data presented in tables, graphs and diagrams

A data table contains a column of calculated values derived from two measured columns. The derived values are quoted to six significant figures. Why is this problematic?

  1. The calculated values should be rounded to reflect the significant figures of the least precise input. Correct answer.
  2. Derived values should be quoted to exactly two significant figures in all cases.
  3. Calculated values should always be quoted to more figures than the inputs.
  4. The number of significant figures in a calculation is unimportant.

Explanation

A calculated result cannot be more precise than the least precise measurement used to obtain it. Quoting six significant figures implies precision the input data do not support, so the result should be rounded accordingly.

Question 25Interpreting scientific data presented in tables, graphs and diagrams

A diagram of an experimental setup includes a thermometer placed in a water bath, with readings recorded every minute in a table. The temperature rises quickly then slowly approaches a constant value. What does the constant final reading most likely represent?

  1. A systematic error in the thermometer.
  2. The temperature at which heat input balances heat loss, giving a steady state. Correct answer.
  3. The maximum temperature the thermometer can register.
  4. The point at which the water has completely boiled away.

Explanation

When a heated system levels off, the rate of heat input equals the rate of heat loss, producing a steady-state temperature. The plateau is a physical equilibrium, not an instrument limit.

Question 26Interpreting scientific data presented in tables, graphs and diagrams

A data table records the mass of a sample as 12.4 g, 12.6 g, 12.5 g and 12.5 g. The balance used has a resolution of 0.1 g. Which statement best describes the precision of these measurements?

  1. The readings are neither precise nor accurate because no accepted value is given.
  2. The readings are accurate because they are all close to 12.5 g.
  3. The readings are precise because they agree closely with each other within the balance resolution. Correct answer.
  4. The readings are imprecise because the balance resolution is too coarse.

Explanation

Precision concerns how closely repeated readings agree with one another, and these four values lie within 0.2 g of each other, consistent with a 0.1 g resolution. Accuracy instead requires comparison with a true or accepted value, which is not supplied here.

Question 27Interpreting scientific data presented in tables, graphs and diagrams

A bar chart compares the mean height of seedlings grown under three light intensities. The error bars on the middle bar overlap the error bars of both other bars. What is the most reasonable interpretation?

  1. The difference between the middle treatment and the others may not be statistically meaningful. Correct answer.
  2. The middle treatment must be discarded because its data are unreliable.
  3. The error bars show the seedlings in the middle group grew at different rates.
  4. The middle treatment definitely produced the tallest seedlings.

Explanation

Overlapping error bars indicate that the uncertainty ranges of the means intersect, so the apparent differences may arise from random variation rather than a real treatment effect. A cautious interpretation is that the difference is not clearly established without further statistical testing.

Question 28Interpreting scientific data presented in tables, graphs and diagrams

A line graph plots temperature on the vertical axis against time on the horizontal axis for a cooling liquid. The curve falls steeply at first and then flattens towards a constant value. What does the flattening of the curve indicate?

  1. The liquid has completely frozen at that temperature.
  2. The liquid is being heated at a constant rate.
  3. The thermometer has stopped recording accurately.
  4. The rate of cooling decreases as the liquid approaches the surrounding temperature. Correct answer.

Explanation

A cooling curve flattens because the temperature difference between the liquid and its surroundings shrinks, reducing the rate of heat loss. The curve approaches the ambient temperature asymptotically rather than indicating a fault or a phase change.

Question 29Interpreting scientific data presented in tables, graphs and diagrams

A scatter graph is plotted with the independent variable on the horizontal axis and the dependent variable on the vertical axis. Which convention does this follow?

  1. The variable with the larger numerical range is always placed on the x-axis.
  2. Either variable may be placed on either axis without affecting interpretation.
  3. The responding variable is placed on the x-axis and the manipulated variable on the y-axis.
  4. The manipulated variable is placed on the x-axis and the responding variable on the y-axis. Correct answer.

Explanation

By convention the independent (manipulated) variable is plotted on the horizontal axis and the dependent (responding) variable on the vertical axis. This allows the graph to show how the dependent variable responds to changes in the independent variable.

Question 30Interpreting scientific data presented in tables, graphs and diagrams

A table lists the volume of gas produced at five time intervals during a reaction. The values are 0, 15, 30, 45 and 60 cm³ at 0, 10, 20, 30 and 40 s. What does the constant increase per interval show?

  1. The reaction has reached completion.
  2. The gas volume is being measured with poor precision.
  3. The reaction proceeds at a constant rate over this period. Correct answer.
  4. The reaction rate is increasing steadily.

Explanation

A constant increase in product volume for each equal time interval means the gradient of the volume–time graph is constant, so the rate is steady. An increasing rate would show larger increments at later intervals.

Question 31Interpreting scientific data presented in tables, graphs and diagrams

A diagram of a transverse wave labels the vertical distance from the equilibrium line to a crest as 3 cm. What is the amplitude of the wave?

  1. 3 cm Correct answer.
  2. 6 cm
  3. 12 cm
  4. 1.5 cm

Explanation

Amplitude is defined as the maximum displacement from the equilibrium position to a crest or trough, so the labelled 3 cm is the amplitude. The peak-to-trough distance would be twice this value, but that is not what is marked.

Question 32Interpreting scientific data presented in tables, graphs and diagrams

A pie chart shows the composition of household waste. The food waste sector subtends 144° at the centre. What percentage of the total waste is food waste?

  1. 36%
  2. 40% Correct answer.
  3. 44%
  4. 25%

Explanation

A full circle is 360°, so the fraction is 144/360 = 0.4, which corresponds to 40% of the total. The angle is converted to a percentage by dividing by 360 and multiplying by 100.

Question 33Interpreting scientific data presented in tables, graphs and diagrams

A results table shows a measured value of 5.0 with an absolute uncertainty of ±0.2. What is the percentage uncertainty in the measurement?

  1. 4% Correct answer.
  2. 0.04%
  3. 0.4%
  4. 2%

Explanation

Percentage uncertainty is the absolute uncertainty divided by the measured value, multiplied by 100: (0.2/5.0) × 100 = 4%. This expresses the uncertainty as a proportion of the reading.

Question 34Interpreting scientific data presented in tables, graphs and diagrams

A graph plots the pressure of a fixed mass of gas against 1/volume at constant temperature. The points form a straight line through the origin. What does the gradient of this line represent?

  1. The product of pressure and volume, which is constant Correct answer.
  2. The number of moles of gas only
  3. The temperature of the gas in kelvin
  4. The reciprocal of the gas constant

Explanation

Since pressure is proportional to 1/volume at constant temperature, plotting pressure against 1/volume gives a straight line whose gradient equals the constant product pV. That product depends only on the amount of gas and the temperature.

Question 35Interpreting scientific data presented in tables, graphs and diagrams

A table records the counts of a radioactive source over successive one-minute intervals as 800, 400, 200 and 100. What is the half-life of the source?

  1. 1 minute Correct answer.
  2. 4 minutes
  3. 2 minutes
  4. 0.5 minutes

Explanation

The count halves from 800 to 400 to 200 to 100 in successive one-minute intervals, so the half-life is the time for one halving, which is 1 minute. Each interval represents exactly one half-life.

Question 36Interpreting scientific data presented in tables, graphs and diagrams

A distance–time graph shows a straight line from the origin with a gradient of 4 m/s, followed by a horizontal section. What does the horizontal section represent?

  1. The object is returning to its starting point.
  2. The object is stationary during that time interval. Correct answer.
  3. The object is accelerating.
  4. The object is moving at a constant 4 m/s.

Explanation

On a distance–time graph the gradient gives speed, so a horizontal section (zero gradient) means zero speed and the object is at rest. The earlier sloped section corresponds to the constant 4 m/s.

Question 37Interpreting scientific data presented in tables, graphs and diagrams

A calibration curve is linear and passes through the origin. A sample gives an instrument reading of 36 units, and a standard of concentration 4 mol/dm³ gives a reading of 24 units. What is the concentration of the sample?

  1. 4 mol/dm³
  2. 9 mol/dm³
  3. 6 mol/dm³ Correct answer.
  4. 1.5 mol/dm³

Explanation

Because the line passes through the origin, concentration is proportional to reading, so concentration = (36/24) × 4 = 6 mol/dm³. The proportionality constant here is 4/24 = 1/6 mol/dm³ per unit.

Question 38Interpreting scientific data presented in tables, graphs and diagrams

A table shows that as the concentration of a reactant is doubled, the initial rate increases by a factor of four. What is the order of reaction with respect to that reactant?

  1. Second order Correct answer.
  2. Zero order
  3. Third order
  4. First order

Explanation

Doubling the concentration and observing a fourfold increase in rate means the rate is proportional to the square of the concentration, which is second order. For first order the rate would double, and for zero order it would not change.

Question 39Interpreting scientific data presented in tables, graphs and diagrams

A diagram shows a circuit with a cell and two resistors in series, with a voltmeter connected across one resistor. The cell voltage is 12 V and the two resistors are equal. What does the voltmeter read?

  1. 0 V
  2. 12 V
  3. 6 V Correct answer.
  4. 24 V

Explanation

In a series circuit the total voltage is shared between the resistors in proportion to their resistance. With two equal resistors, the 12 V is divided equally, so each resistor has 6 V across it.

Question 40Interpreting scientific data presented in tables, graphs and diagrams

A scatter graph of enzyme activity against temperature shows a rising curve, a peak at 37 °C, and a steep fall after the peak. What does the steep fall most likely indicate?

  1. Denaturation of the enzyme at higher temperatures Correct answer.
  2. A decrease in substrate concentration
  3. A fault in the measuring instrument
  4. An increase in enzyme concentration

Explanation

The rise reflects increased kinetic energy and collision frequency, while the sharp fall after the optimum indicates that the enzyme's active site is being denatured at high temperature. This loss of shape reduces activity rapidly.

Question 41Interpreting scientific data presented in tables, graphs and diagrams

A table reports a derived quantity calculated by multiplying two measured values, each with a percentage uncertainty of 2%. What is the percentage uncertainty in the derived quantity?

  1. 4% Correct answer.
  2. 2%
  3. 1%
  4. 0%

Explanation

When measured quantities are multiplied or divided, their percentage uncertainties add, so 2% + 2% = 4%. This rule applies regardless of the numerical values of the measurements.

Question 42Interpreting scientific data presented in tables, graphs and diagrams

A histogram shows the distribution of measured lengths. The bars form a roughly symmetrical bell shape centred on 25 mm. What does this shape suggest about the measurements?

  1. The measurements contain no uncertainty.
  2. Systematic error has shifted all readings from the true value.
  3. All readings are identical, showing high precision.
  4. Random errors are present and the mean is a good estimate of the true value. Correct answer.

Explanation

A symmetrical bell-shaped distribution is characteristic of random errors scattered about a central value, which makes the mean a reliable estimate. Systematic error would shift the whole distribution away from the true value rather than produce symmetry.

Question 43Interpreting scientific data presented in tables, graphs and diagrams

A graph shows two lines for the same gas at different pressures, plotting volume against temperature. The line for the higher pressure lies below and has a smaller gradient. Why does the higher-pressure line lie below the other?

  1. At higher pressure the gas occupies less volume at any given temperature. Correct answer.
  2. The higher-pressure line represents a larger amount of gas.
  3. Pressure does not affect the volume of a gas.
  4. At higher pressure the gas occupies more volume at any given temperature.

Explanation

For a fixed amount of gas, volume is inversely related to pressure at constant temperature, so raising the pressure reduces the volume at every temperature. This shifts the whole line downwards on a volume–temperature graph.

Question 44Interpreting scientific data presented in tables, graphs and diagrams

A table gives the following readings for a titration: 23.4, 23.5, 23.4 and 27.9 cm³. What is the best estimate of the titre?

  1. 27.9 cm³
  2. 23.4 cm³ Correct answer.
  3. 24.6 cm³
  4. 23.5 cm³

Explanation

The value 27.9 cm³ lies far from the cluster of the other three readings and is treated as an anomalous result to be excluded. Averaging the remaining concordant values (23.4, 23.5, 23.4) gives approximately 23.4 cm³.

Question 45Interpreting scientific data presented in tables, graphs and diagrams

A bar chart uses a broken vertical axis that starts at 90 rather than 0. The bars for two categories look very different in height. What caution should be applied when interpreting this chart?

  1. The bars represent percentages rather than raw values.
  2. The visual difference exaggerates the true difference between the values. Correct answer.
  3. The vertical axis must always start at zero for any chart.
  4. The chart cannot show any valid data.

Explanation

A truncated axis compresses the visible range so that small absolute differences appear as large height differences, exaggerating the contrast. The data remain valid, but the visual impression overstates the true size of the difference.

Question 46Interpreting scientific data presented in tables, graphs and diagrams

A diagram shows a ray of light striking a mirror at 30° to the mirror surface. What is the angle of reflection measured from the normal?

  1. 120°
  2. 90°
  3. 30°
  4. 60° Correct answer.

Explanation

The angle of incidence is measured between the ray and the normal, so a ray at 30° to the surface is 60° from the normal. By the law of reflection the angle of reflection equals the angle of incidence, giving 60°.

Question 47Interpreting scientific data presented in tables, graphs and diagrams

A line graph plots the logarithm of the rate of a reaction against 1/temperature and gives a straight line with a negative gradient. What can be deduced from this result?

  1. The activation energy is zero.
  2. The reaction rate is independent of temperature.
  3. The reaction is zero order with respect to all reactants.
  4. The reaction follows the Arrhenius relationship and the gradient relates to the activation energy. Correct answer.

Explanation

The Arrhenius equation predicts a linear relationship between ln(rate) and 1/T, with a gradient equal to −Ea/R. A straight line with negative gradient therefore confirms Arrhenius behaviour and allows the activation energy to be determined.

Question 48Interpreting scientific data presented in tables, graphs and diagrams

A table gives values of a quantity y at equally spaced values of x, and the second differences of y are constant and positive. What type of relationship does this indicate?

  1. An inverse proportional relationship
  2. A quadratic relationship with a positive coefficient of x² Correct answer.
  3. An exponential decay relationship
  4. A linear relationship with positive gradient

Explanation

Constant second differences indicate that the data follow a quadratic (parabolic) pattern, and positive second differences mean the curve is concave upward. A linear relationship would have constant first differences and zero second differences.

Question 49Interpreting scientific data presented in tables, graphs and diagrams

A graph shows the Maxwell–Boltzmann distribution of molecular energies at two temperatures. The curve for the higher temperature is flatter and shifted to the right. What does the area under the curve beyond the activation energy represent?

  1. The average energy of all the molecules
  2. The activation energy of the reaction
  3. The total number of molecules present
  4. The proportion of molecules with enough energy to react Correct answer.

Explanation

The area under the distribution curve beyond the activation energy corresponds to the fraction of molecules possessing sufficient energy to overcome the barrier. At higher temperature this area is larger, explaining the increased rate.

Question 50Interpreting scientific data presented in tables, graphs and diagrams

A set of measurements is taken and the mean is calculated as 50.0 with a standard deviation of 2.0. Assuming a normal distribution, approximately what percentage of readings lie between 48.0 and 52.0?

  1. About 99.7%
  2. About 95%
  3. About 68% Correct answer.
  4. About 50%

Explanation

The interval 48.0 to 52.0 is one standard deviation either side of the mean (50.0 ± 2.0). For a normal distribution approximately 68% of values fall within one standard deviation of the mean.