CTJan27 Online JMSS - Science Reasoning 22052026

Which of the following correctly represents the electron arrangement in a Bohr-Rutherford diagram for a neutral atom of Magnesium ($_{12}Mg$)?

How does the atomic radius generally change as you move from left to right across a period in the periodic table, and what is the primary reason for this trend?

Which of the following pairs of elements would most likely form an ionic bond?

What is the correct chemical name for the covalent compound with the formula $N_2O_4$?

You have a mixture of sand, salt, and water. Which sequence of separation techniques would be most effective to separate all three components?

The technique of distillation is used to separate components of a liquid mixture. On which property of the components does this technique primarily depend?

What is the primary energy transformation that occurs in a hydroelectric power plant to generate electricity?

An electric motor uses 500 J of electrical energy to produce 350 J of useful mechanical energy. The remaining energy is lost as heat and sound. What is the efficiency of the motor?

When you warm your hands over a campfire, you feel the heat primarily due to which mode of heat transfer?

Which statement best describes the process of heat conduction through a solid material?

According to Newton's First Law of Motion, why does a passenger without a seatbelt lurch forward when a car suddenly stops?

A box on a table is being pushed to the right with a force of 25 N. At the same time, it is being pulled to the left with a force of 10 N. The force of friction opposing the motion is 5 N. What is the net force on the box?

What happens to the total resistance of a parallel circuit when another resistor is added in parallel with the existing ones?

According to Ohm's Law, if a simple circuit has a resistance of $6 \Omega$ and a current of $2$ A is flowing through it, what is the voltage supplied by the power source?

A river carries small pieces of sand, silt, and pebbles into a lake. Over time, these sediments settle in layers. Later, the layers are buried, pressed together, and cemented into solid rock.

Which sequence best describes the formation of this type of rock?

Within the rock cycle, what process is required to transform an existing igneous rock into a metamorphic rock?

In a forest ecosystem, grass is eaten by rabbits, which are then eaten by foxes. Bacteria break down dead organic matter. Which organism represents the primary consumer trophic level?

If the producers in a food web store 10,000 kJ of energy, what is the approximate amount of energy that would be available to the organisms at the secondary consumer level, assuming a 10% energy transfer efficiency at each level?

A scientist observes that plant cells can maintain a more fixed, box-like shape than typical animal cells. Which plant-cell structure is mainly responsible for this rigid support?

Some fish that live in arctic waters have proteins in their blood that prevent it from freezing. What type of adaptation is this?

A student investigates how the colour of light affects the growth of bean plants. Four identical bean plants are used. Each plant is placed under a different colour of light: white, red, blue, or green. All plants are grown for two weeks.

To make the experiment fair, which set of variables should be kept the same for all four plants?

A graph of snowshoe hare and lynx populations in a Canadian forest over 100 years shows cyclical fluctuations. The peaks in the lynx (predator) population consistently occur approximately one to two years after the peaks in the snowshoe hare (prey) population. What is the most likely scientific explanation for this observed lag?

A microbiologist tests the effectiveness of three different antibiotics on two types of bacteria, E. coli and S. aureus. The results are measured as the diameter of the zone of inhibition (the clear area where bacteria cannot grow) in millimetres (mm). A larger zone means the antibiotic is more effective.

Based on this data, which conclusion is the most accurate?

In dragons, the allele for fire-breathing (F) is dominant over the allele for non-fire-breathing (f). A heterozygous male dragon (Ff) mates with a heterozygous female dragon (Ff). What is the probability that their offspring will be a non-fire-breather?

An analyst uses the following classification key to identify five metal samples.

1. Does the metal react with cold water?
   • Yes -> Go to 2
   • No -> Go to 3
2. Is the metal less dense than water (does it float)?
   • Yes -> Metal A
   • No -> Metal B
3. Does the metal react with dilute acid?
   • Yes -> Go to 4
   • No -> Metal C
4. Is the metal magnetic?
   • Yes -> Metal D
   • No -> Metal E

A new sample, iron, is tested. Iron does not react with cold water, it reacts with dilute acid, and it is magnetic. Which metal is iron?

A student investigates the rate of a chemical reaction by mixing reactant X and reactant Y and measuring the time it takes for the solution to turn cloudy. The experiment is repeated at different temperatures. The results are shown below.

The student concludes: "For this reaction, doubling the temperature will always halve the reaction time." Which statement is the best evaluation of this conclusion?

Two pure substances, Substance X and Substance Y, are tested. The results are below:

• Substance X: A shiny, malleable solid with a melting point of 1085°C. It is an excellent conductor of electricity in the solid state.
• Substance Y: A white crystalline solid with a melting point of 801°C. It does not conduct electricity as a solid but does when molten or dissolved in water.

Based on these properties, what are the most likely types of chemical bonding in X and Y?

In a simple circuit, a battery is connected to a lamp using wires and a closed switch. The lamp lights up.

Which energy transformation occurs mainly inside the battery while the circuit is operating?

A student uses three different levers to lift an identical load. The student measures the input force (effort) required and calculates the work input for each lever. The useful work output (lifting the load) is 100 J for all three trials. The data is recorded below.

Efficiency is calculated as (Useful Work Output / Work Input) x 100%. Which statement correctly compares the levers?

The motion of a car is represented by the speed-time graph below. The graph consists of three segments: from 0 to 10 seconds, the speed increases linearly from 0 to 20 m/s. From 10 to 30 seconds, the speed remains constant at 20 m/s. From 30 to 40 seconds, the speed decreases linearly from 20 m/s to 0 m/s.

Which statement accurately describes the car's motion?

A textbook rests motionless on a horizontal table. According to Newton's Third Law of Motion, what is the 'reaction' force to the force of gravity pulling the book down?

A simplified weather map of southern Australia is shown. A large high-pressure system (H) is centered over Adelaide, and a cold front, marked with triangular barbs, is moving eastwards across the Great Australian Bight towards the system. The isobars around the high-pressure system are widely spaced.

Based on this map, what weather is Perth, located to the far west and now behind the front, most likely experiencing?

The diagram shows a cross-section of rock strata. Layer A is at the bottom, followed by B, C, and D. A fault (a crack and displacement in the rock) has cut through layers A and B, but does not extend into layer C. A magma intrusion has pushed up through layers A, B, and C, and has solidified. Layer D is at the very top and is undisturbed.

Which of the following represents the correct sequence of events from oldest to youngest?

The table below provides data for planets in our Solar System. 'Orbital Period' is the time taken to complete one orbit around the Sun. 'AU' stands for Astronomical Unit, where 1 AU is the average distance from the Earth to the Sun.

Based on the table, which generalisation is best supported by the data?

A geologist examines a rock sample with a magnifying glass. The rock is composed of distinct, rounded grains of sand that have been cemented together. It is quite brittle and fossils are visible within its structure. How would this rock most likely be classified?

A student designs an experiment to test which material is the best thermal conductor. They take three rods made of copper, glass, and wood, all of the same length and thickness. They attach a small wax bead to the end of each rod using a drop of melted wax. The other ends of the rods are placed simultaneously into a beaker of boiling water. The student times how long it takes for the wax bead on each rod to melt and fall off.

To ensure the validity of the conclusion drawn from this experiment, which of these variables is LEAST critical to control?

In a forest ecosystem, owls hunt mice for food. The grass in the forest produces seeds that are the primary food for the mice. A prolonged drought causes much of the grass to die.

What are the most likely direct consequences for the mouse and owl populations?

A student is given a mixture containing iron filings (small pieces of iron), sand (insoluble in water), and salt (soluble in water). The student's goal is to separate the iron filings from the other two substances. Which of the following methods would be the most effective first step?

A scientist is comparing a typical plant cell with a typical animal cell. Which of the following organelles would the scientist find in the plant cell but NOT in the animal cell?

A researcher investigates the kinetics of the enzyme catalase, which breaks down hydrogen peroxide ($H_2O_2$) into water and oxygen gas ($O_2$). Five separate trials are set up, each containing the same concentration of catalase and maintained at a constant temperature of 37°C and a pH of 7.0. In each trial, a different initial concentration of $H_2O_2$ substrate (0.4 M, 0.8 M, 1.2 M, 1.6 M, and 2.0 M) is added. 

The volume of $O_2$ gas evolved is measured at regular intervals over three minutes.The researcher then uses the graph of oxygen volume against time to calculate the initial reaction rate for each substrate concentration.

What is the main dependent variable calculated in this investigation? What is the dependent variable?

The graph below shows the population fluctuations of a predator species (Canada Lynx) and its primary prey species (Snowshoe Hare) in a Canadian ecosystem over several decades.

Based on the data presented in the graph, which statement is the most reasonable inference?

A microbiologist tested the effectiveness of four different antibiotics (P, Q, R, S) on a specific strain of bacteria, E. coli. The antibiotics were placed on a petri dish coated with the bacteria. The effectiveness was measured by the diameter of the 'zone of inhibition'—a clear circular area around the antibiotic disc where bacteria could not grow. A larger zone means the antibiotic is more effective. The results are shown in the bar chart.

A student reviewed the data and concluded, "Antibiotic R is the most powerful antibiotic and should be used to treat all bacterial infections." Why is this conclusion not scientifically valid based only on the information provided?

An experiment was performed to investigate the effect of temperature on the rate of reaction between zinc metal and excess hydrochloric acid. The volume of hydrogen gas produced was measured over time at two different temperatures, 20°C and 40°C. The results are plotted on the graph below.

Which statement provides the best evaluation of the experiment's outcome as shown in the graph?

The graph below shows the solubility of four different chemical salts in water at various temperatures. A student prepares a solution by completely dissolving 40 g of Potassium Nitrate (KNO₃) in 100 g of water at a temperature of 50°C. The student then allows the solution to cool slowly to 20°C.

Based on the information in the graph, what is the most likely observation as the solution cools to 20°C?

A student uses the following classification key to identify four unknown substances. Key: 1a. Substance conducts electricity --> Go to 2 1b. Substance does not conduct electricity --> Go to 3 2a. Substance is malleable (can be bent) --> Substance W 2b. Substance is brittle (shatters) --> Substance X 3a. Substance dissolves in water --> Substance Y 3b. Substance does not dissolve in water --> Substance Z

A fifth, unknown substance is tested. The observations are: it is a crystalline solid, it is brittle, and a solution of it dissolved in water conducts electricity, but the solid form does not.

Based on the key and observations, what is the most likely classification?

A simple electrical circuit is constructed using a 9-volt battery, a switch, and two identical light bulbs connected in series. When the switch is closed, both bulbs light up.

What is the primary energy transformation that takes place within each operating light bulb?

To lift a heavy 20 kg box to a platform 1.5 metres high, a worker can use one of two frictionless ramps. Ramp A is 3 metres long. Ramp B is 6 metres long. The work done against gravity is calculated as $W = mgh$, where $m$ is mass, $g$ is gravitational acceleration (approx. $10 \text{ m/s}^2$), and $h$ is vertical height. The force required to push the box up the ramp is Work / distance.

Which statement correctly compares the work done and the force required when using Ramp A versus Ramp B?

The distance-time graph below represents the motion of a cyclist during a 40-second period. The journey is divided into four segments: P, Q, R, and S.

During which segment was the cyclist moving at the highest constant speed?

A diagram represents a cross-section of rock layers. Layers 1, 2 and 3 are sedimentary. A fault, F, has displaced these layers. Layer 4 was then deposited on top. Subsequently, a magma intrusion, M, pushed through all four layers and the fault. Finally, layer 5 was deposited on the very top.

Based on the principles of stratigraphy (superposition and cross-cutting relationships), which of the following sequences correctly lists three geological features in order from oldest to youngest?

A microbiologist investigated the effectiveness of four new antibiotic compounds (X, Y, Z, and W) against the bacterium Escherichia coli. Discs containing each antibiotic, along with a placebo disc (P) containing only the solvent, were placed on a petri dish evenly coated with the bacteria. After a 24-hour incubation period, the diameter of the clear zone around each disc, known as the 'zone of inhibition' where bacteria could not grow, was measured. The average results from multiple trials are presented in the chart below.

Based on the results presented in the chart, which of the following is the most valid scientific conclusion?