Class 9 Exploration: Entering the World of Secondary Science Mock Test (CBSE)

Exploration: Entering the World of Secondary Science practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following instruments is most appropriate for measuring the internal diameter of a test tube with high precision?

   1. (a)Spring balance
   2. (b)Meter scale
   3. (c)Measuring cylinder
   4. (d)Vernier calipers
   Show answer and step marks

   1. Correct option: (d) Vernier calipers+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   While heating a liquid in a test tube using a laboratory burner, the correct safety practice is to

   1. (a)fill the test tube nearly to the top so it heats evenly.
   2. (b)hold the tube upright and heat one spot at its bottom.
   3. (c)point its mouth away from everyone and shake it gently.
   4. (d)close its mouth with a cork so that the liquid cannot splash.
   Show answer and step marks

   1. Correct option: (c) point its mouth away from everyone and shake it gently.+1

   Answer: (c)
3. Q3Short answer·2 marks
   State two important steps involved in the systematic scientific investigation of a natural phenomenon.
   Show answer and step marks

   1. First step, any one of: observing the phenomenon and identifying the problem or question; formulating a testable hypothesis; designing and performing a controlled experiment; collecting and analysing data; drawing a conclusion and checking it against the hypothesis; communicating the results; or any other valid step.+1
   2. Second step, a different one from the same list.+1

   Answer: Any two of: observing and identifying the problem, formulating a testable hypothesis, performing a controlled experiment, collecting and analysing data, drawing a conclusion, communicating the results.
4. Q4Short answer·3 marks
   A student sets up an experiment to test how the surface area of water affects its rate of evaporation. State three important variables that the student must keep constant during the experiment to ensure reliable and valid results.
   Show answer and step marks

   1. First controlled variable, any one of: the initial volume of water; the duration of the experiment (time allowed for evaporation); the temperature of the surroundings; air movement and humidity around the containers; the material of the containers.+1
   2. Second controlled variable, a different one from the same list.+1
   3. Third controlled variable, a different one from the same list.+1

   Answer: Any three of: initial volume of water, duration of the experiment, temperature of the surroundings, air movement/humidity, container material.
5. Q5Long answer·5 marks
   A student conducts an investigation to study the factors affecting the rate of evaporation of a liquid. (a) State three factors that influence the rate of evaporation and briefly explain how each factor affects it. (3 marks) (b) Explain why a desert cooler cools much better on a hot, dry day compared to a hot, humid day. Give two scientific reasons. (2 marks)
   Show answer and step marks

   1. (a) First factor with its effect, any one of: surface area (a larger exposed surface gives faster evaporation); temperature (a higher temperature gives faster evaporation); humidity (lower humidity of the air gives faster evaporation); wind speed (a faster wind gives faster evaporation); nature of the liquid (a more volatile liquid evaporates faster); or any other valid factor.+1
   2. (a) Second factor with its effect, a different one from the same list.+1
   3. (a) Third factor with its effect, a different one from the remaining ones in the list.+1
   4. (b) Dry air contains little water vapour, so water in the wet pads of the cooler evaporates quickly; on a humid day the air is already nearly saturated, so evaporation is slow.+1
   5. (b) Evaporation absorbs latent heat of vaporisation from the air passing through the pads, so the faster evaporation on a dry day cools that air much more.+1

   Answer: (a) Any three of: larger surface area, higher temperature, lower humidity, higher wind speed, a more volatile liquid; each increases the rate of evaporation. (b) Dry air holds little water vapour, so water in the cooler pads evaporates fast (slowly in humid, nearly saturated air), and evaporation takes latent heat from the air blown through the pads, so a dry day gives much more cooling.
6. Q6Long answer·5 marks
   A student wants to investigate how the concentration of a specific mineral nutrient affects the rate of stem elongation in tomato seedlings over a period of three weeks. (a) Formulate a clear, testable scientific hypothesis for this investigation. (1 mark) (b) Identify the independent variable, the dependent variable, and state two key controlled variables that must be maintained throughout the experiment. (2 marks) (c) Describe two distinct potential sources of experimental error in setting up this investigation and explain how each can be minimized to ensure reliable data. (2 marks)
   Show answer and step marks

   1. (a) A testable hypothesis linking nutrient concentration to the rate of stem elongation, e.g. 'As the concentration of the mineral nutrient increases (up to an optimum level), the rate of stem elongation of the tomato seedlings increases'; or any other clear, testable hypothesis.+1
   2. (b) Independent variable: the concentration of the mineral nutrient.+0.5
   3. (b) Dependent variable: the rate of stem elongation (increase in stem length per day or week).+0.5
   4. (b) First controlled variable, any one of: light intensity and duration; temperature; volume of nutrient solution or water given; variety, age and initial size of the seedlings; type of growing medium or pot; amounts of the other nutrients; or any other valid controlled variable.+0.5
   5. (b) Second controlled variable, a different one from the same list.+0.5
   6. (c) First error with how to minimise it, any one of: seedlings differ in initial size or health (use seedlings of the same variety, age and size); uneven light across pots (give equal light or rotate pot positions daily); evaporation changes the solution concentration (cover containers and top up to a fixed volume); inaccurate length measurements (measure from a fixed marked point with the same ruler and average repeated readings); too few plants per concentration (use several seedlings per group and take the average); or any other valid error with a suitable remedy.+1
   7. (c) Second error with how to minimise it, a different one from the same list.+1

   Answer: (a) e.g. As nutrient concentration increases (up to an optimum), the rate of stem elongation increases. (b) Independent variable: nutrient concentration; dependent variable: rate of stem elongation; any two controlled variables, e.g. light, temperature, volume of solution, seedling variety/age/size. (c) Any two errors with remedies, e.g. unequal seedlings (use uniform seedlings), uneven light (rotate pots), evaporation changing concentration (cover and top up), measurement error (fixed reference point, repeat and average).

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