Skill Enhancement Questions Dec- First week

A student takes a green leaf from the plant and boils it in an alcohol bath for removal of chlorophyll. After this treatment, the student adds a few drops of iodine to the boiled leaf using syringe dropper. After some time, the student observes that the leaf turns blue-black in color. What can be evaluated from this

• The iodine reacts with the starch present in the leaf that indicates the occurrence of photosynthesis

• The iodine reacts with water present in the leaf that indicates the occurrence of photosynthesis.

• The iodine reacts with the oxygen present in the leaf that indicates the occurrence of photosynthesis.

• The iodine reacts with carbon dioxide present in the leaf that indicates the occurrence of photosynthesis.

Several nails were attached to a metallic rod, through its length by using drops of wax as adhesive. This rod was placed horizontally with one end subjected to the flame of a burner.

Nails closer to point Y begin to fall. If the burner is removed after a short while, nails closer to point X, remained affixed. Which end of the rod is hotter, and why ?

• X is hotter as the wax and nails both remained stuck to the rod

• X is hotter because heat moved from Y and was transferred to X

•  Y is hotter as the wax melted quicker due to the heat of the rod

• Y is hotter as the gravity acted faster near Y, dropping the nail

When an iron nail is dropped into a beaker containing a solution of copper sulphate, after a while, both the solution and the iron nail change colour. The nail gets a brownish coating and the solution turns green. The nail has a coating of Copper on its surface and the solution is detected to have the presence of an iron containing compound

Change of colour can indicate both, a chemical or a physical change. Which kind of change does this experiment signify and why?

• Physical change, because the nail only changes color on the surface not the whole.

•  Chemical change, due to deposit of a new substance on the nail.

• Physical change, due to deposit of a different substance on the nail’s surface.

• Chemical change, because both, solution and solvent have a change

A student requires a magnet for his science project. He decides to prepare a magnet of his own. Which of these arrangements would produce a magnet

• 
• 
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Which of the following constitutes wastewater

• Harvested rainwater

• Water used for laundry

• Water taken up by plants

• Water present in a bird-bath

Cuscuta is a yellow wiry branched structure climbs on other plants as it lacks chlorophyll. A student sets up an experiment using two potted plants, one with Cuscuta and others without it as shown.

Which of these plants will show more growth?

• Plant A, as Cuscuta provides valuable nutrients to host plants for photosynthesis.

• Plant B, as Cuscuta shares chlorophyll of the host plants to synthesis its own food.

• Plant B, as Cuscuta uses readymade food of the plant A that weakens the host plant.

• Plant A, as Cuscuta shares its readymade food with host plants to increase their combined growth

A student collects wax from a burning candle. He melts it and then adds a new wick to it and leaves it to cool. Can a new and functional candle be created by this process? Why or why not?

• Yes; it is a reversible physical change in state of wax.

• No; it is a physical change that cannot be reversed.

• No; it is an irreversible chemical change with the formation of a new substance

• Yes; it a chemical change causing the wax to change from one state to another

Aloe Vera is a plant kept by people inside their houses as it can clean air. Aloe Vera is adapted to survive in low light conditions. What likely is the adaptation of Aloe Vera to survive in low-light conditions

• The curved shape of its leaves

• The presence of spines on its leaves

• The presence of gel present inside the leaves

• The presence of chlorophyll in excess amount in its leaves

The table shows the number of pulse beats counted by two students from their left hand for 2 minutes.

What likely be concluded from this observation?

• The pulse rate of student A is higher than the normal pulse rate.

• The pulse rate of student B is lower than the normal pulse rate.

• The pulse rate of student A and student B is equivalent to the normal pulse rate.

• The pulse rate of both student A and student B is higher than the normal pulse rate.

A student observes the positions of two vehicles at different instants of time as shown

Which of these statements explains the motion of the vehicles?

• Car A is in motion as it changed its position with respect to the surroundings

• Car B is in motion as it changed its position with respect to the surroundings

• Car A is in motion as it did not change its position with respect to the surroundings

• Car B is in motion as it did not change its position with respect to the surroundings