List of top Science Questions

Define the term “tissue”.
What do you mean by a precipitation reaction? Explain by giving examples.
An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
A ball is gently dropped from a height of \(20\) \(m\). If its velocity increases uniformly at the rate of \(10\) \(m s^{-2}\), with what velocity will it strike the ground? After what time will it strike the ground?
In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
What are amphoteric oxides? Give two examples of amphoteric oxides.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
You are given a hammer, a battery, a bulb, wires and a switch.
  1. How could you use them to distinguish between samples of metals and non-metals?
  2. Assess the usefulness of these tests in distinguishing between metals and non-metals.
A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of \(3.0\) \(m s^{–2}\) for \(8.0\) \(s\). How far does the boat travel during this time?
Food cans are coated with tin and not with zinc because
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging (a) from A to B and (b) from A to C?
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Which of the following pairs will give displacement reactions?
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Why is respiration considered an exothermic reaction? Explain.
What does one mean by exothermic and endothermic reactions? Give examples.
Write the balanced chemical equation for the following and identify the type of reaction in each case. 
(a) Potassium bromide(aq) + Barium iodide(aq) \(→\) Potassium iodide(aq) + Barium bromide(s) 
(b) Zinc carbonate(s) \(→\) Zinc oxide(s) + Carbon dioxide(g) 
(c) Hydrogen(g) + Chlorine(g) \(→\) Hydrogen chloride(g) 
(d) Magnesium(s) + Hydrochloric acid(aq) \(→\) Magnesium chloride(aq) + Hydrogen(g)
What is osmosis?
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
Carry out the following osmosis experiment: Take four peeled potato halves and scoos each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now, 
  1. Keep cup A empty 
  2. Put one teaspoon sugar in cup B 
  3. Put one teaspoon salt in cup C 
  4. Put one teaspoon sugar in the boiled potato cup D. Keep these for two hours. Then observe the four potato cups and answer the following: 
  1. Explain why water gathers in the hollowed portion of B and C. 
  2.  Why is potato A necessary for this experiment? 
  3. Explain why water does not gather in the hollowed-out portions of A and D.
How does an Amoeba obtain its food?
Where do the lipids and proteins constituting the cell membrane get synthesized?