You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Copper metal reacts with atmospheric carbon dioxide and forms copper carbonate and as a result, which copper vessel loses its shiny brown surface and forms a green layer of copper carbonate. Lemon or tamarind contain acid that neutralises the base copper carbonate and dissolves the layer. So, tarnished copper vessels using lemon and tamarind, copper vessels retain their shine.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
State Fleming’s left-hand rule.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
What are the components of the transport system in highly organised plants?
Explain the terms analogous and homologous organs with examples.
Where do plants get each of the raw materials required for photosynthesis?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
What is an homologous series? Explain with an example.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?