What change will you observe if you test soap with litmus paper (red and blue)?
Since soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue, because soap is sodium salt of fatty acid. It is obtained by treatment of oil with caustic soda. Sodium stearate is thus a salt of weak acid and strong base, so it is alkaline in nature.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
What is an homologous series? Explain with an example.
How would you name the following compounds?
(i) CH3 -- CH2 -- Br
(ii)
(iii)
What will be the formula and electron dot structure of cyclopentane?
Explain the nature of the covalent bond using the bond formation in CH3Cl.
Why are carbon and its compounds used as fuels for most applications?
How many structural isomers can you draw for pentane?
Explain the mechanism of the cleaning action of soaps.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Explain the formation of scum when hard water is treated with soap.
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
What is the role of the acid in our stomach?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Describe the structure and functioning of nephrons.
What are the components of the transport system in human beings? What are the functions of these components?
How do auxins promote the growth of a tendril around a support?
Give an example of a double displacement reaction other than the one given in activity 1.10.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Why is the use of iodised salt advisable?
A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
How does our body respond when adrenaline is secreted into the blood?