Explain the following giving examples.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension
(a) A solution in which no more solute can be dissolved at a particular temperature. i.e. it contains the maximum amount of salute. Example: an aqueous sugаr solution in which more sugar cannot be added.
(b) The substance which is formed by only one kind of particle and having a constant. Composition of chemicals and characteristics. Properties throughout the sample. Example :- sugar and salt contains only one kind of particle and have the name composition throughout.
(c) It is a heterogeneous mixture having salute size greater than Ihm and smaller than 100 mm. They can scatter beams of light passing through. Example :- in milk, rubber, clouds etc.
(d) These are heterogenous mixtures of solids dispersed in liquids. The solute particles are insoluble and remain suspended throughout the bulk of medium. the solute size is greater than 100 mm. Example - dust article in air, muddy water etc
Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
Why is the atmosphere essential for life?
What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Why are we normally advised to take bland and nourishing food when we are sick?
Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?
In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
• if you get jaundice,
• if you get lice,
• if you get acne.
Why?
Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.
A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field?
Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?
Name the regions in which parenchyma tissue is present.
Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
Why is the weight of an object on the moon 1/6th its weight on the earth?
Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
If bromine atom is available in the form of, say, two isotopes 7935 Br (49.7%) and 8135 Br (50.3%), calculate the average atomic mass of bromine atom.
Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)