Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle.
(a). Growth of a plant is a chemical change because at the time of photosynthesis, plants convert sunlight into chemical energy and this is an irreversible process.
(b). Rusting of iron is a chemical change because there is formation of new substance i.e.- Fe2O3, xH2O (Rust).
(c). Mixing of iron filings and sand is a physical change process.
(d). Cooking of food in a chemical change because there is change in chemical composition by supplying heat in addition to some food additives, oil, butter etc.
(e). Digestion of food is à chemical change because the enzyme present in stomach are break large macromolecules into simple molecules.
(f). Freezing of water is a physical change. because there is change in physical state of water notinitis composition.
(g). Burning of a candle is a chemical change because there is emission of CO2 and water vapours during the burning of candles.
How are sol, solution and suspension different from each other?
Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
Differentiate between homogeneous and heterogeneous mixtures with examples.
Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.
Explain the following giving examples.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension
List the points of differences between homogeneous and heterogeneous mixtures.
Classify the following into elements, compounds and mixtures.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood
Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Which of the following will show “Tyndall effect”?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.
Which of the following materials fall in the category of a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air.
Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?
State the universal law of gravitation.
Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?
How does the sound produced by a vibrating object in a medium reach your ear?
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.
sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water
What are canal rays?
State any two conditions essential for good health.
How is our atmosphere different from the atmospheres on Venus and Mars?
Who discovered cells, and how?
The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?
Convert the following temperature to celsius scale:
a. 300 K b. 573 K.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
An echo returned in 3 s. What is the distance of the reflecting surface from the source, given that the speed of sound is 342 m s-1?
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
In which of the three media, air, water or iron, does sound travel the fastest at a particular temperature?
What is the greenhouse effect?
Why are sound waves called mechanical waves?
What is the acceleration of free fall?
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?