(c)
Iron pipes coated with zinc do not get rusted easily. (True/False)
(d)
Iron and rust are the same substances. (True/False)
(e)
Condensation of steam is not a chemical change. (True/False)
3. Fill in the blanks in the following statements:
When carbon dioxide is passed through lime water, it turns milky
due to the formation of
(b)
The chemical name of baking soda is
(c) Two methods by which rusting of iron can be prevented are
and
(d) Changes in which only properties of a substance change
are called physical changes.
(e) Changes in which new substances are formed are called
changes.
4. When baking soda is mixed with lemon juice, bubbles are formed with
the evolution of a gas. What type of change is it? Explain.
5. When a candle burns, both physical and chemical changes take place.
Identify these changes. Give another example of a familiar process in
which both the chemical and physical changes take place.
6. How would you show that setting of curd is a chemical change?
7. Explain why burning of wood and cutting it into small pieces are
considered as two different types of changes.
8. Describe how crystals of copper sulphate are prepared.
9. Explain how painting of an iron gate prevents it from rusting.
10. Explain why rusting of iron objects is faster in coastal areas than in
deserts.
11. The gas we use in the kitchen is called liquified petroleum gas (LPG). In
the cylinder it exist as a liquid. When it comes out from the cylinder it
becomes a gas (Change - A) then it burns (Change - B). The following
statements pertain to these changes. Choose the correct one.
(1) Process - A is a chemical change.
(11) Process - B is a chemical change.
(lil) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.
12. Anaerobic bacteria digest animal waste and produce biogas (Change - A).
The biogas is then burnt as fuel (Change - B). The follडिस्क्राइब हाउ क्रिस्टल ऑफ कॉपर सल्फेट आर प्रिपेयर्ड
Answers
Answer:
c) true
d) false
e) false
f/b
a)When carbon dioxide is passed through lime water, it turns milky due to the formation of calcium carbonat.
The chemical name of baking soda is sodium hydrogen carbonate.
(c) Two methods by which rusting of iron can be prevented are galvanization and painting.
(d) Changes in which only physical properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called chemical changes.
5) picture
6) curd is a chemical change as we cannot get the substance (milk )back.
7) cutting of wood is a physical change and burning of wood is a chemical change as in burning of wood we get new substance as coal and we do not get original substance back and in as we cutting the tree wood we will get wood back.
8)Crystallization is the process by which we can obtain crystals of copper sulphate. In this process, a few drops of dilute sulphuric acid is added to water. The water is then boiled & as it starts boiling, copper sulphate powder is added with stirring. The powder must be added on till the solution becomes saturated. Afterwards, it is filtered into a china dish and allowed to cool, undisturbed. After some time the crystals of copper sulphate separate out.
9)Rusting of iron happens when it comes in contact with air and moisture. By painting the iron gate, we basically we are preventing the contact of water and air from iron.
10)The presence of moisture in the air promotes rusting of iron. The quantity of moisture in coastal areas is quite high, as compared to deserts, where moisture content in the air is very low.
11)Option (ii) is correct.
12)Option (iii) is correct.
