Question

1. i. How does evaporation differ from boiling? Differentiate giving at
Least 4 points. Also discuss the various factors which affect the rate of evaporation.
ii. Latent heat of evaporation of two liquids- A and B is 100 J/kg and
150 J/kg respectively. Which one can produce more cooling effect and why?
2. Why do solids have a regular geometrical shape?
3. Trees acquire more leaves during summer. Give reasons.
4. Can a rubber band change its shape on stretching? Is it a solid?
5. It is a hot summer day. Atul and Salim are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?
6. Why does the temperature of a substance remain constant during its melting or boiling point?
7. Doctors often advise to put strips of wet cloth on the forehead of a person having high fever. Give reasons.
8. Differentiate between a true solution and a colloid (giving 4 points only)
9. Classify brass and diamond as element and mixture. Justify by giving any two differences.
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10.
11.
You are provided with a mixture containing sand, iron filings, ammonium chloride and sodium chloride. Describe the procedures you would use to separate these constituents from the mixture.
Iron filings and sulphur were mixed together and divided into two parts ‘A’ and ‘S’. Part ‘A’ was heated strongly while Part ‘S’ was not heated. Dilute hydrochloric acid was added to both the parts and evolution of gas was seen in both the cases. How will you identify the gases evolved?
12. i. Why is crystallization technique better than evaporation?
ii. Name the technique used to separate butter from curd.
13. “Properties of a compound are different from its constituents, while a mixture shows the properties of its constituent elements”. Justify this statement taking the example of iron and sulphur.
14. Draw a labelled diagram to show the process of separation of two immiscible liquids.
15. Write any two physical properties each of metals and non-metals.

Answer 1

Answer:

To summarize, evaporation is slower, occurs only from the surface of the liquid, does not produce bubbles, and leads to cooling. Boiling is faster, can occur throughout the liquid, produces lots of bubbles, and does not result in cooling.