1. The lowest temperature at which a Substance catches fire is called its-
2. In a soda-acid type fire extinguisher………. Reacts with sulphuric acid to give out carbon dioxide.
3. Explosion is the evolution of –-------- and -------
4. Substance which vaporise during Burning gives -------
5. Yellow colour in the flame denotes ------ zone
6. Fe(OH)2 + O2 + H2O ---> ----------------
7. The rocky impurities, including silica and earthly particles, present in an ore are called------
8. ---------- is the only liquid non-metal at room temperature.
9. The property by which an element can be beaten into thin sheets is called------
10. ----- react at room temperature so it is stored under kerosene to prevent its reaction with oxygen, moisture and carbon dioxide present in air.
Section_ B _ 3 _marks (any 10 questions)
11. List the conditions under which combustion can take place.
12. Name and give chemical equation to show the products of the combustion reaction in
(1) limited supply of air (2) sufficient supply of air.
13. Give reasons why Water is not used to control the fire involving electrical equipment?
14. In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180000 kJ. Calculate the calorific value of the fuel.
15. Name the different zones of a candle flame. Give details of the conditions in each zone.
16. Define three different types of combustion?
17. What happens when iron reacts with oxygen and water? Give the chemical reaction involved.
18. Discuss the reaction of metals and non–metals with oxygen
19. What happens when iron nails are put in copper sulphate solution?
20. Why metals ate good conductor of electricity?
21. Define (i) amalgam, (ii) Mineral(iii) Ore and (iv) Gangue
22. Differentiate between metals and non-metals on the basis of their physical properties?
23. Explain why, Zinc metal can displace copper from copper sulphate solution but copper cannot displace zinc from zinc sulphate solution
24. Give an example of metal which: (i) Is liquid at room temperature (ii) Can be easily cut with knife (ii) is the best conductor of heat and electricity.
25. Why gold is preferred in making jewellery?