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Science form-4-chapter-5 5.2
- 1. SCIENCE FORM 4 CHAPTER 5: ENERGY AND CHEMICAL CHANGES
- 2. 5.2 HEAT CHANGE IN CHEMICAL REACTIONS •There are two types of chemical reactions: (i) Exothermic reactions 放热反应 - Reactions which release heat to the surroundings - Temperature of the surroundings increases.
- 3. EXOTHERMIC REACTION 出产 / 放热反应
- 4. (ii) Endothermic reactions 吸热反应 - Reactions which absorb heat from the surroundings. - Temperature of the surroundings decreases.
- 5. During chemical reactions, old bonds in the reactants are broken and new bonds in the products are formed. The breaking down of old bonds absorbs heat energy whereas the formation of new bonds releases heat energy.
- 6. (i) Exothermic (ii) Endothermic reactions reactions Breaking an old bond absorbs heat energy Forming a new bond releases heat energy
- 7. •In exothermic reactions, the heat energy absorbed to break the old bonds in the reactants is less than the heat energy released when new bonds are formed in the products. There is a net of heat energy loss. •The temperature of the surroundings increases due to the heat energy that is released.
- 8. •In endothermic reactions, the heat energy absorbed to break the old bonds in the reactants is greater than the heat energy released when the new bonds are formed in the products. There is a net of heat energy gain. •The temperature of the surroundings decreases due to heat energy is absorbed from the surroundings.
- 9. 5.2 HEAT CHANGE IN CHEMICAL REACTIONS In exothermic reactions, the heat energy absorbed to break the old bonds in the reactants is less than the heat energy released when the new bonds are formed in the products
- 10. 5.2 HEAT CHANGE IN CHEMICAL REACTIONS In endothermic reactions, the heat energy absorbed to break the old bonds in the reactants is greater than the heat energy released when the new bonds are formed in the products
- 12. Endothermic
- 13. Exothermic
- 16. DISPLACEMENT OF METAL • https://www.youtube.com/watch?v=4Hf7PH9ZYgA • https://www.youtube.com/watch?v=UII0P3btVNI
- 17. INDUSTRIAL CHEMICAL REACTIONS A. The production of ammonia https://www.youtube.com/watch?v=uMkzx V_y7tY B. The production of sulphuric acid https://www.youtube.com/watch?v=mym1r RPX6F4
- 18. AMMONIA
- 19. • Ammonia is an important material for making nitrogenous fertilisers. • In the Haber process, nitrogen and hydrogen gases are mixed together. The mixture is passed over an iron catalyst 催化剂. Iron catalyst Nitrogen + Hydrogen Ammonia 450 °C 200 atm A. THE PRODUCTION OF AMMONIA - HABER PROCESS
- 20. 5.2 HEAT CHANGE IN CHEMICAL REACTIONS Iron catalyst Reactor Coolant out Coolant in Condenser Leftover H2 + N2 Liquid ammonia H2 + N2 Haber process
- 27. • Step 1: Sulphur is burnt in air to produce sulphur dioxide. Sulphur + Oxygen Sulphur dioxide • Step 2: A mixture of sulphur dioxide and air are passed over Vanadium(V) oxide (catalyst) at 450 °C to produce sulphur trioxide. B. The Production of Sulphuric Acid - CONTACT PROCESS
- 28. • Step 3: Sulphur trioxide is dissolved in concentrated sulphuric acid to produce oleum. Sulphur + Concentrated Oleum trioxide sulphuric acid Vanadium(V) oxide catalyst Sulphur dioxide + Oxygen Sulphur trioxide 450 °C
- 29. • Step 4: The oleum is diluted with water to produce concentrated sulphuric acid. Oleum + Water Concentrated sulphuric acid
- 30. 5.2 HEAT CHANGE IN CHEMICAL REACTIONS Sulphur Dry air Furnace SO2 + O2 SO3 Converter Concentrated sulphuric acid Waste gas Oleum Concentrated sulphuric acid Water Absorber Vanadium(V) oxide (catalyst) Contact process
- 31. OLEUM • Oleum (Latin oleum, meaning oil), or fuming sulfuric acid, is a solution of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid). • Oleums can be described by the formula ySO3.H2O where y is the total molar sulfur trioxide content.
- 34. PEKA 2 SCIENCE MODULE P.100 • https://www.youtube.com/watch?v=xJhjdFEHDv8 • Endothermic reaction • https://www.youtube.com/watch?v=POSsNRnK-_c • Exothermic reaction
- 35. AMMONIA • The human body makes ammonia when the body breaks down foods containing protein into amino acids and ammonia, then converting the ammonia into urea. • Ammonium hydroxide – commonly known as household ammonia – is an ingredient in many everyday household cleaning products. • Ammonia is a basic building block for ammonium nitrate fertilizer, which releases nitrogen, an essential nutrient for growing plants, including farm crops and lawns.
- 36. USES OF AMMONIA • Ammonia in Fertiliser • Ammonia in Household Cleaning Products -used as a refrigerant gas and in air-conditioning equipment -to purify water supplies and as a building block in the manufacture of many products including plastics, explosives, fabrics, pesticides and dyes -used in the waste and wastewater treatment, cold storage, rubber, pulp and paper and food and beverage industries as a stabilizer, neutraliser.
- 37. USES OF SULPHURIC ACID • The major use of sulfuric acid is in the production of fertilisers, e.g., superphosphate of lime and ammonium sulfate. • used in the manufacture of chemicals, e.g., in making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and pigments, explosives, and drugs. • used in petroleum refining to wash impurities out of gasoline and other refinery products. • Rayon is made with sulfuric acid. • It serves as the electrolyte in the lead-acid storage battery commonly used in motor vehicles
- 38. CHAPTER 5: ENERGY AND CHEMICAL CHANGES QUIZ 9. An endothermic reaction is one in which A. heat is absorbed from the surrounding B. heat is released to the surroundings C. heat is neither released nor absorbed D. temperature of the surroundings increases