Friday 27th April Vegetable Oils Learning Objectives Starter: Vegetable oils are made from plants. Write down at least two ways that you could complete the following sentence: Plants get their energy from …
How do we get vegetable oils? There are two options: Pressing nuts/seeds: 2. Distillation
2. Distillation A) 3 B) 2 C) 4 D) 1
Saturated oils tend to be solid at room temperature, and are sometimes called vegetable fats instead of oils. • This makes them suitable for making margarine, or for commercial use in the making of cakes and pastry. • Lard is an example of a saturated oil.
Unsaturated oils tend to be liquid at room temperature, and are useful for frying food. They can be divided into two categories: • Monounsaturated fats have one double bond in each fatty acid • Polyunsaturated fats have many double bonds.
Questions to Check Understanding • What is a saturated compound? • What is an unsaturated compound? • Describe the differences between the properties of unsaturated and saturated fats.
Next Lesson • Testing for saturation. • How do we do it?????
Practical: Testing oils for saturation • Aim: To determine whether each oil is saturated or unsaturated • Theory: • An oil that contains a double bond is said to be ____________ and will make bromine water __________ • An oil that only contains single bonds is said to be _____________ and will make the bromine water _______ • Safety • We are using more concentrated bromine water than usual so that we can see any colour change clearly. This is toxic if inhaled or swallowed and causes burns to skin. So do not breathe in the fumes, wear goggles and if any gets in your eye tell the teacher immediately and wash it with water.
Mini Plenary: Summary Questions so far: have you met the first two LOs? Copy and complete using the words from below bromine, decolourised, distillation, energy, pressing, unsaturated We can extract vegetable oils from some plants by _____ or _____. Vegetable oils are particularly important as foods as they contain a lot of _____. Some vegetable oils contain carbon-carbon double bonds. We call these _____ vegetable oils. They can be detected by reacting them with _____ water, which will be ________. Challenge: Why might a diet containing too much vegetable oil be unhealthy?
Mini Plenary: Summary Questions so far: have you met the first two LOs? Copy and complete using the words from below bromine, decolourised, distillation, energy, pressing, unsaturated We can extract vegetable oils from some plants by pressing or distillation. Vegetable oils are particularly important as foods as they contain a lot of energy. Some vegetable oils contain carbon-carbon double bonds. We call these unsaturated vegetable oils. They can be detected by reacting them with bromine water, which will be decolourised. Challenge: Why might a diet containing too much vegetable oil be unhealthy?
States of matter task • Label where solid, liquid and gas would be on the thermometer • Water has a melting point of 0˚C and a boiling point of 100˚C. What state is it in at the following temperatures: • -25˚C • 25˚C • 146˚C • Olive oil has a melting point of -6˚C and a boiling point of 300 ˚C. What state is it in at: • -25˚C • 25˚C • 146˚C • CHALLENGE: • If we want to change the properties of oil so that it is solid at room temperature, what do we need to do to its melting and boiling points? • Why might we want to do this? Boiling point Melting/Freezing point
Task: Hardening unsaturated vegetable oilsMake an instruction leaflet explaining how to turn a vegetable oil into a spread (Page 199)
Hydrogenated • Vegetable oils, which are unsaturated, can be hardened to produce solid fats (useful as spreads and making cakes). • The hardening is done by reacting unsaturated vegetables oils with hydrogen to make saturated or less unsaturated fats – Hydrogenated. • This process is carried out at 60OC in the presence of a nickel catalyst. • See table C page 143.
Hydrogenation of vegetable oils • Can produce some unsaturated fats called trans fats. They are thought to cause more damage to the heart than saturated fats. They are found in many foods. Eg processed and fast foods. • We can use bromine water to see if a fat or oil is saturated or unsaturated. • Bromine water turns colourless in the presence of unsaturated fats. • Bromine water stays yellow-orange in the presence of saturated fats. • Fats and oils can be analysed to measure the amount of unsaturation – more unsaturated a molecule the more bromine water it reacts with.
Test: Questions 1-4 Page 195 a) cracking, b) decomposition, c) fuel, d) colourless, e)CnH2n(5 marks) a) letters – 1 mark, brackets with bonds through them – 1 mark, subscript n – 1 mark b) a large number c) monomers d)poly(butene) e)C3H6 (7 marks) 3. a) one environmental advantage of ethanol from plants: renewable, carbon neutral, resources conserved b)one economic disadvantage: more labour intensive, takes longer, more steps involved to make pure ethanol c)environmental disadvantage of ethanol from plants: lands, crops used that could be for food or deforestation d) if we use 10% ethanol in current petrol then we do not need to change cars or the system (4 marks)
4. a) • i) differences: contains oxygen, has a double bond, is not a hydrocarbon, different monomer/repeating unit (1) • ii) similarities: made from monomers, has a repeating unit (1) • iii) Bioplastic: plastic that is made from plant materials (1) • iv) Two reasons from: Replace non-biodegradable plastics, it is biodegradable, it comes from renewable sources, cornstarch is cheap and readily available, keeps farmers in jobs (2) • b) Award two marks if written well (spelling, punctuation, grammar). Ideas: • less hydrocarbon fuel used • less energy used • less electricity used • CO2 emissions reduced • Less pollution from SO2, less acid rain • Conserve copper resources • Reduces waste • Reduces need to dig pits/mines (6) (11 marks) Total available: 27 22-27 = A* 19-21 = A 16-18 = B 14-15 = C 11-13 = D 0 – 10 = U