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This question is about vegetable oils - AQA - GCSE Chemistry - Question 5 - 2016 - Paper 1
Question 5
This question is about vegetable oils. 5 (a) Explain why using vegetable oils as biofuels does not increase global warming. 5 (b) Describe how and explain why vege... show full transcript
Worked Solution & Example Answer:This question is about vegetable oils - AQA - GCSE Chemistry - Question 5 - 2016 - Paper 1
Step 1
Explain why using vegetable oils as biofuels does not increase global warming.
Answer
Using vegetable oils as biofuels does not increase global warming due to several key reasons:
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Carbon Dioxide Release: When vegetable oils are burned as biofuels, they release carbon dioxide (CO₂) into the atmosphere, similar to fossil fuels.
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Carbon Neutrality: The growth of plants that produce vegetable oils absorbs CO₂ from the atmosphere, making the overall carbon cycle neutral. Specifically, while the biofuel emits CO₂ during combustion, the plants absorb an equal amount of CO₂ during their growth. Therefore, there is no net increase in CO₂ levels in the atmosphere.
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Sustainable Cycle: The cycle of growing plants to produce biofuels allows for continuous absorption of CO₂, effectively balancing emissions and absorption without contributing to global warming beyond natural levels.
Step 2
Describe how and explain why vegetable oils are hardened for use in foods.
Answer
Vegetable oils are hardened to improve their properties for food use, and this is done through the following steps:
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Hydrogenation Process: The oil is reacted with hydrogen (hydrogenation) in the presence of a nickel catalyst, typically at a temperature of around 60°C. This process converts unsaturated fats to saturated fats.
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Formation of Solid Oils: The unsaturated fatty acid chains present in vegetable oils have double bonds, which make them liquid at room temperature. During hydrogenation, these double bonds are converted into single bonds, resulting in the formation of solid or semi-solid fats.
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Improved Texture and Stability: The primary reasons for hardening vegetable oils are to increase their melting point (making them more spreadable) and to enhance their stability in cooking and food storage. Hardened oils are ideal for making margarine and other spreads, while remaining unsuitable for butter production due to differences in fat composition.