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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 for several reasons:
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Carbon Dioxide Absorption: The plants from which the vegetable oils are extracted absorb carbon dioxide (CO₂) from the atmosphere during their growth. This process reduces the overall levels of CO₂ in the atmosphere while the plants are alive.
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Carbon Neutrality: When vegetable oils are burnt as biofuels, they release the same amount of CO₂ that the plants absorbed during their growth cycle. Therefore, there is no net increase in the percentage of CO₂ in the atmosphere, making this process effectively carbon neutral.
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Sustainable Energy Source: Using biofuels derived from vegetable oils helps to sustain the agricultural cycle. Instead of adding to atmospheric CO₂ levels, it utilizes existing carbon, thereby not contributing to global warming.
Step 2
Describe how and explain why vegetable oils are hardened for use in foods.
Answer
Vegetable oils are hardened through a process known as hydrogenation. This procedure involves several key steps:
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React with Hydrogen: The vegetable oils react with hydrogen gas in the presence of a nickel catalyst at elevated temperatures, typically around 60 °C.
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Unsaturation Reduction: Vegetable oils contain multiple double bonds, making them unsaturated and fluid at room temperature. Through hydrogenation, these double bonds are converted to single bonds, turning the oil into a more solid form.
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Increased Melting Point: The transformation into saturated fats results in a higher melting point, allowing the oils to be solid at room temperature. This characteristic is crucial for creating products like margarine and improving the spreadability of cooking oils.
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Application in Food Production: Hardened vegetable oils are used in various food products to enhance texture, stability, and shelf life. They can replace butter in many recipes while providing similar properties.