Chemistry 1b
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How are long hydrocarbon chains broken down ?
Thermal decomposition
What is cracking ?
When you split a long-chain hydrocarbon to form more useful hydrocarbons.
Describe the process of cracking
• Hydrocarbon chain is heated • Passed over aluminum oxide catalyst • The molecules CRACK over the catalyst
What’s are the first two Alkenes ?
Ethene and propene
What is a way of testing if an oil is unsaturated ?
Bromine water
How does bromine water show if an oil is unsaturated ?
It reacts with the oil by opening the double bonds this decolorises the usual brown bromine water
What is ethene reacted with to make ethanol ?
Steam (H2O) - in the presence of a catalyst
True or False - ethanol made from ethene is used in alcohol
False
How is ethanol in alcohol made ?
Fermentation
What is a major use for Alkenes ?
Polymers
How are polymers made ?
By joining together lots of the same small alkene molecules to form very large molecules
What is the polymer made from… Ethene Propene
Polythene Polypropene
How are polymers used ? Give three examples
Plastic bags / milk cartons / credit cards / memory foam - any form of plastic
What is a big problem with polymers ?
They are not biodegradable
What Does the word ‘biodegradable’ mean ?
When something is broken down by bacteria
What are the two ways of extracting oil from plants or seeds ?
• Crushing and pressing * Solvents
Explain the process of crushing to extract oil
• Plant material crushed, then placed between metal plates and squash the oil out • It is then separated from the plant material in a centrifuge
What do oils provide when consumed ?
Energy
Why does cooking with oil speed up the process ?
They have higher boiling points than water, so they can be cooked at higher temperatures and therefore quicker
What does ‘monosaturisation’ mean ?
Fats contain one C=C double bond
Explain the process of hydrogenation
Hydrogenation is the process where unsaturated oils are hardened. The oils are reacted with hydrogen bubbles in the presence of a nickel catalyst at 60 degrees
What are trans fats and how do they occur ?
Trans fats are believed to be very bad for you, they are caused when you partially hydrogenate an oil
What do emulsifiers do ?
They make water and oil mix
What part of the emulsifier is hydrophilic (water loving) ?
The head