Chemistry unit one revision aqa lets ask each other questions woop

Can someone go over:

1. limestone, quarrying and the limestone cycle and lime water.

2. fractional distillation - including how and why we seperate air etc.

3. batch process (fermentation - involves sugar cane) and the other process, continuous?

4. extracting vegetable oil (i.e. from olives) - saturated and unsaturated fats

Thanks!

Hey sorry whats Copper Carbonate again?

Emulsions were a tricky concept to understand when I first came across them.

Basically an emulsion is a mixture of two miscible liquids which when mixed together are thicker. Emulsions are present in ice creams, mayo (YUM) and naturally in egg yolk.

An emulsifier increases the time taken to separate the two liquids and this is called immiscible. Please remember it does not stop them from separating, it increases the time taken to separate them.

Emulsifiers work because the they have two ends which you need to know in the exam if you are sitting the higher paper:

Hydrophilic - water loving (the head of the emulsifier molecule)
Hydrophobic - water hating (the tail of the emulsifier molecule)

The hydrophilic end dissolves in water droplets. The hydrophilic end has a negative charge. This means other hydrophilic ends repel each other. The hydrophobic end dissolves in water. Therefore, the two are harder to separate and ultimately increasing the time taken to separate the two liquids.

Damn this is a lot to go through; however, this is for your benefit and also my benefit so why not?

1. Limestone is mainly composed of calcium carbonate (CaCO3 ). However, it contains impurities.

We can break down limestone using heat to produce calcium oxide, more commonly known as quicklime (CaO) and carbon dioxide (CO2) which contributes towards global warming. This reaction is called thermal decomposition - breaking down using heat.

If we add water to calcium oxide it forms calcium hydroxide or it can be referred to as slaked lime (Ca(OH)2). Calcium hydroxide can be used to neutralize acidity in soil and water. Add more water to calcium hydroxide to form calcium hydroxide solution (Ca(OH)2 (aq) or more commonly known as lime water. Aq means aqueous. We can use lime water to test for the presence of carbon dioxide because it will turn cloudy/milky.

Add carbon dioxide to calcium hydroxide solution to get calcium carbonate! That is your cycle!

When we add acid to any carbonate we get water, carbon dioxide and some form of acid.

Quarrying ad +
Creates local employment
Limestone is a valuable material - economy

Quarrying dis -
Disfigures landscape
Noise and traffic
Pollution from vehicles to transport materials
Destroys animal habitat
Particulates produced when dynamite is detonated

2. Fractional distillation in the air. No clue why it is used but the concept from fractional distillation in air can be applied from crude oil.

Heated up
Evaporates
Hot at bottom and cold at top
Cool and condense at different boiling points
Collected

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/earth/earthsatmosphererev6.shtml

3. Fermentation! Easy 2 marks in the exam! We add yeast as a catalyst to sugar cane to produce carbon dioxide and ethanol. Tis process requires renewable energy resources (sugar cane). However, it is a slow, batch process meaning only a certain amount can be produced at one time and the ethanol produced is not 100% pure meaning it needs to be distilled using fossil fuels. You may get asked to compare hydration and fermentation.

4. We can extract olive oil by crushing the eeeds and remove any impurities by distillation (not fractional!). They are then processed and extracted in a factory. That simple. For plants, you boil water so it evaporates and the steam rises up to evaporate the oil in the plants. The oil then cools and condenses into a liquid and is collected to remove any impurities. Done.

Unsaturated fats are thought to be healthier than saturated. Remember:

Saturated = alkane = single covalent bonds and cannot take in anymore atoms
Unsaturated = alkene = double covalent bonds and can take in more atoms

Pretty much it! I might of missed some parts but yeah.

Good luck tomorrow afternoon and I wish you the best of luck!

what causes global dimming?

thank youuuuu !

Thanks!

what causes global dimming?

copper sulfate + iron ------> iron sulfate +iron

this is a displacement reaction and works because iron is more reactive than copper

Solid carbon particles called, guess what? Particulates! They block sunlight reaching the Earth's surface.

Particulates


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its iron sulfate + copper

not + iron

thank you so much .. .
why do copper ions go to the negative electrode? is it because they are positively charged ?

THANK YOU so much x

No. Because the positive ions have a positive charge that means they need to gain electrons to have a stable atom because there are more protons than electrons, ie, overall charge equals 0 so it 'goes to' (poor vocab) to the negative electrode which has more electrons than protons and needs to lose to gain a stable atom.

Here's an example.

Lets say the negative electrode has 12 electrons and 9 protons. It has a charge of -3 because electrons have a -1 charge and there are 3 more electrons than protons. Now lets say the positive electrode or whatever has 9 electrons and 12 protons. This has a positive charge of +3 because protons have a charge of +1 and there are 3 more protons than electrons. Now, when the two atoms want a stable atom so therefore the number of protons has to be equal to the number of electrons. To do this, the negative iron loses 3 electrons and gives it to the positive which gains the 3 electrons to form a stable atom of an overall charge of 0. Now both atoms have an overall charge of 0 and that is why they are attracted to each other.

Damn that was difficult to explain. Please tell me if I have confused you!

Good luck tomorrow!

You're welcome!

Good luck tomorrow afternoon and do your best!

aw thanks you too (if you're doing the exam)

Don't worry i understand it thank you so much... you have been answering some of my questions and you have helped me a lot. By any chance would you like to sit my exam tomorrow instead of me HAHA