is the study of organic carbon compounds

Hydrocarbons

What’s the link?

Do Now

https://www.youtube.com/watch?v=zaXBVYr9Ij0

Draw a cartoon strip to illustrate the creation of fossil fuels

• State what crude oil is.

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• State the names and formulae of the first alkanes.

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• Draw the first four alkanes.

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Hydrocarbons

Learning Objectives

• How many electrons fit on each shell?
• How many electrons are in carbon?
• How many electrons will be on the outer shell?

Hydrocarbons

What is a covalent bond?

Checkpoint

• In the middle of your page, write ‘crude oil’.
• Around it write as many things that you can think of that you know about crude oil.

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Hydrocarbons

What is crude oil?

Starter

https://www.youtube.com/watch?v=62LvVYYqUFA

• Crude oil is a mixture of different compounds, called hydrocarbons.

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• What elements do you think these compounds have in them?

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• Hydrocarbons are made from carbon and hydrogen.

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Hydrocarbons

What is crude oil?

Starter

• The hydrocarbons in crude oil are mostly alkanes.

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• Alkanes are saturated. This means that they have as many hydrogens as they possibly can.

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• Use the molymods. Use one carbon (black). How many hydrogens (white) can you fit on it?

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• What would the chemical formula for this be?

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Hydrocarbons

What are hydrocarbons?

Starter

Hydrocarbons

What is Methane?

• By joining four hydrogens to a carbon atom you have formed a methane molecule.

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• Methane is the first alkane.

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• Its chemical formula is CH₄.

This is how we draw a methane molecule.

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Each line represents a bond.

Hydrocarbons

Where is methane found?

Starter

Hydrocarbons

Use the molymods to build alkanes 2, 3 and 4 carbons.

Task 1

Copy the table and complete as you build.

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• Methane

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• Ethane

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• Propane

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• Butane

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• Pentane

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• Hexane

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Hydrocarbons

Can you make a creative mnemonic?

Task 1:

Can you spot the pattern?

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• What do you think the formula for the 5^th one would be?

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• What about the 8^th?

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• What about the 27^th?

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Hydrocarbons

Look at the chemical formula for the first four elements.

Task 1 Challenge

Hydrocarbons

What is the chemical formulae?

This means that you would be able to work out how many atoms of hydrogen there would be for any number of atoms of carbon.

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C_nH_(2n+2)

1. 7 carbons
2. 12 carbons

3. 25 carbons

4. 87 carbons

5. 135 carbons

6. 1478 carbons

Easiest

Middle

Hardest

A homologous series is a family of hydrocarbons with similar chemical properties who share the same general formula.

Hydrocarbons - Alkanes

What is a homologous series?

• 3 drawings of hydrocarbons
• 2 places where methane is found
• 1 mnemonic to remember the order of the first 6 alkanes

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• Stretch: Recall the formula and calculate the chemical formula for the 29^th alkane

Hydrocarbons

Complete the plenary blast off

Plenary

• To describe the process that changes long chain hydrocarbons to shorter ones.

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• Draw and name the hydrocarbons that are formed from this process.

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• Explain a method of testing for these hydrocarbons.

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Cracking Alkanes

Learning Objectives

Cracking Alkanes

• F_______ d________ is a process that separates c_____ o___ into fr_____ that are more u_______.

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• Where did the longer and shorter chain hydrocarbons come out?

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• Which ones were the most useful?

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Cracking Alkanes

Copy and complete the following

Starter

• Which ones are the least useful?

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• The residue is not particularly useful as it is.

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• We need to do another process to make it more useful.

• Think about the different parts of this term.

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• What do you think it means?

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• Breaking down with heat.

Cracking Alkanes

Cracking Alkanes

Cracking Hydrocarbons

• The hydrocarbons are heated to vaporise the hydrocarbons
• The vapour is passed over a hot catalyst
• The hydrocarbons are cracked as thermal decomposition takes place

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Cracking Alkanes

Long Useless Alkanes

• Using the molymods, make an alkane with 7 carbons in it.

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• What is its name?

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• What is its chemical formula.

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• Draw its chemical structure.

Cracking Alkanes

Long Useless Alkanes

• Now split your heptane up so that you have a butane molecule, and some other stuff.

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• What is the chemical formula of what’s left?

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• Without adding any atoms, can you make it so that all of the bonds of the carbon are full?

Cracking Alkanes

Shorter Useful Alkanes & Alkenes

• We’re left with C₃H₆.

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• To get this to work we need to use a double bond.

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• This makes a hydrocarbon called an alkene.

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• If an alkane with 3 carbon atoms is called propane, what do you think an alkene with 3 carbon atoms will be called?

Cracking Alkanes

• Alkenes have a double bond.

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• We say that things with a double bond are unsaturated.

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Hydrocarbons

Alkenes – Names and Formulae

Stretch yourself: Why have I left number one off?

Hydrocarbons

Alkenes – Names and Formulae

Stretch yourself: Why have I left number one off?

Hydrocarbons

Alkenes – Names and Formulae

• Did you notice a pattern for alkenes’ chemical formulae?

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• Could you work out what the chemical formula of the 9^th alkene would be?

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• What about the 23^rd?

Hydrocarbons

Alkenes – Names and Formulae

• You can write a GENERAL FORMULA so for any alkene you can work out the number of carbons or hydrogens it has:

C_nH_2n

What would the formula be for an alkene with:

1. 7carbons b) 30 carbons c) 56 carbons

d) 27 carbons e) 143 carbons f) 698 carbons

PICK YOUR CHALLENGE

Hydrocarbons

Testing for Alkenes

• We can test whether or not something is saturated using a simple test.

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• Watch this demonstration, and pay attention as you will need to write about what you see.

Hydrocarbons

Testing for Saturation

• We can test to see if something is saturated by adding ______ water.

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• If the substance is unsaturated, like an alkene then the _______ water will change colour from _____ to ________.

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• If the substance is saturated, like an alkane, then the bromine water will stay ______.

Hydrocarbons

To Finish: Is it saturated?

• You’ve been asked if peanut oil is saturated.

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• How would you test some to find out if it is?

• Mix and shake alkenes with bromine = colourless

Hydrocarbons

Hydrocarbons