Science lesson plan · 9th grade (Year 10 in England) · 45 minutes
Alkanes and the fractions of crude oil
Chemical reactions, acids and bases
CCSS NGSS.HS-PS1-1CCSS NGSS.HS-ESS3-2England: GCSE Combined Science: Organic chemistry
Objective and success criteria
Students will: Alkanes and the fractions of crude oil.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Choose the right technique to separate a mixture
Leads to: Cracking, alkenes and the bromine water test
Materials: Teacher demo or video, Indicator color chart, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Choose the right technique to separate a mixture). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Which technique is best to separate sand from water? (fractional distillation / chromatography / simple distillation / filtration) → filtrationPrompt: Is the solid dissolved or not? Do you want to keep the liquid?
- Countries such as Saudi Arabia get much of their drinking water from the sea. Which method is used on a large scale? (chromatography / desalination by distillation or reverse osmosis / filtration through sand only / adding more salt) → desalination by distillation or reverse osmosisPrompt: Dissolved salt cannot be removed by a simple filter.
- Which technique is best to separate salt from salt water? (evaporation or crystallisation / fractional distillation / filtration / chromatography) → evaporation or crystallisationPrompt: Is the solid dissolved or not? Do you want to keep the liquid?
Hook · 5 min
- Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
- Share the objective: Alkanes and the fractions of crude oil. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Alkanes have the general formula CₙH₂ₙ₊₂. How many hydrogen atoms are in an alkane with 11 carbon atoms?
- Step 1: 2 × 11 + 2 = 24
- Step 2: So the answer is: 24
- Answer: 24
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- What is the molecular formula of propane, the alkane with 3 carbon atoms? (C₄H₈ / C₃H₅ / C₃H₈ / C₃H₆) → C₃H₈Prompt: Use CₙH₂ₙ₊₂.
- Which fraction is the most flammable? (heavy fuel oil / bitumen / diesel oil / refinery gases (shortest chains)) → refinery gases (shortest chains)Prompt: Short-chain hydrocarbons ignite most easily.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Why is crude oil called a finite (non-renewable) resource? (It never runs out / It formed over millions of years and is used much faster than it forms / It is made from sunlight each day / It is made in factories) → It formed over millions of years and is used much faster than it formsPrompt: Crude oil came from ancient plankton buried in mud.
- Alkanes have the general formula CₙH₂ₙ₊₂. How many hydrogen atoms are in an alkane with 12 carbon atoms? → 26Prompt: Substitute n into 2n + 2.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Choose the right technique to separate a mixture.
- Use concrete materials: teacher demo or video.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Cracking, alkenes and the bromine water test.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.
Free lesson plan from eurekami.com/lesson-plan-builder