Maths
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Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
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eloise
13/12/2025
Chemistry
A Level Chemistry Ocr A - Module 1 Notes
195
•
13 Dec 2025
•
eloise
@luveloise
Ever wondered how scientists ensure their experiments actually work and... Show more
There are two main ways scientists gather information: primary research (collecting brand new data yourself) and secondary research (using data from other people's studies). Before diving into any investigation, you'll need a clear aim - basically the question you want to answer or the idea you want to test.
Once you've got your aim sorted, you can form a hypothesis - your educated guess about what will happen based on scientific knowledge. Think of it as your prediction before the experiment begins.
Surveys let you observe things that are already happening naturally, whilst experiments involve deliberately changing something to see what happens. There's also meta-analysis, where researchers combine data from loads of different studies to spot bigger patterns.
Quick Tip: Valid results are ones that actually help you achieve your aim - always check your method will give you the right type of data!
When it comes to data types, you'll work with quantitative data (numbers you can measure) or qualitative data (descriptions of what you observe). Qualitative data can be a bit tricky because it's easy to only notice what seems important to you, but filming experiments can help reduce this bias.
Understanding variables is crucial for any decent experiment. Your independent variable is what you deliberately change (it goes in the first column of your results table), whilst the dependent variable is what you measure as a result. Control variables must stay exactly the same throughout to make fair comparisons.
Watch out for extraneous variables - these are factors that might affect your results but aren't part of your main investigation. Sometimes you can't control them, and they might cause errors in your data.
When choosing equipment for quantitative data, think about resolution (the smallest change your instrument can detect) and accuracy (how close your measurements are to the true value). Better equipment usually means more reliable results.
Remember: List all your control variables before starting - you need to measure them each time but don't record them in your main results table.
Planning your variable ranges might be limited by your equipment or time constraints, so be realistic about what you can actually achieve in your investigation.
A proper method is like a recipe that anyone can follow to get the same results. List all your equipment and chemicals first, then write step-by-step instructions that are detailed enough for someone else to replicate exactly.
Before you start experimenting, evaluate whether your method will actually let you achieve your aim. Sometimes you might need to tweak your approach or even modify your original question to make sure everything lines up properly.
Let's look at a real example: investigating how carbon chain length affects the enthalpy of combustion in primary alcohols. You'd burn different alcohols (methanol, ethanol, propanol) using spirit burners and measure temperature changes in water using calorimetry.
Pro Tip: Always check if your method is valid by working backwards - can the data you'll collect actually answer your original question?
The key is using the equation q = mcΔT to calculate energy changes, then converting this to enthalpy per mole so you can fairly compare different alcohols. This makes your investigation scientifically sound and meaningful.
Getting your data organised properly makes analysis so much easier later on. Always put your independent variable in the first column (you can fill this in before starting), and add dependent variable data as you go through the experiment.
Data loggers can be brilliant for real-time analysis - they automatically record measurements and can show trends as they happen. No more trying to read tricky scales or missing important changes during your experiment.
Different types of variables need different display methods. Continuous variables (like temperature) can be any number, discrete variables (like atomic number) are specific whole numbers, and categoric variables (like colour) are descriptions rather than numbers.
Golden Rule: Independent variable always goes on the x-axis, dependent variable on the y-axis - no exceptions!
Choose your graph type wisely: scatter plots with lines of best fit work for continuous data, line graphs suit discrete or categoric independent variables, and bar charts are great for comparing categories or discrete data sets.
Scatter graphs don't always need to start at (0,0) - choose scales that show your data clearly. Plot points as crosses (more accurate than dots) and only draw a line of best fit if there's actually a pattern to follow.
If you spot a data point that doesn't fit the trend, circle it and ignore it when drawing your line - these anomalous results happen and shouldn't mess up your analysis. Use a ruler for straight lines and smoothly curve your hand for curved patterns.
Calculating gradients helps you understand relationships between variables. For straight lines, pick two clear points and use gradient = Δy/Δx. For curves, draw a tangent line first, then calculate the gradient of that straight line.
Data Quality Check: Look for concordant results - values that are close to each other show your experiment is working reliably.
Averages from concordant results give you much more trustworthy conclusions than single measurements. Always include proper units when calculating gradients (dependent variable units ÷ independent variable units).
Ask yourself two key questions about your results: are they repeatable (do you get similar results each time you repeat the experiment?) and reproducible (do other people get similar results when they try your method?). Both are essential for trustworthy science.
You need at least five data points for a meaningful line of best fit. Sometimes your equipment simply can't measure what you need, which means modifying your procedure rather than accepting dodgy results.
Watch out for false positives - when your chemical test gives a positive result but not for the reason you think. This can completely throw off your conclusions if you're not careful.
Reality Check: Every piece of equipment has limitations that can affect your results - acknowledge these honestly in your evaluation.
Systematic errors affect every measurement the same way (like uncalibrated equipment), whilst random errors vary each time (like environmental factors you can't control). Understanding which type you're dealing with helps you improve future experiments.
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
eloise
@luveloise
Ever wondered how scientists ensure their experiments actually work and give reliable results? Experimental design is the backbone of all scientific research - it's about planning smart investigations that produce trustworthy data you can actually use to answer questions or... Show more
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There are two main ways scientists gather information: primary research (collecting brand new data yourself) and secondary research (using data from other people's studies). Before diving into any investigation, you'll need a clear aim - basically the question you want to answer or the idea you want to test.
Once you've got your aim sorted, you can form a hypothesis - your educated guess about what will happen based on scientific knowledge. Think of it as your prediction before the experiment begins.
Surveys let you observe things that are already happening naturally, whilst experiments involve deliberately changing something to see what happens. There's also meta-analysis, where researchers combine data from loads of different studies to spot bigger patterns.
Quick Tip: Valid results are ones that actually help you achieve your aim - always check your method will give you the right type of data!
When it comes to data types, you'll work with quantitative data (numbers you can measure) or qualitative data (descriptions of what you observe). Qualitative data can be a bit tricky because it's easy to only notice what seems important to you, but filming experiments can help reduce this bias.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Understanding variables is crucial for any decent experiment. Your independent variable is what you deliberately change (it goes in the first column of your results table), whilst the dependent variable is what you measure as a result. Control variables must stay exactly the same throughout to make fair comparisons.
Watch out for extraneous variables - these are factors that might affect your results but aren't part of your main investigation. Sometimes you can't control them, and they might cause errors in your data.
When choosing equipment for quantitative data, think about resolution (the smallest change your instrument can detect) and accuracy (how close your measurements are to the true value). Better equipment usually means more reliable results.
Remember: List all your control variables before starting - you need to measure them each time but don't record them in your main results table.
Planning your variable ranges might be limited by your equipment or time constraints, so be realistic about what you can actually achieve in your investigation.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
A proper method is like a recipe that anyone can follow to get the same results. List all your equipment and chemicals first, then write step-by-step instructions that are detailed enough for someone else to replicate exactly.
Before you start experimenting, evaluate whether your method will actually let you achieve your aim. Sometimes you might need to tweak your approach or even modify your original question to make sure everything lines up properly.
Let's look at a real example: investigating how carbon chain length affects the enthalpy of combustion in primary alcohols. You'd burn different alcohols (methanol, ethanol, propanol) using spirit burners and measure temperature changes in water using calorimetry.
Pro Tip: Always check if your method is valid by working backwards - can the data you'll collect actually answer your original question?
The key is using the equation q = mcΔT to calculate energy changes, then converting this to enthalpy per mole so you can fairly compare different alcohols. This makes your investigation scientifically sound and meaningful.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Getting your data organised properly makes analysis so much easier later on. Always put your independent variable in the first column (you can fill this in before starting), and add dependent variable data as you go through the experiment.
Data loggers can be brilliant for real-time analysis - they automatically record measurements and can show trends as they happen. No more trying to read tricky scales or missing important changes during your experiment.
Different types of variables need different display methods. Continuous variables (like temperature) can be any number, discrete variables (like atomic number) are specific whole numbers, and categoric variables (like colour) are descriptions rather than numbers.
Golden Rule: Independent variable always goes on the x-axis, dependent variable on the y-axis - no exceptions!
Choose your graph type wisely: scatter plots with lines of best fit work for continuous data, line graphs suit discrete or categoric independent variables, and bar charts are great for comparing categories or discrete data sets.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scatter graphs don't always need to start at (0,0) - choose scales that show your data clearly. Plot points as crosses (more accurate than dots) and only draw a line of best fit if there's actually a pattern to follow.
If you spot a data point that doesn't fit the trend, circle it and ignore it when drawing your line - these anomalous results happen and shouldn't mess up your analysis. Use a ruler for straight lines and smoothly curve your hand for curved patterns.
Calculating gradients helps you understand relationships between variables. For straight lines, pick two clear points and use gradient = Δy/Δx. For curves, draw a tangent line first, then calculate the gradient of that straight line.
Data Quality Check: Look for concordant results - values that are close to each other show your experiment is working reliably.
Averages from concordant results give you much more trustworthy conclusions than single measurements. Always include proper units when calculating gradients (dependent variable units ÷ independent variable units).
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ask yourself two key questions about your results: are they repeatable (do you get similar results each time you repeat the experiment?) and reproducible (do other people get similar results when they try your method?). Both are essential for trustworthy science.
You need at least five data points for a meaningful line of best fit. Sometimes your equipment simply can't measure what you need, which means modifying your procedure rather than accepting dodgy results.
Watch out for false positives - when your chemical test gives a positive result but not for the reason you think. This can completely throw off your conclusions if you're not careful.
Reality Check: Every piece of equipment has limitations that can affect your results - acknowledge these honestly in your evaluation.
Systematic errors affect every measurement the same way (like uncalibrated equipment), whilst random errors vary each time (like environmental factors you can't control). Understanding which type you're dealing with helps you improve future experiments.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology