The Chemistry of Swimming Pools – Why You Smell Chlorine

 

The Chemistry of Swimming Pools – Why You Smell Chlorine

You know that “chlorine smell” you notice the moment you walk into a swimming pool?
Here’s the twist — it’s not actually chlorine you’re smelling.

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💧 What’s in Pool Water?

Most pools are disinfected with chlorine-based compounds, often sodium hypochlorite or calcium hypochlorite.
When added to water, these release hypochlorous acid (HOCl), a powerful disinfectant that kills bacteria, viruses, and algae.

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🧪 So Where Does the Smell Come From?

The familiar “pool smell” comes from chloramines, which are formed when chlorine reacts with:

• Sweat

• Urine

• Dead skin cells

• Other organic material brought in by swimmers

One common culprit is trichloramine (NCl₃), which has a sharp, pungent odour.

Trichloramine (NCl₃), also known as nitrogen trichloride, is a chemical compound that's a volatile, irritating by-product of chlorination in swimming pools. It's formed when chlorine reacts with nitrogen-containing compounds like ammonia and urea present in the water. Trichloramine is known for its strong, irritating odour and can cause respiratory and eye irritation, especially in indoor swimming pools. 

Here's a more detailed explanation:

Formation:

• Chlorination Byproduct: Trichloramine is a disinfection byproduct, specifically formed when chlorine reacts with nitrogenous compounds in water.
• Precursors: Common precursors include ammonia, ammonium ions, urea, and α-amino acids, which are often found in swimming pool water.
pH Dependence: The formation of trichloramine is favoured at acidic and neutral pH levels. 

Properties:

Volatility: Trichloramine is a volatile compound, meaning it readily evaporates into the air. 
Irritant: It's a known irritant, causing irritation to the eyes and upper respiratory tract. 
Odour: Trichloramine has a distinct, pungent odour. 
Explosive: In higher concentrations, it can be explosive. 

Health Effects:

Eye and Respiratory Irritation:
Swimmers and pool workers are often exposed to trichloramine, leading to eye and respiratory irritation. 
Asthma:
Some studies suggest a link between trichloramine exposure and an increased risk of asthma development, particularly among children who frequent swimming pools. 
Occupational Asthma:
There have been reports of occupational asthma among swimming pool workers exposed to trichloramine. 
Lung Function:
Studies have investigated the impact of trichloramine exposure on lung function, with some showing changes in lung permeability and respiratory symptoms. 

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🧠 The Irony

The stronger the smell, the dirtier the water might be — because more contaminants mean more chloramine formation.
A well-maintained pool with balanced chlorine levels often smells far less.

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⚖️ Pool Chemistry in Balance

Keeping a pool safe (and pleasant) involves:

• Free chlorine: The amount available to disinfect.

• Combined chlorine: The amount tied up in chloramines.

• pH levels: Should be kept between 7.2 and 7.8 for optimal chlorine efficiency.

• Shock treatments: Adding a higher dose of chlorine to break down chloramines.

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🔬 Classroom Demonstrations

Mini Pool Chemistry Experiment

1. Use small beakers of water with added sodium hypochlorite.

2. Introduce small amounts of ammonia solution to simulate contamination.

3. Measure free and combined chlorine using test strips or a Chlorine Meter.

4. Discuss how pH and temperature affect results.

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🎓 Curriculum Links

• GCSE & A-Level Chemistry: Reactions between acids, bases, and ammonia derivatives.

• Real-life chemistry in public health and hygiene.

• Equilibrium concepts and how they apply to water treatment.

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💡 Fun Fact for Students

Olympic-sized pools contain millions of litres of water — but it only takes a small chemical imbalance to make them smell and irritate your eyes.

At Philip M Russell Ltd, we use real experiments, high-quality video demonstrations, and engaging stories to bring chemistry to life. Understanding why pools smell the way they do helps the students understand more about life and the chemistry that is going on around them..

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📅 Now enrolling for 1:1 GCSE and A-Level Chemistry Tuition
In our lab, classroom, or online via Zoom.
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Measuring UV the Video

 We try out several hats. Which ones will protect you from the UV rays?

Measuring UV – Testing the Shade of Different Hats and Parasols

Measuring UV – Testing the Shade of Different Hats and Parasols

We’ve all been told that wearing a hat or sitting under a parasol will help protect us from the sun’s harmful rays. But how much protection do they actually give — and does it vary by material, colour, or style?

Armed with a @pascoscientific wireless Light sensor, I decided to find out. This Light sensor can detect and measure the UV Index as well as the amounts of UVA and UVB reaching it.

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Why Measure UV?

Sunlight contains ultraviolet radiation, which can cause sunburn, premature skin ageing, and increase the risk of skin cancer. While sunscreen is an obvious defence, many people rely on hats, sunglasses, or parasols for extra shade. Measuring the UV passing through these barriers tells us just how effective they really are.

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The Experiment

Equipment:

• PASCO Wireless Light Sensor

• A selection of hats: straw sun hat, cotton baseball cap, wide-brimmed synthetic hat

• A collection of parasols: light fabric, dark fabric, reflective silver coating

• A sunny summer afternoon (the most difficult thing to arrange in the UK!)

Method:

1. Place the UV sensor in full sun to record a baseline reading.

2. Position the sensor under each hat or parasol in turn.

3. Record the UV reading for 30 seconds to average out any small fluctuations.

4. Compare the results as a percentage of the baseline.

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What We Found

• Straw sun hat – Let through surprisingly high amounts of UV due to the gaps in the weave. Stylish, but not much help on its own.

• Cotton baseball cap – Good protection for the top of the head, but leaves the face, ears, and neck exposed.

• Wide-brimmed synthetic hat – Excellent coverage and low UV penetration, especially when the fabric had a dark colour.

• Light fabric parasol – Reduced UV but still let through a fair amount, especially when the sun was high overhead.

• Dark fabric parasol – Significantly better than the light fabric, with lower UV readings underneath.

• Silver-coated parasol – The clear winner, blocking almost all UV in the measured range.

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Key Takeaways

• Fabric density matters – tightly woven materials block more UV.

• Colour counts – darker colours tend to absorb more UV than lighter ones.

• Coverage is crucial – a hat might protect your scalp, but without a brim or neck flap, other areas are still at risk.

• Reflective coatings work – parasols with a metallic or silver underside can dramatically reduce UV exposure.

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Why This Matters for Everyday Life

If you’re spending long hours outside, whether gardening, sailing, or enjoying a café terrace, it’s worth knowing how effective your shade really is. Your hat may keep you cool, but it might not be keeping you safe.

With the right choice of material and design, hats and parasols can become powerful allies in UV protection — and our measurements prove it.

🎓 Science Outdoors, Made Easy

At Philip M Russell Ltd, we believe science happens everywhere — not just in a lab. With wireless sensors, simple experiments, and a curious mindset, we help students explore physics in the real world.

Whether it’s tracking sunlight in the garden or building graphs from everyday items, we teach GCSE and A-Level Physics through discovery and data.

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📅 Now enrolling for 1:1 Physics Tuition – online and in-person, in the Lab
With experiments, real data, and clear explanations.
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Holiday Budgeting – The Real Maths of Spending on a Trip

 

Holiday Budgeting – The Real Maths of Spending on a Trip

A holiday is meant to be relaxing — until you check your bank account and realise that ice cream, sun hats, and “just one more souvenir” have somehow eaten half your spending money.
Good budgeting isn’t about being stingy — it’s about making the numbers work so you can enjoy your trip without worrying.

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📊 Step 1: Work Out Your Total Budget

Before you even start packing:

1. Decide how much you can spend.

2. Split it into categories:

   • Accommodation

   • Food & drink

   • Transport

   • Activities

   • Souvenirs

   • Emergencies / extras

Tip: Always set aside at least 10% for unexpected costs (the “Oh no, the bus didn’t show up” fund).

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📏 Step 2: Do the Daily Maths

Divide your budget by the number of days away.
Example:
A £1,000 budget for 7 days = £142/day.
This helps you decide whether that spontaneous dolphin-watching trip is a go or a “maybe next year.”

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🍦 Step 3: Spot the Hidden Costs

Holiday spending often disappears into “little extras”:

• Snacks at the airport

• Hotel minibar

• Taxis instead of public transport

• That cute sunhat you had to buy

Write down every purchase. Apps make this easy — and surprisingly satisfying.

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🧮 Step 4: Use Real Maths in Decision-Making

• Opportunity cost: If you splurge on a fancy dinner, what activity might you have to skip?

• Cost per use: That £40 snorkel set you’ll use once? Probably better to rent.

• Currency conversion: Factor in exchange rates and card fees before you swipe.

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🎓 Teaching Link

Holiday budgeting is a brilliant way to teach GCSE Maths:

• Percentages & ratio

• Division & proportionality

• Data handling (spending logs & pie charts)

• Real-life problem-solving

Students see how numbers affect choices in the real world.

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💡 Bonus Classroom Activity

Have students plan a fictional trip with a set budget, comparing:

• Luxury vs budget accommodation

• Public vs private transport

• Self-catering vs eating out

They’ll quickly learn that maths isn’t just in the classroom — it’s in every decision they make.

Camping Physics – How to Stay Warm (or Cool) in a Tent

 

⛺ Camping Physics – How to Stay Warm (or Cool) in a Tent

Whether you’re pitching up on a windswept hillside or a sunny coastal meadow, your tent becomes your home – and your personal physics lab.
Staying comfortable while camping is all about understanding heat transfer: conduction, convection, and radiation.

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🔥 The Three Ways You Lose (or Gain) Heat

1. Conduction – The Ground Beneath You
The Earth is a giant heat sink. Lie directly on it and you’ll lose heat fast.

• Tip: Use a sleeping mat or inflatable mattress to trap insulating air between you and the ground.

• In summer, the same principle works in reverse: a groundsheet can help stop the hot earth from radiating heat up into your tent.

2. Convection – Air Flow in the Tent
Air moves heat around. In winter, unwanted draughts suck warmth away; in summer, a breeze is welcome relief.

• Tip: Adjust vents strategically. Close them on cold nights, open them fully on hot days.

3. Radiation – Heat from the Sun (or You)
On a sunny day, a tent can turn into an oven thanks to solar radiation heating the fabric and the air inside.

• Tip: Choose light-coloured tents in hot climates to reflect sunlight, and dark-coloured tents in cooler seasons to absorb warmth.

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🧠 The Physics in Action

• Winter Camping:
  Your body generates heat (metabolic radiation), which gets trapped in your sleeping bag.
  Reduce conduction by using mats, stop convection with draught stoppers, and minimise radiation loss by using reflective liners.

• Summer Camping:
  Position the tent in shade, encourage convection by creating cross-breezes, and reduce radiant heating by using reflective flysheets.

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🛠 Simple Experiments for Students

1. Conduction Test: Place a PASCO wireless temperature sensor under different sleeping mats overnight and compare data.

2. Convection Observation: Use smoke or a fine mist to visualise airflow patterns through tent vents.

3. Radiation Check: Measure inside temperatures of light vs dark tents under the same sun.

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🎓 Curriculum Links

• GCSE & A-Level Physics: Energy transfers, insulation, and thermal properties.

• Environmental science: How shelters interact with their surroundings.

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🏕 The Takeaway

Camping comfort isn’t just about buying the right gear – it’s about using it with an understanding of physics. Master heat transfer, and you can sleep soundly whether it’s frosty or sweltering.

🎓 Learn Physics Through Real Experiences

At Philip M Russell Ltd, science should be felt as well as understood. Whether we’re measuring temperature with sensors or tracing smoke streams in the air, seeinmg and doing science helps students understand.

Our lessons are:

• Hands-on

• Visual and dynamic

• Available in our lab, classroom or online studio

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📅 Now enrolling for 1:1 GCSE and A-Level Physics tuition
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Strawberry DNA

 DNA on Your Dining Table – Extracting DNA from Strawberries

🧬 DNA on Your Dining Table – Extracting DNA from Strawberries

You’ve eaten them in pies, smoothies, and straight out of the punnet — but have you ever seen the DNA inside a strawberry?
With a few simple household ingredients, you can make the invisible visible, and hold strands of genetic material right in your hand.

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🍓 Why Strawberries?

Strawberries are ideal for DNA extraction because:

• They’re octoploid — meaning each cell has eight copies of its DNA.

• They’re soft and easy to mash, releasing cells without heavy equipment.

• They contain lots of DNA compared to many other fruits.

More DNA = more visible results.

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🔬 The Science Behind the Steps

To get the DNA out, you have to:

1. Break open the cells (mechanical disruption — mashing).

2. Dissolve the membranes (chemical disruption with soap).

3. Remove proteins that are bound to the DNA (using salt).

4. Make DNA clump together (by adding cold alcohol).

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🥼 What You’ll Need

• 2–3 ripe strawberries

• A zip-lock bag

• A splash of washing-up liquid

• A pinch of table salt

• Water

• Coffee filter or kitchen paper

• A clear glass

• Cold surgical spirit or isopropyl alcohol (chilled in freezer)

• A wooden stir stick or skewer

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🧪 Step-by-Step

1. Mash the Strawberries
Place the strawberries in the bag, squeeze out the air, and mash until you have a pulpy mix. This breaks open the cell walls.

2. Add Extraction Solution
Mix a little water, washing-up liquid, and salt. Pour into the bag, seal, and gently massage.

• Soap dissolves the fatty cell membranes.

• Salt breaks up protein–DNA complexes.

3. Filter the Mixture
Pour the contents through a coffee filter into a glass. This separates solids from the liquid containing the DNA.

4. Add Cold Alcohol
Gently pour cold alcohol down the side of the glass so it forms a layer on top. DNA is not soluble in alcohol — it will precipitate.

5. Watch the DNA Appear
White, stringy clumps will form at the alcohol–liquid boundary. Use the skewer to spool them out.

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🔍 What You’re Looking At

That white, tangled mess?
It’s the blueprint of life — the same code found in nearly every living organism. In strawberries, these strands contain the instructions for making seeds, leaves, roots, and fruit.

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🧠 Extending the Experiment

• Try other fruits — bananas, kiwis, grapes — and compare the DNA yield.

• Use a magnifying glass or a microscope to look at the strands up close.

• For older students, discuss how DNA extraction is used in genetics, forensics, and medicine.

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📚 Teaching Note

This practical is perfect for GCSE Biology (cell structure, DNA, genetic material) and A-Level Biology (nucleic acids, extraction techniques).
It’s low-cost, safe, and gives students that instant “wow” moment.

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At Philip M Russell Ltd, we bring science to life — whether it’s in the lab, classroom, or online. Experiments like this don’t just teach; they inspire curiosity.

Why Do We Go on Holiday? A Sociological Take on Leisure and Escape

 From package tours to ‘finding yourself’ — what does your holiday say about society?

Why Do We Go on Holiday? A Sociological Take on Leisure and Escape

Sunshine, sandy beaches, sightseeing tours — holidays are often seen as a simple break from work. But from a sociological perspective, going on holiday is much more than just rest and relaxation. It’s about identity, status, ritual, and even resistance.

Let’s explore what motivates us to pack our bags — and what a holiday says about who we are and how society works.

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🧠 1. Functionalism – The Need to Recharge

From a functionalist viewpoint, leisure — including holidays — plays a crucial role in maintaining the stability of society.

• We work, we get tired, we need a break.

• Holidays restore our energy, keeping us productive.

• They reinforce social bonds (family holidays) and support social order.

Emile Durkheim might argue that holidays serve as a kind of collective ritual, reinforcing social norms and giving people space to reconnect.

🏡 Think of the traditional British summer holiday — it’s practically an institution.

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🪩 2. Marxism – Escaping, but Not for Long

From a Marxist perspective, holidays are a way to temporarily escape alienation caused by capitalist labour.

• We’re told to “treat ourselves” — but only when we’ve earned it.

• Travel and leisure become commodities, sold to us as a reward.

• The holiday industry profits from our desire to escape the very system it’s part of.

Holidays are marketed as freedom — but are often just a short break from returning to the same pressures of work and consumption.

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🧳 3. Postmodernism – Constructing the Holiday Identity

In the postmodern world, holidays are about self-expression and identity.

• We don’t just go on holiday — we curate the experience.

• Instagrammable destinations, travel blogs, #vanlife — holidays become social capital.

• We seek authenticity, individualism, and narrative.

A short trip to Bali becomes a personal brand. A weekend in Cornwall becomes a wellness retreat. Postmodern thinkers argue holidays are no longer just leisure — they’re performative acts.

✈️ “You are what you post — even on holiday.”

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🧑‍🤝‍🧑 4. Feminism – Who Gets to Rest?

From a feminist perspective, holidays also highlight gendered divisions of labour:

• Women often do the bulk of holiday planning, packing, and child care — even when “on holiday”.

• Solo travel is empowering for some, but riskier for others.

• Access to leisure is still influenced by gender roles, safety, and domestic expectations.

Feminist sociologists ask: Who truly gets to relax — and who’s still working, just in a different setting?

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🌍 5. Globalisation – Where Do We Go, and Why?

Globalisation has reshaped travel:

• Budget airlines make global travel more accessible (to some).

• Cultural tourism markets “exotic” places to Western tourists.

• Tourism shapes economies and local identities, often reinforcing inequalities.

Sociologists explore how holidaymakers interact with local communities — and whether travel is mutually enriching or exploitative.

🍹 Are we sipping cocktails in a resort while the locals earn minimum wage in service jobs?

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🎓 Perfect for A-Level Sociology Topics:

This topic can link with:

• Culture and identity

• Social stratification

• The role of the media

• Leisure and consumption

• Feminist and Marxist critiques of capitalism

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👓 Holiday? Or Sociological Case Study?

Next time you head off on a break, consider:

• Who’s working to make your holiday happen?

• What messages does the location send about class, race, or culture?

• How much is your holiday about escape — and how much about status?

Sociology helps us dig deeper — even when we’re lying on a sunbed.

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📚 Want to Think Differently?

At Philip M Russell Ltd, we teach A-Level Sociology through real-world examples and critical thinking. Whether it’s travel, TikTok, or Tesco, we help students analyse the society around them — not just memorise names and dates.

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