Chemistry
Chemistry projects for class 6 to 8: 50 ideas.
Each project below opens to its own page with what it shows, the science behind it, the materials, safety, step-by-step instructions, what you should see and viva questions. Many can be made from things at home; where a kit helps, the page links one.
Other subjects for class 6 to 8: Physics, Biology, Maths, Earth and space, Electronics and robotics, Environment, Computing and coding.
Rainbow in a glass (density tower)
Water with more sugar dissolved in it is denser, so it sinks below water with less sugar. Layers of differently sweetened, coloured water stack up like a rainbow.
Erupting volcano model
Vinegar (an acid) reacts with baking soda (a base) and gives off carbon dioxide gas, which pushes the foam out. Real volcanoes erupt molten rock, so the model shows the shape of a volcano, not its cause.
Red cabbage indicator
Red cabbage juice changes colour with acids and bases: pink or red in acids, purple when neutral, and blue, green or yellow in bases.
Lemon and potato battery
Two different metals in an acidic juice make an electric cell, turning chemical energy into electrical energy. One lemon gives less than one volt, so several are joined in series to light an LED.
What makes iron rust?
Iron rusts only when both air (oxygen) and water are present, and salt water speeds it up. Nails kept dry, or in boiled water sealed with a layer of oil, stay bright.
Paper chromatography of inks
Many inks are mixtures of colours. As water climbs the paper, each colour travels a different distance, depending on how well it dissolves and how strongly it sticks to the paper.
Turmeric paper strips that spot soaps and acids
Turmeric contains a yellow dye called curcumin that turns reddish brown in a base such as soap water and stays yellow in an acid such as lemon juice. Home-made turmeric strips work like litmus paper and let you sort kitchen liquids into acids, bases and neutrals.
Hibiscus petal indicator with a kitchen colour chart
The red pigment in hibiscus (gudhal) petals is an anthocyanin that turns pink red in acids and greenish or dark in bases. By testing kitchen liquids you can build a colour chart that places each liquid roughly on a scale from strong acid to strong base.
Growing sugar crystals on a string, like mishri
Hot water dissolves far more sugar than cold water. As a very strong sugar solution cools and slowly loses water, the extra sugar comes out of solution as crystals that grow on a string, which is exactly how mishri is made.
Alum (fitkari) crystal geode inside an eggshell
Alum dissolves easily in hot water and much less in cold water. A saturated alum solution left in half an eggshell slowly deposits sparkling crystals on the shell wall, making a model of a geode, the hollow rocks lined with crystals that form in the same way underground.
Stirring or warm water: which dissolves sugar faster?
Dissolving gets faster when the water is warmer, when the liquid is stirred, and when the sugar is in smaller pieces. A fair test with a stopwatch shows which of these three has the biggest effect.
Separating a mixture of sand, salt and iron filings
A mixture keeps the properties of each part, so each part can be removed by a method that suits it: a magnet for iron, dissolving for salt, filtering for sand and evaporation to get the salt back. The project shows four separation methods in one go.
Measuring the gas from baking soda and vinegar with a balloon
Baking soda and vinegar react to make carbon dioxide gas, which inflates a balloon fitted over the bottle. Using more baking soda makes a bigger balloon, until the vinegar is used up and extra baking soda does nothing.
Lemon juice invisible ink revealed with a warm iron
Lemon juice dries clear on paper, but gentle heat from a clothes iron turns the written lines brown before the rest of the paper changes. The acid in the juice weakens the paper fibres, so they scorch at a lower temperature than clean paper.
Chromatography of the colours in candy coatings
The coloured coating on candies such as Gems is often a mixture of several food dyes. Water climbing up filter paper carries the dyes at different speeds, so a single dot of colour spreads into separate bands and shows what the mixture contains.
Lava bottle with oil, water and a fizzing tablet
Oil floats on water because it is less dense, and the two do not mix. A piece of fizzing antacid tablet (ENO or similar) dropped in makes carbon dioxide bubbles that lift blobs of coloured water up through the oil and let them fall again, like a lava lamp.
Floating egg: how many spoons of salt does it take?
A fresh egg sinks in plain water but floats once enough salt is dissolved, because dissolving salt makes the water denser than the egg. Counting the spoons needed turns a trick into a measurement of density.
Which coating stops a nail from rusting?
Iron rusts when both water and air reach it. Coating a nail with oil, paint, nail polish, wax or petroleum jelly keeps them away. Comparing coated nails with a bare one over ten days shows which coating protects best and why painted gates and oiled tools last longer.
Cleaning copper coins with vinegar, then growing green patina
Dull old copper or brass coins shine again in a dip of vinegar and salt, because the acid dissolves the dark copper oxide layer. If the coins are then left wet with vinegar in the air, a blue green coating forms, the same patina seen on old temple bells and statues.
Milk plastic buttons made with vinegar (casein)
Adding vinegar to hot milk makes the milk protein casein clump into curds. Pressed and dried, the curds set into a hard, mouldable plastic. Buttons and ornaments were made this way before petroleum plastics existed.
Cleaning muddy water by settling, decanting and filtering
Muddy monsoon water can be made clear in stages: heavy soil settles, the clearer water is poured off, and a home-made sand and cloth filter removes the fine particles. The water looks clean but is still not safe to drink, which the project explains.
Evaporation race: water, hand sanitiser and oil on a plate
Equal drops of water, alcohol-based hand sanitiser and cooking oil evaporate at very different speeds: the sanitiser disappears in minutes, water in about an hour, and oil hardly at all. The difference shows how strongly each liquid’s molecules hold on to each other.
Fizzing sherbet powder from citric acid and baking soda
Dry citric acid and baking soda do nothing together, but the moment they get wet, on the tongue or in water, they react and release carbon dioxide bubbles. The project shows that many reactions need water to start, and lets you find the mix that fizzes most.
Naked bouncy egg: vinegar dissolves the shell
An eggshell is calcium carbonate, which reacts with the acid in vinegar and fizzes away as carbon dioxide, leaving the egg held only by its soft membrane. The rubbery egg also swells, showing that water passes into it through the membrane.
Baking soda, baking powder or neither: which cupcake rises?
Cakes rise because gas bubbles form in the batter. Baking powder contains both an acid and a base and makes gas on its own when wet and heated; baking soda alone needs an acid like curd or lemon in the batter. Baking four small cakes with different raising agents shows which rise and why.
Home-made bath bombs: fizz time in warm and cold water
A bath bomb is a pressed mix of baking soda and citric acid held together by a little oil. Dropped in water it fizzes as carbon dioxide forms. Timing identical bombs in cold and warm water shows that the same reaction runs faster when the water is warmer.
Chalk and marble chips in vinegar: a model of acid rain damage
Chalk and marble are both calcium carbonate, which acid rain slowly eats away on old buildings such as the Taj Mahal. Pieces in vinegar fizz and lose mass, while pieces in plain water stay unchanged, so the loss can be measured and compared.
Testing kitchen foods for starch with diluted iodine
A drop of diluted tincture of iodine turns blue black on anything that contains starch, such as potato, rice and bread, and stays brown on foods without starch, such as cheese or oil. It is a quick chemical test that sorts foods and can expose starch added to milk or spices.
Frost on a tin can using only ice and salt
Crushed ice mixed with salt gets colder than ice alone, below the freezing point of water. The outside of a tin filled with the mix becomes so cold that water vapour from the air freezes on it as a white frost, which never happens with plain ice.
Does dissolved sugar still weigh the same?
When sugar disappears into water, its mass does not disappear: the sugar water weighs exactly as much as the sugar and the water did separately. Weighing before and after shows that dissolving spreads the sugar out but destroys nothing.
Yeast and sugar balloon: which sweetener makes most gas?
Yeast feeds on sugar and releases carbon dioxide gas, which inflates a balloon over the bottle. Comparing plain sugar, jaggery, honey and an artificial sweetener shows which foods the yeast can actually turn into gas, the same reaction that makes bread rise.
Ice cream in a bag: why salted ice gets colder than ice
Salt dissolving in the thin layer of melt water on ice lowers its freezing point, so the ice bath drops below 0 C and freezes a sweet milk mixture into soft ice cream. A thermometer shows how much colder salted ice gets.
Baking soda or baking powder: which makes more bubbles?
Baking soda needs an acid to give carbon dioxide, while baking powder already has its own acid and only needs water. Testing both with vinegar, curd water and plain water shows why recipes pick one or the other.
Why apple slices turn brown and what stops it
A cut apple turns brown when enzymes in it react with oxygen in the air. Lemon juice, salt water, sugar water and cold slow or stop the change, which shows how cooks keep fruit looking fresh.
Which kitchen ingredient keeps oil and water mixed?
Oil and water do not mix, but some kitchen ingredients called emulsifiers surround the tiny oil drops and keep them spread in the water. You shake the oil and water with different ingredients and time how long they take to separate.
Hot water against cold water: how fast tea colour spreads
Particles move faster in hot water, so colour from a tea bag spreads, or diffuses, much faster there than in cold water. Measuring the time to colour a glass shows how temperature affects diffusion and dissolving.
Candy colour race: hidden dyes in coated sweets
Coloured sweets often use a mix of dyes, and water carrying them up paper moves different dyes at different speeds. You split the colours of several sweets and learn how to separate a mixture without any chemicals.
Which liquid removes turmeric and tea stains from cotton?
Different stains need different cleaners: tea stains respond to mild acids and detergents, while turmeric responds to sunlight and detergent. You test cleaning liquids on identical stains and score the result.
Longer-lasting soap bubbles with glycerine or sugar
A soap bubble is a thin film of water held between two layers of soap. Adding glycerine or sugar slows the evaporation of the water, so the bubbles live longer. You time bubble lifetimes for different recipes.
Which fabric soaks up the most water: cotton, nylon, wool or polyester?
Cotton and wool fibres absorb a lot of water, while nylon and polyester absorb little. By weighing identical fabric squares before and after soaking, you find which fabric is best for towels and which for raincoats.
Flour paste, rice paste and school glue: which sticks hardest?
Glues stick by filling the tiny gaps in the surfaces and hardening, and starch paste from the kitchen works for paper. You compare the strength of flour paste, rice paste and school glue by hanging load from glued strips.
Are all steel utensils magnetic? Testing a kitchen full of metals
Plain iron and some kinds of steel are attracted by a magnet, but many stainless steels with nickel are not, or only slightly. By testing kitchen items you learn why steel types differ and how to sort the metals around you.
pH of garden, farm and roadside soil using red cabbage indicator
Soils can be acidic, neutral or alkaline, and crops grow best in a suitable range. A homemade indicator sorts soils from different places by colour.
Walking rainbow: colours that climb a paper towel
Water climbs up paper and carries colours with it. When red and yellow meet in the middle they make orange, and blue and yellow make green.
Water drops on a coin: how many drops fit?
Water drops hold together like a skin and make a dome. A coin can hold many drops before the water spills over.
What dissolves in water? A kitchen tray test
Some things disappear in water, such as salt and sugar, and some do not, such as sand and flour. We call the first group soluble.
Soap bubble wands: do square wands make square bubbles?
Bubbles are always round, whatever the shape of the wand. Soap film pulls itself into the shape with the least surface, which is a sphere.
Why diet cans float and regular cans sink: sugar and density
Sealed cans of regular and diet soft drinks look the same, but in a tub of water the regular one sinks and the diet one floats. The sugar dissolved in the regular drink raises its density above that of water.
Diaper crystals: how much water do they hold, and what does salt do?
The white powder inside a baby diaper is a polymer that soaks up many times its mass of fresh water and turns to gel. It absorbs far less from salty water, which shows how dissolved salt changes the way it works.
Cornflour and water oobleck: a mixture that acts both solid and liquid
A thick mix of cornflour and water flows slowly when poured but turns hard when it is hit or squeezed. It is a suspension whose behaviour depends on how fast you push it.