18 experiments found
Clear filtersIndicators change colour in acids and bases
Use red cabbage indicator to sort everyday liquids into acids, bases and neutral substances.
Natural fibres come from plants (cotton, jute, coir, flax) or animals (wool, silk, pashmina); man-made fibres such as nylon, polyester and acrylic are made from chemicals; plant fibres burn like paper, animal fibres smell of burning hair, and synthetic fibres melt
Look at twelve fibres, from cotton and jute to pashmina, silk and nylon. Find where each comes from and how a thread of it burns, then sort them into plant fibres, animal fibres and man-made fibres.
Evaporation turns liquid water into vapour; condensation turns vapour back into liquid
Heat salt water until the water evaporates and leaves salt behind, and watch water vapour condense on a cold lid.
The state of matter depends on how particles are arranged and how fast they move
Heat and cool water and wax, and watch how their particles are arranged and how fast they move in each state.
Physical changes can be reversed; chemical changes make new substances
Heat and cool ice, wax, sugar and egg white. Find out which changes can be reversed and which make a new substance.
Filtration separates insoluble solids from liquids
Filter muddy water and salty water. Discover what filter paper can and cannot remove.
Heavy insoluble particles settle, so the liquid above can be poured off
Stir sand into water, let it settle, then pour off the clear water without disturbing the sand.
A magnet separates magnetic materials from non-magnetic ones
Mix sand and iron filings, then use a magnet to pull the iron out. Find out why a magnet cannot separate salt from sand.
Some solids dissolve, and water can dissolve only a limited amount
Stir salt, sugar and sand into water. Find out which ones dissolve, and how much salt water can hold.
Heat, stirring and smaller pieces make a solid dissolve faster
Race sugar cubes and granulated sugar in cold and hot water, stirred and unstirred, and time how long each takes to dissolve.
Solids keep their shape, liquids flow and take the shape of their container, and gases spread out to fill any space
Test everyday materials for shape, flow and how they fill a container, then sort them into solids, liquids and gases.
Every atom is made of protons and neutrons in a tiny nucleus with electrons around it; the number of protons decides which element it is
Add protons, neutrons and electrons one by one and see the atom you make: its name, its mass and how its electrons sit in shells. Then turn carbon into nitrogen with a single proton.
NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂: one mole (84 g) of baking soda gives one mole (44 g, about 24 L) of carbon dioxide and needs one mole (60 g) of acetic acid
Drop 2 to 20 g of baking soda into vinegar and blow up a balloon with the carbon dioxide. Use the equation and moles to find the mass and volume of the gas and how much vinegar the soda needs.
Solubility is the most of a substance that dissolves in 100 g of water at a given temperature; sugar's solubility rises steeply with temperature, but salt's hardly changes
Stir sugar or salt into water at different temperatures until no more dissolves. See how hot water dissolves far more sugar, while salt hardly changes, and why syrup for sweets is made hot.
Food spoils when microbes grow in it; microbes need water, warmth and time, so food keeps longer when we take the water out, keep it cold, heat it to kill the germs, or pickle it in acid or oil
Look at twelve kitchen foods, from sun-dried fish to mango achar, find out how long each keeps and what stops the microbes, and sort them by the way they are preserved: drying, cold, heat or pickling.
Dissolving salt makes water denser; an object floats when the liquid is denser than the object, so an egg floats once the salty water is denser than the egg
Drop an egg into a glass of water and stir in salt, a spoonful at a time, until the egg floats. Then try an old egg, which floats in plain water, and find out why cooks use this to test eggs.
Water boils when its vapour pushes as hard as the air above it; higher up the air pressure is lower, so water boils at a lower temperature (about 1 °C lower for every 300 m) and food cooks more slowly
Boil a pot of water at the seaside, in Kathmandu, Shimla, Leh and at Everest base camp. See how the boiling point falls as you climb, and why dal takes so much longer to cook up high.
Each fuel gives a fixed heat per gram, its calorific value, but a stove passes only part of it to the pot; grams burnt = heat needed ÷ (calorific value × efficiency), so a good fuel in a good stove burns far less
Boil 1, 2 or 5 litres of water on an LPG stove, a kerosene stove, a coal stove, an open wood fire or a dung-cake chulo. See the heat the water needs and how many grams of each fuel burn to give it.