19 experiments found
Clear filtersAn acid reacts with a base to make a salt and water
React black copper oxide with warm dilute sulfuric acid, filter off the excess, and evaporate the blue solution to grow crystals of a salt.
Acids react with metals and carbonates and turn blue litmus red; bases turn red litmus blue
Test dilute hydrochloric acid and sodium hydroxide solution with zinc, marble chips, litmus and phenolphthalein to discover how acids and bases behave.
Hydrocarbons contain only carbon and hydrogen; alkanes have only single bonds, alkenes have a double bond and alkynes a triple bond
Build models of hydrocarbons, test them with bromine water, learn their uses, and sort them into alkanes, alkenes and alkynes.
Ionic bonds form when a metal transfers electrons to a non-metal; covalent bonds form when non-metal atoms share electrons
Look at which elements each compound contains, model how their electrons are transferred or shared, and sort the compounds into ionic and covalent.
Marble (calcium carbonate) reacts with dilute hydrochloric acid to give carbon dioxide: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂; the reaction goes faster with a bigger surface area (powder), a stronger acid and a higher temperature
Make carbon dioxide from marble and dilute hydrochloric acid, and time how long the reaction takes. Change the size of the marble pieces, the strength of the acid and its temperature.
Oxidation is gain of oxygen; reduction is loss of oxygen
Heat shiny copper in air until it turns black, then heat black copper oxide with carbon to get the copper back.
Reactions can be classified by how the reactants rearrange: A + B → AB, AB → A + B, A + BC → AC + B, and AB + CD → AD + CB
Look at the pattern of each chemical equation and sort the reactions into combination, decomposition, displacement and double displacement.
The modern periodic law says the properties of elements are a periodic function of their atomic numbers; elements are placed by electronic configuration, and the subshell that gets the last electron decides the block: s, p, d or f
Write the electronic configuration of sixteen elements, from hydrogen and sodium to iron and uranium, find their group and period, and sort them into the s, p, d and f blocks.
An electric current decomposes an electrolyte: positive ions go to the cathode, negative ions to the anode
Pass a low-voltage current through acidified water and copper(II) sulfate solution, collect the gases, and see copper plate onto an electrode.
Common gases can be identified by simple tests: oxygen relights a glowing splint, hydrogen pops, carbon dioxide turns limewater milky, ammonia turns red litmus blue
Collect gases from different reactions, test each with a glowing splint, a burning splint, limewater and damp litmus, and identify it.
The method of extracting a metal depends on its place in the reactivity series: the most reactive metals are got by electrolysis of their molten ores, metals in the middle by heating their oxides with carbon, and the least reactive are found free
Find fourteen metals on the reactivity series, from potassium to platinum, look at their ores and uses, and sort them by how they are extracted.
Hard water contains dissolved calcium and magnesium salts that stop soap lathering
Shake soap with soft and hard water to compare lather and scum, then soften hard water by boiling and with washing soda.
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.