15 experiments found
Clear filtersThe pH scale from 0 to 14 measures how acidic or basic a solution is
Use universal indicator to measure the pH of seven household liquids, from lemon juice to limewater, and place each on the pH scale.
Air is matter: it takes up space, can be compressed, exerts pressure and expands when heated
Push the plunger of a sealed syringe full of air, then warm and cool a flask with a balloon on its neck.
Carbon dioxide turns limewater milky
Make carbon dioxide from marble chips and acid, then bubble it, your breath and fresh air through limewater to see which turn it milky.
Atoms join to form molecules; a molecule of an element has one kind of atom, and a molecule of a compound has two or more kinds
Build ball-and-stick models of common substances, count their atoms, and sort them into single atoms, molecules of elements and molecules of compounds.
Valency is the combining power of an atom, set by its outer electrons; atoms join so that their valencies balance, which the criss-cross rule turns into a formula
Join a metal with a non-metal. See each atom's electron shells, find its valency from its outer electrons, and build the formula: NaCl, MgO, Al₂O₃, CaCl₂ and water.
In electroplating the object is the cathode (−) and the coating metal the anode (+); the metal deposited is proportional to the charge passed, current × time
Hang a steel spoon in a solution of a metal salt and pass a current. Change the coating metal, the current and the time, and see how much metal is deposited and how thick the coat on the spoon grows.
Burning needs fuel, oxygen and heat (the fire triangle); take away any one and the fire goes out
Cover a burning candle with jars of different sizes and time how long it burns, then put the flame out by removing oxygen, heat or fuel.
Metals are shiny, malleable, sonorous and good conductors; non-metals are usually dull, brittle and poor conductors, with a few exceptions
Test elements for shine, hammering, ringing and electrical conduction, then sort them into metals and non-metals.
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.