12 experiments found
Clear filtersGas, a new solid or a colour change can show a chemical reaction
Mix kitchen substances and look for evidence that a new substance has formed: gas bubbles or a new solid.
Iron rusts when both water and oxygen are present; salt speeds it up and coatings prevent it
Leave iron nails in six test tubes with different conditions for several days and find out what rusting needs, and how paint and zinc protect iron.
Natural materials come from plants, animals or the ground; synthetic materials are made in factories, mostly from petroleum, and behave differently when burnt and in the soil
Find out where eleven everyday materials come from, from Dhaka cloth and pashmina to nylon and plastic bags, test a thread of each in a flame, and sort them into natural and synthetic.
An element has one kind of atom, a compound has different atoms chemically joined in fixed amounts, and a mixture has substances mixed but not joined
Look at particle models of everyday substances, test whether they can be separated, and sort them into elements, compounds and mixtures.
Several separation methods can be combined to separate a mixture
Use dissolving, filtration and evaporation one after another to separate salt from sand and collect salt crystals.
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.