science experiments ideas

Light a candle, let it burn for a while, and blow it out again. White smoke rises from the wick. If you hold a burning match in the smoke, a jet of flame shoots down to the wick, and it re lights.
After the flame is blown out the stearin is still so hot that it continues to evaporate and produce a vapour. But as this is combustible, it can be re lighted at once by a naked flame. The experiment shows that solid substances first become gaseous at the surface before they will burn in a supply of oxygen.

Roll a thin piece of tin foil round a pencil to make a tube about four inches long, and hold it with one end in the middle of a candle flame. If you hold a burning match at the other end of the tube, a second flame will be lit there.
Like all solid and liquid fuels, stearin produces combustible gases when heated, and these accumulate inside a flame. They burn, with the oxygen of the air, in the outer layer and tip of the flame. The unburnt stearin vapour in the middle can be drawn off, like town gas from the gas works.

Fix two plastic bags to the ends of a piece of wooden beading about 18 inches long and let it swing like a balance on a drawing pin. Pour some bicarbonate of soda and some vinegar into a glass. It begins to froth, because a gas is escaping. If you tilt the glass over one of the bags, the balance falls.
The gas, which is given off during the chemical reaction, is carbon dioxide. It is heavier than air, so it can be poured into the bag and weighed. If you were to fill a balloon with the gas it would never rise, and for this purpose other gases are used, which are lighter than air.

Light a candle stump in an empty glass, and mix in another glass as in the previous experiment a teaspoonful of bicarbonate of soda with some vinegar and let it froth. If you tilt the glass over the candle, the flame goes out.
The carbon dioxide formed in the chemical reaction in the top glass displaces the air needed for the flame, because It is heavier, and because it is non combustible the flame is smothered. Many fire extinguishers work in the same way the sprayed foam consists of bubbles filled with carbon dioxide. It surrounds the flame and blocks the supply of oxygen.

Press a handful of steel wool firmly into a glass tumbler and moisten it. Invert the tumbler over a dish containing water. At first the air in the tumbler prevents the water entering, but soon the level of water in the dish becomes lower while that in the glass rises.
After the steel wool is moistened, it begins to rust. The iron combines with the oxygen in the air, and we call this process combustion or oxidation. Since the air consists of about one fifth oxygen, the water rises in the tumbler until after some hours it fills one fifth of the space. However, an imperceptible amount of heat is set free in the process.

Would you have thought that even iron could be made to burn with a flame! Twist some fine steel wool round a small piece of wood and hold it in a candle flame. The metal begins to blaze and scatter sparks like a sparkler.
The oxidation, which was slow in the previous experiment, is rapid in this case. The iron combines with the oxygen in the air to form iron oxide. The temperature thus produced is higher than the melting point of iron. Because of the falling red hot particles of iron it is advisable to carry out the experiment in a basin.

Put a piece of aluminium foil with a copper coin on it into a glass of water, and let it stand for a day. After this the water looks cloudy and at the place where the coin was lying the aluminium foil is perforated.This process of decomposition is known as corrosion. It often occurs at the point where two different metals are directly joined together. With metal mixtures alloys it is particularly common if the metals are not evenly distributed. In our experiment the water becomes cloudy due to dissolved aluminium. A fairly small electric current is also produced in this process.

Stick finger length pieces of copper and zinc wire one at a time into a raw potato. If you hold an earphone on the wires, you will hear distinct crackling.produce an electric current in the same way as a torch battery,but only a very weak one. The sap of the potato reacts with the metals in a chemical process and also produces electrical energy. We speak of a galvanic cell because the Italian doctor Galvani first observed this process in a similar experiment in 1789.

Place several copper coins and pieces of sheet zinc of the same size alternately above one another, and between each metal pair insert a piece of blotting paper soaked in salt water. Electrical energy, which you can detect, is set free. Wind thin, covered copper wire about 50 times round a compass, and holds one of the bare ends on the last coin and one on the last zinc disk. The current causes a deflection of the compass needle.
In a similar experiment the Italian physicist Volta obtained a current. The salt solution acts on the metal like the sap in the potato in the previous experiment.

Connect a torch bulb with a battery by means of a pair of scissors and a pencil. The bulb lights up.From the long tongue of the battery, the negative pole,the current flows through the metal of the scissors to the lamp. It makes it glow, and flows through the graphite shaft to the positive pole of the battery. Therefore graphite is a good conductor so much electricity flows even through a pencil lead on paper, that you can hear crackling in earphones.