204 Simple Science Experiments ~ {ERG}

[LoneRanger]



16. Violet becomes red

If you ever come across an anthill in the woods, you can there and then do a small chemical experiment. Hold a violet flower, e.g. a bluebell, firmly over the ants. The insects feel threatened and spray a sharp smelling liquid over the flower.

The places hit turn red. The ants make a corrosive protective liquid in their hindquarters. You notice it if an ant nips you, though it is generally quite harmless. Since the flower turns red where the drops fall, you know
that they are acid. The acid is called formic acid.

[LoneRanger]



17. Invisible ink

If you ever want to write a secret message on paper, simply use vinegar, lemon, or onion juice, as the invisible ink. Write with it as usual on white writing paper. After it dries the writing is invisible. The person who receives the letter must know that the paper has to be held over a candle flame: the writing turns brown and is clearly visible.

Vinegar, and lemon or onion juice, cause a chemical change in the paper to a sub- stance’ similar to cellophane. Because its ignition temperature is lower than that of the paper, the parts written on singe.

[LoneRanger]



18. Bleached rose

A piece of sulfur is ignited in a jam jar. Since a pungent vapor is produced, you should do the experiment out-of-doors. Hold a red rose in the jar. The color of the flower becomes visibly paler until it is white.

When sulfur is burned, sulfur dioxide is formed. As well as its germicidal action in sterilization, the gas has a bleaching effect, and the dye of the flower is destroyed by it. Sulfur dioxide also destroys the chlorophyll of plants, which explains their poor growth in industrial areas, where the gas
pollutes the air.

[LoneRanger]



19. Transfer pictures

Photos and drawings from newspapers can be copied easily. Mix two spoonfuls of water one spoonful of turpentine and one spoonful of liquid detergent and dab this liquid with a sponge on the newspaper page.

Lay a piece of writing paper on top, and after vigorous rubbing with a spoon the picture is clearly transferred to the paper.

Turpentine and liquid detergent when mixed form an emulsion, which penetrates between the dye and oil particles of the dry printing ink and make it liquid again. Only newspaper printing ink can be dissolved, though.

[LoneRanger]



20. Sugar fire

Place a piece of cube sugar on a tin lid and try to set it alight.

You will not succeed. However, if you dab a corner of the cube with a trace of cigarette ash and hold a burning match there, the sugar begins to burn with a blue flame until it is completely gone.

Cigarette ash and sugar cannot be separately ignited, but the ash initiates the combustion of the sugar. We call a substance, which brings about a chemical reaction, without itself being changed a catalyst.

[LoneRanger]



21. Jet of flame

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 steam is still so hot that it continues to evaporate and produce a vapor. 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.

[LoneRanger]



22. Gas pipe

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, searing 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 searing vapor in the middle can be drawn off, like town gas from the gas works.

[LoneRanger]



23. Gas balance

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.

[LoneRanger]



24. Fire extinguisher

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.

[LoneRanger]



25. Burning without a flame

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.

[LoneRanger]



26. Burning iron

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.

[LoneRanger]



27. Destroyed metal

Put a piece of aluminum 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 aluminum 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 aluminum. A fairly small electric current is also produced in this process

[LoneRanger]



28. Electricity Potato battery

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.

An electric current causes the noise. The potato and wires 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.

[LoneRanger]



29. Coin current

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.

[LoneRanger]



30. Graphite Conductor

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.