Today I bring you a list of scientific experiments for secondary school with which you can learn concepts of physics, chemistry and biology. Doing scientific experiments means visualizing phenomena and corroborating theories; They also represent an opportunity to become familiar with the scientific method.
All experiments are easy to execute and use everyday equipment and materials. For the interpretation of the results, at least one level of secondary education student is required. Figure 1. Experimentation is a fundamental part of Science. Source: Pixabay. 1- Construction of a homemade electromagnetMaterials
-1.5V alkaline batteries (2 or 3 batteries)
-Thin and enamelled copper wire (varnished) for windings.
-Iron nails. Figure 2. Materials for the construction of an electromagnet Source: youtube. Procedure
-Wind the enamelled copper wire on one of the steel screws.
-With a cutter or a knife scrape the varnish from the free ends of the copper wire that was wound into the steel screw.
-Place the batteries in the battery holder and connect the ends to the terminals of the battery holder. Experiment
-Bring the tip of the screw closer to the nails and observe that they are attracted.
-Note that when disconnecting the wire from the winding the electromagnet stops working.
-Increase the power of the magnet by connecting more batteries in series.
-Increase the magnetic field of the electromagnet by placing more winding turns. Points to check
-The magnetic force is greater with more current.
-With the same current the magnetic force increases if the number of turns increases.
-With the same number of turns (each turn is a loop) and current the power of the electromagnet increases if the turns are tightened or close to each other.
-If the screw is unscrewed and the spiral is left alone, the magnetic effect continues but weakens substantially. 2- Convection CurrentMaterials:A sheet of paperA piece of threadA candleLighterProcedure
-On the sheet of paper draw a spiral.
-Cut and make a hole in the center of the spiral.
-Pass the piece of thread through the spiral. Make a knot at the end of the thread so that it does not come out of the spiral.
-Lift the spiral with the thread, so that a helical is formed. Experiment
-Place the paper helicoid already suspended by the thread, on the lit candle.
Caution: the paper propeller should be away from the flame, so that it does not ignite. Figure 3. Paper propeller that rotates because of the updraft of thermal convection. Source: youtube. Points to check
-Notice that the helicoid begins to rotate. The reason is the updraft of hot air. Warm air rises because it is lighter than cold air.
-Increase the speed of rotation by placing two candles instead of one. 3- Refraction of lightMaterials
-Place the coin on the table.
-Then put the glass cup on the coin. Experiment A
-Look at the coin under the glass, from an oblique position and from above.
Now place water in the glass and repeat the observation from a side angle and from above. Points to check
-When the glass is empty the coin can be seen through the glass both laterally and from above. But if the glass is filled with water while we observe from a 45º angle to the coin we notice that it suddenly disappears from our sight.
-If we look directly from above we notice that the coin is still there. The phenomenon is explained by the fact that light is deflected when it passes from one medium to another.
-When the water is added at the interface between the glass and the water, there is a deviation of the grazing light to the bottom of the glass and therefore the coin is not displayed. Experiment B
-Now place the pencil in the glass cup with water so that one part is submerged and the other in the air. Points to check
-Look at the pencil from the side: it seems that it has broken. Again the explanation of this phenomenon is the deviation that a light ray suffers when it passes from one medium to another. Figure 4. Refraction of a semi-submerged pencil. Source: Wikimedia Commons. 4- See the germs of the mouth with home microscopeMaterials:A couple of glasses or glassesA syringe without the needleA sewing needleA laser pointerAdhesive tapeProcedure
-We support the fins of the syringe to the walls of the two glasses that will act as columns and support of the syringe.
-Squeeze the syringe gently until a drop forms at the tip that is held by surface tension at the edges of the tip of the syringe.
-Pass the adhesive tape around the laser button so that it is turned on.
-Point the laser light at the drop and see the projection on the wall. Experiment
-Rub the sewing needle carefully, without pricking, on the inside wall of the mouth.
-Touch with the tip of the needle previously rubbed in the mouth, the drop of water on the tip of the syringe.
-Observe the projection and notice the differences. Figure 5. Germs from the mouth amplified and projected with laser light. Source: youtube. Points to check
-In the projection of laser light on the wall, the germs of the mouth are amplified.
-You can repeat the experiment, using water from a vase for the syringe, which may contain microorganisms such as paramecium and amoeba. 5- Lemon BatteryMaterials
-Copper coins, or bare copper wire.
-Clamps for alligator cableProcedure
-A lemon is taken and a piggy bank style slot is made to insert the copper coin.
-On the science experiments opposite side you screw and insert the galvanized screw.
-The alligator clamps are adapted and connected to the voltmeter cables.
-The alligator of the positive is connected to the copper coin.
-The voltmeter negative alligator is connected to the galvanized screw. Figure 6. Lemon stack and voltmeter. Source: youtube. Points to check
-Measure the voltage produced by the lemon battery. This voltage should be a little less than one volt.
-Build a second and third lemon battery, connect in series and check the voltage.
-Try to turn on a flashlight bulb. Try one or several lemon stacks in series.
-Connect the lemon batteries in parallel now. Check the voltage.
-Apply the parallel combination of lemon batteries to the flashlight bulb.
-Draw your conclusions. 6- Homemade pH indicatorMaterials:
-Cook the cabbage pieces in a pot for 10 minutes.
-Remove from the burner and let stand until cool.
-Strain or filter into a clean container, preferably glass.
-Store the liquid extracted from the purple cabbage, which will serve as a pH indicator. Points to check
-The pH indicator works like this:
(i) For an acidic substance it turns from pink to red.
(ii) If it is a neutral substance, it retains its dark blue colour.
(iii) When tested on an alkaline or basic substance, it turns green. Try different substances
-Acids that are safe to handle: vinegar and lemon juice.
-Homemade bleach or ammonia (wear plastic gloves, do not touch with hands or clothes)
-To do the tests it is useful to make some strips of absorbent paper that are impregnated with the pH indicator.
-Write down in a notebook, sort in descending order, from the most acidic to the most alkaline substances.
Very strong acids and bases can cause burns and irritation to the skin, mucous membranes and eyes. It is advisable to wear plastic gloves throughout the experiment, especially if you have sensitive skin. 7- Extraction and observation of DNAMaterials
-Liquid detergent for washing dishes
-Meat-tenderizing enzymes, such as papaya juice or meat tenderizer powder.
-Ethyl alcohol without dye
-Beaker with graduations
-Elongated glass container or test tube. Procedure
-Place raw chicken liver in the blender glass.
-Add a little water and blend until you get a creamy paste.