When zinc and hydrochloric acid react, they produce an effervescent known as hydrogen. This gas causes the substance to fizz, and oxidation-reduction occurs.

When copper sulfate and iron react, the copper is displaced from the solution and ferrous sulfate is produced, which causes the substance to turn green, though copper sulfate is a blue solution.

The products of copper and nitric acid include a red-brown nitrogen dioxide gas and a hot, concentrated solution of copper nitrate, which turns blue. These color changes are results of the bonds of the reactants rearranging to produce these new substances.

When magnesium is dropped into water, there is no apparent reaction until the substance is heated. Then, magnesium hydroxide is produced, which allows the product to turn light purple after being heated for a period of time.

When limestone and hydrochloric acid make contact, they undergo a reaction in which bubbles of carbon dioxide are released. Therefore, fizzing occurs because the carbon dioxide must be released.

When sugar is subjected to heat, the bonds weaken and the substance breaks down into carbon and water vapor. Additionally, caramelization occurs, which is why a strong, sweet scent is produced.

When chlorine gas and sodium metal react, table salt is ultimately produced. This is because chlorine, which has seven valence electrons, takes one of sodium's electrons from its outer shell so that it can have a full outer shell. This ionic bond leaves sodium with only one valence electron.

When magnesium is heated and it reacts with the oxygen in the air, magnesium oxide is created. This is because oxygen, which has six valence electrons, takes magnesium's two valence electrons, therefore filling it's shells.

When sodium chloride and silver nitrate react, a precipitate of silver chloride forms in the liquid. This is due to the solid (AgCl) being insoluble in the liquid.

When silver nitrate and potassium chloride are combined, a white, solid precipitate called silver chloride is observed. Additionally, potassium nitrate is produced in this reaction. The reason for the precipitate forming is because there is an insoluble substance that forms.

When you combine magnesium sulfate, sodium carbonate, and water, particles of a white solid form. This is called a precipitate, and it forms because there is an insoluble ionic solid that forms in the solution. Magnesium carbonate and sodium sulfate are produced.

The combination of calcium chloride and baking soda in water produces heat. This is because excess energy is produced due to some bonds requiring less energy to break than others in the solution. Because there is energy being released, this is an exothermic reaction. The temperature of the solution increases from about 20°C to about 45°C. Carbon dioxide gas is produced and a white cloudy precipitate, calcium carbonate, is formed.

When sodium hydroxide and water mix, the products warms up because the substance is giving off energy to its surroundings. This is called an exothermic reaction.

When steel wool, which is made prominently of iron, is exposed to both water and oxygen, it produces rust after a period of time. This chemical reaction is a result of oxidation.

When given enough time, match heads and ammonia begin to chemically combine, therefore producing ammonium sulfide, which has a very strong, disgusting smell.

When sodium metal and water react, they produce hydrogen gas. Sodium has a lower density than water, so when the jets of hydrogen are produced, they caused the substance to swerve around until so much energy and heat is produced that, oftentimes, an explosion occurs. This is an exothermic reaction.