Everyday Science

During photosynthesis, plants and trees take in carbon dioxide and release oxygen as a byproduct. Therefore, the gas they give out during photosynthesis is oxygen.

All usable forms of energy eventually degrade into heat energy due to the second law of thermodynamics, which states that energy transformations increase entropy, often releasing energy as heat.

Divers use mixtures of gases as artificial atmospheres to breathe underwater safely. Helium is commonly used as an inert gas to reduce nitrogen narcosis at depth. The other gas used alongside helium is oxygen, not nitrogen. Mixtures like heliox (helium and oxygen) are standard for deep diving to avoid nitrogen narcosis and oxygen toxicity is managed by controlling oxygen partial pressure. Nitrogen is the main inert gas in normal air and nitrox mixtures but is replaced by helium in heliox. Pure oxygen is toxic at depth and carbon monoxide is never used due to its toxicity. Neon is not used in diving gas mixtures. Therefore, the correct answer is oxygen (B).

Sound travels fastest in solids because the particles are more tightly packed, allowing vibrations to transfer more quickly compared to liquids or gases.

A mixture of potassium nitrate, powdered charcoal, and sulphur is known as gunpowder, which is a common explosive and propellant.

The Montgolfier brothers, Joseph-Michel and Jacques-Étienne, are credited with inventing the hot air balloon in the 18th century. They successfully launched the first manned flight in 1783, making option B the correct answer.

PVC stands for Polyvinyl chloride, which is a widely used plastic polymer in the industry. The other options are incorrect chemical names that do not correspond to PVC.

Pyrex glass is a type of borosilicate glass known for its high heat resistance, making it suitable for laboratory glassware and cookware. Other types like bottle glass, flint glass, and hard glass do not have the same level of heat resistance.

Chlorine acts as a bleaching agent primarily through oxidation, where it breaks down colored compounds by oxidizing them, thus removing color.

Epsom salt is the common name for magnesium sulfate, a chemical compound with the formula MgSO4. It is widely used in bath salts and as a laxative.