Weather And Climate - Section 1 - The Air Around You

Explanation
Oxygen is essential for both the process of combustion and respiration. When oxygen combines with fuel, it supports the chemical reaction that produces heat and light, allowing candles to burn. Additionally, oxygen is necessary for the process of respiration in living organisms, including humans, enabling us to breathe and obtain energy from the food we consume.

Explanation
The correct answer is Nitrogen and Carbon Dioxide. Earth's atmosphere is primarily composed of nitrogen (about 78%) and oxygen (about 21%). However, it also contains trace amounts of other gases, including carbon dioxide, water vapor, and various particles of liquids and solids.

Explanation
The correct answer is 78, 21, 1. This means that nitrogen makes up 78% of the air, oxygen makes up 21% of the air, and the remaining 1% is composed of other gases.

Explanation
Each nitrogen molecule consists of 2 nitrogen atoms. This is because the atomic number of nitrogen is 7, which means that each nitrogen atom has 7 protons in its nucleus. In order to achieve a stable configuration, nitrogen atoms form a covalent bond with each other, sharing a pair of electrons. This results in a molecule with 2 nitrogen atoms bonded together.

Explanation
Plants and animals take oxygen directly from the air and use it to release energy through a process called respiration. Oxygen is essential for the breakdown of glucose molecules in cells, which produces energy in the form of ATP. This process occurs in both plants and animals, allowing them to carry out various physiological functions and sustain life. Neon and argon, on the other hand, are inert gases that do not play a role in energy production or metabolism.

Explanation
Oxygen molecules consist of two oxygen atoms bonded together. This is represented by the chemical formula O2. Therefore, the correct answer is 2.

Explanation
When fuels such as coal and gasoline are burned, they undergo a chemical reaction called combustion. During this process, the carbon present in the fuels combines with oxygen from the air to form carbon dioxide (CO2) as a waste product. Carbon dioxide is a greenhouse gas that contributes to climate change and global warming.

Explanation
A water molecule consists of two hydrogen atoms and one oxygen atom. This is because the chemical formula for water is H2O, which indicates that there are two hydrogen atoms bonded to one oxygen atom.

Explanation
The amount of water vapor can change or fluctuate from one location to another and also from one moment to another. It is not constant and can vary based on factors such as temperature, humidity, and atmospheric conditions. Therefore, the correct answer is "varies".

Explanation
Clouds form when water vapor condenses out of the air to form tiny droplets of liquid. Condensation occurs when warm, moist air rises and cools, causing the water vapor to change from a gas to a liquid state. This process is essential for cloud formation, as the cooled air cannot hold as much moisture, leading to the formation of visible water droplets or ice crystals.

Explanation
Pure air only contains gases, while pure water only contains liquid. Therefore, the correct answer is "Both A and B" because both air and water can exist in a pure form, but air consists of gases and water consists of liquid.

Explanation
Earth's atmosphere contains oxygen, which is essential for the survival of living things. Oxygen is required for the process of respiration, where organisms convert food into energy. It is also involved in the combustion of fuels, which is necessary for various human activities. Moreover, oxygen plays a crucial role in the ozone layer, protecting life on Earth from harmful ultraviolet radiation. Therefore, the presence of oxygen in Earth's atmosphere is vital for the survival of living things.

Explanation
The Earth's atmosphere acts as a shield, protecting living organisms from harmful radiation emitted by the sun. This radiation includes not only UV rays but also other forms of radiation like X-rays and gamma rays. Without the atmosphere, these high-energy radiations would reach the Earth's surface and cause severe damage to living things. Therefore, the correct answer is radiation.