Olympiad Test: Air And Water-1 - Class 6 MCQ

The pH of pure water is 7. In general, water with a pH lower than 7 is considered acidic, and with a pH greater than 7 is considered basic. The normal range for pH in surface water systems is 6.5 to 8.5, and the pH range for groundwater systems is between 6 to 8.5.

Plants regulate the rate of transpiration by controlling the size of the stomatal apertures. The rate of transpiration is also influenced by the evaporative demand of the atmosphere surrounding the leaf such as boundary layer conductance, humidity, temperature, wind and incident sunlight.

During daylight, photosynthesis is the dominant process as a result amount of O 2 O_2 O2 released during day time is ten times greater than the amount of O 2 O_2 O2 utilized in day time. Because, respiration is more dominant in night time than day time

Given information:

• When water gains heat, it changes into water vapor.
• 1 cm³ of water forms more than 1000 cm³ of water vapor.
• The amount of particles (matter) in water remains the same.

Inferences:
Based on the given information, we can infer or conclude the following:
1. The spacing between the particles increases when water changes into water vapor:

• Water vapor occupies more volume than liquid water, indicating that the particles are spread out more in the vapor phase.
• The conversion of liquid water to water vapor involves the particles gaining energy and moving further apart from each other.

2. Water can exist in three interchangeable states:

• The information states that water changes from its liquid state to the vapor state when it gains heat.
• This suggests that water can exist in three states: solid (ice), liquid (water), and gas (water vapor).
• The ability of water to exist in these three states is due to its unique molecular structure and the presence of hydrogen bonding.

Therefore, the correct inference or conclusion from the given information is option B: 2 only.

Why pure and distilled water is not used for drinking:

1. Availability: Pure and distilled water is not easily available for drinking purposes. It requires specific equipment and processes to obtain pure and distilled water, which are not commonly found in households or easily accessible.
2. Bacterial Contamination: Contrary to common belief, pure and distilled water is not completely free from bacteria. While the distillation process does remove many impurities, including most bacteria and viruses, it is not foolproof. Some bacteria can survive the distillation process, and if the water is not stored properly, it can become contaminated.
3. High Solubility: Pure water has a high solubility, meaning it can dissolve various substances easily. This can be problematic for drinking purposes as it can absorb minerals and other contaminants from the environment, which may not be suitable for consumption.
4. Lack of Essential Minerals: Pure and distilled water lacks essential minerals that are beneficial for our health. These minerals are usually present in tap water or mineral water and provide important nutrients to our body.
5. Potential Toxicity: While pure water itself is not poisonous, consuming large quantities of pure and distilled water over a prolonged period can disrupt the electrolyte balance in our bodies. This can lead to electrolyte imbalances and potentially cause health issues.

Considering these factors, it is recommended to drink filtered or tap water that meets the safety standards and contains essential minerals for overall health and well-being.

Saline solution for intravenous infusion. Saline, also known as saline solution, is a mixture of sodium chloride in water and has a number of uses in medicine. Applied to the affected area it is used to clean wounds, help remove contact lenses, and help with dry eyes. The medical use of saline began around 1831.

All the Plants Require Nitrogen for:
A. Transpiration:

• Nitrogen is not directly involved in the process of transpiration.
• Transpiration is the process by which plants lose water through their leaves, and it is primarily driven by factors such as temperature, humidity, and the presence of stomata.

B. Reproduction:

• Nitrogen is important for the reproductive processes of plants.
• It is involved in the production of proteins and nucleic acids, which are essential for the development of flowers, fruits, and seeds.
• Nitrogen deficiency can lead to poor flower and fruit development, ultimately affecting reproduction.

C. Photosynthesis:

• Nitrogen is crucial for photosynthesis, the process by which plants convert sunlight, water, and carbon dioxide into glucose and oxygen.
• Nitrogen is a key component of chlorophyll, the pigment responsible for capturing sunlight and converting it into chemical energy.
• Without sufficient nitrogen, plants may exhibit chlorosis (yellowing of leaves) and have reduced photosynthetic capacity.

D. Growth:

• Nitrogen is essential for plant growth and development.
• It is a major component of amino acids, which are the building blocks of proteins.
• Proteins are involved in various cellular processes and are essential for cell division, enzyme activity, and the synthesis of new tissues.
• Nitrogen deficiency can lead to stunted growth, reduced leaf size, and overall poor plant development.

To summarize, while nitrogen is not directly involved in transpiration, it plays a vital role in the reproductive processes, photosynthesis, and overall growth of plants.

Present in the air:

• Oxygen is one of the main components of the Earth's atmosphere.
• It makes up about 21% of the air we breathe.

Needed by the human body to produce energy:

• Oxygen is essential for cellular respiration, which is the process by which our cells produce energy.
• During respiration, oxygen is used to break down glucose and other molecules, releasing energy in the form of ATP.

Enters the lungs when breathing in:

• When we inhale, air enters our lungs through the respiratory system.
• The oxygen in the air diffuses into the bloodstream through the alveoli in the lungs, where it binds to hemoglobin in red blood cells.
• The oxygen-rich blood is then pumped to various parts of the body to provide energy.

Therefore, based on the given information, the correct answer is Oxygen (D).

Factors to keep constant for a fair test:

1. Size of the beaker: The size of the beaker can affect the heat distribution and therefore the time taken for the solution to reach boiling point. By keeping the size of the beaker constant, Abhilasha ensures that the heat distribution is consistent across all the solutions.
2. Amount of solution: The amount of solution in each beaker can affect the rate at which it heats up. By keeping the amount of solution constant, Abhilasha ensures that the heat is applied evenly to each solution, allowing for a fair comparison of the time taken to reach boiling point.
3. Starting temperature of the solution: The starting temperature of the solution can affect the time taken to reach boiling point. By keeping the starting temperature constant, Abhilasha eliminates the variable of initial temperature and focuses solely on the time taken for the solutions to boil.
4. Final temperature of the solution: The final temperature of the solution is not necessary to keep constant in order to carry out a fair test. The objective is to compare the time taken for the solutions to reach boiling point, and the final temperature may vary depending on the specific solution.

Therefore, to carry out a fair test in comparing the time taken for different solutions to reach boiling point, Abhilasha must keep the following factors constant: 1. Size of the beaker, 2. Amount of solution, and 3. Starting temperature of the solution. The final temperature of the solution does not need to be kept constant.

Groundwater is the major source of fresh water. It is the water found beneath the Earth's surface in soil pore spaces and in the fractures of rock formations. Groundwater is a crucial source of water for drinking, irrigation, and other uses, especially in areas where surface water like rivers and lakes is not readily available or is polluted.

• Sea-water is salty and not suitable for direct consumption without desalination.
• Lake water can be a source of fresh water, but it is much smaller compared to groundwater reserves.
• None of the above is incorrect because groundwater is indeed the major source of fresh water.

The water cycle, also known as the hydrological cycle, is powered by the sun's energy. Here's why each option is evaluated as true or false:

• A: Rain drops falling into the sea do not contain salt. Rainwater is generally fresh, as it is formed from the evaporation of water, which leaves salts and impurities behind.
• B: The energy for the water cycle comes from the sun, which drives the processes of evaporation, condensation, and precipitation.
• C: Clouds are not water in the gaseous state, but rather collections of tiny water droplets or ice crystals suspended in the air. Water vapour is the gaseous state, and clouds form when this vapour condenses.
• D: Water does not condense to form water vapour. Water vapour is formed through evaporation or transpiration. Condensation is the process by which water vapour changes back into liquid water.

Thus, the correct answer is B) The energy for the water cycle comes from the sun.

Water Harvesting

It means storing rain where it falls or storing the run off in your own village or town. And taking measures to keep that water clean by not allowing polluting activities to take place in our locality.

It can be done by two major processes:

1. Rainwater harvesting: It is a method of collection and storage of rainwater into natural reservoirs or tanks or the infiltration of surface water into subsurface aquifers.

2. Groundwater harvesting : Groundwater harvesting is a method to save water placed under the ground to control the groundwater flow in an aquifer and to raise the water table.

When water freezes:

1. State: The state of water changes from liquid to solid (ice).
2. Volume: Water expands as it freezes, so its volume increases. This is why ice floats on water.
3. Temperature: The temperature decreases as water freezes, typically at 0°C (32°F) under normal conditions.

Mass remains constant during freezing. The mass of the water does not change, it simply transitions from liquid to solid state.

Thus, the correct answer is B) 1, 3 and 4.

It is because the groundwater is continuously used. Also rainfall occurs for short spells of high intensity. Because of such intensities and short duration of heavy rains, most of the rain falling on the land flows away rapidly, leaving very little water for the recharge of underground water. 

Oceans play an important role in supplying the water that we use. Oceans provide evaporated water to the water cycle and it is the most important source of water vapor in the water cycle. Oceans are the storehouse of water in nature and run the water cycle.
Hence, option B is correct.

Rainwater harvesting cannot be practiced in bathroom as the bathroom is a closed area and rain water cannot directly come into it. Playgrounds and rooftops are open areas and rainwater directly falls on them. In these areas, we can practice rainwater harvesting.

The water vapour in the air comes from multiple sources:

• A: Sweat from animals evaporates due to heat, contributing to the moisture in the air.
• B: The evaporation of water from oceans, rivers, lakes, and streams adds water vapour to the atmosphere.
• C: Water vapours are also released by plants through their leaves during the process of transpiration.

All these processes contribute to the presence of water vapour in the air, so the correct answer is D) All of the above.

In general, water harvesting is the activity of the direct collection of rainwater. The rainwater collected can be stored for direct use or can be recharged into the groundwater. Rain is the first form of water that we know in the hydrological cycle, hence is a primary source of water for us. It is also the infiltration of surface water into subsurface aquifers (before it is lost as surface runoff). 

Hence, option D is correct.

Hard water, water that contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates. Water hardness that is caused by calcium bicarbonate is known as temporary, because boiling converts the bicarbonate to the insoluble carbonate; hardness from the other salts is called permanent.

Region having low annual rainfall and large population can suffer from water scarcity because of overuse of water resources. Region having high annual rainfall but water is highly polluted also suffers from water scarcity because polluted water is unusable for humans.