Questions Related to NCERT

Yes, the impact will be different for different trophic levels. Each level plays an important role in the ecosystem.

1. If producers (like plants) are removed, all other levels will die due to lack of food.
2. If primary consumers (like herbivores) are removed, carnivores will not get food, and plants may grow too much.
3. If top consumers are removed, the number of herbivores may increase a lot and harm plant life.

No trophic level can be removed without causing damage. Each level is needed to keep the balance in the ecosystem.

If we kill all the organisms in one trophic level, the food chain will get disturbed.

1. The next level will not get food and may die.
2. The previous level may increase too much and cause imbalance.

So, it will harm the balance of nature and affect the whole ecosystem.

Correct answer: (d) All of the above

Reason: All options help reduce pollution and save resources, making them environment-friendly practices.

Correct answer: (b) Grass, goat and human

Reason: It shows a proper food chain – plant ---->   herbivore ---> human.

Correct answer: (c) Fruit-peels, cake and lime-juice

Reason: All items in option (c) are natural and easily decompose, so they are biodegradable.

Ozone (O₃) is a gas made up of three oxygen atoms. It is found in the upper layer of the atmosphere, called the stratosphere, and forms the ozone layer.

How ozone affects the ecosystem:

1. Protects living beings from harmful UV rays:
        The ozone layer absorbs most of the Sun's ultraviolet (UV) rays, which are harmful to humans, animals, and plants. Without           it, UV rays can cause skin cancer, eye damage, and harm crops.

2. Maintains balance in the ecosystem:
         By blocking harmful radiation, ozone helps protect ecosystems like forests, oceans, and farms, allowing plants and animals           to survive and grow properly.

Two ways in which non-biodegradable substances affect the environment:

1. They cause land and water pollution: - Non-biodegradable substances like plastic and glass do not break down easily. When they are thrown into the environment, they stay there for a long time and pollute the soil and water.

2. They harm animals and plants: -   Animals may eat plastic thinking it is food, which can harm or even kill them. These substances can also block sunlight and air from reaching plants, affecting their growth.

Two ways in which biodegradable substances affect the environment:

1. They make the soil fertile:--  When biodegradable substances like food waste and dead plants break down, they release nutrients into the soil. This helps plants grow better.
2. They can cause pollution if not managed properly:--  If too much biodegradable waste is thrown in one place and left to rot, it can smell bad and attract flies and insects. It can also pollute the land and water around it.

Substances are classified as biodegradable or non-biodegradable based on how they are broken down in nature.

Biodegradable Substances:

These are materials that can be broken down by natural processes, mainly by microorganisms like bacteria and fungi.
Examples: Food waste, paper, wood, cotton.
Reason:- These substances are made from natural materials that microorganisms can easily decompose into simpler, harmless substances.

Non-biodegradable Substances:

These are materials that cannot be broken down by natural processes or take a very long time to decompose.
Examples: Plastic, glass, synthetic fibers, metals.
Reason: -These substances are made from synthetic (man-made) materials or chemicals that microorganisms cannot break down easily. They remain in the environment for a long time and can cause pollution.

Role of Decomposers in the Ecosystem:

Decomposers are organisms like bacteria and fungi that break down the dead bodies of plants and animals into simpler substances.

Their main roles are:

1. Break Down Dead Matter: -  They decompose dead plants, animals, and waste materials.
2. Recycle Nutrients: -  They return important nutrients like nitrogen, carbon, and minerals back to the soil, making it fertile.
3. Maintain Balance in the Ecosystem:-  By cleaning up dead matter and waste, they help keep the environment clean.
4. Support Producers: -  The nutrients they release into the soil are used by plants (producers) to grow.

Trophic Levels:

Trophic levels are the different steps in a food chain. Each step represents a level of feeding or energy transfer in an ecosystem.

Example of a Food Chain:
Grass → Grasshopper → Frog → Snake → Hawk

Trophic Levels in this Food Chain:

1. Grass – Producer (1st trophic level)
2. Grasshopper – Primary consumer (2nd trophic level)
3. Frog – Secondary consumer (3rd trophic level)
4. Snake – Tertiary consumer (4th trophic level)
5. Hawk – Top consumer or quaternary consumer (5th trophic level)

Why copper is used to make hot water tanks and not steel:

Resistance to rust and corrosion:
Steel, which contains iron, easily reacts with water and oxygen to form rust (iron oxide). Rust weakens the steel, making it less durable and unsafe for storing water. Copper, on the other hand, is much more resistant to corrosion and does not rust easily. This means copper tanks last longer and stay safe for water storage.

Better heat conduction:
Copper is an excellent conductor of heat. This means it can quickly and evenly transfer heat to the water inside the tank. This helps in heating the water faster and saves energy. Steel is not as good a conductor, so it heats water more slowly.

Non-toxic and safe:
Copper does not release harmful substances into water, making it safe for storing hot water used for household purposes.

Maintenance and durability:
Because copper does not rust and conducts heat well, copper tanks require less maintenance and have a longer life compared to steel tanks, which may need frequent repairs due to rust.

The man used a strong acid (like aqua regia or a mixture of strong acids) to clean the gold bangles. This solution can dissolve impurities and dirt on the surface, making the bangles sparkle like new.

However, if the bangles were not pure gold but gold-plated or alloyed with cheaper metals, the acid would have dissolved some of the metal along with the impurities, reducing their weight drastically.

So, the solution used was an acid that can dissolve metals, which cleaned the bangles but also dissolved some of the metal, making them lighter.

This is why the bangles shined but lost weight.

Simple difference between metals and non-metals based on their chemical properties:

• Reaction with oxygen: - Metals usually form basic or amphoteric oxides. Non-metals form acidic oxides.
• Reaction with acids:- Metals react with dilute acids to produce hydrogen gas. Non-metals usually do not react with acids.
• Reaction with water:- Some metals like sodium and potassium react with water to form hydroxides and hydrogen gas. Non-metals generally do not react with water.
• Electropositivity:- Metals tend to lose electrons and form positive ions. Non-metals tend to gain or share electrons.
• Reaction with non-metals:- Metals generally form ionic compounds with non-metals. Non-metals usually form covalent compounds with each other.

Lemon or tamarind juice is sour because it contains citric acid or tartaric acid. These acids react with the tarnish on copper vessels, which is mainly copper oxide or copper carbonate.
The acids react with the tarnish, dissolving it and turning it into soluble compounds that can be washed away. This makes the copper vessel clean and shiny again. 

So, the sour substances help remove the layer of tarnish by reacting with it chemically.

(a) Why are platinum, gold, and silver used to make jewellery?

Because they are lustrous, shiny, and do not react easily with air or water. So, they do not rust or tarnish and keep their shine for a long time.

(b) Why are sodium, potassium, and lithium stored under oil?

Because these metals react very quickly with air and water, sometimes catching fire. Storing them under oil stops them from coming in contact with air and moisture.

(c) Why is aluminium, a highly reactive metal, used to make cooking utensils?

Because aluminium forms a thin, tough layer of oxide on its surface which protects it from further reaction. This makes it safe and durable for cooking.

(d) Why are carbonate and sulphide ores usually converted into oxides during extraction?

Because oxides are easier to reduce to the metal in the extraction process, usually by heating with carbon or carbon monoxide.

When non-metals combine with oxygen, they form acidic oxides. 

Example:- 
Carbon + Oxygen    ---------->    Carbon dioxide (CO₂)
CO₂ is an acidic oxide because it dissolves in water to form an acid:
CO₂ + H₂O → H₂CO₃ (carbonic acid)

So, non-metals form acidic oxides when they react with oxygen.

Two simple ways to prevent the rusting of iron:

1. Painting or Coating with Oil/Grease:- This creates a barrier that prevents air and moisture from reaching the iron surface.
2. Galvanization: - This means coating the iron with a thin layer of zinc. Zinc protects the iron by preventing contact with air and water and also acts as a sacrificial metal.

In the electrolytic refining of a metal M:

1. Anode: Impure metal M (this is the metal you want to purify)
2. Cathode: Pure metal M (a thin strip of the same metal)
3. Electrolyte: A solution of a salt of metal M (like M nitrate or M sulfate)

What happens during refining:

• The impure metal at the anode dissolves into the solution.
• Pure metal gets deposited on the cathode.
• Impurities either stay in the solution or settle down as anode mud.

Example with copper:

• Anode: Impure copper
• Cathode: Pure copper
• Electrolyte: Copper sulfate (CuSO₄) solution

Metals that will displace hydrogen from dilute acids:

These are more reactive than hydrogen and can replace it in a chemical reaction.

1. Zinc (Zn)
2. Iron (Fe)

Example reaction:
Zn + 2HCl → ZnCl₂ + H₂↑

Metals that will not displace hydrogen from dilute acids:

These are less reactive than hydrogen and do not react with dilute acids to release hydrogen gas.

1. Copper (Cu)
2. Silver (Ag)

These metals do not react with dilute hydrochloric acid or sulfuric acid under normal condition