General everyday-science
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Short Questions & Answers of General Science

Best notes for short questions & answers of General Science / Everyday Science are available here which is useful for all defence forces tests. Particularly, for the admission in cadet colleges. These questions also helps in all jobs of  Pak Forces. 

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Short Answers of General Science (Part-1) 

Q. Define Fertilization and explain it in flowering plants?



  • The process of fusion of sperm with the egg is called Fertilization.

Pollen tube formation:  

  • Pollen grains stick to the stigma of carpal. A pollen tube grows downward from each pollen grain. The nucleus of the pollen tube is divided to form two sperms and one tube nucleus. Pollen tube passes through style and reaches the ovule in the ovary. It releases its sperms into the ovule. One sperm fuse with the egg to form a zygote. The second sperm combines with the nucleus of the ovule to form a tissue that stores the food. This type of fusion is called double Fertilization. After Fertilization, several changes take place in the flower. The sepal, petal, and stamen dry up and fall off. The fertilized egg inside the ovary develops into an embryo. Ovules become a seed.


  • The ovary grows large and develops into a fruit. The fruit protects the seed or seeds.

Q. Define seed and fruit.


  • Ovule:   An unripened ovule is called a seed. The seed protects the embryo inside it. Embryo produces new plants.
  • Fruit: The ripened ovary is called fruit. It protects the seed. It helps in the dispersal of seeds.

Q. Explain the structure of the seed?



  • After Fertilization, an ovule becomes a seed. A tough seed coat covers the embryo and its food store. The most important part of a seed is its embryo. The embryo grows into a new plant. The embryo consists of the following parts.


  • This part of the embryo develops into the first root of the new plant


  • This part of the embryo develops into the new plant’s first shoot (stem).


  • This part of the embryo supplies food to the growing young plants.

Q. Write a note on fruit?


  • The ripened ovary is called fruit. The ovary wall forms the fruit wall, which is called the pericarp. The fruits like mangoes contain a single seed, and fruits like watermelon contain many seeds.


  • The wall of the fruit is called a pericarp. It is composed of three layers in most fruits like peaches and mangoes. The outer layer is skin, the middle layer is fleshy, and the inner layer is tough. Some fruit had hard and dry pericarp, e.g., nuts.

Q. What helps the pollen grain stay on the tip of the style after they land there?


  • The stigma of the carpal is sticky. It helps the pollen grains to stay on the tip of the carpal.

Q. Grasses do not have bright-colored flowers. How might this be related to the way these plants are pollinated?


  • The grasses are pollinated by wind or water.

Q. The papaya plant has male and female parts on separate plants. Why is a lonely papaya tree hard to see with fruit?


  • For sexual reproduction, the male and female plants should be side by side. The alone plant can produce only one type of gametes, male or female. So lonely plants cannot reproduce.

Q. Which fruits are eaten as a vegetable?


  • Tomato ,Bingil ,ladyfinger.

Short Answers of General Science (Part-2) 

Q. Define reproduction?


  • Reproduction is a process in which organisms produce new organisms ( off-springs ) like themselves.

Q. How many parts does a flower have? Write their names?


A flower has four parts:

  1. Sepals
  2. Petals
  3. Stamens
  4. Carpals

Q. Differentiate between sepals and petals.



  • Sepals have a green color like a leaf.
  • Sepals protect a flower from sun rain when it is in bud form.


  • Bright color petals are present inside the sepals.
  • A petal attracts insects and animals for the pollination of pollen grains.

Q. Define stamen?


  • The male part of a flower is called the stamen. A stamen has two main parts another and filament. Anther produces pollen grains.

Q. What is a carpel?


  • The female part of a flower is called a carpel. A carpel has three prominent parts stigma, style, and ovary. Ovules are present in the ovary.

Q. Define pollination?


  • Pollination is the transfer of pollen grains from the anther to the stigma.

Q. Write the importance of pollination?


  • The male sex cell (sperms) reaches the female sex cell (eggs) by pollination. The pollen grains are transferred from one flower to another. 

Q. What are gametes?


  • Sex cells are called gametes. Such as male sex cells (sperms) and female sex cells (eggs) are collectively called gametes.

 Q. By which method are pollen grains transferred?


  • Various methods transfer pollen grains. Such as by the wind, water, insects and animals, etc.

Q. Define self-pollination?


  • The transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower on the same plant is called self-pollination, i.e., pea, tomato, etc.

Q. Define cross-pollination?


  • The transfer of pollen grains from the anther of a flower to the stigma of a flower on another plant of the same kind is called cross-pollination, i.e., poplar, willow, apple, etc.

Q. What are the characteristics of cross-pollination?


  • For cross-pollination, the plants must grow flowers at the same time. Cross-pollination usually happens in a plant near each other.

Q. Write advantages of cross-pollination.


  • Cross-pollination produces stronger plants as compared to self-pollination. Some flowers have special features that favor cross-pollination, e.g., colored petals and long and sticky stigmas.

Q. Define pollinators.


  • The agents of pollination are called pollinators, which are wind, water, birds, insects, etc.

Q. How are pollen grains dispersed through the wind?


  • Pollen grains have feathers and hair-like structures that help them blow from one flower to the other.

Q. How are animals useful in pollination?


  • Insects and other animals can transfer pollen grains which they move or fly through the flowers. The bright colors of petals, nectar juice, and pleasant fragrance attract animals to the flowers.

Q. How are pollen grains dispersed through water?


  • Pollination by wind, pollen grains move slowly along the water currents and reach other aquatic animals.

Q. Bees help in pollination. How?


  • Some pollen grains are sticky when honey bees visit flowers for food. They stick to the body of bees. In such a way, bees help in pollination.

Q. How do plants reproduce?


  • Plants reproduce themselves in two ways:
      1. Flowering plants reproduce by seed
      2. Non-flowering plants reproduce by spores. 

Short Answers of General Science (Part-3) 

Q. Define Asexual reproduction?


  • When a cell from only one parent develops into offspring’s is called asexual reproduction.

Q. What is meant by ecosystem?


  • Living organisms and nonliving things interact to form a system called an ecosystem.
  • The size of the ecosystem is different. A large ecosystem like a desert and a small ecosystem a decaying log. Deserts, rivers, mountains, oceans, grasslands, and forests are some ecosystems. The ecosystem is self-sufficient.
  • The ecosystem may consist of two parts:
        1. Living organism or biotic factors.
        2. Non-living things or Abiotic factors.

Q. Describe parts of the ecosystem or explain biotic and Abiotic factors.


  • There are two parts of an ecosystem. Biotic or living part and Abiotic or non-living part.

Biotic components

  • Plants, animals, fungi, and microorganisms are biotic factors or biotic parts of an ecosystem.

1. Population: 

  • The organism of the same kind living and reproducing in a particular area is called population.

2. Community:

  • All the populations of different organisms living together in an area make a community.
      • Plants:      Plants are the producers of the ecosystem.
      • Animals:    Animals are the consumers of the ecosystem.
      • Fungi and Microorganism:     Fungi and Microorganism act as a decomposer.

Q. Define habitat?

Ans: Habitat:

  • The place where an animal or plant lives and reproduces is called its habitat. Habitat provides the things an organism needs, i.e., food, water, shelter, etc., many populations of organisms live in each habitat.

Q. What is a habitat? Describes any habitat.



  • The place where organisms live and reproduce is called the habitat.

Following are the kinds of habitats:

Grassland habitat:

  • The grassy, windy, partly dry area. The soil here is very fertile. They receive a medium amount of rain. So they have good grasslands for grazing. Grazing animals like sheep, goats, cows, antipopes, and dear are a few examples found in a grassland. Flesh eaters like cheetahs, foxes, wolves, and a few birds like owls, eagles, hawks, etc., are also found in this habitat. Lots of kinds of insects are also found here.

Q. What is pond habitat? Explain it?


The pond habitat:

  • A pond is an aquatic habitat that is rich in life. Plants like algae, duckweed, water lily, etc., are found in water. The animals like fishes, ponds, skaters, wolf spiders, snails, and microscopic organisms are also found in the pond habitat.

Q. What is desert habitat explained?


  • Deserts are dry where is less annual rainfall than average. Mostly leafless plants are found there like cactus, bushes, etc. The animals have to think of scaly skin like snakes, lizards, and other reptiles.

Q . Describe factors that cause a change in habitat and population size?


  • Light, Temperature, air, soil, and water are abiotic factors of the environment. Changes in these conditions will bring changes in the population of the environment.


  • It is the primary source of energy. Plants use solar energy to make their food. This food is the source of energy for all other living things. Light intensity affects the number of plants in a habitat. Decreases in the number of plants may result in the decrease of animals in the same habitat.


  • Any abrupt and extraordinary change in Temperature may disturb the habitat. For example, warm water contains less oxygen.


  • It is an essential factor in life. More the water in an area, more organisms will be there. Water changes will change the habitat greatly.


  • Migration also changes the size of the pollution of a habitat. When few organisms leave the habitat or enter a habitat, that will increase or decrease the size of that area’s population.

Natural disaster:

  • Natural disasters such as droughts, floods, and earthquakes can bring changes in habitat.

Q. Enlist the natural disaster and Explain them.


  • Natural disasters such as droughts, floods, earthquakes, etc.


  • It is a period when there is no rainfall for a long time in the area. The water of ponds and streams dry up in the drought. Pond plants and animals die or migrate to other ponds. Some crops do not grow in the affected area.


  • A Lots of rain in an area for a long time will result in a flood. Many plants and animals die due to flooding. Crops vanish, and diseases are produced there.


  • Lightning strikes a tree in a forest and causes the first in the forest. Plants and trees are burned and destroyed. Few animals die, and few migrate to other places.


  • The sudden shocks to the earth’s surface due to the movement of earth plates are called earthquakes. It changes the habitat quickly. On 8 October 2005, massive earthquakes damaged a widespread area in Pakistan. Over 70000 people lost their lives. A large number of animals and plants were destroyed.

Q. How the people change their habitat? Explain.


  • Human activities are a big source of change o0f habitat. On changing the habitat, the organisms made die or leave the habitat.


  • It is important for human survival. People cut the forest to clear the land for crops cultivation. They also cut down the trees to get wood, paper, wood, or timber.


  • Pollution is another agent that brings changes in the habitat. Pollution harms the land, water, and air. It is harmful to people, animals, and plants.
  • Land pollution affects the land, destroying life, the environment, and its habitat. Air pollution affects the air in which we breathe. Air pollination-causing agents are factories, motor vehicles, and other combusting agents. It damages health and the environment.

Short Answers of General Science (Part-4) 

Q. Describe how we can protect our environment?


  • Everyone can help to protect the habitat by saving resources. Reducing, reusing, and recycling are three ways to save resources and protect the ecosystem.
  • Reduce means to cut down on the use of resources.
  • Reuse means not throwing away things that can be used again.
  • Recycling means making new things from the used material.

Q. What are the adaptations of organisms to live in a habitat?


  • Plants and animals develop special features to live in a habitat. Those special features are called adaptation.

Type of adaptation:

    1. Change in organism’s body.
    2. Change in organism’s behavior.
    3. Change in their defense habits.

Q. Explain the adaptation for aquatic life.


  • Animals and plants have special body parts that help them to live in water.

Streamlined body:    

  • The special adaptation which helps the organisms to swim is the streamlined body.

2. Webbed feed: 

  • Some animals like seagulls, ducks, and frogs have webbed feet. These feet work like ores and help to move in the water.

3. Lettuce of plant body:

  • Hyacinth, duckweed, and water lettuce have floating leaves and submerged roots. There are airspaces in their body. These leaves also have waxy layers.

Q. Adaptation for the land habitat. Explain them. 


  • Animals and plants living in inland habitats have the following adaptations.

1. FUR and feathers

  • The arctic fox and polar bear have thick fur on their bodies. This thick fur keeps the body of these animals warms in the cold. The snowy owl has a thick coat of feathers that keep its body warm.

2. Adaptation for aquatic life:

  • Plants and animals of deserts have adaptations for living in the scorching heat. Desert plants have tough, thick surfaces. They have thin spiny leaves to reduce water loss from their body.
  • Most animals converse water by living underground during the day and coming out at night, e.g., lizards, jackrabbits.
  • Camel’s feet and large stomach help it to live in the desert.

3. Sounds of the animals:

  • Animals and birds receive messages by using sounds.

4. Tall stem and thin leaves: 

  • Trees in the rainforest grow very tall to get sunlight.

Q. Define and explain producers and consumers.



  • Energy is the basic need for the living organism. The primary source of energy is sunlight. Plants use this sunlight and make food. Thus plants are called producers. The energy flow from producers to other animals.


  • Animals cannot make their food. The source of food for the plants. They eat plants or animals which feed on plants. These animals are called a consumer. They have the following types: 

1. Herbivores:

  • The animals that directly feed on plants are called herbivores. Or primary consumer.

2. Carnivores:

  • The animals which eat flesh are called carnivores.

3. Omnivores:

  • The animals which feed on both animals and plants are called omnivores.

4. Secondary consumers:

  • The animals which feed on herbivores are called secondary consumers.

Q. What is a food chain?


  • The feeding relationship between organisms is called a food chain.
  • Food chains start with producers
        • 1 Food chain- Grass >>> 
        • Zebra >>> Lion
        • 2 Food chain- Leaves >>> 
        • Caterpillar >>> Bird >>> Hawk
  • In the above food chain, grass and leaves are producers. Zebra and caterpillar are primary and herbivores: lion and bird are carnivores and secondary consumers.

Examples of the food chain:

    1. In a grassland habitat, a grasshopper eats grass. A snake may eat this grasshopper. This snake may become the food of the hawk.
    2. Algae are the producers in this seafood chain, while others are consumers.

Q. Explain the food web?


  • All the food chains in the ecosystem overlap to form a network called the food web. Following are the examples of the food web:
  • Example 1: A lion feeds goat, jackal, dear, etc. jackal feeds goat and rabbit. Goat rabbit, and dear eat plants. Lion and jackal are involved in two food chains. These three kinds of food chains are from the food web.
  • Example 2:  A snake does not feed alone on a frog. It also eats rats, birds, and even rabbits. Birds eat grains. They also eat insects, spiders, and worms. If we arrange food chains in an ecosystem, it takes the form of a web.

Short Answers of General Science (Part-5) 

Q. What is meant by decomposer?



  • Bacteria and fungi are decomposers. They break down the dead bodies of plants and animals into simpler substances. These substances mix with soil and again are available to green plants to make their food. Without decomposers, recycling nutrients is impossible.

Q. Explain why a limited plant and animal life is found in deserts?


  • Deserts have less rain, and water supply, so fewer plants and fewer animals will be.

Q. How is the sun important to the food supply of an ecosystem?


  • Sunlight is necessary for food formation in plants, so a change in the intensity of sunlight will change the quantity of food formation.

Q. Two kinds of birds live in the same tree. Kind A eats ants that live in the tree. Kind B eats ants and caterpillars. Which species is more likely to survive if the ant’s population decreases? Why?


  • Kinds B eats ants and caterpillars. It will eat caterpillars only and survive if ants decrease.

Q. All the plants and animals of an aquatic habitat will find difficulty in living in other habitats? Why?


  • Plant and animals have aquatic adaptation, which only assists them in living in water but not outside the water.

Q. Even though secondary consumers do not eat plants, how are plants important to their food supply?


  • Secondary consumers eat primary consumers. Primary consumers eat plants that become the food of secondary consumers.

Q. What will happen to all food web animals if green plants are removed?


  • Green plants are the primary source of food. If the primary source is removed, then all animals die.

Q. Which factor causes a change in a habitat?


  • Light, temperature, air, soil, and water are biotic factors of the environment. Changes in these factors will bright change the population of the environment.

Q. How does Migration affect the habitat?


  • Migration also changes the size of the population of a habitat when few organisms leave the habitat or enter into a habitat that will increase or decrease the size of the population in that area.

Q. What are the causes of floods?


  • A loss of rain in an area for a long time will result in a flood. Many plants and animals die due to flooding.

Q. What are the physical properties of water?


  • The most common compound on earth is water. 71% of the earth is covered with water. Its physical properties are:
    1. Its M.P. and B.P. are 0Oc and 100oC, respectively.
    2. It exists in three physical states gas, liquid and solid.
    3. The temperature at which it converts into ice is called its freezing point.

Q. Water molecule is made up of which atoms?


  • A water molecule is formed by joining two elements together. A water molecule has three atoms. Two hydrogens (H) and one oxygen (O). a single drop of water contains billions of water molecules.

Q. How water is our life? Explain.



  • All living things need water to survive. Green plants need water to make food during photosynthesis. Some animals and plants only live in water. Aquatic animals use oxygen which is dissolved in water. Aquatic plants use carbon dioxide dissolved in water.

Human body:

  • Two third of the human body is made up of water. It helps to digest food and to remove waste products from our bodies. It keeps our body cool in hot weather by sweating.

Q. Describe the main sources of water?


  • Water is present above the surface and below the surface.

(a)    Surface-water: surface water is of two types.

1. Ocean water 2.   Freshwater

(b) Water beneath the surface.

Q. Explain the percentage of surface water and what are its types?


  • 97% of the surface water is in the, and 3% is freshwater present on the surface, air, and ground.

Ocean water:

  • Ocean water has dissolved gasses and salts in it.


  • Nitrogen, oxygen, and carbon dioxide are major dissolved gasses in ocean water.


  • The major dissolved salts are sodium chloride, magnesium chloride, magnesium sulfate, etc. sodium chloride is more abundant. It is not used for drinking because it has many dissolved salts in it.


  • The water on the land is called freshwater. Freshwater is mostly found in frozen states on-mountain in the form of a glacier. Snow makes ice sheets on the mountain. These ice sheets are called a glacier.

1. Wetlands: The water in streams, rivers, lakes, and ponds is also freshwater. Water stays for a part of the year and makes the lower ground wet. Such places are called wetlands pugri, kur, and kharkr are a few wetlands in Sindh province. The wetland’s water moves down into the soil and becomes a part of the groundwater.

Q. What is meant by water beneath the surface of the earth? Explain.



  • The water that soaks into the ground is called groundwater.

Water table:

  • The top level of groundwater in an aquifer is the water table. The level of the water table changes during the year. It rises in the rain and lowers in the drought. Peoples Dig wells to bring groundwater to the surface.

Q. Describe water pollution and water pollutants briefly.


Pollution :

  • The addition of harmful substances in the water is called water pollution.


  • Harmful and unwanted substances in the water are called pollutants.
  • Pollutants are classified into the following:

1. Microorganism:

  • Bacteria, viruses, and other microorganisms are disease-causing pollutants.

2. Chemicals:

  • Acids, salts, etc., are water-soluble pollutants. These pollutants increase the growth of algae in the water. The algae on the upper surface of water blocks the sunlight .aquatic plants cannot make their food, and they die.

3. Rages:

  • Plastic, oils, and pesticides are harmful to plants and animals in the water.

Short Answers of General Science (Part-6) 

Q. What are the sources of water pollution?


  • The three major sources of water pollution are human wastes, industrial wastes, and chemical runoff.

Human wastes:    

  • People release sewage into drains which carry it to the river. Sewage from houses contains fat, toilet wastes, food particles, detergents, etc . these human wastes cause disease in human beings and destroy aquatic life.

Industrial wastes:

  • Industries release many toxic chemicals into rivers, and canals smoke and toxic gasses from industries also cause the rainwater to become acid rain. These chemicals can kill fish and other aquatic animals and plants.


  • Farmers use fertilization and pesticides in their crops. The rainwater carries these chemicals to water resources and causes water pollution. This polluted water is not fit for aquatic plants and animals.

Q. What is meant by soft and hard water?


Soft water:

  • The water which gives more lather with soap is called soft water. Soft water is used in houses.

Hard water:

  • The water that does not give much lather is called hard water.sea water is hard water. When chloride, sulfate, or bicarbonates of calcium and magnesium are dissolved in water, they become hard water.

Q. Define purification of water? 


Purification of water:

  • Removing germs, dirt, salts, and other impurities from the water are called the purification of water.

Q. Describe the process of filtration for the purification of water.



  • We can purify water by this method on a small scale in the laboratory. Impure water bus passed through a filter paper.
  • Suspended particles and insoluble salts are left on the filter paper, whereas clear water is obtained in the beaker.
  • To remove dissolved substances present in the water, special membranes can be used. These membranes have microscopic pores to separate dissolved substances from water.

Q. Explain the purification of water by boiling and chlorination.


By Boiling:  

  • The safest way to purify the water is by boiling it. Bacteria, germs, and other microorganisms present in the water are killed by boiling for 15 to 30 minutes.

By Chlorination:

  • Household bleach s used to purify the water. Bleach contains chlorine which kills the microorganisms by producing atomic oxygen.

Q. Write cleaning of water by potassium (phatkurri).


Add powder potassium to the after to purify it. It will settle down the impurities like clay, sand, or other suspended impurities. Water will be pure by decantation.

Q. What is the process of distillation?



The water is heated to convert to steam, then steam is cooled down into liquid water, called distilled water, and the process is called distillation.


Water is boiled in a closed container like a flask. The vapors of water are passed through a pipe called a condenser. The condenser comprises a small inner tube and an outer large tube-like jacket. The vapors pass through the inner tube, and water flows through the outer tube. This water-cooled down the steam into liquid water called distilled water. This water is collected in a beaker or container. Solid impurities remain in the flask.

Q. What are the uses of water?


  • Following are the uses of water:

1. In homes:

  • In homes, the water is used for drinking, cleaning, brushing the teeth, flushing the toilet, cooking, and drinking. Most of the water is used in their kitchen and bathrooms.

2. In Agriculture:

  • The plant needs water to grow. 80% of our freshwater is used in fields to grow crops and vegetables.

3. In Industries:

  • There are different ways to use water in industries. Water is used as raw material in the beverage and food industries. Factories use water to clean and wash the metal surface.

Q. How is water used as a source of energy?


  • Water is used to produce hydroelectricity. The potential energy of the water is used to move the propellers of turbines. Then turbines run generators which produce electricity. That is called hydroelectricity. Five major and several small hydroelectric projects are working in Pakistan.

Q. Explain the methods to conserve the water.


  • There is only a limited amount of freshwater that we can use. We can save water by acting upon the following tips:
  • Turn off the tap when you brush your teeth or take water in a tumbler.
  • Wash fruits and vegetables in a bowl.
  • Don’t wash dishes under running water.
  • Only use a washing machine with a full load.
  • Check regularly the leaks in water pipes, and get them repaired immediately.

Q. How does water help us to live?


  • All the body’s chemical reactions take place in the water. These reactions produce energy to do life functions.

Q. What is spring or geyser?


  • In some places, the water table rises and reaches near the soil’s surface. This water may come out in the form of a spring or geyser. Several natural springs are found in Nathia Gali.

Q. You are hiking, and you are thirsty. Would you drink water from a stream?


  • The water of the streams comes from glaciers. On the way, it may get many impurities in its dissolves form. So we cannot drink it.

Q. What do you mean by wetland?


  • Water stays for a part of the year and makes the low ground wet. Such places are called wetlands. Puri, kurandkhar K.R. are a few wet places in Sindh province.

Q. How does the water table level change during the year?


  • The level of the water table changes during the year. It rises in the 5rains and lowers in the drought. People dig wells to bring groundwater to the surface.

Q. How do pollutants help in the growth of algae.


  • Acids and salts are water-soluble pollutants that help in the growth of algae. The algae on the upper surface of the water block the sunlight. Aquatic plants cannot make their food. They die.

Q. How do fertilizers cause water pollution?


  • Farmers use fertilizers in their crops. The rainwater carries these chemicals to water resources and causes water pollution.

Q. Define atom. 


  • The smallest particle of matter cannot exist independently. Everything in the universe is made up of atoms.

Q. What is the structure of the atom?


  • An atom comprises small particles called electrons, protons, and neutrons.
  • Atoms have mainly two parts:


  • Proton has a positive charge. The number of protons in an atom is always equal to the number of electrons. Its mass is 1837 times greater than that of the electron.


  • Neutrons has no charge on it. It is also present in the nucleus. The mass of neutrons is almost equal to the mass of a proton.


  • Electrons revolve around the nucleus on the circular path called an orbit. Electrons have a negative charge on them. Its mass is extremely small.

Short Answers of General Science (Part-7) 

Q. Why is the atom a neutral particle?


  • Electrons and protons in an atom have changed, but the atom as a whole has no charge. In an atom, the number of protons equals the number of electrons. As a result, the total positive charge of the positive charge of protons balances the total negative charge of electrons. Because of it, the atom is neutral.  

Q. Define and Explain atomic number and mass number.


Atomic number:

  • The number of protons present in the nucleus of an atom is called the atomic number. It is represented by z. hydrogen has one proton in the nucleus, so its atomic number is one. Carbon has six protons, so the atomic number is six. Oxygen has eight protons, so its atomic number is eight. We can identify the elements by knowing their atomic number.

Mass number or atomic mass:

  • The sum of neutrons and protons in the nucleus is the mass number. It is represented by a. hydrogen has only one proton in the nucleus, so its mass number is one. Carbon has six protons and six neutrons, so its mass number is twelve. 

Calculation of neutron:

  • The atomic number is equal to the number of protons, and the mass number is equal to the sum of neutrons and protons. 
      • Mass number (A)= number of protons(z)+number of neutrons
      • So number o neutrons = A-Z
      • For example: for oxygen
      • Mass number =16 ,atomic number=18
      • Proton=8, electron=8,neutron=16-5=8

Q. Define shells and explain the distribution of electrons in shells.



  • The paths of the movement of electrons around the nucleus are called shells. Shells are also called energy levels. The shells are labeled as K, L, M, N, O, P, Q, etc. K is the first shell, L shell has the second shell, and so on
  • We can calculate the number of electrons in a shell by 2n2: “n” is the number of shells.

Q. Why do we combine atoms?


  • Atoms combine each other to become stable by completing their outermost shell. Their outermost shell is completed by eight electrons in the outer shell or 2 electrons of the atom, which has only one k-shell.
  • To complete eight electrons in the outer shell, the atom will lose, gain or share its electrons with other atoms.


  • Two hydrogen atoms combine to form a hydrogen molecule (H2) BY Sharing electrons.

                                     H + H = H2

Q. Define Valency, for example.



  • The capacity of an atom to combine eighth other atoms is called valiancy.
  • For example, sodium “Na” loses one electron, its valiancy is +1, fluorine (F) gains one electron, its valiancy is -1, hydrogen (h) shares one electron, so its valiancy is 1, copper, magnesium lose two electrons and oxygen gains two electrons, so their valiancy is 2, valiancy of aluminum and nitrogen is 3, and the valiancy of carbon is 4.

Q.     Define ions and explain their types?



  • An atom with a positive or negative charge is called an ion, e.g., sodium ion Na+, chlorine ion Cl-, oxide O₂-, copper ion Cu₂+, etc.

There are two types of ions:

1. Cations:

  • When an atom releases one or more electrons from its outermost shell, the number of protons becomes greater than the number of electrons. It becomes a positive ion or cation.

2. Anions:

  • When an atom absorbs one r more than one electron, the number of electrons increases. It became a negative ion or anion.

Some common ions

  • Cations
  • Anions

Q. Explain how NaCl is formed?


Transfer of Transfers


1.   One electron transfers from the sodium atom to the chlorine atom. The sodium atom has 1 electron in its outermost shell. A chlorine atom has 7 electrons in its outermost shell.

Na. →Cl.

2. After losing one electron, the sodium atom becomes a sodium ion (Na+). the chlorine atom gains one electron to become a chloride ion( Cl-) 

+Na Cl

Sodium-ion Chloride ion 

Combining’s of ions:

3. Negative and positive ions attract each other to form sodium chloride (NaCl).     

Q. Define isotopes? Why isotopes are formed. Explain with examples.



  • The atom of the same elements having the same atomic number but different mass numbers are called isotopes. Isotopes are a different number of neutrons. Hydrogen (H) has three isotopes. An atom of hydrogen may have zero, one, or two neutrons in its nucleus. Protium (H), Deuterium(H), and tritium(h) are three types of hydrogen.
  • Hydrogen has three naturally occurring isotopes.

Q. Explain the uses of isotopes?


  • Isotopes are of great importance in the fields of medicine and agriculture.
      1. Carbon 14 can be used to calculate the age of plants.
      2. Nitrogen-15 can be used to study the effects of nitrogenous fertilizers in plants.
      3. Sodium-24 can be used to study the circulation of blood.
      4. Phosphorus-32 can be used to treat blood cancer and bone diseases.
      5. Chromium-51 can study red blood cells in patients with blood deficiency.
      6. Iron-59 can be used to study iron absorption in the human body.
      7. Cobalt-60 can be used in cancer treatment.
      8. Iodine-131 can be used to treat a disease called goiter.

Q. Define molecule, and give some examples of molecules.



  • The smallest particle of an element or a compound that can exist independently and shows all the properties of that element or compound is called a molecule.

Monoatomic molecule:

  • The molecule is formed by one atom, e.g., helium (He), Neon(Ne), Argon(Ar), etc.

Polyatomic molecule:

  • The molecule formed by three or more atoms is called a polyatomic molecule.
  • e.g., H₂O water, CO₂ carbon dioxide, C₆H₁₂O₆ glucose.

Q. Define and explain the chemical formula?


Chemical formula:

  • Representation of an element or compound with the help of symbols according to their valences is called chemical formula. 

Properties of the chemical formula:

  • 1. It shows the kinds of elements in the molecules. 
  • 2. It shows the number of atoms of each element.


  • 1. H₂ represents a molecule f hydrogen gas. Hydrogen molecule (H₂)
  • 2. CO₂ represents carbon dioxide, Carbon dioxide molecule (CO₂)

Q. Describe the process of writing chemical formulas?


Writing of chemical formula comprises of following steps:

  • 1. Write the symbols of all the elements present in the molecule H+O2-.
  • 2. Now write their vacancies at the subscript of opposite atoms H2O1.

There is no need to write 1. So, H₂O.

  • Method to pronounce a formula:
      • 1. H₂O water is pronounced as H two O.
      • 2. C₁₂H₂₂O₁₁ (glucose) C twelve, H twenty–two, o eleven.

Q. Write in detail the making of the chemical formula of compounds.


Making of chemical formula of ionic compounds:

  • Positively charged ion (cation) and negatively charged ion (anion) attract each other to form an ionic compound. E.g., sodium chloride NaCl, magnesium chloride MgCl₂, etc. 
    • Step 1: write cation on the left and anion on the right side. Mg₂+Cl₂
    • Step 2: Put each ion’s valiancy number with its charge on its top side.
    • Step 3: inter charge the valiancy number of both ions and write them on the lower right side of each ion.

Q.  Define and explain the law of constant composition?


  • In 1700 a, French scientist Joseph Proust studied the chemical compound amended presented law.


  • “The law states that the composition of compound is always the same, regard – less of how the compound was made or obtained.”
      • 1. Water obtains from the river, well, sea, etc., but its composition is always the same. There are two atoms of hydrogen and one atom of oxygen present in molecules of water H₂O.
      • 2. Carbon dioxide CO₂ is produced in several ways, but one molecule always consists of a carbon atom and two oxygen atoms.

Short Answers of General Science (Part-8) 

Q. How protons, neutrons, and electrons are alike and different?


  • Proton has a positive charge. Electrons have negative charges, and neutrons have no charges, so they differ according to the charge present.

Q. Tungsten is an element with 74 protons and 109 neutrons. What is tungsten’s atomic number? How many electrons does tungsten have?


  • Atomic number =74, mass number =109+74=183
  • Several positive protons equal negative electrons, which are 74.

Q. Atomic number of sodium (Na) is 17, and its mass number is 35. Calculate the number of protons and neutrons in a sodium atom.


Proton=17 , neutron = 35-17=18.

Q. What is a nucleus?


  • The nucleus is a central part of an atom. It consists of protons and neutrons.

Q.   Differentiate b/w cation & anion:


  • Cation
  • Anion

1. It is a positive ion.

2. It is formed when an atom releases O.N.E. or more than one electron from its outermost shell, e.g., H+

1 . It is a negative ion.

2. It is formed when an atom absorbs one or more than one electron from another atom’s, E.g., F-1

Q. Define physical changes and explain with example?


Physical changes:

  • A physical change is when only the physical properties change, and its chemical composition remains in size. Size, shape, color, etc., are the substance’s physical properties.

Example of physical changes:

  • Physical changes are temporary and can easily be reversed. Freezing of water, cutting fruit into pieces, switching on the bulb, dissolving something into n another, etc., are examples of physical changes. Ice melts or water freezes. It does not change the composition of water. Melting of ice or freezing of water is a physical change.

Q. Define chemical changes and explain with examples. 


Chemical changes:

  • A chemical change Is one in which the physical and chemical properties of a substance change.

Examples of chemical changes:

  • Chemical changes are permanent and are not easy to reverse. Burning of paper, rusting of iron, turning milk into yogurt, cooking food, etc., are some examples of chemical changes.
  • Coal is carbon. When we burn coal, it changes into smoke, energy, and ash, so the burning of coal is a chemical change because new substances are formed during this process.

Q. What is the application of chemical changes?


  • Through chemical changes, new products are formed. Chemical changes are taking place in our bodies, in our vehicles, and in our environment. Sometimes chemical changes form harmful substances. These substances are changing our environment.

Q. Write a note on plastics?


  • Plastics are materials that can be molded or changed into any shape or form. Plastics are large molecules made from monomers.


  • Monomers are small units of plastic that are obtained from crude oil.


  • Plastics are large molecules formed from many monomers called polymers.


  • Polyethylene polyvinyl chloride (P.V.C.) etc.

Properties of plastics:

  • Plastics can be molded into several shapes. We can make toys, cups, bottles, utensils, and many other things from plastics.


  • Plastics do not decay, and they cause pollution. Plastic can be recycled. So it is the only and best way to manage the plastics.

 Q. What are hydrocarbons? Explain its uses as fuel.



  • A hydrocarbon is a compound consisting of only hydrogen and carbon atoms there. The hydrocarbons are mostly obtained from crude oil. When hydrocarbons burn in the presence of oxygen, their chemical composition changes. As a result of burning, a lot of heat is produced. It is used in factories etc.

Q. Write a note on fertilizers?


  • A substance that adds minerals to the soil is called fertilizer. It may be a natural fertilizer or a chemical fertilizer.

Chemical fertilizer:

  • Chemical fertilizers are prepared in factories. Many chemical changes take place during their preparation. , fertilizers supply nitrogen(n), phosphorous(K). element to the soil.

Physical properties of fertilizer:

  • The physical properties of fertilizers rich in particle size and hardness are very important. Small size particles of a fertilizer dissolve easily in water. Head particles are better than sift ones because they release nutrients gradually.

Liquid fertilizer:

  • Liquid fertilizer is a clear solution. It contains the nutrients essential for plants. Liquid fertilizers are ductless, and they reach every plant easily.

Q. Discuss the effect of improper use of fertilizers.


  • In case of excessive spreading, some fertilizers are nit absorbs by the plants. These fertilizers may reach into canals and rivers, causing water pollution and increasing the growth of algae. During the manufacture of chemical fertilizers, a lot of fossils fuel, coal, and natural gas are used, due to which our fuel reverse A.R.E. Reducing quickly.

Q. What is manure?


  • Waste material from plants and animals is called manure. Manure is rich in nutrients needed by the soil. A chemical change in nature increases the production of crops.

Q.   Define and explain hydrogenation.


  • A chemical process called hydrogenation changes vegetable oil into solid fat (vanaspati ghee). When hydrogen passes through the vegetable oil in the presence of nickel, it converts into solid fat. This process is called hydrogenation.
  • Vegetable oil is liquid, while fat (ghee) is solid at room temperature. A large amount of heat is used to bring about this chemical change.

                            Vegetable oil + Hydrogen= Banaspati ghee 

Q. What is margarine?


  • Margarine is a result of chemical changes. It is a mixture of hydrogenated vegetable oil and skimmed milk. In hydrogenating, hydrogen is passed through the vegetable oil. Some people use margarine in place of butter.

Q. Define Reversible changes?


  • The change that can go forward as well as backward is called a reversible change. It is a temporary change. We can get the same thing again. Melting ice into liquid water, switching on a tube light, increasing heartbeat during the run, etc., are reversible changes.

Q. Define Irreversible changes. 


  • A change that cannot act is called an irreversible change. It is a permanent change. We cannot get the things in their original form turning milk into yogurt, mixing plasters of Paris with water, rotting egg or fruit, etc. These are an example of irreversible changes.

Q. Do you know about the making of plastic soft drink bottles?


Making of plastic soft drink bottles:

Amazingly, the making of plastic drinks bottle is the same as blowing up a Balloon.

1. A tube of warm polyethylene is placed inside a bottle-shaped mold.

2. Compressed air is blown into the polyethylene tube after closing the mold. The tube expands and takes the shape of the mold.

The mold is then opened. Your soft drinks bottle is ready for filling.

Q. How do we decide which bag should be used for groceries.


1. Paper bags can hold more items than plastic bags. Paper bags come from trees.

2. Plastic bags are lightweight and waterproof. Plastic bags are not biodegradable. They cause land pollution. Plastic bags can be recycled.

The right choice:

  • Both paper and plastic bags have some advantages and some disadvantages. But the best choice may be neither paper nor plastic. One reusable cloth bag could replace hundreds of paper and plastic bags.

Q. Explain the presence of a puddle of water on the sidewalk one day and its absence the next day.


  • A puddle of water evaporated the next day. It is a physical phenomenon.

Q. When we chew food, what type of change are we causing to the food, a physical change or a chemical change?


  • The changing process cut down the food into smaller pieces. This is a physical change.

Q. What clue did you observe that a chemical change occurs inside the bottle after mixing baking soda with the vinegar?


  • The gas evolved, which expanded.

Q. Why do you think chopping wood is a physical change, but burning wood is a chemical change?


  • Chopping the wood changes it to smaller prices, but its chemical properties remain the same. The burning of food change wood into carbon dioxide and water. So burning of wood is a chemical change.

Q. What sugar is heated for a long time forms a solid black substance. Identify it as a reversible or irreversible change?


  • After heating sugar for a long time, it changes into carbon black, and water will be evaporated from it. It is a chemical change.

Q. Define thermal energy and heat?


Thermal energy:

  • The energy due to the motion of particles in matter is called thermal energy.


  • The thermal energy flow from one body to another. Heat always flows from an object at high energy to the object at lower energy.

Short Answers of General Science (Part-9) 

Q. What do you know about the transition of energy?

Ans: The transfer of heat from one object to another is called the transmission of heat. Heat energy is transferred in three ways:

      1. Conduction
      2. Convection
      3. Radiation

Q. What is conduction? Explain it with an experiment.

Ans: The transfer of heat through matter without the actual movement of particles from their opposition is called conduction. Conduction occurs in solids. Mostly liquid salts conduct heat.


  • Take a spoon and heat it with a flame. The other end will also be heated up after some time. The heat is transferred from one end to the other end without the actual movement of molecules. Heat is transferred from one particle to another by the vibration of particles. The transfer of heat is called the conduction of heat.

Method of conduction:

  • The solid particle is held very close to each other. The particle vibrates. When we heat one side of the solid, the particle begins to vibrate faster, collide with particles on the side, and transfer their energy. That particle began to vibrate faster and transfer energy to the next, and so on. In this way, one particle is caused to vibrate another particle and transfer heat from the hotter part to the colder part.

Q. What is meant by the good and bad conductor?


Good conductor:

  • The material which allows heat to flow through them is called good conductors. E.g. . , silver, copper, aluminum, iron, mercury.

Bad conductors:

  • The material which does not allow the heat to pass through them easily is called bad conductors of heat or heat insulators. e.g., air or any gas, cork, glass, plastic.

Q. Explain why metals are better conductors of heat than non-metals. 


  • All solids (metals or non-metals) are made up of tiny particles called atoms or molecules.

Close packing:

  • Particles of the metals are packed more closely than non-metals. Atoms of metals collide with neighbor atoms more easily to transfer their vibrations than non-metals.

Free electrons:

  • Metals also have free electrons, which speed up the transformation of heat in metals.


  • Take a metal spoon and a plastic spoon. Heat them separately on flame. In a metal spoon, the heat increases the vibration of atoms and the kinetic energy of electrons. This will conduct the heat from one end of the spoon to the other end very less, too, me. The spoon will heat up early. But on the other hand, nothing will happen with the plastic spoon. It will melt down instead of conducting heat. It is non-metal. So metals are good conductor of heat than non-metals.

Q. Explain conduction in liquids and gases. 


Conduction in liquids and gases :

  • The process of conduction in liquids and gases is very slow compared to solids (metals). The particles in liquid and gases are not held closely together. The particles have less chance to collide with other particles in liquid and even lesser in gases. That is why the transfer of heat energy from fast-moving molecules to neighboring molecules is slow. Water and air are bad conductors. Water and air, almost other liquids except for mercury, are bad conductors.

Q. Give some applications of heat from everyday life.


Everyday applications of conduction of heat: 

  • Conduction plays an important role in our lives:


  • Cooking utensils, electric kettles, irons, etc., are made up of metals to conduct heat quickly. Their handles are made of plastic or wood, which are bad conductors.

Feathers of birds:

  • Birds have feathers that keep their bodies warm because feathers are a bad conductor of heat.

Woolen clothes:

  • Woolen clothes and blankets slow down the transfer of heat. It happens so because the wool traps air in it. The air is a bad conductor of heat.


  • Ice is covered with jute rags to reduce its melting speed. Jute is a bad conductor of heat. 

Insulating material:

  • An insulating material (e.g., Styrofoam) is filled between the double walls. It reduces the transfer of heat across the walls of the refrigerator.

Double pan windows:

  • Double pane windows are used in buildings to slow the transfer of heat. The air between the two layers of glass acts as an insulator.

Thermos bottles:

  • Thermos bottles use air or a vacuum to slow heat transfer by conduction.

Q. Define convection. Explain it with the help of an example?


  • The transfer of heat in which the medium particles actually move to the source of heat energy to absorb heat and then move away from it is called convection.
  • Convection occurs in liquids and gases. Their molecules are free to move. So they move to the source of heat, take up heat from there and move away.


  • Stake a beaker and put small pieces of paper in it. Fill half of the beaker with water. Heat the beaker with a spirit lamp. We shall see that pieces of paper rise to the top of the water, move sideways, and sink to the bottom. The water in the beaker also gets warm. The water molecules absorb heat energy from the bottom of the beaker and rise to the top. Other molecules of water come to the bottom to absorb heat energy. The movement of papers pieces confirms this phenomenon.

Q. Explain what happens to the liquid during convection or how the ocean currents are produced.


  • When water is heated, it expands. The expanded water has less density than the surrounding colder water. Colder water moves downward as it has more density.

Convection current:

  • A convection current is the movement of warmer water upward and colder water downward.
  • The convection current will be continuously produced in the water till all the water gets heated.

Q. Explain how the wind system works or explain wind blows?


  • The sun’s heat heats the earth’s surface, and near the surface gets hot.
  • Hot air expands and gets lighter. This air rises, leaving the space empty there.
  • The colder gases from nearby areas move in to fill this space. The rising warm air reaches the cold layer and gets cold and heavier.
  • This as well moves down, and the gas from near the surface will move up. Thus convection currents are set up in nature, and the wind system goes on.

Q. Explain how oceans currents are set up?


  • Ocean currents are set up due to the convection of heat. The water of hot regions gets hot and expands. This expanded gets lighter. The water in colder regions remains cold and heavy. Hot water moves along the surface of the ocean towards the colder regions. The cold water flows below the surface towards the hot regions. In this way, ocean currents are set up.

Q. How do the gliding flights of birds and convection currents take place?


  • The heat of the sun warms the air on the surface. This warm air expands  and becomes lighter. This air rises. The colder air from nearby comes to occupy the space. In this way, convection currents are produced in the atmosphere.

Gliding flights:

  • Birds like eagles, hawks, vultures, and gulls take advantage of this phenomenon. They enjoy gliding. Flight birds do not move their wigs during gliding but glide in air currents. The top of energy is sand during gliding.

Q. Discuss the application of convection currents in everyday life.


Everyday application of convection currents:

  • We can observe the use of convection currents in our surroundings:

1. Household ventilation can make our houses cool. The air we breathe out is warmer and lighter. It moves up in the room to go out of the ventilators near the top sides of the wall. Fresh be hot. And cool air enters the room through windows and doors.

2. In a domestic water heater, water is heated in the boiler by a gas burner or heating coil. The hot water expands and becomes lighter in weight. This water rises and flows into the upper part of the water heater. To take the place of hot water, cold water from the storage tank to the lower part of the heater water to be hot. We take the hot water from the tap attached to the water heater. Convection currents help attach to the water heater, and convection currents help in the continuous supply of hot water.

3. An air conditioner also uses convection currents to cool a room. Air conditioners are installed near the ceiling. The rotator fan of an air-conditioned releases cool, dry air. The cool air is heavier in weight, so it sinks. The warm air of the room rises because it is lighter in weight. The air conditioner draws this warm air to make it cool. In this way, the air circulates again, and the desired temperature is gained.

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