class 7 Science

Short Q&A:

Q1: What is litmus and how is it used to identify acids and bases?
Ans: Litmus is a natural material made from lichens and comes as blue and red paper strips. It helps identify substances: acids turn blue litmus paper red, and bases turn red litmus paper blue.

LitmusQ2: How is red rose extract prepared and how does it act as an indicator?
Ans: Red rose extract is made by crushing fresh rose petals, soaking them in hot water, and filtering the liquid. It changes color to red in acidic substances and green in basic substances, helping to identify them.

Red Rose Petas immersed in Hot WaterQ3: What color change does turmeric paper show when it comes in contact with a base?
Ans: Turmeric paper, which is yellow, turns red when it touches a basic substance. It does not change color with acidic or neutral substances.

Q4: What are olfactory indicators and give an example?
Ans: Olfactory indicators are substances whose smell changes when mixed with acids or bases. For example, a cloth soaked in onion juice loses its smell when put in acidic tamarind water or basic baking soda solution.

Q5: Name two other natural indicators besides litmus and red rose extract.
Ans: Beetroot and purple cabbage are natural indicators. They change color when mixed with acidic or basic substances.

IndicatorsQ6: Red litmus paper is dipped in a solution; it remains red, what is the nature of the solution?
Ans : Red litmus paper when dipped in a solution, if it remains red then the nature of the solution is neutral.

Q7: What are salts? Give examples.
Ans : Salts are the ionic compounds generally formed by neutralisation of an acid with base. They can be acidic, basic as well as neutral. Example acidic salts: sodium bicarbonate, basic salts: magnesium chloride, neutral salt: sodium chloride.

Q8: Give examples of some acids and bases
Ans : Curd, lemon juice, vinegar, orange juice etc. are acids and baking soda, lime water etc. are bases.

Q9: Define indicators along with examples.
Ans : Indicators are special type of substance that are used to taste whether a substance is acidic or basic in nature. It change the colour of acidic or basis substances when added into it. Turmeric, litmus, etc. are some natural indicators.

Turmeric as IndicatorQ10: What do you mean by neutral substance, explain with examples?
Ans : The substances which are neither acidic, nor basic are called neutral substance. These substances neither turn blue litmus red nor red litmus blue, for example distilled water, sugar solution etc.

Q11: Rena is trying to wash turmeric stain on her cloth with soap, she noticed the stain colour changed to red, explain why?
Ans : Turmeric is a natural indicator which when reacts with bases turns it into red colour; here soap solution is basic so it turns red.

Q12: Explain why factory waste should be neutralised before disposing it into the water bodies.

Ans : The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances into it.

Long Q&A:

Q1:  State few properties of acids.

Ans : Acids are substances known for their sour taste (though tasting them is not safe). The word “acid” is derived from the Latin word ‘ACERE’, meaning sour. 

Properties of Acids: 

• Sour in taste. 
• Turn blue litmus paper red. 
• Turn China rose solution dark pink or magenta.

Examples of acidic substances include curd, vinegar, lemon, and orange juice, which all contain natural acids. 

Citrus Fruits are Acidic in Nature

Q2: State few properties of bases.

Ans : Bases are substances with a bitter taste and a slippery feel. 
Properties of Bases: 

• Bitter in taste. 
• Turn red litmus paper blue. 
• Turn turmeric paper reddish-brown. 
• Turn China rose solution green.

Some common examples of bases include baking soda, milk of magnesia, and soap. The chemical nature of these substances is referred to as basic. 

Q3: What are the differences between acids and bases?

Ans : 

Q4: Describe the process of neutralisation with the help of an example.

Ans : 

Neutralisation is a process in which an acid solution when mixed with base solution, react with each other to produce a salt and water along with generation of heat. Salt so produced, may be acidic, basic or neutral in nature. In this process the acidic nature of the acid and the basic nature of the base are destroyed.

NeutralizationAcid + base → salt + water. (heat is evolved)

For example: HCl + NaOH→ NaCl + H₂O.
Hydrochloric acid  + Sodiumhydroxide → Sodium chloride + Water 

Q5: Explain the process and treatment of an ant bite.

Ans: When an ant bites, it injects an acidic liquid called formic acid into the skin, causing burning pain, redness, and irritation. The effect of the acid can be neutralized by applying a mild base to the affected area.

Two common treatments are:

1. Baking soda solution: Baking soda (sodium hydrogen carbonate) neutralizes the acid and reduces the pain and irritation.
2. Calamine solution: Calamine contains zinc carbonate, which also neutralizes the acidic effect and provides relief.

Applying either of these substances helps neutralize the acid and reduce the discomfort caused by the ant bite.

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In This chapter there are no question. So we have added

🔍 Short Answer Questions

1. Q: What is science according to the introduction in Chapter 1?
   A: Science is described as a process of curiosity, asking questions, performing experiments, and exploring the world to understand natural phenomena.
2. Q: How does the textbook encourage students to learn science?
   A: By urging them to ask questions, do experiments, explore surroundings, and connect real-life experiences with science.
3. Q: What inspired early flight experiments as per the chapter?
   A: Observations of bird wings and simple paper planes inspired early inventors to study flight.
4. Q: What is meant by ‘the ever-evolving world of science’?
   A: It refers to the continuously growing and changing nature of scientific knowledge and discovery.
5. Q: How is the layout of the textbook described?
   A: The page numbers follow the playful path of a butterfly and a paper plane, symbolizing free exploration.

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🧠 Conceptual Questions

6. Q: Why does the textbook call science a way of thinking?
   A: Because science involves curiosity, questioning, reasoning, and openness to new information—not just memorizing facts.
7. Q: Give an example of how one area of science connects to another.
   A: Learning about light (physics) helps understand plant growth (biology) through photosynthesis.
8. Q: What does the chapter say about reversible and irreversible changes?
   A: Some changes like melting ice are reversible, while others like ripening fruits or burning wood are irreversible.
9. Q: What role does heat play in physical changes?
   A: Heat can cause substances to change state (like melting or evaporating) and can also speed up certain changes.
10. Q: How does the Sun contribute to the water cycle?
    A: The Sun heats water, causing evaporation, which leads to condensation and rainfall.

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✨ Creative & Exploratory Questions

11. Q: What question might lead to the answer “Because the cat’s teeth were crooked”?
    A: Why did the cat need braces?
12. Q: Suggest a question for the answer “Just add some milk.”
    A: How do I fix overly spicy cereal?
13. Q: Create a question that fits the answer “Don’t panic, I have my towel.”
    A: What did the space traveller say when the spaceship lost signal?
14. Q: What could be the question if the answer is “42”?
    A: What is the answer to life, the universe, and everything? (From The Hitchhiker’s Guide to the Galaxy)

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🧪 Activity-Based or Thinking Questions

15. Q: What kind of materials help a bulb glow in a simple circuit?
    A: Conductors like copper wires help the current pass and make the bulb glow.
16. Q: Why is it important to do experiments outside the textbook?
    A: Real-life experiments help connect theory with observation and develop scientific thinking.
17. Q: What is the link between human activity and environmental change as discussed?
    A: Human activities can disrupt natural balance, and science helps us understand and correct these effects.
18. Q: How does observing shadows help us understand time?
    A: Ancient humans used the changing position of shadows to estimate time, leading to sundials.

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✍️ Long Answer Questions

Q: Summarize how science is both discovery and responsibility as per the chapter.
A: Science helps us discover how nature works, but it also makes us aware of how human actions affect the environment. Being responsible means using scientific knowledge to build a more sustainable world.

Q: Explain how light helps us beyond just visibility, as explained in the chapter.
A: Light not only enables vision but also leads to scientific understanding of the universe. Its study helps explain shadows, time measurement, eclipses, and even the structure of the universe.

Q1: What is a partial solar eclipse?
Ans: A partial solar eclipse occurs when the Moon partially blocks the Sun.

Q2: Why is the Moon able to block the Sun during a solar eclipse?
Ans: The Moon is much smaller than the Sun, but it is much closer to the Earth, making it appear to cover the Sun.

Q3: What is rotation?
Ans: Rotation is the spinning of an object around its own axis.

Q4: What is the Earth’s axis of rotation?
Ans: It is an imaginary line that passes through the North and South poles.

Q5: How long does it take for the Earth to complete one rotation?
Ans: About 24 hours.

Q6: Which direction does the Earth rotate when viewed from the North Pole?
Ans: The Earth rotates in the anti-clockwise direction, from West to East.

Q7: What causes day and night on Earth?
Ans: The Earth’s rotation causes day and night.

Q8: What happens during the rotation of the Earth on its axis?
Ans: Half of the Earth faces the Sun and experiences daytime, while the other half experiences nighttime.

Q9: What direction does the Sun appear to move in the sky?
Ans: The Sun appears to rise in the East and set in the West.

Q10: What causes the stars to appear to move in the sky?
Ans: The Earth’s rotation causes the apparent movement of stars.

Q11: What is revolution?
Ans: Revolution is the movement of the Earth around the Sun along its orbit.

Q12: How long does the Earth take to complete one revolution around the Sun?
Ans: About 365 days and 6 hours.

Q13: Why do the stars in the night sky change over the course of a year?
Ans: The changing position of the Earth in its orbit around the Sun causes different stars to be visible at different times.

Q14: What causes the seasons on Earth?
Ans: The tilt of the Earth’s axis and its orbit around the Sun causes the seasons.

Q15: When does the Northern Hemisphere experience summer?
Ans: In June, when the Northern Hemisphere is tilted towards the Sun.

Q16: When does the Northern Hemisphere experience winter?
Ans: In December, when the Northern Hemisphere is tilted away from the Sun.

Q17: What is the
Ans: The longest day in the Northern Hemisphere, occurring around 21 June.

Q18: What happens during a solar eclipse?
Ans: The Moon blocks the Sun’s light from reaching the Earth.

Q19: What is a lunar eclipse?
Ans: A lunar eclipse occurs when the Earth blocks the Sun’s light from reaching the Moon.

Q20: Why should we not look directly at a solar eclipse?
Ans: Directly viewing a solar eclipse can damage the eyes and cause blindness.

Q1: Name an artificial source of light.
Ans: Electric bulbs.

Q2: What do fireflies use to communicate?
Ans: Fireflies use light to communicate.

Q3: What is a luminous object?
Ans: An object that emits its light.

Q4: Does the Moon produce its light?
Ans: No, the Moon reflects sunlight.

Q5: How does light travel under normal conditions?
Ans: Light travels in a straight line.

Q6: Name a natural source of light.
Ans: The Sun.

Q7: Give an example of a non-luminous object.
Ans: The Moon.

Q8:  Why are LED lamps promoted by the Indian government?
Ans: Because they are energy-efficient, brighter, and environmentally friendly.

Q9: What device uses two mirrors to see objects that are not directly visible?
Ans: A periscope.

Q10: What is the reflection of light?
Ans: When light bounces off a surface and changes direction.

Q11: What happens when light passes through aligned holes in a straight line?
Ans: It creates a bright spot on a screen.

Q12: What is a transparent material?
Ans: A material that lets light pass through almost completely, like glass.

Q13: What kind of material allows only some light to pass through?
Ans: Translucent material.

Q14: What is formed when an object blocks light?
Ans: A shadow.

Q15: What kind of shadow does an opaque object create?
Ans: A dark and well-defined shadow.

Q16: How does a pinhole camera form an image?
Ans: Light passes through a tiny hole and forms an upside-down image on a screen.

Q17: What type of image does a plane mirror form?
Ans: A virtual, upright, same-size, laterally inverted image.

Q18: What is lateral inversion in a mirror image?
Ans: The left side appears as the right side and vice versa.

Q19: What causes light pollution?
Ans: Excess artificial light from cities and towns.

Q20: What type of shadow do translucent objects create?
Ans: Lighter and less distinct shadows.

Q1: Name some components of food.
Ans: Carbohydrates, proteins, fats, vitamins, and minerals.

Q2: Define nutrients.
Ans: Carbohydrates, proteins, fats, vitamins, and minerals are essential components of food, these components are called nutrients.

Q3: Give an example of autotrophs.
Ans: All green plants.

Q4: Give an example of heterotrophs.
Ans: Animals and human beings.

Q5: Plants prepare their food by using raw materials present in their ______________.
Ans: Surrounding.

Q6: What do you mean by nutrition?
Ans: Nutrition is the mode of taking food by an organism and its utilization by the body.

Q7: Name the food factories of plants.
Ans: Leaves.

Q8: Name the tiny pores present on the surface of leaves.
Ans: Stomata.

Q9: Name the green pigment present in leaves.
Ans: Chlorophyll.

Q10: ____________ helps leaves to capture the energy of sunlight.
Ans: Chlorophyll.

Q11: Why is photosynthesis named so?
Ans: Because the synthesis of food occurs in the presence of sunlight.

Q12: Sun is the ultimate source of energy for all living organisms. True / False.
Ans: True.

Q13: State the equation for the process of photosynthesis.
Ans: Carbon dioxide + water → carbohydrate + Oxygen (in the presence of sunlight).

Q14: Why are algae present in stagnant water bodies green in color?
Ans: Because they contain the green pigment chlorophyll.

Q15: During photosynthesis, plants take in _______________ and release _______________.
Ans: Carbon dioxide and oxygen.

Q16: During photosynthesis solar energy is converted into chemical energy. True / False.
Ans: True.

Q17: The product of photosynthesis is
a. Carbohydrate
b. Protein
c. Fats
d. All of these
Ans: a. Carbohydrate.

Q18: Name a plant that has both autotrophic and heterotrophic modes of nutrition.
Ans: Insectivorous plants.

Q19: Name the pores present in leaves through which exchange of gases takes place.
Ans: Stomata.

Q20:What do plants need to grow?

Ans: Plants need sunlight, water, air, and nutrients to grow.

Q21. How do plants make their own food?

Ans: Plants make food through photosynthesis.

Q22. What is the role of sunlight in plant growth?

Ans: Sunlight provides energy for food production.

Q23. What do roots absorb from the soil?
Ans: Roots absorb water and minerals.

Q24.  What gas do plants take from air during photosynthesis?
Ans:  Plants take in carbon dioxide.

Q25. Where does photosynthesis mainly take place?
Ans: Photosynthesis mainly takes place in leaves.

Q1: Name the largest gland in the human body.
Ans: Liver

Q2: Animal nutrition includes
a. Nutrient requirements
b. Mode of intake of food
c. Utilization of food in the body
d. All of the above.
Ans: All of the above

Q3: Define digestion.
Ans: The process of breaking down complex substances of food into simpler forms is called digestion.

Q4: Name the parts of the alimentary canal.
Ans: Buccal cavity, oesophagus, stomach, small intestine, large intestine, rectum, and anus.

Q5: Name the glands that secrete digestive juice__________________.
Ans: Salivary gland, pancreas, and liver

Q6: The process of taking food into the body is called __________.
Ans: Ingestion

Q7: Name the different types of teeth.
Ans: Incisor, canine, premolar, and molar

Q8: The saliva breaks down starch into sugars. True/ False.
Ans: True

Q9: Name the mode of feeding of ants and mosquitoes.
Ans: The feeding mode of ants is Chewing (they use mandibles to bite and chew), and the mode of feeding of mosquitoes is sucking.

Q10: The tongue helps in mixing food with saliva. True/ False.
Ans: True.

Q11: Name ruminants.
Ans: Grazing animals like cows, buffaloes, and deer.

Q12: Name the finger-like projection present in the inner wall of the small intestine.
Ans: Villi

Q13: Name the organ responsible for removing undigested and unabsorbed residues from the human body.
Ans: Anus

Q14: Bile juice is stored in a sac called__________________
Ans: Gall bladder

Q15: Bile is responsible for the digestion of
a. Fat
b. Protein
c. Vitamins
d. Both a and b
e. None of these
Ans: Fat

Q16: What is the location of the pancreas?
Ans: The Pancreas is located just below the stomach.

Q17: The pancreatic juice acts on
a. Carbohydrates
b. Fats
c. Proteins
d. All of the above
Ans: All of the above.

Q18: Name the end products of carbohydrates.
Ans: Simple sugars such as glucose

Q19: Define egestion.
Ans: The process of removal of faecal matter from the body through the anus is called egestion.

Q20: How is food pushed down from mouth to stomach?
Ans: Food is pushed down by the movement of the wall of the food pipe.

Q21: The digestion of cellulose takes place in ________________ present in all ruminants.
Ans: Rumen

Q22: Name the part of the digestive canal involved in the absorption of food.
Ans: Small intestine

Q23: Name the part of the digestive canal that kills bacteria.
Ans: Stomach

Q24: Name the part of the digestive canal involved in the formation of faeces.
Ans: Large intestine

Q25: Name the part of the digestive canal involved in chewing food.
Ans: Mouth or Buccal cavity

Q1: The basic unit of speed is

(i) Km/ min

(ii) m/ min

(iii) Km/ sec

(iv) m/ sec

Ans : (iv) m/ sec

Speed is defined as the rate at which an object covers distance. It is measured in terms of how much distance is traveled per unit of time. In the metric system, the unit for distance is meters (m) and the unit for time is seconds (sec). Therefore, the basic unit of speed is meters per second (m/sec).

Q2: What is motion?

Ans : Motion is a change in the position of an object with time.

Q3: Define average speed.

Ans : The average speed of a moving object is defined as the total distance covered by it divided by the total time taken.

Q4: What do you mean by the statement; “car is moving with the speed of 50 Km per hour”?

Ans : Car is moving with the speed of 50 Km per hour it means it will cover a distance of 50 Km in one hour

Q5: What is a simple pendulum’s periodic motion?

Ans: A simple pendulum’s periodic motion involves oscillations back and forth from a center point.

Q6: What information can be interpreted from a distance-time graph?

Ans: A distance-time graph shows how distance changes over time and helps determine the speed of a moving object.

Q7: How do you define uniform motion?

Ans: Uniform motion occurs when an object moves along a straight line with a constant speed.

Q8: What is the time period of a simple pendulum?

Ans: The time period of a simple pendulum is the time taken for the pendulum to complete one full oscillation.

Q9:How is non-uniform motion different from uniform motion?

Ans: In non-uniform motion, the speed or direction of the object changes, whereas in uniform motion, the speed remains constant.

Q10: How do we measure speed using a speedometer and an odometer?

Ans: Speedometers measure and display the speed of a vehicle in km/h, while odometers record the distance traveled by the vehicle in kilometers (km).

Q11: The metallic ball in pendulum is called __________ of the pendulum. 

Ans: Bob

Q12: Give an example of oscillatory motion. 

Ans: To and fro motion of a simple pendulum

Q13: What is uniform motion?

Ans: Uniform motion is when an object covers equal distances in equal intervals of time.

Q14: Name the device used to measure speed. 

Ans: Speedometer

Q15: What is non-uniform motion?

Ans: Non-uniform motion is when an object covers unequal distances in equal intervals of time.

Q1: Define temperature.

Ans: The measure of hotness or coldness of an object is called temperature. It is usually measured in “degrees”.

Q2: Name the device used to measure temperature.

Ans: A thermometer is a device used to measure temperature.

Thermometer

Q3: What is the unit of temperature as adopted by India?

Ans: Degree Celsius (°C)

Q4: The bulb of the laboratory thermometer should not touch the surface of the ________________.

Ans: Container.

Q5: Give an example to show the transfer of heat from one body to another.

Ans: Any utensil kept on flame becomes hot because heat transfers from flame to the utensil.

Q6: Heat always flows from a hotter object to ________________.

Ans: Colder object

Q7: In solid heat is transferred by the process of

a. Conduction
b. Convection
c. Radiation
d. None of these

Ans: Conduction.

Q8: Give examples of conductors.

Ans: Aluminium, copper, iron, etc.

Q9: Give examples of insulators.

Ans: Wood, plastic, rubber

Q10: Insulators are ________ conductors of heat.

Ans: Poor

Q11: Conductors are _____________ conductors of heat.

Ans: Good

Q12: Name the process by which heat transfers in air.

Ans: Convection.

Q13: From the sun, the heat comes to us by the process called ________________.

Ans: Radiation.

Q14: Which of the two absorbs more radiation- a dark-coloured object or a light-coloured object?

Ans: A dark-coloured object.

Q15: Land breeze blows at the time of __________.

Ans: Night

Q16: Sea breeze blows at the time of _________.

Ans: Day

Q17: Which type of clothing should be preferred for the month of June?

Ans: Light-coloured clothes

Q18: Which type of clothing should be preferred in January?

Ans: Dark coloured clothes.

This should now be in the correct order without any missing questions! Let me know if you’d like further changes.

Q1: At what age does adolescence typically begin?
Ans: Around the age of 10.

Q2: What causes pimples to appear during adolescence?
Ans: Pimples appear due to an increase in oily secretions from the skin during adolescence.

Q3: What are secondary sexual characteristics?
Ans: Secondary sexual characteristics are signs that the body is preparing for adulthood, like voice changes and body hair growth.

Q4: What marks the onset of adolescence?
Ans: The onset of adolescence is marked by rapid growth and development.

Q5: What happens to boys’ voices during adolescence?
Ans: Boys’ voices become hoarse due to the growth of the voice box, leading to the appearance of an Adam’s apple.

Q6: What is the growth of facial hair in boys a sign of?
Ans: The growth of facial hair in boys is a sign of puberty and the transition to adulthood.

Q7: What is menstruation, and when does it start?
Ans: Menstruation is the discharge of blood from the body, starting around puberty in girls.

Q8: How often does the menstrual cycle typically occur?
Ans: The menstrual cycle generally occurs every 28-30 days.

Q9: What are the two main emotional changes during adolescence?
Ans: Mood swings and increased sensitivity.

Q10: What is a common health issue faced by girls during adolescence?
Ans: Acne, caused by increased oily secretions from the skin.

Q11: What are some examples of secondary sexual characteristics in girls?
Ans: Development of breasts and widening of hips.

Q12: What can help improve reproductive health in adolescent girls?
Ans: A balanced diet, proper hygiene, and the use of sanitary pads during menstruation.

Q13: What should be avoided to ensure good health during adolescence?
Ans: Harmful substances such as tobacco, alcohol, and drugs.

Q14: What is the role of hormones in adolescence?
Ans: Hormones regulate physical and emotional changes and control growth and development.

Q15: What physical change occurs in boys’ bodies that is different from girls?
Ans: The development of a moustache and beard.

Q16: What is the importance of exercise during adolescence?
Ans: Regular exercise helps maintain physical and mental health, builds stamina, and boosts mood.

Q17: What is a good source of calcium for adolescents?
Ans: Milk, cheese, and paneer.

Q18: What is the significance of iron in adolescent girls’ diet?
Ans: Iron is important for the formation of blood and to prevent anaemia.

Q19: What is the ?
Ans: It is a campaign to raise awareness about avoiding substance abuse.

Q20: How can adolescents ensure responsible social media use?
Ans: By being respectful, protecting privacy, and avoiding sharing personal photos with strangers.

Q1: Is cooking food a desirable change?
Ans: Yes, it is a beneficial change.

Q2: What is added to steel to make it stainless?

Ans: Stainless steel is made by mixing iron with carbon and metals like chromium, nickel, and manganese.

Q3: Can physical changes be reversed?
Ans: Yes, like freezing water.

Q4: What is a chemical change?

Ans: A change, in which a new substance with different properties is formed, is known as a chemical change.

Q5: A change, in which a new substance with different properties is formed, is known as a _________________

Ans: Chemical change

Q6: What is the fire triangle?
Ans: The three requirements for combustion: fuel, oxygen, and heat.

Q7: What is erosion?
Ans: The movement of rocks, soil, or sediments by wind or water.

Q8: State the two important conditions for rusting.

Ans: Presence of water and presence of oxygen

Q9: What is weathering?
Ans: The breakdown of rocks into smaller pieces through physical or chemical processes.

Q10: What is the ignition temperature?
Ans: The minimum temperature at which a substance catches fire.

Q11: What is melting?

Ans: Melting is the process of turning a solid to a liquid.

Q12: Name the process by which water molecules continuously change to vapour.

Ans: Evaporation

Q13: What is an irreversible change?
Ans: A change that cannot be undone, like burning wood.

Q14: What is bioluminescence?
Ans: Light produced by living organisms, like fireflies, through a chemical change.

Q15: A medicine is the end product of the chain of ________________________

Ans: Chemical reaction

Q16: Condensation of steam is a chemical process or physical change?

Ans: Physical change

Q17: Cutting of log of wood into pieces is a chemical process or physical change?

Ans: Physical change

Q18: Name the two methods by which rusting of iron can be prevented.

Ans: By painting or greasing and by galvanizing with Zinc