Text Book Solutions All Class

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

Q1: What is the property that allows metals like gold to be stretched into thin wires?
Ans: Ductility.

Q2: What items do ironsmiths generally make?
Ans: Flat pans, buckets, tongs, spades, axes, trowels, and rakes.

Q3: What material is mainly used to make these items?
Ans: Iron metal.

Q4: What is used to heat the iron in the furnace?
Ans: Coal.

Q5: What is the property that allows metals to be beaten into thin sheets?
Ans: Malleability.

Q6: Which metal is the most malleable?
Ans: Gold.

Q7: What happens to metals like copper and aluminum when beaten with a hammer?
Ans: They flatten.

Q8: What is the name of the process when metals break into pieces?
Ans: Brittle behavior.

Q9: What does ductility allow metals to do?
Ans: Be drawn into wires.

Q10: Which metal is used for making electric wires?
Ans: Copper.

Q11: What is the ringing sound produced by metal called?
Ans: Sonority.

Q12: What property of metals makes them good for cooking vessels?
Ans: Conduction of heat.

Q13: What is the term for the process when iron gets damaged by exposure to air and water?
Ans: Rusting.

Q14: What is the brown deposit formed on iron due to rusting called?
Ans: Rust.

Q15: Which metal reacts vigorously with water and is stored in kerosene?
Ans: Sodium.

Q16: What is the nature of the oxide of magnesium?
Ans: Basic.

Q17: What type of reaction occurs when magnesium burns in air?
Ans: It forms magnesium oxide.

Q18: What is the purpose of applying a protective layer of zinc on iron?
Ans: To prevent rusting.

Q19: Which non-metal is essential for respiration?
Ans: Oxygen.

Q20: What is formed when sulfur reacts with oxygen?
Ans: Sulfur dioxide.

Q1: Circuit diagram is a simplified conventional pictorial representation of an_______________

Ans: Electrical circuit

Q2: A circuit diagram uses standard symbols for electric components. True/ False.

Ans: True.

Q3: Define electric circuit.

Ans: A closed path formed by connecting electrical components allows electric current to flow. This arrangement is known as an electric circuit.

Q4: What is a cell holder?

Ans: A compartment that holds two or more cells together to form a battery is called a cell holder.

Q5: The combination of two or more cells is called a __________________.

Ans: Battery

Q6: A circuit is said to be open circuit or complete when current flows through it. True/ False.

Ans: False

Q7: What is a battery?

Ans: A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another.

Q8: The symbol for a battery is

a. 

b. 

c. 

d. None of These

Ans:  C

Q10: Draw the symbol for an electric bulb in an electric circuit.

Ans:  Symbol of Electric bulb​

Q9: What is a circuit diagram?

Ans: A circuit diagram is a simplified representation of an electrical circuit using symbols to depict various components.

Q10: Why do we use copper wires in electrical circuits?

Ans: Copper is a good conductor of electricity, which allows the current to flow easily through the wires.

Q11: A Longer line in the symbol for a cell represents its ——- terminal.

Ans: Positive

Q12: What is an electric circuit?

Ans: Electric Circuit: The closed path in which electric current flows.

Q13: What happens when the current is switched ‘on’ in a room heater?

Ans: It becomes red hot and gives out heat.

Q14: Would any of the bulbs glow when the switch is in the ‘OFF’ position in a circuit?

Ans: No, the bulb will not glow when the switch is “OFF” because there is no closed circuit for current to flow.

Q15: What type of electricity is used in homes and industries?
Ans: Alternating Current (AC).

Q16: What happens if the filament in an incandescent lamp breaks?
Ans: The lamp stops glowing because the circuit is broken.

Q17: How does a torchlight produce light?
Ans: By passing current through a lamp powered by electric cells.

Q18: What is the purpose of using insulators in circuits?
Ans: To prevent electric shocks and ensure safety.

Q19: What material is used to make the body of most electric cells?
Ans: Metal.

Q20: What direction does current flow in a circuit?
Ans: From the positive terminal of the cell to the negative terminal.

Q1: The substances used to test whether a substance is acidic or basic are known as ________

Ans: The substances used to test whether a substance is acidic or basic are known as Indicators

Q2: Name the most commonly used indicator.

Ans: Litmus paper

Q3: From where do we extract litmus to be used as an indicator?

Ans: Lichens

Q4: In acidic solution, litmus paper turns into ______

Ans: In acidic solution, litmus paper turns into Red
Litmus paper is a pH indicator that turns red in acidic solutions, indicating the presence of acids.

Q5: In basic solution, litmus paper turns into ____

Ans: In basic solution, litmus paper turns into Blue
Litmus paper changes to blue in basic solutions, indicating the presence of bases.

Q6: In distilled water, litmus paper turns into _________

Ans: In distilled water, litmus paper turns into purple
Litmus paper remains purple in neutral distilled water, as it is neither acidic nor basic.

Q7: The reaction between an acid and a base is known as _________

Ans: The reaction between an acid and a base is known as neutralization.
Neutralization is the chemical reaction that occurs when an acid and a base react to form water and a salt.

Q8: Red rose indicator turns acidic solutions _______

a. Dark pink
b. Purple
c. Blue
d. None of these

Ans: a. Dark pink
China rose indicator changes to dark pink in acidic solutions, indicating their acidic nature.

Q9: Red/ China rose indicator turns basic solutions to ______

a. Dark pink
b. Purple
c. Blue
d. Green

Ans: d. Green
The China rose indicator changes the colour of basic solutions to green.
In contrast, it turns acidic solutions to dark pink.

Q10: Salt and water are produced in the neutralization process with the evolution of ____________

Ans: Salt and water are produced in the neutralization process with the evolution of Heat

Q11: Name the acid present in our stomach.

Ans: HCL is present in our stomach.
Hydrochloric acid helps break down food and activates digestive enzymes, facilitating the digestion process.

Q12: Name the acid present in the sting of an ant.

Ans: Formic acid is present in the sting of an ant.

Q13: State the nature of the soap solution.

Ans: Basic

Q14: State the nature of baking soda.

Ans: Basic

Q15: State the nature of lemon juice.

Ans: Acidic

Q16: Why does lemon juice and orange juice taste sour?

Ans: Because they contain acids.

Q17: Why does baking soda taste bitter?

Ans: Because it is basic in nature.

Q18: State one property of acids.

Ans: Acids are sour in taste.

Q19: State one property of bases.

Ans: Bases are bitter in taste.

Q20: Tina rubs a solution between her fingers and feels soapy; what is the nature of that solution?

Ans: Basic

Q21: Complete the following reaction:
HCl + NaOH —-> ______ + H2O

Ans: NaCl

Q22: Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. Its nature _______________

Ans: Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. Its nature is Basic

Q23: The wastes of many factories contain____________

Ans: The wastes of many factories contain Acids

Q24: Blue litmus paper is dipped in a solution. It remains blue, what is the nature of the solution?

Ans: Basic

Q25: Hydrogen ion is common to all acids. True/False

Ans: True

Q26: Name a base that is also used in soda acid fire extinguishers.

Ans: Baking soda.

Q27: Aqueous solution of acid conducts electricity due to ______________ present in it.

Ans: ion

Q28: Define pH.

Ans: pH is the measure of the Acidity or Alkalinity of a solution. The term pH stands for a negative log of hydrogen ion concentration.

Q29: The bases that dissolve in water are known as alkalies. True/ False.

Ans: True

Q30: Phenolphthalein becomes colourless in __________ and pink in_________.

Ans: Colourless in acid and pink in base.

PhenolphthaleinQ31: Name the acid present in vinegar.

Ans: Acetic acid

Q32: Name the acid present in lemon.

Ans: citric acid

Q33: Change of colour in an acid or base depends on

a. Type of indicator
b. The acidic property of that substance
c. Basic property of that substance
d. None of these

Ans: Type of indicator

Q34: Name the acid present in curd.

Ans: Lactic acid

Q1: What is the shape of the Earth’s orbit around the Sun?
Answer: The Earth moves around the Sun in a nearly circular path called an orbit.

Q2: What inspired real scientific explorations of flight?
Answer: Paper planes helped scientists understand how objects can fly through the air.

Q3: What is the duration of the Earth’s revolution around the Sun?
Answer: It takes the Earth one whole year (365 days) to complete one trip around the Sun.

Earth’s RevolutionQ4: What does the tilt of the Earth’s axis cause?
Answer: The tilt makes different parts of Earth get sunlight differently, creating seasons.

Q5: What can be explored with electric batteries, lamps, and wires?
Answer: These tools help us study how electricity works and flows.

Q6: What happens to materials when they are heated?
Answer: Heating can make materials change their shape, size, or state.

Q7: What is one example of an irreversible change?
Answer: Once a battery is used up, it cannot be changed back to new again.

Reversible and Irreversible ChangesQ8: How does water flow in the environment?
Answer: Water moves below the ground through soil and rocks.

Q9: What are life processes essential for survival?
Answer: Eating gives energy needed for all life activities.

Q10: Do plants also need food to grow?
Answer: Plants make their own food using sunlight to grow healthy.

Q11: What was the way early humans measured time?
Answer: They used the length and position of shadows to tell the time.

Q12: Why is light important for us?
Answer: Light helps our eyes see things around us.

Q13: What causes eclipses?
Answer: Eclipses happen when one object’s shadow falls on another.

EclipsesQ14: How does the Earth rotate to cause day and night?
Answer: Earth spins around its axis, making day and night.

Q15: How does the Earth’s movement around the Sun affect us?
Answer: As Earth moves around the Sun, the tilt causes different seasons.

Q16: What happens during a solar eclipse?
Answer: The Moon blocks the Sun’s light, causing a solar eclipse.

Q17: What is a lunar eclipse?
Answer: The Earth’s shadow falls on the Moon, causing a lunar eclipse.

Q18: Can we safely view a lunar eclipse with our naked eye?
Answer: Lunar eclipses are safe to watch without special glasses.

Q19: What causes the stars to appear to move in the sky?
Answer: Earth’s spinning makes stars seem like they move across the sky.

Q20: How is the Earth’s axis related to the seasons?
Answer: The slant (tilt) of Earth’s axis causes seasons to change.