Why should a magnesium ribbon be cleaned before burning in air?

Write a balanced equation for the reaction of hydrogen with chlorine and name the type of reaction.

What is a displacement reaction? Give one example.

Why is respiration considered an exothermic reaction?

What is meant by a precipitation reaction? Give an example.

Why do we apply paint on iron articles?

Explain oxidation and reduction with one example.

Why is the amount of gas collected in one test tube of the water electrolysis experiment double the other?

Why should a magnesium ribbon be cleaned before burning it in air?

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

What is rancidity? How can it be prevented?

Identify the type of reaction: 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ on heating.

What is a precipitation reaction? Give an example.

Why is it important to balance a chemical equation?

Why does an aqueous solution of an acid conduct electricity?

What happens when a base reacts with a metal? Write one equation.

What is the pH range of the human body? Why is it important?

Why does dry HCl gas not change the colour of dry litmus paper?

Write the chemical formula and one use each of bleaching powder, baking soda and washing soda.

What happens when plaster of Paris is mixed with water?

Why should curd and sour substances not be kept in brass and copper vessels?

Why do HCl and HNO₃ show acidic characters in aqueous solution while alcohol and glucose do not?

What is plaster of Paris? How is it obtained and what are its uses?

Why is it recommended that people suffering from acidity be given baking soda (sodium bicarbonate)?

What is the chemical name of bleaching powder and how is it prepared?

Why does distilled water not conduct electricity, whereas rain water does?

What is the difference between strong acids/bases and weak acids/bases?

Why are ionic compounds solids with high melting points?

What is an alloy? Why is it useful?

What is thermite reaction? Where is it used?

Why is sodium kept immersed in kerosene oil?

Explain the steps used to extract a metal of medium reactivity from its sulphide ore.

Why do ionic compounds conduct electricity in molten state but not in solid state?

What is meant by galvanisation? Why is it done?

What are amphoteric oxides? Give two examples.

Why do ionic compounds have high melting points?

How are metals arranged in the reactivity series? Why is sodium stored in kerosene?

What happens when zinc is added to a solution of copper sulphate? Write the equation.

Define roasting and calcination with one example each.

Why does calcium float in water after reacting with it?

Why does carbon form covalent bonds?

What is a homologous series? Give one example.

Why is the conversion of ethanol to ethanoic acid called an oxidation reaction?

Explain the cleansing action of soap.

Why do soaps not work well with hard water?

What is catenation? Why does carbon show it so strongly?

Why is a mixture of ethanol and ethanoic acid warmed with conc. H₂SO₄? Name the product.

Why does carbon form compounds mainly by covalent bonding?

Why are carbon and its compounds used as fuels for most applications?

Why do carbon compounds generally have low melting and boiling points?

Draw the structure and write the formula for the simplest ketone.

How does the cleansing action of soap work?

What are esters? How are they prepared and what is a common use?

Differentiate between autotrophic and heterotrophic nutrition.

What are the components of transport system in human beings?

How is the small intestine designed to absorb digested food?

Describe the structure and functioning of a nephron.

Why is the rate of breathing much faster in aquatic organisms than in terrestrial organisms?

Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

What is the role of saliva in the digestion of food?

Why is the separation of oxygenated and deoxygenated blood necessary in mammals and birds?

Describe the structure and functioning of nephrons.

Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

How are fats digested in our bodies? Where does this process occur?

How are the alveoli designed to maximise the exchange of gases?

What are the differences between the transport of materials in xylem and phloem?

What is a reflex action? Draw the path of a reflex arc in words.

What is a reflex arc? Why are reflex actions necessary?

Name the hormone secreted by the thyroid gland and state its function. What happens on its deficiency?

How does chemical coordination take place in plants?

Which part of the brain maintains posture and balance of the body?

What is the difference between a reflex action and walking?

Why is iodised salt advised in the diet?

Why is the use of iodised salt advisable?

How does chemical coordination occur in plants?

What is the function of the brain in human beings? Name its three main parts.

How does the human eye detect a change in light intensity?

What is the difference between the way movement takes place in a sensitive plant and in our legs?

What is the importance of DNA copying in reproduction?

Why is variation beneficial to the species but not necessarily for the individual?

How does binary fission differ from multiple fission?

What are the functions performed by the testis in human beings?

Why does menstruation occur?

What are the different methods of contraception?

What are the advantages of sexual reproduction over asexual reproduction?

What is placenta? State its function.

Describe the structure and function of ovary in human females.

How do Mendel's experiments show that traits may be dominant or recessive?

How do Mendel's experiments show that traits are inherited independently?

How is the sex of the child determined in human beings?

A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell which trait (A or O) is dominant?

How does the creation of two different cells by binary fission in Leishmania differ from the creation of gametes in human beings?

State Mendel's law of dominance.

State the laws of reflection of light.

An object is placed 20 cm from a concave mirror of focal length 15 cm. Find the image distance.

State the laws of refraction of light.

Why do we prefer a convex mirror as a rear-view mirror in vehicles?

An object is placed 10 cm from a concave mirror of focal length 15 cm. Find the image position and nature.

Define power of a lens. What is its SI unit?

Why does a ray of light bend when it travels from one medium to another?

Name the type of mirror used in (a) headlights of a car (b) side/rear-view mirror of a vehicle (c) solar furnace.

An object 5 cm high is placed 25 cm from a convex lens of focal length 10 cm. Find the position, nature and size of the image.

The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should the object be placed?

Name the type of mirror used in motor car headlights and in rear-view mirrors. Why?

Define the power of a lens. Find the power of a concave lens of focal length 2 m.

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. The image is equal in size to the object. Find the focal length.

What is meant by power of accommodation of the eye?

A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Why do stars twinkle?

Explain why the planets do not twinkle.

Why does the sky appear dark instead of blue to an astronaut?

What is presbyopia? How is it corrected?

Why do we see a rainbow after rainfall?

Why does the Sun appear reddish early in the morning?

What is the far point and near point of the human eye?

State Ohm's law and write its mathematical form.

Why is tungsten used for filaments of electric lamps?

On what factors does the resistance of a conductor depend?

Why are the coils of electric toasters and irons made of an alloy rather than a pure metal?

Why are appliances at home connected in parallel and not in series?

An electric bulb is rated 220 V and 100 W. Find the current drawn and its resistance.

Why are coils of electric toasters and irons made of an alloy rather than a pure metal?

Why is the series arrangement not used for domestic circuits?

Which uses more energy: a 250 W TV set in 1 hour, or a 1200 W toaster in 10 minutes?

An electric bulb is rated 220 V, 100 W. Calculate the resistance of its filament.

What is meant by saying that the potential difference between two points is 1 volt?

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

How does the resistance of a conductor depend on its length and area of cross-section?

State Fleming's left-hand rule.

What is electromagnetic induction? Who discovered it?

Why do two magnetic field lines never intersect each other?

What is the role of an earth wire? Why is it necessary for metallic appliances?

Why don't two magnetic field lines intersect each other?

What is the function of an earth wire? Why is it necessary to earth metallic appliances?

List the properties of magnetic field lines.

State the rule used to find the direction of the magnetic field produced around a current-carrying straight conductor.

Why does a current-carrying conductor kept in a magnetic field experience a force? State the factors affecting its direction.

Name a device based on electromagnetic induction used to generate electricity.

Why are some substances biodegradable and some non-biodegradable?

What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

What is ozone and how does it affect any ecosystem?

Give any two ways in which non-biodegradable substances affect the environment.

Why do we need to manage our resources with proper planning?