CLASS 8 PHYSICS : HEAT

What is the main reason that molecules on the surface of a liquid evaporate?

How does evaporation affect the temperature of the remaining liquid?

What is the relationship between inter-molecular force and the rate of evaporation?

Which of the following is NOT a factor affecting the rate of evaporation?

What happens to the molecules that escape during evaporation?

Which of the following statements about evaporation is TRUE?

What is the effect of wind on the rate of evaporation?

What is the kinetic energy of a molecule primarily determined by?

What distinguishes evaporation from boiling?

Which factor does NOT affect the rate of evaporation?

What is thermal expansion?

What happens to the average kinetic energy of molecules during boiling?

Which of the following materials has the highest coefficient of linear expansion?

How does the length of a metal rod affect its expansion when heated?

Why do telephone wires break in winter?

What is a common effect of heating a solid object?

When a steel girder in a bridge is mounted on rollers, what phenomenon does it accommodate?

Which liquid expands the least when heated?

What causes evaporation to create a cooling effect?

Why is there a gap left between cement slabs during construction?

How is vapor formation during evaporation characterized?

What is needed for a liquid to evaporate?

Why do only molecules on the surface of a liquid participate in evaporation?

Which of the following statements accurately describes the process of evaporation?

What is the primary force that must be overcome for a liquid molecule to evaporate?

How does the kinetic energy of molecules affect the rate of evaporation?

Which of the following is NOT a factor that governs the rate of evaporation?

What is the key characteristic that distinguishes evaporation from boiling?

Which of the following statements is TRUE based on the provided information?

Based on the information, what happens to the remaining liquid during evaporation?

Which of the following factors will increase the rate of evaporation of a liquid?

Why does the rate of evaporation increase with an increase in temperature?

Which of the following is a key difference between evaporation and boiling?

What happens to the average kinetic energy of molecules when a liquid is heated to its boiling point?

Why does the expansion of a metal rod depend on its original length?

Which of the following statements about thermal expansion is TRUE?

How does the phenomenon of thermal expansion affect telephone wires in winter?

How does thermal expansion explain the process of fitting an iron rim on a wooden wheel?

Why are gaps left between sections of concrete roadways?

Why is one end of a steel girder in a bridge placed on rollers?

Which of the following liquids expands the most when heated, assuming they are all heated to the same temperature?

Why does the density of a substance decrease when heated?

What happens to the air inside a glass bottle when it is heated, assuming it is sealed?

Why are iron rims made slightly smaller in diameter than the wooden wheel they are intended to fit on?

A liquid is placed in a sealed container. Which statement accurately describes the molecules that evaporate from the liquid?

Which of the following conditions would lead to an increase in the rate of evaporation of a liquid?

Two identical containers are filled with different liquids, A and B. Liquid A has a higher vapor pressure than liquid B. Which of the following statements is likely to be TRUE?

While studying evaporation, a scientist makes the following observations: the rate of evaporation decreases, the temperature of the remaining liquid decreases, and the vapor pressure above the liquid increases. Which of the following statements is the BEST explanation for these observations?

A student sets up an experiment to study the rate of evaporation of a liquid. They note that the rate of evaporation increases when the liquid is heated. What is the best explanation for this observation?

Why is evaporation considered a cooling process?

A liquid is placed in a sealed container with a small opening at the top. As the liquid evaporates, the vapor pressure inside the container increases. What is the mechanism by which this occurs?

Imagine you have two identical containers, both filled with the same liquid. Container A is open to the air, while container B is sealed. How would the rate of evaporation differ between the two containers?

Which of the following statements accurately describes the effect of INCREASING surface area on the rate of evaporation?

A glass of water is left open to the air on a windy day. Which of the following factors explains why the water evaporates more quickly in this scenario?

A metal rod is heated to a certain temperature. Assuming all other factors remain constant, which of the following will have the GREATEST impact on the amount of expansion the rod undergoes?

Consider two identical metal rods made of the same material. Rod A is heated to 50°C, and Rod B is heated to 100°C. Which statement accurately describes the relative expansion of the two rods?

Why is it necessary to leave gaps between sections of concrete roadways during construction?

A metal ball is heated and then attempts to be passed through a ring. Which of the following explains why the ball may initially NOT pass through the ring, but then passes through it after cooling down?

A metal rod is heated from room temperature to a higher temperature. Which of the following statements best describes the change in its density?

Two identical empty glass bottles, Bottle A and Bottle B, are filled with air at room temperature. Bottle A is tightly sealed, while Bottle B has a tube inserted through its cork, allowing air to escape into water. Both bottles are then heated to the same temperature. Which bottle will experience the greatest pressure increase?

Which of the following statements best explains why it is easier to remove a glass stopper from a bottle after pouring hot water onto the bottle's neck?

Consider three liquids: water, alcohol, and benzene. All are heated to the same temperature. Which liquid will expand the MOST?

Which of the following BEST explains why a metal rim is made slightly smaller in diameter than the wooden wheel it is intended to fit on before it is heated?

Two identical iron rods, Rod A and Rod B, are heated to the same temperature. Rod A is solid, and Rod B is hollow. Which of the following statements accurately describes the expansion of the two rods?

A metal plate is heated to a certain temperature. Assuming all other factors remain constant, which of the following will have the GREATEST impact on the amount of area expansion the plate undergoes?

Why is one end of a steel girder in a bridge often placed on rollers instead of being fixed to the pillar?

Why does the density of a substance decrease when heated, assuming the mass remains constant?

All molecules of a liquid take part in evaporation.

The inter-molecular force of attraction is stronger in liquids than in solids.

Evaporation occurs only when heat is added to a liquid.

Molecules with lower kinetic energy are more likely to escape into the vapor phase during evaporation.

The process of evaporation stops when all the liquid has evaporated.

The temperature of the remaining liquid decreases during evaporation.

Evaporation can occur at any temperature.

Liquids with weaker intermolecular forces evaporate at a slower rate.

Evaporation is a process where a liquid changes into a gas, and this process requires heat energy.

The rate of evaporation increases when the surface area of the liquid is increased.

The rate of evaporation decreases with an increase in temperature.

Boiling is a process where a liquid changes into a gas throughout the entire liquid mass, not just at the surface.

When a liquid is heated, the average kinetic energy of its molecules decreases.

The expansion of a metal rod depends only on the material of the rod.

A copper rod heated to 10°C will expand less than a copper rod heated to 5°C.

For the same rise in temperature, an iron rod will expand more than a copper rod.

A solid ball will pass through a ring if the ball is heated.

Telephone wires can break in winter due to contraction.

Heating a solid object always causes its density to increase.

The expansion of a metal plate is independent of the material of the plate.

When a glass bottle is heated, the air inside expands and escapes as bubbles in the surrounding water.

Benzene expands more than alcohol and water when heated to the same temperature.

The density of a substance remains the same when its temperature increases.

The molecules with the lowest kinetic energy are the ones that escape from the liquid's surface during evaporation.

Evaporation can happen even if no heat is added to the liquid.

Evaporation is a process that occurs only on the surface of a liquid, not throughout the entire volume.

The intermolecular forces between molecules in a liquid are stronger than those in a solid.

Evaporation can occur at any temperature, as long as the liquid is exposed to air.

The process of evaporation requires energy to be added to the liquid from the surroundings.

Evaporation is a cooling process because the molecules that escape are the ones with the lowest kinetic energy.

The speed at which a liquid evaporates is called the evaporation rate.

Evaporation occurs only from the surface of a liquid.

Boiling and evaporation are the same processes occurring at different temperatures.

Increasing the temperature of a liquid decreases the rate of evaporation.

A liquid can draw necessary heat for evaporation from its surroundings.

The coefficient of linear expansion for copper is lower than that of iron.

The length of a rod does not affect its thermal expansion when heated.

Cooling causes solids to expand in size.

The density of a substance decreases with an increase in temperature as its volume increases.

Air inside a sealed glass bottle expands and escapes when heated.

When an iron rim expands, it can easily fit over a wooden wheel.

Telephone wires become loose in winter due to thermal expansion.

Pouring hot water on a stuck glass stopper will make it fit tighter.

The process of evaporation requires a constant supply of external heat to occur.

The rate of evaporation is directly proportional to the inter-molecular force of attraction between the liquid molecules.

All liquid molecules have an equal chance of escaping the liquid during evaporation.

The vapor pressure of a liquid at a particular temperature is directly related to the rate of evaporation.

The evaporation of a liquid can result in a decrease in the temperature of the remaining liquid.

In the process of evaporation, the escaping liquid molecules gain kinetic energy from the surrounding environment.

Evaporation is an example of a physical change.

The rate of evaporation is independent of the surface area of the liquid.

The rate of evaporation is directly proportional to the surface area of the liquid.

In the process of boiling, heat is absorbed into the liquid to break the intermolecular bonds between molecules.

The rate of evaporation of a liquid is inversely proportional to the strength of the intermolecular forces between the liquid molecules.

The rate of evaporation of a liquid is independent of the presence of wind or air currents.

Evaporation is a surface phenomenon, meaning it only occurs at the liquid's surface.

The volume of a gas decreases when the temperature decreases.

The expansion of a solid is independent of the material it is made from.

A solid expands more than a liquid when subjected to the same temperature change.

The thermal expansion of a substance is always linear, meaning the increase in length is directly proportional to the temperature change.

The concept of thermal expansion applies only to solids and liquids.

A metal rod will expand the same amount if heated from 0°C to 10°C or from 10°C to 20°C.

Thermal expansion is a reversible process, meaning when a material is cooled, it returns to its original size.

A hollow metal sphere will expand more than a solid metal sphere of the same size when heated to the same temperature.

The density of a substance increases with an increase in temperature.

The expansion of a liquid is independent of the nature of the liquid.

A matter is something that has ______, occupies space, and can be perceived by our senses.

The change of liquid into its vapour at all temperatures from its surface is called ______.

The ______ force of attraction is lesser in liquids as compared to solids.

Molecules with higher ______ reach the surface of the liquid.

The higher energy molecules on the surface absorb some more heat from the surroundings to gain sufficient ______ to do work against the force of attraction on them due to other molecules inside the liquid and escape out from the surface into space.

These escaping molecules form the ______ of the liquid.

Due to weak ______ force of attraction, the molecules of a liquid move freely inside it.

Molecules with higher ______ reach the surface of the liquid while those with lesser kinetic energy remain inside the liquid.

Evaporation is a ______ phenomenon

In evaporation, no ______ heat is supplied.

Blowing air above the surface of the liquid takes away the ______ escaping from the liquid surface.

On increasing the ______ area of the liquid, the number of molecules escaping out of the surface increases.

The change from the liquid state to the gaseous state on heating at a constant temperature is called ______.

When a liquid is heated, the average ______ energy of the liquid molecules increases.

The expansion of a substance when heated is called ______ expansion.

The three factors on which the ______ expansion of a metal rod on heating depends are: Original length of the rod, Increase in temperature, Material of the rod.

The Iron rod that is 10 m long will expand more than the rod of 5 m length because if two rods of different lengths but of the same metal are heated to the same temperature, the ______ rod will expand more than the shorter one.

The copper rod heated by 10°C will expand more than the rod heated by 5°C because if two identical rods of the same metal and the same length are heated to different temperatures, the rod heated to ______ temperature expands more than the rod heated to lower temperature.

The increase in length of the rod depends on the ______ of the rod.

The empty glass bottle is filled with ______.

Benzene will expand more than alcohol and water because the expansion of a liquid depends upon the ______ of the liquid since volume and temperature are same.

When a substance is heated, its ______ increases while its mass remains the same.

A ______ is something that has mass, occupies space and can be perceived by our senses.

Matter is composed of tiny particles called ______.

Molecules with higher kinetic energy reach the surface of the ______ while those with lesser kinetic energy remain inside.

The higher energy molecules on the surface absorb some more heat from the surroundings to gain sufficient kinetic energy to do work against the force of attraction on them due to other ______ inside the liquid and escape out from the surface into space.

Due to weak inter-molecular force of attraction the molecules of a ______ move freely inside it.

The ______ of a substance when heated is called thermal expansion.

The ______ kinetic energy of the liquid molecules increases during boiling of the liquid at its boiling point.

The three factors on which the linear expansion of a metal rod on heating depends are: Original length of the rod, Increase in ______, Material of the rod.

The ______ of the rod will expand more than the rod of 5 m length.

When the molecules acquire sufficient kinetic energy to overcome the force of attraction of other molecules, they escape out in form of ______.

In evaporation, no external heat is supplied so the liquid will draw the necessary heat from its ______.

The higher energy molecules on the surface absorb some more heat from the ______ to gain sufficient kinetic energy to do work against the force of attraction on them due to other molecules inside the liquid and escape out from the surface into space.

One end of a steel girder in a bridge is kept on ______ instead of fixing it in a pillar.

The average kinetic energy of molecules of a liquid increases during ______ of the liquid at its boiling point.

The iron rims are made slightly smaller in ______ than the wooden wheel.

In summer season due to rise in ______, each rail expands in length.

When hot water is poured on the neck of the bottle, the neck expands and the glass stopper stuck in it gets ______ to loosen and then can be easily removed.

Explain how evaporation affects the temperature of the remaining liquid?

Describe the relationship between inter-molecular force and the rate of evaporation.

Explain why only the molecules on the surface of a liquid participate in evaporation.

Describe what happens to the average kinetic energy of molecules when a liquid is heated to its boiling point.

What is the primary difference between evaporation and boiling?

How do evaporation and boiling contribute to the change of a liquid to a gaseous state?

Explain the process of evaporation in terms of molecular movement.

What is the effect of increasing the temperature on the rate of evaporation?

Why does evaporation lead to a cooling effect?

Explain the process of boiling in terms of molecular movement.

What are three factors that affect the linear expansion of a metal rod?

How does the original length of a rod affect its expansion?

How does the temperature change affect the expansion of a rod?

What is thermal expansion, and what are some everyday examples of it?

Explain how thermal expansion is used in fitting iron rims onto wooden wheels.

Explain how a glass stopper stuck in a bottle can be loosened using hot water.

What is the effect of heating a substance on its density?

Explain why the density of a liquid decreases when it is heated.

Why is evaporation considered a surface phenomenon?

Explain how blowing air above the surface of a liquid increases the rate of evaporation.

Describe the relationship between temperature and the rate of evaporation of a liquid.

What is the key difference between evaporation and boiling?

Explain why a liquid cools down as it evaporates.

How does the original length of a metal rod influence its linear expansion upon heating?

Explain how the coefficient of linear expansion affects the expansion of different metal rods when heated to the same temperature.

Describe how the thermal expansion of a steel girder is addressed in bridge construction.

Explain why benzene expands more than alcohol or water when heated.

Explain how the process of fitting an iron rim onto a wooden wheel utilizes thermal expansion.

Describe how the density of a substance changes with temperature, and explain why the change is more noticeable in liquids and gases compared to solids.

Explain why evaporation is considered a cooling process.

Describe the role of intermolecular forces in evaporation.

Explain why only molecules on the surface of a liquid can evaporate.

What is the relationship between the kinetic energy of liquid molecules and the rate of evaporation? Explain.

What are two factors that affect the rate of evaporation?

Describe how evaporation differs from boiling.

Given the information provided, describe the process of evaporation, explaining how it is different from boiling.

If a liquid is sealed in an airtight container, what will happen to the rate of evaporation over time, and why?

Explain how the kinetic energy of molecules is involved in the process of evaporation and influences whether a molecule will escape the liquid's surface.

Why is evaporation considered a cooling process? Explain how this relates to the transfer of energy between the liquid and its surroundings.

How does the inter-molecular force of attraction between molecules influence the rate of evaporation of a liquid? Explain the relationship.

Identify two factors, besides temperature, that can influence the rate of evaporation of a liquid. Explain how each factor impacts the process.

Explain why evaporation can occur even if no heat is supplied to the liquid.

Describe the role of collisions between molecules in the process of evaporation. Explain how collisions contribute to the escape of molecules from the liquid's surface.

Explain why a liquid evaporates only from its surface and not throughout its entire volume.

Describe the role of kinetic energy in the process of evaporation.

Explain how blowing air above a liquid surface can increase the rate of evaporation.

Why does increasing the surface area of a liquid increase its rate of evaporation?

Explain how the temperature of a liquid influences the rate of evaporation.

What is the relationship between the boiling point of a liquid and the average kinetic energy of its molecules?

Describe why evaporation is considered a cooling process.

What are three factors that influence the linear expansion of a metal rod?

Why does a hot iron rim fit snugly on a wooden wheel after it cools down?

Explain why gaps are left between sections of concrete roadways, and how this relates to thermal expansion.

Describe the phenomenon of thermal expansion and how it applies to a steel girder in a bridge that is kept on rollers at one end.

Explain why the density of a substance decreases when its temperature increases.

How does thermal expansion affect the air inside a sealed glass bottle when it is heated, and what causes the bubbles that form in the water?

Why does a glass stopper become stuck in a bottle when heated, and how can it be loosened?

Why is it important to leave gaps between cement slabs during construction?