Matter in our surroundings - class-IX

The common unit of measuring volume is litre (L).

Both solids and liquids have a fixed volume but gases do not have a fixed volume. This is because liquids and solids have strong intermolecular forces of attraction compared to gases.

A distinctive property of the liquid state is surface tension, leading to wetting phenomena. Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion).

The top of a liquid will usually have a flat surface. That flat surface is the result of gravity pulling on the liquid molecules. If you put an ice cube (solid) into the cup, it will sit there and not change shape. As the cube warms and melts, the liquid water will fill the bottom of the cup and have a flat surface on top.

Liquids are found between the solid and gas states. A trait of liquids is that they are difficult to compress.

The rate of diffusion of liquids is higher than that of solids. This is due to the fact that in the liquid state, particles move freely and have greater space between each other as compared to particles in the solid state.

Viscosity is a measure of how much a liquid resists flowing freely. Viscosity can usually be reduced by heating the liquid. When heated, the particles of the liquid move faster, allowing the liquid to flow more easily.

Only two elements are liquid at standard conditions for temperature and pressure i.e. mercury and bromine. 

Volatile liquids have low boiling point. As a result, they evaporate very easily at room temperature. Because of their low boiling points, volatile liquids convert to the gas phase at a lower temperature and the gas molecules can diffuse faster than the molecules of a non-volatile liquid.

The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. 

Liquids tend to have better thermal conductivity than gases, and the ability to flow makes a liquid suitable for removing excess heat from mechanical components. 

The movement of the particles causes the liquid to be variable in shape. Liquids will flow and fill the lowest portion of a container, taking on the shape of the container but not changing in volume. The limited amount of space between particles means that liquids have only very limited compressibility. 

A liquid flows. 

The property of liquids to resist their flow is called viscosity.

Liquid state of a matter has a definite volume but not a definite shape because the liquid molecules are bound with weak forces of attraction.

Liquids have a definite volume but indefinite shape and size. This is because the intermolecular forces of attraction in liquids are quite weak as compared to the solid states.

Liquids do not occupy the entire volume of the container in which they are placed. They occupy only the volume equal to their volume in the container. This is because there is a strong intermolecular force of attraction present between the molecules of the liquid.

The rate of diffusion is higher in liquids as they have more inter-molecular space so there is more space to diffuse.

Any matter that is a solid has a definite shape and a definite volume. The molecules in a solid are in fixed positions and are close together. Although the molecules can still vibrate, they cannot move from one part of the solid to another part. As a result, a solid does not easily change its shape or its volume.

Matter has three main state of matter that is solid, liquid and gas. Vapour is the type of substance which forms when liquid converts into the gaseous phase. It is a matter but not a state of matter.

The inter-molecular force of attraction is very weak in case of gases. So, gases are highly fluid in nature.

In case of solid the inter-molecular force of attraction is very strong and inter-particle spaces are very small. So, it is very difficult to compress the solid.

Solids have highest force of attraction between particles. The molecules are very tightly packed.

Among all the states of matter, gases exert pressure in all directions. Liquids and solids exert pressure along the gravity (generally).

When an object absorbs heat the temperature of the object increases. For eg; on boiling water the temperature of water increases and vaporizes.

Gases are highly miscible as the molecules are loosely bounded and can easily mix with each other.

Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.

The latent heat is used in change of states of matter, such as from solid to liquid or from liquid to gas without rising in temperature. When solid changes into liquid, the heat required for changing the state without rise in temperature is called the Latent Heat of Fusion. When liquid changes into gas because of rise in temperature, the heat required changing the state without rising in temperature is called the Latent Heat of vaporization.

A black object absorbs all wavelengths of light and reflects none. Objects that are white, on the other hand, reflect all wavelengths of light and therefore absorb the least heat.

Heat is thermal energy. It can be transferred from one place to another by conduction. Metals are good conductors of heat, but non-metals and gases are usually poor conductors. Poor conductors are called insulators.

A solid has a definite volume. It also has a definite shape.
The intermolecular forces in the case of a solid are very high compared to liquids and gases and hence a solid are held together tightly. Thus, a solid has a definite shape.

The intermolecular forces in the case of gas are very very weak and hence the gas molecules are not at all held tightly. Thus a gas doesn't have a fixed shape at all.
Gases do not have a fixed volume too. It has the volume of the container in which it is kept.

Mechanical work is important in systems that undergo appreciable change in volume. 

solids can be crystalline as well as amorphous in nature.

The kinetic theory considers all matter( substances) to be made up of particles which are in continuous motion. 

Theoretically, heating a solid to higher and higher temperatures changes its phase to a liquid, and finally to a gas.
A solid consists of low kinetic energy vibrating particles locked into position by interparticle attractive forces. When heat is applied, energy is absorbed and the particles start vibrating more vigorously.

A solid consists of low kinetic energy vibrating particles locked into position by interparticle attractive forces. When heat is applied, energy is absorbed and the particles start vibrating more vigorously.

Molecules in solid are tightly packed together and cannot move.

In liquid and solid states the bond lengths and bond angles are slightly changed due tohydrogen bonding.

Water vapour at 373K has more energy than water at 373K as the steam has absorbed latent heat of vaporisation to change the state. Therefore the more burning sensation.

Solids do not mix with each other as there is very less space between the atoms of solids and are tightly packed.

Solid has highest inter-molecular force of attraction. Liquids has inter-molecular force of attraction less than solid but greater than Gas. So, it has indefinite shape but definite volume.

The kinetic energy of gases is maximum because inter-molecular force of attraction is minimum and kinetic energy is minimum in solid .

Solids have most number of particles per unit area. The molecules are very tightly packed and solids have high density.

Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process that is specified in some way. An example is latent heat of fusion for a phase change, melting, at a specified temperature and pressure. Latent heat is associated with the phase changes of atmospheric water vapor, mostly vaporization and sublimation.

The more light the object absorbs, the more heat absorbed since light is energy. If you consider it a color, black absorbs the most heat. A black object absorbs all wavelengths of light and reflects none. Objects that are white, on the other hand, reflect all wavelengths of light and therefore absorb the least heat.

The more light the object absorbs, the more heat absorbed since light is energy. If you consider it a color, black absorbs the most heat. A black object absorbs all wavelengths of light and reflects none. Objects that are white, on the other hand, reflect all wavelengths of light and therefore absorb the least heat.

Conduction, convection, radiation, all the 3 processes involves heat transfer.

Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection. Conduction is the transfer of energy through matter from particle to particle. 

Sublimation- It is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. 

Condensation- It is the change of the physical state of matter from gas phase into liquid phase.

Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance.

Deposition is a thermodynamic process, a phase transition in which gas transforms into solid.

Melting (also known as fusion) is a physical process that results in the phase transition of a substance from a solid to a liquid.

When liquid changes into gas because of rise in temperature, the heat required changing the state without rising in temperature is called the Latent Heat of vaporization. The latent heat of vaporization of water is the energy which is used to change the state of water (liquid) to vapor (gas).

A liquid has a particular volume but it doesn't have a definite shape. Liquid takes the shape of the container in which it is kept.
The inter-molecular forces in case of a liquid are not as strong as in solids and hence a liquid is not held together tightly. Thus, the liquid takes up the shape of the container in which it is kept.

In a solid, the particles are held together by strong intermolecular forces between them and hence there is very little scope of movement for the particles in solid. So, kinetic energy of solid is very low.

On heating solids, intermolecular attraction between the particles decreases as the particles gain energy to move randomly.

On heating liquids, intermolecular space between molecules increases as the particles gain enough kinetic energy to overcome the force of attraction.

On heating solids, the intermolecular space between the molecules increases due to the movement of molecules randomly.

Change of solid state into liquid state is known as fusion.

The temperature at which particles slow down and convert into a solid is known as solidification point.

On heating a liquid, heat absorbed by its molecules is absorbed and stored in the form of potential energy.

The solid formed by directly cooling a gaseous substance through a process of sublimation is known as sublimate.

On heating liquids, intermolecular attraction decreases as the particles gain enough kinetic energy to overcome the attraction.

Condensation takes place when the atoms or molecules come together and clump due to increased inter-molecular attraction.

At boiling point, the particles of liquid  get converted into a gas.

On cooling gases and liquids, temperature falls intermolecular attraction increases intermolecular space between molecules decreases.

The temperature at which the particles slow down and converts into a liquid is known as liquefaction point.

On the heating matter, the kinetic energy of particles increases, so they gain energy and on the cooling matter, the particle's the motion of particles decreases, so they lose energy.

At melting point, the particles get converted into a liquid.

On cooling a gas, the temperature falls down and the stored potential energy is released in the form of heat energy so that the temperature fall and the gas becomes cool.

The phenomenon of change from one state of matter to another and then back to the original state is called the inter-conversion of states of matter.

Inter-conversion of states of matter is affected by 1. Changing the temperature.
2. Increasing or decreasing the pressure.
3. Changing both temperature and pressure.

Solids have the lowest kinetic energy whereas gases have the highest kinetic energy. Hence, hydrogen has the highest kinetic energy among the above examples.

At freezing point, particles slow down, come close and get converted into a solid. Inter-molecular forces increase.

The change of state of a substance directly from solid to gas without changing into a liquid state is known as sublimation.

Solids have least amount of kinetic energy. When the kinetic energy increases, the velocity of particles increases. The particles collide with a greater force. Thus, the ordered arrangement of solid breaks which results in phase change.

On cooling gases/liquid, the temperature falls. Particles gain energy. Intermolecular attraction increases. Intermolecular space between the particles/molecules of gases decreases.

At the boiling point, particles become completely free and convert into gas/vapor.

Option D is the correct answer.

Option B is the correct answer.

At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. 

Evaporation occurs below the boiling point of the liquid. The particles escape from the surface of the liquid to form gas. Evaporation differs from boiling in that it only takes place at the surface of the liquid and it is very slow. On the other hand, boiling takes place throughout the liquid and is very fast.

During melting, the temperature remains constant. This is because the heat energy is taken in by the particles to overcome forces between them instead of being used to raise the temperature.

Option A is the correct answer.

In addiiton to the temperatre steam has latent heat of vapourization which it acquires after converting into steam from water.

A solid consists of low kinetic energy vibrating particles locked into position by interparticle attractive forces. When heat is applied, energy is absorbed and the particles start vibrating more vigorously.
Finally, the vibrations become energetic enough to overcome the attractive forces, and the particles start sliding out of their positions to flow about. The solid is now melting into a liquid.

Evaporation involves conversion of liquid to vapor which happens when latent heat is absorbed by the liquid.

During freezing, inter-molecular attraction increases and the motion of particles becomes slow.

Molecular kinetic energy is maximum in gases and least in solids. Hence, a substance is melted from solid to liquid state, its kinetic energy increases.

When hydrogen gas leaks out of the container, the molecules of the gas remaining in the container have more free space. Hence, distance between the gas molecules increases. By increasing the volume of the container also increases the distance between the molecules.

When a pure substance undergoes a phase change from solid to liquid state,there will increases in temperature so,the collision rate do not increases which implies that there is no change in kinetic energy,the entire heat involves a change in potential energy.It involves change in entropy because more free particles are generated from solid to liquid.

Deposition is a phase transition in which gas transforms into solid without passing through the liquid phase.

Condensation is a process in which gaseous molecules lose energy and gets converted to liquid state.

$T$ $\alpha$  $KE$
Higher the temperature higher will be kinetic energy .
Hence, as the water heats up from 280 K to 310 K, the average kinetic energy of the its molecules will increase.

Evaporation is a physical change because when water evaporates no new substances are being made or nothing is being taken away from it, so in that case its still water. All the other options involve making new substances, so they all are chemical changes.