Chapter-1 Matter in Our Surroundings

The items that are matter are chair, air, almonds, cold, lemon water and the smell of perfume.

Chair and almonds are examples of solid matter. 

Air and the smell of perfume are examples of gas matter, while lemon water is an example of liquid matter.

Smell, love, hate, thought, are not matter since they are not physical substances that occupy space and have mass.

The observation can be explained by the fact that the rate of diffusion of odour molecules is higher at higher temperatures. When food is hot and sizzling, the temperature of the food is high, which causes the odour molecules to move faster and spread more quickly into the surrounding air. Therefore, the smell of hot sizzling food can be detected several metres away.

On the other hand, when food is cold, the temperature is lower, and the odour molecules move more slowly and are less likely to diffuse into the surrounding air.

Therefore, to detect the smell of cold food, you have to go closer to it, where the concentration of odour molecules is higher.

Additionally, hot food often produces more steam or vapour than cold food, which can carry odour molecules further away from the food and contribute to the stronger and more easily detectable smell.

The observation that a diver is able to cut through water in a swimming pool shows that matter has the property of "fluidity" or "flow".

Fluidity refers to the ability of matter to flow and change shape when a force is applied. Liquids and gases are considered fluids because they can flow and take the shape of their containers.

In the case of the diver cutting through water, the force applied by the diver's body pushes the water aside, allowing the diver to move through it. This shows that water, as a liquid, has the property of fluidity.

The characteristics are as follows:

1. Particles have mass: All particles of matter have mass, which means they occupy space and have weight.

2. Particles have volume: Particles of matter occupy space, which means they have a certain volume.

3. Particles are constantly in motion: Particles of matter are in constant motion, whether in the form of solids, liquids or gases. The motion of the particles is influenced by various factors such as temperature, pressure and external forces.

4. Particles attract each other: Particles of matter are attracted to each other by various types of intermolecular forces such as ionic, covalent, metallic, or van der Waals forces.

5. Particles have energy: Particles of matter possess energy in various forms such as kinetic, potential, or thermal energy. This energy is related to the motion, position, and temperature of the particles.

6. Particles have space between them: There is space between the particles of matter, which determines the density of the substance.

7. Particles may be arranged in an orderly or random manner: Depending on the state of matter, the particles may be arranged in an orderly or random manner. In solids, the particles are tightly packed and arranged in a regular pattern, while in liquids and gases, the particles are arranged randomly.

Overall, the characteristics of the particles of matter determine the properties and behaviour of matter in different states.

The order of increasing density is:

1. Air (approx. 1.2 kg/m³)

2. Exhaust from chimneys (varies, but generally denser than air; as it is a mixture of air with various chemical substances)

3. Cotton (approx. 150 kg/m³)

4. Water (approx. 1000 kg/m³)

5. Honey (approx. 1400 kg/m³)

6. Chalk (approx. 2500 kg/m³)

7. Iron (approx. 7870 kg/m³)

So, the correct order of increasing density from least to greatest is: air, exhaust from chimneys, cotton, water, honey, chalk, and iron.

a) Here is a table highlighting the differences in the characteristics of matter:

These are general characteristics, and there can be exceptions based on specific substances, conditions, and other factors.

b) Here are the definitions:

1.  Rigidity: Rigidity refers to the property of matter that describes how resistant it is to deformation. Solids have high rigidity because their particles are tightly packed and strongly held together. Liquids and gases have lower rigidity because their particles are more loosely packed and can move past one another.

2. Compressibility: Compressibility is the property of matter that dictates how easily it can be compressed or squeezed. Solids are almost incompressible, whereas liquids and gases are compressible to varying degrees.

3. Fluidity: Fluidity is the property of matter that describes how easily it can flow. Liquids and gases have high fluidity because their particles can move past one another easily. Solids have lower fluidity because their particles are held more rigidly in place.

4. Filling a gas container: Gases have the ability to fill the entire volume of a container, taking the shape of the container. This is because gas particles have high kinetic energy and are in constant, random motion. They collide with one another and with the walls of the container, filling the available space.

5. Shape: The shape of matter is determined by the arrangement of its particles. Solids have a fixed shape because their particles are arranged in a regular, repeating pattern. Liquids and gases take the shape of their container because their particles are not arranged in a fixed pattern.

6. Kinetic energy: Kinetic energy is the energy that matter possesses due to its motion. The kinetic energy of particles increases as temperature increases. Solids have the lowest kinetic energy, while gases have the highest kinetic energy.

7. Density: Density is the amount of mass per unit volume of matter. Solids are generally denser than liquids, which are denser than gases. This is because the particles of solids are packed more closely together, while the particles of gases are more spread out. However, there can be exceptions based on specific substances, conditions, and other factors.

a) A gas fills completely the vessel in which it is kept because gas particles have high kinetic energy and are in constant, random motion. They collide with each other and with the walls of the container, filling the available space.

b) A gas exerts pressure on the walls of the container because gas particles have high kinetic energy and are in constant, random motion. When they collide with the walls of the container, they exert a force on the walls, creating pressure.

c) A wooden table should be called a solid because it has a fixed shape and volume, and its particles are tightly packed and held together by strong intermolecular forces. These characteristics are typical of solids.

d) We can easily move our hand in the air, but to do the same through a solid block of wood, we need a karate expert because solids have high rigidity and are resistant to deformation. The particles of a solid are tightly packed and strongly held together, making it difficult to move through them without applying a significant amount of force. In contrast, air particles are widely spaced and have low intermolecular forces, making it easy to move through them.

The fact that ice floats on water is due to a unique property of water known as "anomalous expansion upon freezing." Most substances become more dense when they solidify, which causes them to sink in their liquid state. However, water is different in that it becomes less dense when it freezes. This is because the water molecules in ice are arranged in a crystal lattice structure, with empty space between the molecules, which makes it less dense than liquid water.

As water cools and approaches its freezing point, the molecules start to slow down and come closer together, which would normally result in an increase in density. However, when the temperature of water reaches 4°C, its density starts to decrease instead of increase. This is because, as the water molecules get even closer together, they start to form hydrogen bonds with each other, which push the molecules apart and create empty space in the ice. This causes ice to be less dense than liquid water and float on top of it.

We know that 

0°C = 273K

Using this relation, we have

a) 300K = (300-273)°C = 27°C

b) 573K = (573-273)°C = 300°C

a) At 250°C, water is in a gaseous state or in the form of steam.

b) At 100°C, water can be in either liquid or gaseous state, depending on the pressure. At standard atmospheric pressure (1 atm), water is in a liquid state at 100°C. However, at higher pressures, such as in a pressure cooker, water can remain in a liquid state at temperatures above 100°C. At lower pressures, such as at high altitudes, water may boil at temperatures below 100°C and exist in a gaseous state.

During the change of state of a substance, such as from solid to liquid or liquid to gas, the temperature remains constant because the energy being added or removed from the substance is being used to break or form the intermolecular forces between the particles, rather than to increase or decrease the temperature.

This energy transformation is known as latent heat, and it causes the temperature of the substance to remain constant during the change of state. Once all the intermolecular forces have been broken or formed, any additional heat energy added or removed from the substance will cause a change in temperature.

Atmospheric gases can be liquified by increasing the pressure, decreasing the temperature or both.

In commercial use the process to liquify gases is called cryogenic liquefaction.

The basic steps of cryogenic liquefaction involve compressing the gas to increase its pressure, then cooling it down using a refrigeration system. The gas is then allowed to expand, which causes its temperature to drop even further. This process is repeated until the gas has been cooled to a temperature at which it liquefies.

Water kept in an earthen pot becomes cool during summer due to the natural process called evaporative cooling. The walls of the earthen pot are porous, allowing some of the water to penetrate to the outside surface. When the water comes in contact with the hot air outside the pot, it begins to evaporate.

As the water evaporates, it absorbs heat energy from the remaining water, causing it to cool down.

Our palm feels cold when we put on some acetone or petrol or perfume because of the process of evaporation. These substances evaporate readily when they come in contact with air, which causes the surrounding area to cool down.

As they evaporate, they absorb heat energy from the surroundings, including the skin on our palm. This causes the temperature of the skin to drop, giving us a sensation of coldness.

We are able to sip hot tea or milk faster from a saucer rather than a cup because of the increased surface area available for cooling through evaporation.

This allows more of the liquid to come in contact with the air, which in turn promotes faster cooling through evaporation.

As a result, the liquid in the saucer cools down more quickly than in a cup.

In summer, we should wear clothes that are light in weight, loose-fitting, and made of breathable fabrics that allow air circulation and absorb moisture away from the skin. This helps in keeping our body cool and comfortable in hot and humid weather.

Cotton is a fabric for summer clothing as it is lightweight, breathable and absorbs sweat easily, keeping the body cool and dry. 

Also one should wear  light-coloured clothes as they reflect sunlight and keep us cooler than dark-coloured clothes that absorb heat.

We know that 

0°C = 273K

Using this relation, we have

a) 293K = (293-273)°C = 20 °C

b) 470K = (470-273)°C = 197°C

As we know that

0°C = 273K

Using this relation, we have

a) 25°C = (25 + 273)K = 298K

b) 373°C = (373 + 273)K = 646K

a) Naphthalene balls disappear with time without leaving any solid because they undergo a chemical process called sublimation. At room temperature, some of these molecules escape into the air as a gas without melting into a liquid first. Over time, as more and more naphthalene molecules sublimate, the size of the ball decreases until it eventually disappears completely, leaving no solid residue behind.

b) We can get the smell of perfume while sitting several metres away because the molecules of the perfume are highly volatile and can easily escape into the air as a gas. When we spray perfume, the liquid molecules evaporate and mix with the air, forming a cloud of perfume molecules that can travel long distances through the air.

The increasing order of forces of attraction between the particles is:

oxygen < water < sugar

Oxygen is a gas and exists as individual molecules with weak intermolecular forces of attraction. Water molecules are attracted to each other through hydrogen bonding, which is stronger than the weak van der Waals forces between oxygen molecules. Sugar molecules have even stronger intermolecular forces of attraction, including hydrogen bonding and dipole-dipole interactions.

a) At 25°C, water is usually in the liquid state at this temperature.

b) At 0°C, water can exist in two states of matter: solid and liquid. At this temperature, water freezes and turns into ice, which is a solid.

c) At 100°C, water can exist in two states of matter: liquid and gas. At this temperature, water boils and turns into steam, which is a gas.

a) Water at room temperature is a liquid because:

1. Its molecular structure: Water molecules are made up of one oxygen atom and two hydrogen atoms. They have hydrogen bonds that are strong enough to keep the water molecules close together, which gives water its liquid state.

2. Its melting and boiling points: Water has a melting point of 0°C and a boiling point of 100°C at standard pressure. These temperatures are within the range of room temperature, which is around 20-25°C. This means that water will remain in its liquid state at room temperature, as the temperature is not low enough to freeze it or high enough to boil it.

(b) An iron almirah is a solid at room temperature because:

1. Its molecular structure: Iron has a solid molecular structure held together by strong metallic bonds, which allow the atoms to maintain a fixed position relative to each other. This fixed position gives the iron almirah its solid state at room temperature.

2. Its melting point: Iron has a melting point of 1538°C. This temperature is much higher than room temperature, which means that the iron almirah will not melt at room temperature. Instead, it will remain in its solid state, making it a sturdy and reliable storage option.

Ice requires a significant amount of energy to melt it and convert into liquid water. This energy is known as the latent heat of fusion. As a result, when ice at 273K is used for cooling, it absorbs a large amount of heat from the surroundings to melt and become water at the same temperature. This absorption of heat results in a more efficient cooling effect.

In contrast, water at 273K will not undergo any phase change and will only absorb heat through its specific heat capacity. Therefore, ice at 273K is more effective in cooling than water at the same temperature.

Steam causes more severe burns because steam has more heat energy than boiling water due to its latent heat of vaporisation. When water reaches its boiling point, it converts to steam, which requires a large amount of heat energy. This extra energy is released when the steam comes into contact with a cooler surface, such as skin, and can cause more severe burns than boiling water.

The diagram depicts the interconversion of the three states of matter.

(A): depicts the process of melting; solid to liquid.

(B): shows the process of evaporation; liquid to gas

(C): shows condensation; gas to liquid

(D): depicts solidification; liquid to solid

(E): depicts sublimation; solid to gas

(F): depicts solidification: gas to solid