Chapter 1 Matter In Our Surroundings Note

Matter in Our Surroundings

Matter

• All things which we see around us.
• Use in our everyday life together constitute matter.
• Anything which occupies space and has mass is called matter.
• Matter is made up of particles.

States of Matter

• Matter can be classified on the basis of interparticle forces and the arrangement of particles.
  1. Solid
  2. Liquid
  3. Gas
• These three forms of matter are interconvertible by increasing or decreasing pressure and temperature.
• For example, ice can be converted from solid to a liquid by increasing the temperature.

Atomic view of the three states of matter

Evaporation

• The phenomenon by which molecules in liquid state undergo a spontaneous transition to the gaseous phase at any temperature below its boiling point is called evaporation.
• For example, the gradual drying of damp clothes is caused by the evaporation of water to water vapour.

Factors affecting evaporation

1. Temperature: The rate of evaporation increases with an increase in temperature.
2. Surface area: The rate of evaporation increases with an increase in surface area.
3. Humidity: The rate of evaporation decreases with an increase in humidity.
4. Wind speed: The rate of evaporation increases with an increase in wind speed.

Cooling due to evaporation

• During evaporation, the particles of a liquid absorb energy from the surroundings to overcome the inter-particle forces of attraction and undergo the phase change.
• The absorption of heat from the surrounding makes the surrounding cool.
• For example, sweating cools down our body.

Physical Nature of Matter

• A physical property is that aspect of the matter that can be observed or measured without changing its nature or composition.
• It is independent of the amount of matter present.
• Include appearance, colour, odour, density, texture, melting point, boiling point, solubility, etc.

Characteristics of Particles of Matter

• Matter is anything that has mass and occupies space.
• Everything that we can touch, see, hear, taste and also smell is matter.
• It is made up of really tiny particles which cannot be seen through the eye.
• The particles of which the matter is comprised influence its state and properties (physical and chemical).
• Particles of matter have spaces between them.
• This characteristic is one of the concepts behind the solubility of a substance in other substances.
• For example, on dissolving sugar in water, there is no rise in water level because the particles of sugar get into the interparticle spaces between the water particles.
• Particles of matter are always in motion-Particles of the matter show continuous random movements due to the kinetic energy they possess. A rise in temperature increases the kinetic energy of the particles, making them move more vigorously.
• Particles of matter attract each other
• In every substance, there is an interparticle force of attraction acting between the particles.
• To break a substance, we need to overcome this force.
• The strength of the force differs from one substance to another.

Diffusion

• When the particles of matter intermix on their own with each other, the phenomenon is called diffusion.
• For example: spreading of ink in water.
• During diffusion, the particles occupy the interparticle spaces.
• The rate of diffusion increases with increase in the temperature, due to increase in kinetic energy of the particles.

Effect of change of temperature on state of matter

• On increasing temperature, the kinetic energy of the particles of the matter increases and they begin to vibrate with a higher energy.

• The interparticle force of attraction between the particles reduces and particles get detached from their position and begin to move freely.
• As a result, the state of matter begins to change.

Melting point

• The melting point of a solid is defined as the temperature at which solid melts to become liquid at the atmospheric pressure.
• At melting point, these two phases, i.e., solid and liquid are in equilibrium, i.e., at this point both solid state and liquid state exist simultaneously.

Boiling point

• The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure.

Latent heat of vaporisation

• It is the amount of heat energy that is required to change 1 kg of a liquid into gas at atmospheric pressure at its boiling point.

Sublimation

• The transition of a substance directly from its solid phase to gaseous phase without changing into the liquid phase (or vice versa) is called sublimation.
• Sublimation – Solid to Gas Phase Transformation
• The change of state of a substance directly from a solid to gas, without changing into the liquid state (or vice versa) is called sublimation.
• Example: camphor, naphthalene, ammonium chloride, solid carbon dioxide and iodine.

Types of Matter

• There are two ways in which matter can be classified-
  • On the basis of its physical nature (physical state).
  • On the basis of its chemical constitution.

Characteristics of Particles of Matter

• are very small.
• have spaces between them.
• are continuously moving.
• attract each other.

Diffusion

• Intermixing of particles of two different types of matter on their own is called diffusion.
• The rate of diffusion increases on increasing the temperature of the diffusing substance (by heating).
• Examples of diffusion in gases:
  • The aroma of food being cooked in the kitchen reaches us even from a considerable distance due to diffusion.
  • The fragrance of a perfume spreads due to the diffusion of the perfume particles into air.
• Examples of diffusion in liquids:
  • The spreading of ink in water, on its own, is due to the diffusion of ink particles in the water.
• Examples of diffusion in solids:
  • If two metal blocks are bound together tightly and kept undisturbed for a few years, then the particles of one metal are found to have diffused into the other metal.

TERMS

(a) Melting Point

• The temperature at which a solid melts to become a liquid, at atmospheric pressure, is called its melting point.
• Melting point is the characteristic property of a substance. For example, melting point of ice is 0 degree C (273 K).

(b) Freezing or Solidification

• The process, in which a liquid changes to its solid form, on cooling at a specific temperature, is called freezing or solidification.

(c) Latent heat:

• The hidden heat which breaks the force of attraction between the molecules is known as the latent heat.
• Since, the heat energy is hidden in the bulk of the matter, it is called latent heat.

(d) Latent heat of fusion:

• The heat energy required to convert 1 kilogram of a solid into liquid at atmospheric pressure, at its melting point, is known as the latent heat of fusion.
• When we supply heat energy to water, the particles start moving faster.
• At a certain temperature, a point is reached when the particles have enough energy to break free from the forces of attraction of each other.
• At this temperature, the liquid starts changing into a gas.

(e) Boiling Point: (Liquid → Gas)

• The temperature at which a liquid starts boiling, at atmospheric pressure, is called its boiling point.
• Boiling is a bulk phenomenon.
• Particles from the bulk of the liquid gain energy to change into the gaseous state.
• For example, boiling point of water is 100⁰C.
•  (Or 100⁰C = 273 + 100 = 373 K)

(f) Latent heat of vapourisation:

• The heat energy required to convert 1 kilogram of liquid into gas, at atmospheric pressure, at its boiling point, is known as the latent heat of vapourisation.

(g) Condensation (Gas → Liquid)

• The process, in which a gas, on cooling, turns into a liquid at a specific temperature is called condensation or liquefaction.
• The heat removed from the surface through evaporation is released into the atmosphere by the formation of clouds.
• This process cools the Earth’s climate.

(h) Freezing point (Liquid → Solid)

• The temperature at which the state of a substance changes from a liquid to a solid is called the freezing point of that substance.

(i) Evaporation (Liquid à Gas)

• The process of conversion of a substance from the liquid state to the gaseous state at any temperature below its boiling point is called evaporation or vapourisation.
• Evaporation is a surface phenomenon.

Factors Affecting Evaporation

• The rate of evaporation increases on increasing the surface area of the liquid.
• The rate of evaporation increases with an increase in temperature.
• Decrease in the humidity increases the rate of evaporation.
• An increase in the wind speed increases the rate of evaporation

Effect of Change of Pressure

• Gases can be liquefied by applying pressure and reducing the temperature.
• When a high pressure is applied to a gas, it gets compressed and if the temperature is lowered, the gas is liquefied.

Plasma

• The state consists of super energetic and super excited particles. These particles are in the form of ionised gases.
• The fluorescent tube and neon sign bulbs consist of plasma.