Session1

Separation of mixtures, Lesson 1

States of matter Matter is anything that occupies space and has mass.

Matter can exist in three main states:

Solid

Liquid

Gas

We need a theoretical model to explain the properties of the three states of matter.

Properties of the states of matter Solids:

Retain a fixed shape and volume.

Not easily compressible, defined by a constant density.

Liquid: Can flow.

Have defined volume, but not defined shape.

Have constant density.

Gas: Tend to occupy all the volume available.

Assumes the shape and volume of its container.

Kinetic particle theory The kinetic particle theory is the theory that explains the

properties of the three states of matter. The gas consist of very small particles known as atoms or

molecules.

The average distance separating the gas particles is large compared to their size.

These particles are in constant, random and rapid motion.

The particles constantly collide among themselves and with the walls of the container.

The interactions among particles are negligible.

The average kinetic energy of the particles depends only on the absolute temperature of the substance.

Kinetic particle model

GasProperty Why

Assumes the shape and volume of its container

Particles can move past one another

Compressible Lots of free space between particles

Flows easily Particles can move past one another

LiquidProperty Why

Assumes the shape of the part of the container which it occupies

Particles can move or slide past one another

Not easily compressible Little free space between particles

Flows easily Particles can move or slide past one another

SolidProperty Why

Retains a fixed volume and shape Particles locked into place

Not easily compressible Little free space between particles

Does not flows Particles cannot move or slide past one another

Gas, liquid and solid

Question 1 When a bottle of perfume is opened into a room, the

smell of the perfume slowly arrives to all the parts of the room. How can you explain it?

Question 1

The particles of the perfume moves in all directions and tend to occupy all the volume available.

When a bottle of perfume is opened into a room, the smell of the perfume slowly arrives to all the parts of the room. How can you explain it?

Question 2 When heating, pressure in a balloon full of gas gets

bigger. How can you explain it?

Question 2

The average kinetic energy of the particles depends on the temperature of the substance. So, when heating the particles will move faster and so it will collide more strongly with the walls of the container.

When heating, pressure in a balloon full of gas gets bigger. How can you explain it?

State changes Substances can exist as a solid, liquid or gas.

Converting from one state to another involves heating or cooling.

Under certain conditions some solids turn straight into a gas when heated. This process is called sublimation.

Latent head Head must be supplied to a substance for it to melt,

boil or evaporate.

Head must be removed from a substance for it to condense or freeze.

The energy supplied to or removed from a substance during a change of state of matter is called latent head.

Calculation of latent head

Q = m·L

Q: amount of energy (J or cal)

m: mass (kg)

L: specific latent head for a particular substance (J/kg)

Specific latent headSubstance Specific latent head

melting (kJ/kg)Specific latent head vaporization (kJ/kg)

Alcohol 108 855

Ammonia 322,17 1369

Hydrogen 58 455

Lead 23 871

Water 334 2260

Question 3 Calculate the energy supplied to a mass of 3 kg of ice

for it to melt to water. The specific latent head of melting for water is 334 kJ/kg. Give the result in calories by using conversion factors.

Question 3 Calculate the energy supplied to a mass of 3 kg of ice

for it to melt to water. The specific latent head of melting for water is 334 kJ/kg. Give the result in calories by using conversion factors.

Q = m·L = 3·334 = 1002 kJ

1002 kJ· 1000J/1kJ · 0,24 cal/1J =240.480 cal