Lecture 35 States of Matter Ozgur Unal NIS – PHYSICAL SCIENCE Lecture 35 States of Matter Ozgur Unal

States of Matter What are the states of matter? Provide an example for each. There are four states of matter: Solid Liquid Gas Plasma http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html http://preparatorychemistry.com/KMT.html

States of Matter In solid state the particles are packed closely together and constantly vibrating in place. Strong attraction between particles  fixed volume and shape In liquid state, the attractive forces between particles are weaker than in a solid. Particles can slide past each other. Fixed volume, but indefinite shape.

States of Matter In a gas, the particles are much farther apart than in a liquid or a solid  Weak attractive forces between particles. No definite shape nor volume. Gas particles diffuse much faster than the ones in solids and liquids. Plasma is matter consisting of positively and negatively charged particles  very energetic particles No definite shape nor volume. Example: Stars, auroras, lightning bolts etc.

Changing States Changes in the thermal energy of a material can cause it to change from one state to another. Changing from solid to liquid  Melting Changing from liquid to solid  Freezing Changing from liquid to gas  Vaporization Changing from gas to liquid  Condensation During melting the energy of the particles in a solid increases. The energy of the particles becomes high enough to overcome the attractive forces between the particles. The particles can slip out of their ordered arrangement.

Melting and Freezing During melting the energy of the particles in a solid increases, which becomes high enough to overcome the attractive forces between the particles. The particles can slip out of their ordered arrangement. The temperature at which a solid begins to melt is its melting point. The amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point is known as the heat of fusion. Lf (water)= 334 J/g Heat of fusion is also the energy released during freezing.

Vaporization and Evaporation As the temperature of a liquid increases, the particles move faster, eventually the particles become very energetic enough to overcome the attractive force of other particles  Vaporization Vaporization that occurs at the surface of a liquid is called evaporation. Why do we sweat when it is hot?

Boiling A second way that a liquid can vaporize is by boiling. Boiling occurs throughout a liquid at a certain temperature depending on the air pressure at the surface of the liquid. The boiling point of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface. The heat of vaporization is the amount of energy required for 1 kg of the liquid at its boiling point to become a gas. Lv (water)= 2260 J/g

Condensation The heat of vaporization is also the amount of energy released during condensation, when a gas changes into a liquid. Dew is also the result of condensation. Dew forms when the air around matter, such as spider webs, cools enough so that water vapor in the air changes to a liquid.

Heating Curve of a Substance The graph below shows the heating curve of water. Why is the temperature constant during melting and boiling?

Lecture 36 Thermal Expansion Ozgur Unal NIS – PHYSICAL SCIENCE Lecture 36 Thermal Expansion Ozgur Unal

Thermal Expansion An object (whether solid, liguid, gas or plasma) expands as it gets hotter. According to the kinetic theory, the particles in an object move faster as the temperature increases. As they move faster, their motion can overcome the attractive forces between particles and the distances between particles increase  The object expands Similarly, decreasing temperature leads to contraction of objects.

Thermal Expansion of Solids Solids expand with increasing temperature. Expansion occurs in 3 dimensions. The amount of expansion in one dimension can be calculated according to the following formula: ΔL = L * α * (Tf - Ti) L is the initial length of one side of the solid ΔL is the amount of expansion Ti (Tf) is the initial (final) temperature of the solid α is the coefficient of linear expansion, which depends on the type of solid.

Thermal Expansion of Liquids and Gases Liquids also expand as they get hotter  Increase in volume Example: Alcohol thermometer Gases expand even more than solids and liquids when the temperature increases  Increase in volume For a given amount of gas, an increase in volume means a decrease in the density. Example: Hot air balloon