Getting to Know More about Matter

The Heating/Cooling Curve of a Pure Substance

Solid State

A:  -  Substance is at solid state
      -  In a solid state the particles are very close together and in an orderly manner and the forces between them are so strong, they can only vibrate at a fixed position.
      -  Ice is warming from -10 °C to 0 °C


A-B:  -  Heat energy is converted to kinetic energy.  
         -  Kinetic energy increases and the molecules vibrate faster and the temperature increases.


B:  -  The substance is beginning to melt, but is still is a solid.
      -  The temperature remains the same and is called the melting  point.


B-C:  -  This state of is called Melting.
          -  The particles are starting to become more fluid.
*C-B is Freezing or Solidification on a cooling curve.

Liquid State

C:  -  The substance has completely melted.  
      -  The solid has turned into a liquid.


C-D:  -  The substance is heated and the molecules are gaining more heat energy = temperature increases.
          -  Kinetic energy is increasing and the particles are moving faster and faster.


D:  -  Still exists in liquid state.
      -  Ex. if substance is water, the water would be boiling.
      -  The molecules have enough energy to start moving freely
      -  The liquid begins to change into gas state.

Gas State

D-E:  -  The state is called Evaporation.
          -  The unchanged temperature is called boiling point.
*E-D is Condensation on a cooling curve.




E:  -  The liquid has turned to gas.


E - end point:  -  The gas particles continue to absorb more energy and move faster as heating continues = increase in temperature.


A - end point:  -  The state is Deposition.
*End point - A is the state Sublimation on a cooling curve.

The States of Matter

This is a Cooling Curve

Chapter 2: Finding Out About Matter
Notes on pg. 25-29




Matter in the Microscopic World
Introduction

• Chemists go beyond the picture and make increasingly precise observations and detailed inferences.
• Matter will be closely observed and chemists are supposed differ them from one another, what different kinds have in common, how one kind can be changed to another and even how matter can be kept the same.

2-1: What You Know about Matter

• Water will change to solid when cooled, or to gas when heated.
• Solids such as water (ice) will shatter if smashed, but a metal fork or a wax candle will bend or flatten upon impact.
• The temperature at which matter changes from liquid to a gas is its boiling point, this is still another property that identifies matter.

2-2: Purifying Matter

• A mixture is two (or more) kinds of mater that have separate identifies.
• An example of a mixture is that muddy water will separate into layers of dirt and clear water.
• Matter that is easily separated into component parts is called a mixture or said to be impure.
• Some samples of matter are easily separated while other samples are not.
• Substances that contain impurities scatter light; pure water and solutions do not scatter light.
• By adding things to water you can quickly find that there are mixtures that do not scatter light.
• For example, if table salt or sugar is added to water, it disappears.
• However, taste suggests that the salt or sugar is still there, but it cannot be seen; neither will it scatter light.



Distillation

• Therefore, light scattering cannot be used as a test of whether a material is pure.
• Mixtures like salt water or sugar water that look uniform throughout and do not scatter light are called solutions.
• Solutions like salt water and sugar water can be separated into their component parts using a procedure called distillation.
• Most mixtures can be separated by distillation, but some cannot.
• For example, household ammonia or alcoholic beverages such as whiskey.
• Only when there is no way to separate the matter into components can you conclude that it is pure.

2-3: Characteristics of Pure Substances 

• As a solution of a salt water is boiled, the temperature gradually rises as the water boils away.
• However, if you boil the water collected in this way, you will find that the temperature will remain constant from the time the water first boils until it all disappears.
• Pure substances have a constant boiling point; mixtures ordinarily do not.
• The temperature at which a liquid changes to a solid is called its freezing point.
• The freezing point is the same as the melting point, the temperature at which a solid becomes a liquid.

By: Hikari Hoshika               

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