SCIE 4001
Unit 1
Introduction
About Matter
Nature of Matter
Properties of Matter
States of Matter
Kinetic Theory of Gases
 
 
 
Brownian Motion
 

Unit 1-1.b States of Matter

Properties of Materials and the Kinetic Theory

Demonstrate that matter commonly exists in three distinct forms which have characteristic properties.

Recall:

Matter has

tiny building blocks which may be single atoms or pairs or other groups of atoms.

physical properties

has chemical properties

Scientific Thinking constructs a world that is provisional... by its

attempts to add to the 'body of scientific knowledge' by observing and explaining phenomena in the natural or physical world.

when data collected is proven to be reliable, repeatable and observable by scientific peer review, then and only then this data is recorded in the 'body of scientific knowledge'.

— when rules developed to explain phenomena are proven to be consistent over time and space they are called laws, then and only then these rules are recorded in the 'body of scientific knowledge'.

use of a particular method of investiagation called a 'scientific method' to change the 'body of scientific knowledge'.

propose the existence of new unobserved phenomena based on new evidence and/or re-examination of evidence from the 'body of scientific knowledge'.

propose new rules to explain new evidence and/or re-examination of evidence from the 'body of scientific knowledge'.

proposes hypothesis to test these proposed rules and/or new/predicted phenomenon.

devises investigations to test hypotheses.

If after scientific peer review the evidence from investigation is alligned to hypothesis () then rules (laws) and data are recorded in the 'body of scientific knowledge'.

If after scientific peer review evidence from investigation is NOT alligned to hypothesis thenhypothesis is redesigned to the the new evidence and retested.

Scientific knowledge is only good untill new scientific knowledge replaces it.

 

Hypothesis:

1. All Atoms and molecules in solids can only rotate and vibrate.

2.All Atoms and molecules in solids have very strong inter-molecular forces.

solids

Fig 1.1.38

Atomic arrangement in Solids.

— If molecules in solids are closely packed then they will not compress (maintain volume).

— Do solids compress? No! However, some materials are flexible like rubber and seem to compress, but note that the material swells out somewhere else.... other materials may have spaces in them and only seem to compress as molecules are pushed into these spaces.

— Do solids maintain their volume? Yes!

If molecules in solids move by vibration and rotation only (no translation) about a fixed mean position then they will maintain shape and have well defined surfaces.

Do solids maintain their shape? Yes!

— Do solids have well defined surfaces? Yes!

If molecules in solids have very strong inter-molecular forces they will will maintain shape, volume and have well defined surfaces and display little or no evaporation.

Do solids maintain their volume & shape and have well defined surfaces? Yes!

Do solids evaporate easily? No!

 

— So are hypotheses 1 & 2 supported? Yes!

Hypothesis:

3.All Atoms and molecules in liquids can rotate, vibrate and translate in the bulk of the liquid.

4. All Atoms and molecules in liquids have strong inter-molecular forces but not as strong as in solids.

liquids

Fig 1.1.39

Atomic arrangement in Liquids.

If molecules in liquids are more loosely packed then they will be very little compression (maintain volume).

— Do liquids maintain their volume? Yes!

If molecules in liquids can translate within the bulk of the liquid (bounded by the surfaces of the liquid) then they will NOT maintain shape.

Do liquids maintain their shape? No!

If molecules in liquids can vibrate, rotate and translate within the bulk of the liquid (bounded by the surfaces of the liquid) then they will have well defined surface which exhibit “surface tension”.

Do liquids have well defined surface which exhibits “surface tension”? Yes!

If molecules in liquids have weaker inter-molecular forces then they will evaporate.

Do liquids evaporate? Yes!

If molecules in liquids can translate within the bulk of the liquid (bounded by the surfaces of the liquid) and collide with container walls they will will display liquid pressure.

Do liquids have pressure? Yes!

If molecules in liquids can vibrate, rotate and translate within the bulk of the liquid (bounded by the surfaces of the liquid) they will diffuse.

Do liquids diffuse? Yes!

If molecules in liquids can vibrate, rotate and translate within the bulk of the liquid (bounded by the surfaces of the liquid) they will exhibit Brownian Motion.

Do liquids exhibit Brownian Motion? Yes!

 

— So are hypothesis 3 & 4 supported? Yes!

 

Hypothesis:

5. All Atoms and molecules in gases can rotate, vibrate and translate freely.

6. All Atoms and molecules in gases have little or no inter-molecular forces.

gas

Fig 1.1.40 - Gas in open container

Atomic arrangement in Gases.

If molecules in gases are more loosely packed then they will compress easily (NOT maintain volume).

— Do gases compress easily (NOT maintain volume)? Yes!

If molecules in gases can translate freely then they will NOT maintain shape.

Do gases maintain their shape? No!

If molecules in gases can vibrate, rotate and translate freely then they will NOT have well defined surface which exhibit “surface tension”.

Do gases have well defined surface which exhibits “surface tension”? No!

If molecules in gases have weaker inter-molecular forces then they will spread out to occupy all space.

Do gases spread out to occupy all space? Yes!

If molecules in gases can translate freely and collide with container walls they will will display gaseous pressure.

Do gases have pressure? Yes!

If molecules in gases can vibrate, rotate and translate freely they will diffuse.

Do gases diffuse? Yes!

If molecules in gases can vibrate, rotate and translate freely they will exhibit Brownian Motion.

Do gases exhibit Brownian Motion? Yes!

 

— So are hypothesis 3 & 4 supported? Yes!

gas

Fig 1.1.41 - Gas in closed container

 

NOTE: The spaces between the atoms are empty NOT AIR filled.

So what do we know about molecular movement in materials?

 

Molecules in solids

can only rotate and vibrate.

— have very strong inter-molecular forces.

Molecules in liquids

— can rotate, vibrate and translate in the bulk of the liquid.

— have strong inter-molecular forces but not as strong as in solids.

— diffuse.

— show Brownian motion.

Molecules in liquids

— can rotate, vibrate and translatefreely.

— have little or no inter-molecular forces.

— diffuse.

— show Brownian motion.

 

Questions

Why are gases easy to compress but solids and liquids are virtually incompressiable?

Why do solids have a distinct shape?

Explain the differences among the three states of matter.

The following is a simulation from PhET Interactive Simulations
University of Colorado
http://phet.colorado.edu

If you have difficulty running it click here to my Q & A Page

 

 

Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.