Grade 9 Chemistry

     Notes        

Unit ​​1:​ ​The​ ​particulate​ ​nature​ ​of matter

 

1.State the distinguishing properties of solids, liquids and gases

The​ ​three​ ​states​ ​of​ ​matter​ ​are​ ​solid,​ ​liquid​ ​and​ ​gas

 ● Melting​ ​and​ ​freezing​ ​take​ ​place​ ​at​ ​the​ ​melting​ ​point 

● Boiling​ ​and​ ​condensing​ ​take​ ​place​ ​at​ ​the​ ​boiling​ ​point

 

 

● They​ ​can​ ​be​ ​represented​ ​by​ ​the​ ​simple​ ​model​ ​above,​ ​particles​ ​are​ ​represented by​ ​small​ ​solid​ ​spheres 

● solids-​ ​particles​ ​have​ ​a​ ​regular​ ​arrangement​ ​and​ ​are​ ​close​ ​together

● liquids-​ ​particles​ ​have​ ​a​ ​random​ ​arrangement​ ​and​ ​are​ ​close​ ​together

 ● gases-​ ​particles​ ​have​ ​a​ ​random​ ​arrangement​ ​and​ ​are​ ​spread​ ​apart

 

2.Describe the structure of solids, liquids and gases in terms of particle separation, arrangement and types of motion.

 

·        Gas:​ ​particles​ ​have​ ​the​ ​most​ ​energy​ ​–​ ​shown​ ​by​ ​the​ ​diagram,​ ​as​ ​the​ ​particles​ ​are the​ ​most​ ​spread​ ​apart,​ ​motion​ ​is​ ​more​ ​random​ ​and​ ​frequent 

● Liquid:​ ​particles​ ​have​ ​more​ ​energy​ ​than​ ​those​ ​in​ ​a​ ​solid,​ ​but​ ​less​ ​than​ ​those​ ​in​ ​a gas

● Solid​ ​has​ ​least​ ​energy​ ​–​ ​particles​ ​are​ ​not​ ​moving/are​ ​just​ ​vibrating

 

3.Describe changes of state in terms of melting, boiling, evaporation, freezing, condensation and sublimation

Physical​ ​changes​ ​–​ ​therefore​ ​involves​ ​the​ ​forces​ ​between​ ​the​ ​particles​ ​of​ ​the substances,​ ​instead​ ​of​ ​these​ ​changes​ ​of​ ​state​ ​being​ ​chemical​ ​changes

 Evaporation​ ​=​ ​happens​ ​at​ ​the​ ​surface,​ ​molecules​ ​have​ ​enough​ ​energy​ ​to evaporate​ ( start to change Liquid to gas)

 Freezing​ ​=​ ​liquid​ ​to​ ​solid 

Melting​ ​=​ ​solid​ ​to​ ​liquid 

 Boiling​ ​=​ ​happens​ ​throughout​ ​the​ ​liquid,​ ​liquid​ ​to​ ​gas ( Formation of bubbles)

  Condensation​ ​=​ ​gas​ ​to​ ​liquid

  Sublimation​ ​=​ ​solid​ ​to​ ​gas

 

4.Explain changes of state in terms of the kinetic theory.

Kinetic​ ​theory​ ​can​ ​help​ ​to​ ​explain​ ​melting,​ ​boiling,​ ​freezing​ ​and​ ​condensing…

o The​ ​amount​ ​of​ ​energy​ ​needed​ ​to​ ​change​ ​state​ ​from​ ​solid​ ​to​ ​liquid​ ​and from​ ​liquid​ ​to​ ​gas​ ​depends​ ​on​ ​the​ ​strength​ ​of​ ​the​ ​forces​ ​between​ ​the particles​ ​of​ ​the​ ​substance.

o The​ ​nature​ ​of​ ​the​ ​particles​ ​involved​ ​depends​ ​on​ ​the​ ​type​ ​of​ ​bonding​ ​and the​ ​structure​ ​of​ ​the​ ​substance.

o The​ ​stronger​ ​the​ ​forces​ ​between​ ​the​ ​particles​ ​the​ ​higher​ ​the​ ​melting point​ ​and​ ​boiling​ ​point​ ​of​ ​the​ ​substance.

o The​ ​more​ ​kinetic​ ​energy​ ​(from​ ​increased​ ​temperature)​ ​particles​ ​have,​ ​the more​ ​movement,​ ​which​ ​causes​ ​a​ ​change​ ​of​ ​state​ ​from​ ​(s)​ ​to​ ​(l)​ ​to​ ​(g)

 

5. Describe qualitatively the pressure and temperature of a gas in terms of the motion of its particles.

The​ ​higher​ ​the​ ​pressure​ ​=​ ​the​ ​more​ ​motion​ ​of​ ​a​ ​gas’​ ​particles 

● The​ ​higher​ ​the​ ​temperature​ ​=​ ​the​ ​more​ ​motion​ ​of​ ​a​ ​gas’​ ​particles 

 

6. Show an understanding of the random motion of particles in a suspension (sometimes known as Brownian motion) as evidence for the kinetic particle. (atoms, molecules or ions) model of matter

Particles​ ​in​ ​liquids​ ​and​ ​gases​ ​(known​ ​as​ ​fluids)​ ​move​ ​randomly​ ​(this​ ​is​ ​called Brownian​ ​motion) ● This​ ​happens​ ​because​ ​they​ ​collide​ ​with​ ​other​ ​moving​ ​particles​ ​in​ ​the​ ​fluid ● This​ ​is​ ​evidence​ ​for​ ​the​ ​kinetic​ ​particle​ ​model​ ​of​ ​matter-​ ​it​ ​shows​ ​that​ ​there​ ​are individual​ ​particles​ ​which​ ​make​ ​up​ ​solids/liquids/gases

Particles​ ​in​ ​liquids​ ​and​ ​gases​ ​move​ ​randomly​ ​because​ ​they​ ​are​ ​bombarded​ ​by the​ ​other​ ​moving​ ​particles​ ​in​ ​the​ ​fluid.​ ​Larger​ ​particles​ ​can​ ​be​ ​moved​ ​by​ ​light, fast-moving​ ​molecules

Robert​ ​Brown​ ​observed​ ​the​ ​random​ ​movement​ ​of​ ​pollen​ ​grains​ ​within​ ​water, which​ ​showed​ ​that​ ​there​ ​were​ ​separate​ ​particles​ ​within​ ​the​ ​water​ ​that​ ​were moving​ ​randomly​ ​and​ ​caused​ ​the​ ​grain​ ​to​ ​move​ ​(kinetic​ ​theory) 

7.Explain diffusion.

Movement​ ​of​ ​particles​ ​from​ ​an​ ​area​ ​of​ ​high​ ​concentration​ ​to​ ​an​ ​area​ ​of​ ​low concentration ● For​ ​this​ ​to​ ​work,​ ​particles​ ​must​ ​be​ ​able​ ​to​ ​move. Therefore,​ ​diffusion​ ​does​ ​not​ ​occur​ ​in​ ​solids,​ ​since​ ​the​ ​particles​ ​cannot move​ ​from​ ​place​ ​to​ ​place​ ​(only​ ​vibrate).

A​ ​smell​ ​does​ ​not​ ​travel​ ​very​ ​fast,​ ​because​ ​the​ ​partices​ ​collide​ ​with particles​ ​of​ ​air,​ ​changing​ ​direction​ ​randomly​ ​when​ ​they​ ​collide,​ ​taking much​ ​longer​ ​to​ ​travel​ ​from​ ​place​ ​to​ ​place

 

8.Explain dependence of rate of diffusion on molecular mass.

The​ ​smaller​ ​the​ ​molecular​ ​mass,​ ​the​ ​greater​ ​the​ ​average​ ​speed​ ​of​ ​the​ ​molecules (but​ ​all​ ​gases​ ​have​ ​the​ ​same​ ​average​ ​kinetic​ ​energy​ ​at​ ​the​ ​same​ ​temperature) o Therefore,​ ​the​ ​smaller​ ​the​ ​molecular​ ​mass,​ ​the​ ​faster​ ​the​ ​gas​ ​diffuses.