Physical and chemical changes of matterUnit 1:lesson 4

Revision Matter is every thing around us .Matter is anything that has mass and takes up space.Matter is composed of molecules .States of matter : Each matter has different properties.

Physical properties look at a coin in your pocket. It is made from a metal. You can tell it is made from a metal because it is shiny and maybe has a silvery color. Those two descriptions I gave it are called physical properties. A physical property is a characteristic that can be observed or measured without changing the composition.

Chemical properties A new iron nail is made of iron metal, iron that was used to make iron nail is not the most stable of the metals. When it is exposed to oxygen it transforms into rust. This ability to react to oxygen to form rust is called a chemical property Rust has its own properties. First, unlike iron , it is brittle. It's also a dull reddish-brown color.A chemical property is a characteristic that can only be determined by changing the chemical identity of a substance.

Changes of matter

In our daily life we observe that matter can change its not on the same physical and chemical state all the time ,Chocolate and ice cream melt down in hot weather. Iron rusts.Milk go sour .How can we classify these changes ?

When we cut a paper into pieces only its shape changes .We can say that this change is physical change .As the appearance of matter only changed without any change in its structure .(it's still paper)This is called :

Physical change

If you burn a paper it turns into ash .Its not paper anymore .Its shape and structure changes .You can see that ashes is different than paper in shape and structureIts called :

Chemical change

Physical changes of matter

Ice cycle

Ice cycle Materials Glass beaker-glass surface a flame A stand- container ice Procedure Put the ice in the beaker .Heat until ice melts .Continue heating the formed water. Put the glass surface facing the produced water vapor.Put the assembled water in the freezer Observation Ice melts into water.Water boils producing water vapor.Water vapor condensate into water drops.Water changes into ice again in the freezer ,

Conclusion The change from one state to another (melting-evaporation-condensation-freezing )Is a physical change as the shape of water changes but its structure doesnt

Melting of wax Materials Glass watch match stick A candle Procedures Fix candle on the glass.Light the candle .Observation The wax melts and changes into liquid drops.The liquid wax solidifies again Conclusion Melting wax changes its shape but its structure doesn't change Its physical change

Grinding of sugar Materials MortarCube of sugar Procedure Taste the sugar Put the cube in the clean mortar Grind the cube Taste again Observation The sweet taste of sugar doesn't change by grinding but its shape changes into fine powderConclusion Grinding sugar is a physical change as the shape of sugar changes but its structure and properties doesnt change.

Dissolving of table salt in water Steps Observation Taste the salt .Salt taste is salty. Add a spoon of table salt to the water in the beaker Stir to dissolve completely .The salt disappears .Its shape has changed.Pour the content into a crucible .Put the crucible on the flame until the water evaporates .Remove from heat wait to cool taste the residue.The remaining residue is table salt

Dissolving of table salt or sugar in water is a physical change as the shape of table salt or sugar changes but its structure doesn't change

Physical change of matter The change in the appearance of matter without change in its structure

Examples of physical changesChanging of matter from one state to another :melting evaporation & condensation .Grinding sugar or chalk into powder.Dissolving or salt or sugar in water.Malleability of metallic elements to form sheets or wires.Cutting paper or wood into smaller pieces.

Chemical changes of matter

Burning of paperMaterials White paper FlameGlass watch proceduresBend the paper.Burn the paper. Put the product of burning in the watch glass.Compare the characteristics of the paper before and after burning observationThe white paper changes into black ash.The shape and structure of the white paper is different from the black ash .

Conclusion:The paper burns and changes into black ash and cant be returned back to its first form again

Burning paper is a chemical change as the shape and structure of the white paper change by burning .

Burning of sugar Materials Crucible-flame spoon of sugarProcedure Put the sugar in the crucible .Put the crucible on the flame .Taste the residue after cooling.ObservationSugar changes into brown substance.Sugar looses its sweet taste.Conclusion Sugar changes into brown color and loses its sweet taste and cant be returned back to its sweet form Burning sugar is a chemical change as the shape and structure of sugar changed by heating

Iron rust Materials Iron wire which is used in cleaning dishesScissors-crucible-magnifying lens ProcedureCut a piece of wire put it in the crucible .Expose the piece of the wire to wet air for a certain period .Examine by the lensObservation Formation of a brittle brown rust layer Conclusion Rusting is a chemical change as the shape and structure of the cleaning wire changed when exposed to air .

Examples of chemical change Iron rust Burning of substances (paper-wood-fuel-sugar)Production of yogurt from milk .Adding sodium bicarbonate to vinegar

Chemical change of matter

the change in the structure of a substance producing a new substance with different properties

Physical vs chemical

Physical or chemical ?

Comparison between physical and chemical changes Chemical change Physical change Chemical change Change in appearance of a substance Change in the structure of substance Examples Melting of substances Dissolving of salt and sugar Cutting and grinding things Burning of substances Iron rust

Good bye Marwa salah