Presentation on theme: "Physical & Chemical Changes"— Presentation transcript:
1 Physical & Chemical Changes Changing MatterPhysical & Chemical Changes
2 What different ways can we differentiate between people? PropertiesHow we identify something.All substances have properties that we can use to identify them. For example we can identify a person by their face, their voice, height, finger prints, DNA etc.. The more of these properties that we can identify, the better we know the person. In a similar way matter has properties - and there are many of them. There are two basic types of properties that we can associate with matter.
3 Matter has propertiesTwo basic types of properties that we can associate with matter.Physical propertiesChemical properties
4 Physical PropertiesAnything that can be observed without changing the identity of the substance. (Tends to be measurable.)melting pointdensityboiling pointthermal conductivityelectrical conductivityductilitycolormalleability
5 MalleabilityThe ability of an object to be molded into different shapes.Example – metals.Opposite – Brittle, not flexible.
6 DuctilityThe ability of an object to be drawn into thin wires without losing strength.Metals are ductile.
7 Combustion - the process of burning something Chemical PropertiesThe way a substance may change or react to form other substancescombustionReactivity to other chemicalsreactivity with waterPHOxidationFlammabilityChemical properties of matter describes its "potential" to undergo some chemical change or reaction by virtue of its composition. What elements, electrons, and bonding are present to give the potential for chemical change.It is quite difficult to define a chemical property without using the word "change". Eventually you should be able to look at the formula of a compound and state some chemical property. At this time this is very difficult to do and you are not expected to be able to do it.For example hydrogen has the potential to ignite and explode given the right conditions. This is a chemical property.Metals in general have they chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas. This is a chemical property.Combustion - the process of burning something
8 Matter can be changed two ways PhysicallyPhysical reactionPhysical changeChemicallyChemical reactionChemical change
9 Physical Changes Do NOT CHANGE THE TYPE OF MATTER Nothing new or different is formedCould be a change in:MassVolumeDensityChange in stateColorShapeSize
10 Physical ChangesSubstance may seem different, but the way the atoms link up is the same.It changes phase (freezes, boils, evaporates, condenses, sublimates)
11 Examples of Physical Changes BoilingFreezingDissolvingBreakingMaking a mixture2 or more types of matter (substances) mixed togetherNot in specific amountsCan be separated physically
12 Chemical ChangesChemical changes, or chemical reactions, are changes that result in the production of another substance. Changes the way the molecules link up (chemical composition)Makes new substances (new compounds, or compounds are broken down into the elements that make them up)The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.”
13 Chemical Changes Evidence of a chemical reaction Formation of gas Formation of precipitateChange in colorChange in energy (temperature)Endothermic Absorbs heat energy (gets cold)Exothermic Releases heat energy (gets hot)Alka-Seltzer: (Baking soda or sodium bicarbonate) NaHCO3 + Citric acid ---> CO2 + H2O + Sodium Citrate
14 Chemical ChangesAtoms are re-arranged, NOT created or destroyed
15 It’s a chemical change if…. It burnsTemperature changes without heating/cooling
16 It’s a chemical change if…. It bubbles (makes a gas)
17 It’s a chemical change if... It changes colorIt forms a precipitate – (solid that forms from two liquids).
18 Again signs that a Chemical Change has occurred Creation of a gas (bubbles)Creation or loss of heatFireRottingBreaking down (decomposition)Precipitation (Sour milk clumps)CookingRusting (oxidation)
19 Chemical ChangeThe only TRUE sign that a chemical change has taken place is the formation of a new substance.A new substance that was not there before.A new substance with a new chemical composition (Atoms are arranged differently).
20 Basically What You’re Telling Me Is… If you end up with a chemical or chemicals that you did not start with,It is a chemical change!!!!!!!
21 Another Example Is… Eating… Now eating can change food both physically and chemically.Chewing is Physical but…Once the food touches the chemicals in the saliva begin to change the food chemically.
22 Law of Conservation of Matter Matter is conserved type of atoms does not changeNothing is created or destroyed
23 Law of Conservation of Mass Mass is conserved amount of atoms cannot changeNothing is created or destroyed
24 What kind of change is it if someone... Tears up paper?Physical changeMixes salt and water?
25 What kind of change is it if someone... Burns paper?Chemical changeEvaporates salt water?Physical change
26 What kind of change is it if someone... Mixes vinegar and baking soda?Chemical change
27 Physical and Chemical Changes Quiz ……….True or False?? 1. With a physical change, no new substance is formed. 2. With a chemical change, a chemical reaction occurs.3. With a physical change, energy is either given off or absorbed.4. A chemical change can be easily reversed.5. Eating food can be considered both physical and chemical changes.
28 Physical and Chemical Changes Quiz……….Answers! 1. With a physical change, no new substance is formed. TRUE2. With a chemical change, a chemical reaction occurs. TRUE3. With a physical change, energy is either given off or absorbed. FALSE4. A chemical change can be easily reversed. FALSE5. Eating food can be considered both physical and chemical changes. TRUE
30 Physical or Chemical Change? Painting WoodPHYSICAL
31 Physical or Chemical Change? A ring tarnishingCHEMICAL
32 Physical or Chemical Change? Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, magnesium and other similar metals as their outermost layer undergoes a chemical reaction. It causes to lose luster.
33 Physical or Chemical Change? Burning PaperCHEMICAL
34 Physical or Chemical Change? Digestion of foodCHEMICAL
35 Sugar dissolving in water PHYSICAL Physical or Chemical Change?Sugar dissolving in waterPHYSICAL
36 Iron turning red when heated PHYSICAL Physical or Chemical Change?Iron turning red when heatedPHYSICAL
37 Physical or Chemical Change? EvaporationPHYSICAL
38 A pond freezing in winter PHYSICAL Physical or Chemical Change?A pond freezing in winterPHYSICAL
39 Physical or Chemical Change? Melting icePHYSICAL
40 Physical or Chemical Change? Cutting wirePHYSICAL
41 Physical or Chemical Change? Painting fingernailsPHYSICAL
42 Physical or Chemical Change? Cutting fabricPHYSICAL
43 Physical or Chemical Change? Baking muffinsCHEMICAL
44 Physical or Chemical Change? Shattering glassPHYSICAL
45 Decomposition of old leaves CHEMICAL Physical or Chemical Change?Decomposition of old leavesCHEMICAL
46 Physical or Chemical Change? Wrinkling a shirtPHYSICAL
47 Physical or Chemical Change? An old nail rustingCHEMICAL