Ma#er “Food Ma(ers” Is it a Pure Substance or a Mixture? •  Ma(er can be divided into two main categories: –  Pure substances are homogeneous throughout. They have the same chemical properCes no ma(er where the sample is obtained or how large the sample is. –  Mixtures are combinaCons of two or more substances, with each substance retaining its chemical idenCty. “Food Ma(ers” Is it a Pure Substance or a Mixture? •  Consider the various food items throughout the classroom •  On a sheet of notebook paper, write the name of the food and indicate whether you think it’s a Pure Substance or a Mixture. “Food Ma(ers” Is it a Pure Substance or a Mixture? • 
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DisClled Water – PS Bo(led Water – M Tap Water – M OJ – M Milk – M Sugar – PS Salt -­‐ PS Corn Flakes -­‐ M White Vinegar -­‐ M Corn Starch -­‐ PS Plain Choc -­‐ M Crunch Bar -­‐ M Chemistry is the study of … •  ….Ma#er •  Ma(er is anything that takes up space and has mass. •  Light and sound are NOT ma(er!! MATTER IS MADE UP OF… •  …Atoms •  The smallest par<cle of an element •  Indivisible ….that guy is Democritus –  Greek philosopher –  “atomos” What Does an Atom Look Like? •  Atoms are too small to see with the eye, but if we could see them, they would look like this…. •  But we can see GROUPS of atoms. Groups of Atoms are Called… •  …Elements •  …made of IDENTICAL atoms. •  Examples: Anything on the Periodic Table Elements can combine to form… •  …Compounds •  …contain 2 OR MORE DIFFERENT ELEMENTS (atoms) and are BONDED (a(ached) or joined in a fixed propor<on •  Compounds are NOT on the Periodic Table; •  Compounds are NOT MIXTURES (we’ll get to those later…) IdenCfy these as Element(s) or Compound(s). A
B
C
D
1 Element
1 Compound
2 Elements
2 Elements
Classifying Ma(er •  All ma(er is made out of atoms… •  And all ma(er can be classified into different categories! –  Pure Substances –  Mixtures Mixture •  MIXTURES CAN BE SEPARATED! •  Made up of 2 or more elements or compounds –  Yellow – an ELEMENT –  Red/Blue – a COMPOUND (Atoms are not really colored. The different colors represent different elements.) Pure Substances (or simply, a substance) •  CANNOT BE SEPARATED •  Can be made up of all one element OR all one compound •  Examples: –  table salt –  table sugar •  Element •  Compound IdenCfy these as Pure Substances or Mixtures. A
B
C
D
Pure
1 element
Pure
Mixture
Mixture
1 compound
2 elements
2 elements
Pure Substances v. Mixtures Video
Mixtures •  A combinaCon of more than one type of substance •  The properCes of a mixture can vary because the make up of a mixture is not fixed (unlike compounds which have a fixed proporCon) •  2 Types of Mixtures: –  Heterogeneous – the parts of the mixture are no*ceably different from one another –  Homogeneous – the parts of the mixture are so evenly distributed that it appears to be all the same substance (but a mixture is more than one substance!) Time for some PracCce! Elements, Compounds and Mixtures
&
Substances v. Mixtures
SoluCons and Suspensions and Colloids…Oh My! •  A mixture can be further classified into 3 categories based on the size its largest par<cles –  Solu<ons –  Suspensions –  Colloids SoluCons and Suspensions and Colloids…Oh My! •  Solu<ons – homogeneous mixtures –  Examples: Sugar dissolved in water, tap water –  ProperCes of soluCons: •  DO NOT separate into layers over Cme •  If liquid soluCons are poured through a filter none of the substance gets trapped in the filter. •  You can see through liquid soluCons –  All of these relate to the size of the par<cles -­‐ in a soluCon, they are <ny! Homogeneous Mixture •  Substances are evenly distributed •  Appears to contain only one substance •  SoluCons – homogeneous mixtures in which one substance dissolves in another SoluCons and Suspensions and Colloids…Oh My! •  Suspensions – heterogeneous mixtures –  Example: sandy water –  ProperCes of soluCons: •  DO separate into layers over Cme •  If you pour a suspension through a filter some of the substance in the mixture gets trapped in the filter. •  Suspensions are cloudy because light gets sca(ered in all direcCons as it hits larger par<cles. –  All of these relate to the size of the par<cles -­‐ in a suspension, they are bigger! Heterogeneous Mixture •  The parts of the mixture are noCceably different from one another •  Suspensions –  Separate into layers Heterogeneous Mixture •  Suspensions can be mixed (“Shake before serving) but eventually separate out. SoluCons and Suspensions and Colloids…Oh My! •  Colloids– somewhere in between homogeneous and heterogeneous mixtures –  Examples: milk and fog –  ProperCes of colloids: •  DO NOT separate into layers over Cme. •  Cannot use a filter to separate the parts of a colloid •  Light gets sca#ered when it passes into a colloid –  Contain intermediate sized parCcles How Do You Separate A Mixture? •  REMEMBER THE LAB? •  Here are a few other ways to separate mixtures…. SeparaCon of Mixtures •  Compounds and mixtures differ in another way. •  It is difficult to separate a compound into each element. •  Mixtures can be easy to separate into its components because each component keeps its own proper<es. SeparaCon of Mixtures 1.  Magnetic attraction: The magnetic
components of a mixture can be
separated by using a magnet.
SeparaCon of Mixtures 2. Filtration: separates parts of a
heterogeneous mixture by pouring it
though a filter, the larger particles
(residue) will be held in the filter while
the smaller ones (filtrate) will pass
through.
SeparaCon of Mixtures 3.
Distillation: used to
separate components of a
homogeneous mixture
based on their different
boiling points. Solution is
heated and substance with
lower boiling points
evaporates and passes
through a tube where it
cools and turns back into
water in another container.
SeparaCon of Mixtures 4. Evaporation: When a mixture contains
a solvent such as water and a solute
such as salt, the solvent can be allowed
to evaporate, leaving behind the solute.
SeparaCon of Mixtures 5. Sedimenta<on: occurs naturally when solid substances that are heavier than their solvent deposit at the bo(om of the mixture. SeparaCon of Mixtures 6. Decanta<on: a heterogeneous mixture that has dis<nct layers can be separated by slowly pouring one of the layers into another container.