PowerPoint Presentation

Pure Substances vs. MixturesPhysical and Chemical Changes

What's the "Matter"?Anything that has mass and takes up space is called matter.What is matter?2Basic definition of matter.There are 2 types of matter:Pure Substances

Mixtures

What are "pure substances"?Matter that has a fixed composition (Has a chemical formula) and definite properties. (chemical and physical)

ElementsCompoundsThere are two kinds of pure substancesPure substances are CHEMICALLY combined- what does that mean?ElementSubstance that cannot be separated or broken down into simpler substances by normal means.Made of only 1 type of atomExs- any box on the periodic tableRemember atoms are defined by their number of ____________Protons!

Elements can be atoms or moleculesATOMS:Only one atom

MOLECULE:Two atoms (can be of the same element) bonded together

Compounds contSubstance made of atoms of 2 or more different elements that are CHEMICALLY combined. This means they are BONDED at the electrons!Has a chemical formula- ex ______________

When elements combine, it is in a definite way and this changes their properties Na- lethal if ingested Cl- lethal if ingested

NaCl- table salt

Molecules vs CompoundsMolecules are two or more atoms bonded togetherbut compounds must have two different elements

Ex- O2, NaCl, etc.

REMEMBER: Not all molecules are compounds, but all compounds are moleculesexplainCompoundsMolecules made by two or more elements bonded together -always in a definite ratioElementsMolecules made of just one element What is a pure substance?

Na (sodium)NaCl (sodium chloride/salt)

12The two categories of pure chemical substances.Cannot be separated into simpler substances by physical methods (physical changes)Atoms are bonded together in a fixed compositionProperties do not varyCan be expressed with a chemical formulaEx H2O, NaCl, H

Characteristics of Pure Substances13Basic characteristics of pure substance:

What is a mixture?Two or more substances that are physically combined. (NOT chemically combined/bonded like a pure substance)Can be separated into pure substances by physical processesEx- Salt water can be separated into 2 pure sustances: __________ and _____________.May have similar properties to the substances that make it (ex- sugar water)

Examples of Mixtures

Components retain their characteristic properties and can be separated by physical means.

http://videos.howstuffworks.com/hsw/22540-together-but-separate-suspensions-video.htm

Characteristics of Mixtures

This sand and iron filings mixture can be separated using a magnet.17Basic identification of a mixture.Two types of mixtures

Homogenous mixtures look the same throughout Types: solutions, alloys, etc.Example: salt water, brass

Homogenous Mixtures

Have the same composition throughoutComponents are indistinguishableWill not scatter lightParticle size is smallIndicators of Homogenous Mixtures20Brainstorm more examples of homogenous mixtures.Can they still be separated by physical means ?

YES!!! It may be more complicated, but it can be donedistillation , centrifugationHomogeneous mixtures are called solutionsSolutions are homogenous mixtures that do not scatter light.separated by physical means (including distillation or evaporation.)created when something is completely dissolved in pure water. Examples: sugar water, salt water

Parts of a SolutionSolute- substance that dissolves in solvent ex. Salt (U dissolve)Solvent- substance that does the dissolving (ex.water)

Well, not really, because you dont dissolve, but you get the picture Why dont you dissolve?You are not MiscibleMiscible- two or more liquids that can dissolve into each other (aka- soluble)

Immiscible- liquids that do NOT mix (aka- insoluble)Ex- oil and waterHeterogeneous mixtures are composed of large pieces that are easily separated by physical means (ie. density, polarity, metallic properties). Heterogenous MixturesDo not have same composition throughoutComponents are distinguishableParticle size is medium or largeExamples: fruit salad, vegetable soup, etc.Indicators of Heterogenous Mixtures26Brainstorm more examples of heterogenous mixtures.Tyndall EffectScattering of light due to particles

1. Colloid medium particlesParticles stay suspended in the mixture and scatter light (Tyndall effect)Ex- mayonnaise, milk, fog

Types of Heterogenous Mixtures1. Suspension- large particlesTyndall effectParticles will settle out when the mixture is allowed to standEx-muddy water, OJ with pulp

Types of Heterogenous Mixtures

In your notes packet-Make a concept map of these concepts below:

Pure SubstanceMatterHomogeneous Mixture ElementSolutionCompoundMixtureHeterogeneous MixtureColloidSuspension

Properties of Matter

Physical properties are those that we can determine without changing the identity of the substance. Properties we can observe or measure

physical propertiescolor

Melting/boiling pointExamples of physical properties:

Viscosity Resistance to flowing

Maple Syrup- High ViscosityWater- Low ViscosityDuctilityAbility to be drawn into a thin wire

MalleabilityAbility to be hammered into thin sheets without shattering

HardnessResistance to being scratched

ConductivityAbility to carry electricity

High Conductivity (the liquid is able to let electrons flow to complete the circuitLow Conductivity (the liquid is NOT able to let electrons flow to complete the circuitSolubilityAbility to dissolve in waterYes! It is a physical property because you do not need to alter identity of the substance to determine solubility.

DENSITYMass per unit volume

Calculated by: Density= Mass/VolumeD=M/V

Units: g/mLg/cm3Density determines if an object will sink or float in water.- if an object is LESS dense it will FLOAT- If it is MORE dense it will SINK

Density Tower

Density Graphs Y axis= X axis=Slope=

Other examples of physical properties.boiling pointfreezing pointshapetemperaturedensitymelting pointChemical PropertiesDescribe the way a substance can change or react to form other substances. (what bonds they will form)(NOT the actual reaction- thats a chemical change) Must be determined using a process that changes the identity of the substance (chemical reactions involve breaking and making new bonds)

One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens.

In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

How can chemical properties be identified?Exs of Chemical PropertiesReactivity: ability of a substance to combine CHEMICALLY (at the electrons) with another substance (to form a compound)

FlammabilityAbility of a material to burn in the presence of Oxygen.

AlkalinityAbility to neutralize acids

What is a physical change?A change that does not change the chemical composition of a substance.Ex: changes in size, shape, appearance, etc.

Why? The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.)

50Definition of physical changes.What are chemical changes?A chemical change occurs when a substance changes into something new. This occurs due to heating, chemical reaction, etc. You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (bubbles forming, mass changed, etc).

51Definition of chemical change.How to recognize a chemical changeRecall: A chemical change occurs when a substance changes into something new. FoamingBubblesNew odorHeat production or drop in temperatureNew precipitate (solid formed from liquids)52Definition of chemical change.