ChemistryChemistry

The study of The study of ChemicalChemical & & PhysicalPhysical PropertiesProperties and and ChangesChanges of Matter of Matter

ChemistryChemistry

What is Chemistry?What is Chemistry?– The study of the of The study of the of mattermatter

What is What is matter?matter?

How can/will How can/will mattermatter changechange when you do when you do something to it something to it

What is Matter?What is Matter?– Anything that has mass and takes up space (volume)Anything that has mass and takes up space (volume)

All “stuff” around you is matterAll “stuff” around you is matter

All matter is made up of substances or mixturesAll matter is made up of substances or mixtures

Substances v. MixtureSubstances v. Mixture

Substance – All the same stuff (“pure”).Substance – All the same stuff (“pure”).No matter how much you have, it is all still the No matter how much you have, it is all still the

same stuff.same stuff.Ex: a “pure” sample of water is only HEx: a “pure” sample of water is only H2200

Substances v. MixtureSubstances v. Mixture

SubstancesSubstances consists of: consists of:1.1. ElementsElements (single atoms) (single atoms)

i.e. Carbon (C), Oxygen (O) i.e. Carbon (C), Oxygen (O)

2. Molecules2. Molecules (combinations of elements) (combinations of elements) i.e. Water (Hi.e. Water (H22O), Carbon Dioxide (COO), Carbon Dioxide (CO22), Salt (NaCl)), Salt (NaCl)

Sodium Chloride (table salt)Water Carbon Dioxide

Molecules are simply a bunch of atoms “stuck” together!

electron

neutron

proton

Substances v. MixtureSubstances v. Mixture

MixtureMixture– Made of two or more substances – (elements, Made of two or more substances – (elements,

molecules or both) that are together in the molecules or both) that are together in the same place, but same place, but NOT chemically bondedNOT chemically bonded. .

Salt Water Sand/dirt

Salad

Substances v. MixtureSubstances v. Mixture

If it’s a mixture, you can separate out the If it’s a mixture, you can separate out the parts relatively easily. parts relatively easily. – (i.e. filtering/distilling)(i.e. filtering/distilling)

Demo: filter Italian salad dressing

DrainFill

Filter: Pure Substance Leftover

Pure Substance

Mixture

What are Properties?

How do you identify a specific substance?How do you identify a specific substance?-What atoms/molecules make it up!-What atoms/molecules make it up!

Problem: Problem: WE CAN’T SEE THEMWE CAN’T SEE THEM! They are way too small!! They are way too small!

But we can use “But we can use “PropertiesProperties” to identify them” to identify them

Properties are “Properties are “identifying characteristicsidentifying characteristics” (clues) of ” (clues) of elements/substances. All substances have their own elements/substances. All substances have their own properties unlike any other substanceproperties unlike any other substance

Can Identify elements, molecules and substances Can Identify elements, molecules and substances (combination of elements/molecules) if you know enough of the (combination of elements/molecules) if you know enough of the properties (clues)properties (clues)

So what if we have a substance that we need to identify?

Demo: which student am I describing?

Intro: Substance IDIntro: Substance IDTry to Identify the 3 substancesTry to Identify the 3 substances– How do you know or can tell what it is?How do you know or can tell what it is?

Demo: Three Cups: Salt, Sugar & Mystery Substance

Before you are a sample of Sugar, Salt, and a mystery substance

First just look at them and try to tell them apart

Now smell them and try to tell them apart

Now taste them and try to tell them apart

The main point: If we know enough “properties” we can identify a substance from other substances.

2 Types of Properties:2 Types of Properties:

PhysicalPhysical-Describes generally

how a substance appears, feels, etc... Can usually be easily observed without testing anything.

Examples: Taste, Smell, Texture, Color, size, Solid/Liquid/Gas, mass, etc…

ChemicalChemical-Describes how one

substance changes into a new substance. Or how it will act under certain conditions. What can/will it do?

Examples: Oxidation, +/- Charge, release of

bubbles, causes a new smell/color, ALL REACTIONS!

Physical ChangePhysical Change The substance simply

changes shape, size, solid/liquid/gas, etc…

The substance/element DOES NOT CHANGE!!!

It only changes how it appears!!!

EX: Freezing water

Chemical ChangeChemical Change The substance

burns/reacts and can release some of it’s “parts” into the air.

The substance completely changes to something brand new!

EX: Iron Iron Oxide

Demo: Burning Paper

Demo: Breathing Fire

Q: What if we try to do something Q: What if we try to do something to the substance? Change it to the substance? Change it

somehow…somehow…

Identifying MatterIdentifying MatterOur Brains instinctively use physical properties to identify Our Brains instinctively use physical properties to identify matter all the time – but can also be deceiving. matter all the time – but can also be deceiving.

Chemists also use chemical properties to help identify Chemists also use chemical properties to help identify unknown substances. unknown substances.

Ding! Ding! Ding! It’s …

PhysicalCharacteristics

Chemical Characteristics

a characteristic of a pure substance that can be

observed without changing it into another

substance.

a characteristic of a pure substance that describers its ability to change into different substances.

Properties are used to solve Properties are used to solve crimes!crimes!

Ding! Ding! Ding! The answer to the mystery is…

PhysicalCharacteristics

Chemical Characteristics

What do you observe at the crime scene?

Perform some tests to see what chemicals are at the

crime scene.

List Physical Characteristics: List Chemical Characteristics:

Physical ReviewPhysical Review Chemical ReviewChemical Review

Describes how the substance or mixture appears, feels, dimensions, etc...

Describes the substances ability to react with other substances.

An change of the substance w/o changing the substance. Elements and molecules remain the same!

–Bend, twist, crush, tear, melt, boil, etc…

An change of the substance by reacting it with another substance to make it a new substance.

–Burn (combust), rust, tarnish, light, new smell, fizzing, etc…

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