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What's the "Matter"?. Pure Substances vs. Mixtures Physical and Chemical Changes. Anything that has mass and takes up space is called matter. What is matter?. There are 2 types of matter:. Pure Substances Mixtures. What are "pure substances"?.

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pure substances vs mixtures physical and chemical changes

What's the "Matter"?

Pure Substances vs. Mixtures

Physical and Chemical Changes

there are 2 types of matter
There are 2 types of matter:
  • Pure Substances
  • Mixtures
slide4

What are "pure substances"?

Matter that has a fixed composition (Has a chemical formula) and definite properties. (chemical and physical)

element
Element
  • Substance that cannot be separated or broken down into simpler substances by normal means.
  • Made of only 1 type of atom
  • Ex’s- any box on the periodic table
    • Rememberatoms are defined by their number of ____________
      • Protons!
elements can be atoms or molecules
Elements can be atoms or molecules
  • ATOMS:
    • Only one atom
  • MOLECULE:
    • Two atoms (can be of the same element) bonded together
compounds cont
Compounds cont…
  • Substance 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 ______________
slide10

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 compounds
Molecules vs Compounds
  • Molecules are two or more atoms bonded together…but compounds must have two different elements
    • Ex- O2, NaCl, etc.

REMEMBER:

    • Not all molecules are compounds, but all compounds are molecules…explain
slide12

What is a pure substance?

Compounds

  • Molecules made by two or more elements bonded together -always in a definite ratio

Elements

  • Molecules made of just one element

Na (sodium)

NaCl (sodium chloride/salt)

slide13

Characteristics of Pure Substances

  • Cannot be separated into simpler substances by physical methods (physical changes)
  • Atoms are bonded together in a fixed composition
    • Properties do not vary
  • Can be expressed with a chemical formula
    • Ex H2O, NaCl, H
slide15

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 physicalprocesses
    • Ex- Salt water can be separated into 2 pure sustances: __________ and _____________.
    • May have similar properties to the substances that make it (ex- sugar water)
slide17

Characteristics 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

This sand and iron filings mixture can be separated using a magnet.

slide19

Homogenous Mixtures

  • Homogenous mixtures look the same throughout
    • Types: solutions, alloys, etc.
    • Example: salt water, brass
slide20

Indicators of Homogenous Mixtures

  • Have the same composition throughout
  • Components are indistinguishable
  • Will not scatter light
  • Particle size is small
can they still be separated by physical means
Can they still be separated by physical means ?

YES!!! It may be more complicated, but it can be done…distillation , centrifugation

slide22

Homogeneous mixtures are

called solutions

  • Solutions 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
slide23

Parts of a Solution

  • Solute- substance that dissolves in solvent
  • ex. Salt (“U dissolve”)
  • Solvent- substance that does the dissolving (ex.water)

Well, not really, because you don’t dissolve, but you get the picture 

why don t you dissolve
Why don’t you dissolve?
  • You are not “Miscible”
    • Miscible- two or more liquids that can dissolve into each other (aka- soluble)
    • Immiscible- liquids that do NOT mix (aka- insoluble)
      • Ex- oil and water
slide25

Heterogenous Mixtures

Heterogeneous mixtures are composed of medium or large pieces that are easily separated by physical means (ie. density, polarity, metallic properties).

slide26

Indicators of Heterogenous Mixtures

  • Do not have same composition throughout
  • Usually components are distinguishable
  • Particle size is medium or large

Examples: fruit salad, vegetable soup, etc.

tyndall effect
Tyndall Effect
  • Scattering of light due to particles
slide28

Types of

HeterogenousMixtures

1. Colloid –medium particles

  • Particles stay suspended in the mixture and scatter light (Tyndall effect)
  • Ex- mayonnaise, milk, fog
slide29

Types of

HeterogenousMixtures

1. Suspension- large particles

  • Tyndall effect
  • Particles will settle out when the mixture is allowed to stand
  • Ex-muddy water, OJ with pulp
slide31

physical properties

  • Physical properties are those that we can determine without changing the identity of the substance.
  • Properties we can observe or measure
slide32

Examples of physical properties:

  • color
  • Melting/boiling point
viscosity
Viscosity
  • Resistance to flowing

Maple Syrup- High Viscosity

Water- Low Viscosity

ductility
Ductility
  • Ability to be drawn into a thin wire
malleability
Malleability
  • Ability to be hammered into thin sheets without shattering
hardness
Hardness
  • Resistance to being scratched
conductivity
Conductivity
  • Ability to carry electricity

High Conductivity (the liquid is able to let electrons flow to complete the circuit

Low Conductivity (the liquid is NOT able to let electrons flow to complete the circuit

solubility
Solubility
  • Ability to dissolve in water
    • Yes! It is a physical property because you do not need to alter identity of the substance to determine solubility.
density
DENSITY

Mass per unit volume

Calculated by:

Density= Mass/Volume

D=M/V

Units:

g/mL

g/cm3

slide40
Density 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 graphs
Density Graphs
  • Y axis=
  • X axis=
  • Slope=
other examples of physical properties
Other examples of physical properties….

boiling point

shape

density

freezing point

melting point

temperature

chemical properties
Chemical Properties
  • Describe the way a substance can change or react to form other substances. (what bonds they will form)
    • (NOT the actual reaction- that’s a chemical change)
  • Must be determined using a process that changes the identity of the substance
    • (chemical reactions involve breaking and making new bonds)
slide45

How can chemical properties be identified?

  • 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.
ex s of chemical properties
Ex’s of Chemical Properties
  • Reactivity: ability of a substance to combine CHEMICALLY (at the electrons) with another substance (to form a compound)
flammability
Flammability
  • Ability of a material to burn in the presence of Oxygen.
alkalinity
Alkalinity
  • Ability to neutralize acids
slide49

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.)
slide50

What are chemical changes?

  • A chemical change occurs when a substance changes into something new (breaking & reforming new bonds.
  • 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).
slide51

How to recognize a chemical change

  • Recall: A chemical change occurs when a substance changes into something new.
  • Foaming
  • Bubbles
  • New odor
  • Heat production or drop in temperature
  • New precipitate (solid formed from liquids)