Classification of Matter. Matter Matter: Anything that has mass and volume 3 phases of matter.
Compounds, Mixtures, Solutions and Reactions. Classifying Matter Matter Pure SubstancesMixtures...
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Transcript of Compounds, Mixtures, Solutions and Reactions. Classifying Matter Matter Pure SubstancesMixtures...
Classifying MatterMatter
Pure Substances Mixtures
Elements Compounds
Homogeneous Heterogeneous
Fe, O H2O, CO2
milk, tea Rocky Road ice cream, muddy water
What is a Pure Substance?
• A pure substance is a classification of matter that includes both elements and compounds
• Pure substances cannot be separated by physical means such as distillation, filtration, or chromatography
Elements
• We will study elements in depth later, but be sure to know…−An element is made of one kind of
atom− Found on the periodic table
What Is A Compound?
• A compound is a pure substance that is created by 2 or more elements chemically reacting and joining together−Ex: NaCl, H2O, CO2, NH3, NaHCO3, and
C6H12O6
• Notice that elements combine in many ways to make compounds−Ex: H2O, H2O2, CO, and CO2
Why Do Compounds Form?
• Compounds form to allow elements to become more stable−Na is flammable when it comes in
contact with H2O, and Cl2 is a toxic gas
−NaCl is a very stable compound that is neither flammable nor toxic (in normal quantities)
• Compounds that are extremely unstable will break down to form the more stable elements
How Do Compounds Form?• Compounds form by the interaction
between the nuclei and valence electrons of 2 or more elements.
What Do Compounds Have To Do With My Life?
• Compounds are the substances that make up ALL living and non-living things
• Examples: Where would you be without:−H2O—water
−NaCl—table salt
−C3H8O—rubbing alcohol
−C55H98O6—an example of an
unsaturated fat
What Is A Mixture?• A mixture is the physical combination of 2 or more
substances
• It is important to understand that a mixture is not chemically combined
• Mixtures can be separated by physical means such as filtration, distillation, and chromatography
• Mixtures can be divided into 2 groups− Homogenous mixtures− Heterogeneous mixtures
How Do Mixtures Form?
• Mixtures form by physically “junking” 2 or more substances together
• Remember no chemical change is occurring
• The formation of a mixture is not a result of lowering energy
What Is a Homogenous Mixture?
• A homogeneous mixture is a mixture that is evenly distributed
• Homogeneous mixtures are commonly called solutions.− Solution = Solute + Solvent
• Solute: “stuff” being dissolved• Solvent: “stuff” doing the dissolving
• The solvent is present in greater quantity
• The solute is present in the lesser quantity− Ex: Salt water: Salt=solute,
Water=solvent
What Is a Heterogeneous Mixture?
• A heterogeneous mixture is a mixture that is unevenly distributed.
• Examples:− Iced tea: The ice is floating at the top
and therefore is not evenly distributed throughout the tea
−Chex Mix: You may find a different number of pretzels or Chex cereal in each handful; therefore, the mixture is unevenly distributed
How Are Mixtures Important To My Life?
• We encounter mixtures everywhere in our lives
• Where would you be without:− Ice cream−Kool-aid−Shampoo−Soup−Milk−Orange juice
Pop Quiz Question #1• Place an S beside each solution
and an M beside each mixture
_____ seawater
_____ steel
_____ salad
_____ air
_____ handful of confetti
S
S
M
S
M
Solutions
• Solutions can be solids, liquids, or
gases
• One substance dissolves in another
solvent --The substance that does the dissolving
*Water is the most common solvent.
solute
Rule #1: Usually there is more solvent than solute
--The substance that gets dissolved
What Affects Solubility?
• Demo 1: Motion
−Rule #2: stirring helps to break up particles and bring particles in contact with the solvent
• Demo 2: Particle Size/Surface Area
−Rule #3: the smaller the particle, the faster a solute will dissolve
• Demo 3: Pressure
−Rule #4: For gases, the higher the pressure, the more gas that can be dissolved in a liquid
• Demo 4: Temperature
−Rule #5: increase in the temperature of the solution increases the solubility of a solute
−Rule #6: Adding a solute will decrease the freezing point and increase the boiling point
−Rule #7: the more solute in a solution, the less additional solute that will dissolve; the more solvent, the more solute can be dissolved
• Saturated solution: contains the
maximum quantity of solute that can dissolve in a certain quantity of solvent−Supersaturated
Pop Quiz Question #2
• Which is the solute? Which is the solvent?
• A. salt in water
• B. 40% tin in 40% copper
• C. strawberries in cream
• D. carbon dioxide gas in water
Amounts of Solute
• A solution’s concentration depends on the amount of solute dissolved in the solvent−A solution with a high concentration has a large
amount of solute−A solution with a low concentration of solute is
called a dilute solution
Solubility• Solubility is the ability of a substance to dissolve in
another substance
• It is the amount of substance that will dissolve in a certain amount of solvent at a given temperature− If a solute is highly soluble, a solution will be very
concentrated− If a solute has a low solubility, the solution will be
dilute
Solutions/Solubility Video
• http://app.discoveryeducation.com/search?Ntt=solutions+and+solubility&N=18342&N=4294949582&N=4294939055
• Do p. 545 question 1-4 and p.550 questions 1-4
How Can We Change Matter Into New Substances?
• Chemical reaction (also known as a chemical change) is a change in a substance or substances that results in a totally new substance−Ex: 2H2(g) + O2(g) 2H2O(g)
Notice that the reactants (the substances you start with) combine to form a new substance (the product)
How Do I Know If A Chemical Reaction Has Occurred?
• There are 5 indicators of a chemical reaction
1. Evolution of a gas2. Evolution of light3. Evolution of heat4. Color change5. Evolution of a precipitate
Precipitate: an insoluble substance that is produced as result of a chemical reaction
Why Do Chemical Reactions Occur?
• Chemical reactions occur to produce a more stable product than the existing reactants
− Ex: 2Na(s) + Cl2(g) 2NaCl(s)*The sodium is highly unstable and the
chlorine gas is somewhat unstable. The resulting Sodium Chloride is VERY stable.
**It is important to understand that the products have totally different properties than the reactants
Where Does The Matter Go?
• It is important to understand that when matter undergoes a chemical reaction (ie a chemical change) it does not disappear or appear− The atoms are rearranged and form
new bonds, but no matter is lost nor gained
• This is called the Law of Conservation of Matter
What Kind of Chemical Reactions Do I Experience?
• The acidic milk and basic baking soda that produce CO2 gas when a cake bakes
• Paper burning to produce ashes, CO2, and H2O vapor
• Hydrogen peroxide decomposing to produce water and oxygen gas
Exothermic Reactions
• A reaction in which energy is released
• Often produces an increase in temperature
• Reactants = Products + Energy
Exothermic Examples
• Glow sticks- work by a chemical reaction that releases energy as light
• Fireflies- light up by a reaction that takes place between oxygen and a chemical called luciferin
Endothermic Reactions
• A reaction in which energy is absorbed
• Often produces a decrease in temperature
• Reactants + Energy = Products