Properties of-matter-slides

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Properties of-matter-slides

  1. 1. Properties of Matter Understanding our world and being able to use that knowledge to help us means describing things and understanding how they behave.  What are the ways and words we can use to describe “stuff?”  How does “stuff” behave? What does it do when we make changes to it?  Is the “stuff” one thing (pure) or more than one thing (mixture)?  Once we make changes to stuff what are its new characteristics? Can we change new stuff back into the old stuff?” Properties are the characteristics and behaviors we use to describe matter!
  2. 2. Properties of Matter - physical state 1 Matter: anything that has mass (weighs something) & takes up space (has volume). Matter has 3 forms or physical states
  3. 3. 2 Physical & Chemical Properties Properties can be broken down into two types - physical and chemical properties. What’s the difference? Physical: properties of a pure substance, we can see without changing it into a new substance. Examples include: 1. physical state: solid, liquid, gas 2. color 3. shape 4. mass 5. texture 6. melting & boiling point 7. density 8. solubility in water Chemical: properties of a pure substance that describe its ability to combine with or change into a new substance. Examples: 1. Flammability 2. Reactivity
  4. 4. Properties - Pure Substances 3 Matter can either be found in nature as a pure substance or a mixture. What does it mean to be pure? • Pure substance - a substance that contains a single type of matter. When the substance is pure, it has a unique set of properties  Example: pure water contains ONLY molecules of water (H2O) and NOTHING else!! When water is pure it has the following properites:   no color  a defined boiling point (100 °C)  no taste  • a defined melting point (0 °C) a defined density (1 g/mL)  does not burn Pure substances have characteristic properties which we can use to identify the substance… …imagine you had a colorless liquid that boiled at 100° C, melted at 0° C, and had a density of 1 g/mL, you could say it is most likely water!!
  5. 5. 4 Properties of Matter - Mixtures • Mixture - two or more substances mixed together, but not chemically combined. Each component in a mixture keeps its individual properties.  Example: salt water contains water molecules (H2O) and sodium chloride (NaCl) molecules.  • The mixture will behave differently than the two materials separate. Salt water will have a different boiling point than pure water! Because the parts of a mixture are not chemically combined, the parts can often be separated (purified) into their pure forms by taking advantage of their properties.  Salt can be separated from water by distilling the water (heating it to boiling), leaving behind salt, collecting water pure as it condenses.  If you separate salt from water, the two substances will have the same properties as they would before you mixed the two.
  6. 6. Solubility and Solutions 5 Some substances are able to dissolve other materials. If you put sugar into water, the water will dissolve the sugar. The sugar will soon disappear (sugar molecules are dissolved in the water)… • Solubility - the property describing how much of a material can be dissolved.  Salt has a high solubility in water. We can dissolve a lot of salt in water.  Pepper is not soluble in water. We can say pepper is insoluble in water. • Solution - a special type of mixture where one of the components mixes evenly throughout (dissolves) so that you can’t visibly see one of the parts. • Dissolving a substance is an example of a phyiscal change. The substance is STILL THERE, and hasn’t been changed into anything new!
  7. 7. 4 Mixtures Mixture - • - If you separate salt from salt water, the water will have the same properties as it would before you mixed the two - BUT… The mixture as a whole can behave differently (salt water will have a different boiling point than pure water) Solution - • • Components in mixtures can often be separated (purified) into their pure forms by taking advantage of their properties - Salt can be separated from water by distilling the water (heating it to boiling), leaving behind salt, collecting water pure as it condenses - A mixture containing stuff not soluble in water could be filtered, leaving behind the stuff that doesn’t dissolve (sand & water)
  8. 8. Let’s play Solution or Not Solution!! Bottled water? Pure substance! only water - pure The ocean? Mixture! mixture of salts, fish, seaweed… Sprite? Mixture! ingredients & a gas (CO2) Salt? Pure substance! Sodium Chloride - pure
  9. 9. 6 Density Density is the ratio of the mass of an object to its volume. • Density is determined by measuring the mass of an object, and measuring the volume, then dividing the two. Mass is measured in grams (g), volume in milliliters (mL). Density (D) = Mass g (M) Volume mL (V) • Density is a characteristic property of pure substances; it will always be the same under a given set of conditions. Example: density of water at 25 °C is 1 g/mL. • Objects with lower densities tend to float (cork floats in water). Objects with higher densities tend to sink (oil floats because it is less dense). Cork in water Oil floating on top of water
  10. 10. • Lots of things affect density… Density 7 Temperature: cool air sinks, warm air rises Cold water sinks, warm water rises, creating layers of water • Water with salts dissolved in them tend to be more dense than pure water. So, salt water (for example, in the ocean) will sink to the bottom while fresh water will float on top.
  11. 11. 8 Density • The Dead Sea in Israel has such a high concentration of salt (amount dissolved in water) that people can float in the water. • Ocean water is ~3.5% salt. The Dead Sea has a salinity of ~34%!!!! Watch this!
  12. 12. 9 Molecules and Compounds Let’s try to describe matter in some more detail… Matter Pure substances: (water, salt, sugar) Mixtures: (soil, air) can be broken down further into Compounds, Molecules & Elements • Molecule - a single unit of a pure substance, chemically combined (bonded) in a defined ratio. • Examples: water (H2O), hydrogen peroxide (H2O2), sodium chloride (NaCl) • Compound - many molecules of the same pure substance. Example: a glass of water contains many millions of molecules of water.
  13. 13. 10 Elements • Element - a pure substance consisting of a single type of atom - each element has distinctive properties. Some are stable, and can be found by themselves in nature. Others are so reactive, they will only be found combined with other elements. - elements can’t be broken down further and still keep their properties - about 100 different elements - elements identified by 1 or 2 letter symbols. Letters often are the first letters of the name of the element (Chlorine -> Cl) - organized in a specific way into the Periodic Table of the Elements.
  14. 14. Periodic Table of the Elements 11 The Periodic Table organizes elements into a set of patterns, arranged by increasing atomic number, invented by Russian chemist Dimitri Medeleev (1869) Metals: properties include malleability, ductility, good conductors of heat/electricity, magnetic Nonmetals: properties include poor conductors of heat & electricity, solids are brittle & dull Metalloids: have both characteristics of metals and metalloids
  15. 15. 12 Elements: Hydrogen & Oxygen You are probably familiar with certain elements…
  16. 16. Elements: Chlorine & Nitrogen 13
  17. 17. 14 Elements: Carbon & Sodium
  18. 18. Elements: Iron & Aluminum Adding other metals (Nickle, Tungsten) to steel gives different properties. 15
  19. 19. 16 Properties of Elements • Nonmetals: Hydrogen (H2), Oxygen (O2), Carbon (C ), Chlorine (Cl2) - brittle, dull, not magnetic, not malleable - have poor conductivity - good insulators - many are gases, tend to be reactive • Metals: Sodium (Na), Iron (Fe), and Aluminum (Al) - Shininess, magnetic - malleability: ability of a substance to be molded/formed - conductivity: ability of a substance to transfer heat/electricity • Reactivity: willingness and ability to combine with other elements - Many of the elements are so reactive that they are not found alone in nature. Wanna see how reactive?
  20. 20. 17 Describing Matter Matter Pure substances: (water, salt, sugar) Mixtures: (soil, air) can be broken down further into Compounds, Molecules & Elements Elements: pure substance with distinctive properties can’t be broken down further by physical or chemical means and retain their properties are composed of Atoms: smallest building block of which matter is composed
  21. 21. 18 Structure of Atoms • Atoms: smallest building block of which matter is composed, when combined in specific ratios, they make the elements • Theory of atomic structure says that all atoms consist of: Nucleus - contains protons with a positive charge (+) - + and neutrons (neutral, no charge) Electrons - particles with negative charge (-) orbiting nucleus in a “cloud” • An element is identified by the number of protons in its nucleus, called the atomic number. - + + + + + - - An atom having 6 protons in its nucleus is a called a carbon atom
  22. 22. 19 Combining Atoms • Atoms can combine to form a single molecule of a new substance. Remember, a molecule is a single unit of a substance, combined in defined ratios • Atoms in molecules are held together by attractive forces called bonds. Na + Sodium atom Sodium - very + reactive metal Cl Chlorine atom Chlorine - toxic & reactive green gas reaction Na Cl 1 Sodium chloride molecule Sodium chloride - inert (not reactive) colorless solid you can eat! Compounds often have different properties than the elements that make them up!
  23. 23. 20 Combining Atoms • Atoms combining in defined ratios H H + 2 Hydrogen atoms O reaction Oxygen atom Hydrogen - very + Oxygen - colorless gas, light, flammable gas explosive O H H 1 Water molecule Water - needed by all life, can drink it Again, compounds often have different properties than the elements that make them up!
  24. 24. Changes to Matter 21 Now that we have described matter and put it into different catagories, we can describe how matter changes… • Physical properties: characteristic of a pure substance that can be observed without changing it into another substance. - water always has a density of 1 g/mL at 25° C - at atmospheric pressure, water always melts at 0°C, and boils at 100°C • Physical changes: changes to a substance that can be observed without changing its identity. Examples… - Change of state, which is easily reversed. For example, water freezes into ice, boils into water vapor, but it’s still water! - Dissolving a substance into another substance. Salt dissolves in water, but they are not chemically combined. They can be separated (distillation) • Physical changes are sometimes hard to notice…
  25. 25. 22 Chemical Changes • Chemical properties: a characteristic ability of a substance to change into another substance. - Sodium metal is very reactive, never found alone in nature - Examples of chemical properties: flammablility, reactivity (the desire of a substance to combine with and form new susbtances • Chemical changes: changes to a substance that results in a new substance forming. • Chemical changes are often much more obvious than physical changes 1. Color change 2. Light, heat, or energy released (burning) 3. Gases or solids form where there were none before
  26. 26. Chemical Changes 23
  27. 27. 24 From Smallest to Largest Atoms - smallest building blocks of matter (e.g. an atom of Oxygen contains 16 protons) Elements - many atoms of the same kind (e.g. Oxygen) Molecules - several atoms bonded together in a defined ratio to form a pure substance (e.g Oxygen atoms react with Hydrogen atoms to form a single molecule of water) Compounds - many molecules of the same pure substance O H H O
  28. 28. Polarity - a characteristic property 25 Recall that all pure substances have characteristic properties that describe the way they behave, and can be used to identify the substance. • Polarity is a property of all substances resulting from the unequal sharing of electrons in the bonds holding the molecule together • Example: in a water molecule, electrons are found more near the oxygen atom than they are near the hydrogens. Water is said to be polar. • So, one end of the moleule has a positive charge and one end has a negative charge. This gives rise to polarity! (+) Electrons pulled away, more positive charge on this end (+) H H O (-) Electrons pulled here, more negative charge on this end
  29. 29. 26 Polarity - a characteristic property • In some molecules, electrons are distributed over the molecule equally. Such a molecule is said to be non-polar. • An example is Carbon Dioxide (CO2). (-) O C O (-) (+) • We can list substances in order by polarity… very polar Water CH3CH2OH Ethanol: the stuff in beer that makes you loopy (CH3)2O nonpolar H2O Acetone CH3CH2CH2CH2CH2CH2CH2CH3 Long chain hydrocarbons (waxes, oils, greasy stuff) Ok, Mr. Johnson… Why do we care about any of this?
  30. 30. Polarity - a characteristic property We care for a couple of reasons… • Substances with similar polarities dissolve in each other - Water, Ethanol and Acetone can all dissolve or mix in each other (all polar) • Substances with very different polarities do not dissolve in each other - Polar water will not mix with nonpolar oil or wax; they form layers (like ogres) 27
  31. 31. 28 Polarity - a characteristic property Nonpolar hydrocarbons layer on top of each other, sliding against themselves. This is why oils are good for keeping things from sticking to each other (they are slippery and greasy) CH3CH2CH2CH2CH2CH2CH2CH2CH3 CH3CH2CH2CH2CH2CH2CH2CH2CH3 CH3CH2CH2CH2CH2CH2CH2CH2CH3 This is why hydrocarbons make good materials to waterproof, cook with
  32. 32. 1944 Hartford Circus Fire - Do Now Briefly answer the following four questions based on the video “Fire Under the Big Top… You may use your notes! 1. List any two causes/factors for the Hartford Circus Fire. 2. What major world event was going on when the fire occurred? 3. What was the 2-component mixture used to waterproof the circus tent? 4. Who did the public blame - who was the scapegoat - for the fire and the deaths with it? Hand in paper when finished, read article silently…
  33. 33. 1. List any two causes/factors for the Hartford Circus Fire. Many causes/factors: lit match/cigarette, flammable waterproofing material, no fire extinguishers, narrow exits, tents nailed to ground, being unprepared 2. What major world event was going on when the fire occurred? A: World War II 3. What was the 2-component mixture used to waterproof the circus tent? A: parafin wax and gasoline 4. Who did the public blame - who was the scapegoat - for the fire and the deaths with it? A: Most people blamed the circus owners and performers
  34. 34. Surface Tension Activities 1. Obtain a dropper, piece of waxed paper, a penny and a cup of water. 2. Place 1 drop of water in the center of the wax paper. Notice how it looks, write down what you see. Roll the drop around the paper without spilling. What did you notice? 3. Dry off the paper when you are done, return to the center table. 4. Place penny flat on table. Using the dropper, slowly add drops of water onto the penny. See how many you can add until the water flows off the penny. Record the number on your sheet.
  35. 35. Write About It Use information from the video or the article to answer the questions below in complete sentences. 1. Imagine you are a spectator (person in the audience) at the Hartford Circus. When you see the fire, what is the first thing you do. Explain why. 2. Many people went back inside the tent after they had escaped. Why do you think they did this? Would you do the same thing, or something different? 3. Imagine your are an investigator of the Hartford Circus Fire. You now know some of the causes/factors of the fire. What are some suggestions or recommendations you would give the circus owners to prevent future fires?

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