Properties of-matter-slides ka6
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Properties of-matter-slides ka6 Presentation Transcript

  • 1. Understanding our world and being able to use that knowledge to help us means describing things and understanding how they behave. Properties of Matter  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?  Once we make changes to stuff what are its new characteristics? Can we change new stuff back into the old stuff?”  Is the “stuff” one thing (pure) or more than one thing (mixture)? Properties are the characteristics and behaviors we use to describe matter!
  • 2. Matter: anything that has mass (weighs something) & takes up space (has volume). Matter has 3 forms or physical states Properties of Matter - physical state 1
  • 3. Physical: properties of a pure substance, we can see without changing it into a new substance. Examples include: Chemical: properties of a pure substance that describe its ability to combine with or change into a new substance. Examples: 1. physical state: solid, liquid, gas 2. color 3. shape 4. mass 5. texture 6. melting & boiling point 7. density 8. solubility in water 1. Flammability 2. Reactivity Physical & Chemical Properties2 Properties can be broken down into two types - physical and chemical properties. What’s the difference?
  • 4.  a defined density (1 g/mL) • Pure substance - a substance that contains a single type of matter. When the substance is pure, it has a unique set of properties Matter can either be found in nature as a pure substance or a mixture. What does it mean to be pure? …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!! Properties - Pure Substances 3 • Pure substances have characteristic properties which we can use to identify the substance…  Example: pure water contains ONLY molecules of water (H2O) and NOTHING else!! When water is pure it has the following properites:  a defined melting point (0 °C)  a defined boiling point (100 °C)  no color  no taste  does not burn
  • 5. Properties of Matter - Mixtures 4 • Mixture - two or more substances mixed together, but not chemically combined. Each component in a mixture keeps its individual properties.  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.  Example: salt water contains water molecules (H2O) and sodium chloride (NaCl) molecules.  If you separate salt from water, the two substances will have the same properties as they would before you mixed the two.
  • 6. 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 and Solutions 5 • 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. • Solubility - the property describing how much of a material can be dissolved.  Pepper is not soluble in water. We can say pepper is insoluble in water.  Salt has a high solubility in water. We can dissolve a lot of salt in water. • Dissolving a substance is an example of a phyiscal change. The substance is STILL THERE, and hasn’t been changed into anything new!
  • 7. Mixtures 4 • 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) • 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) • Solution -
  • 8. Pure substance! Sprite? Mixture! ingredients & a gas (CO2) mixture of salts, fish, seaweed… only water - pure Pure substance! Sodium Chloride - pure Mixture! Let’s play Solution or Not Solution!! Bottled water? The ocean? Salt?
  • 9. Density6 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 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. Density (D) = Mass g (M) Volume mL (V) • 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. Density 7 • Lots of things affect density… • 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. Temperature: cool air sinks, warm air rises Cold water sinks, warm water rises, creating layers of water
  • 11. Density 8 • 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. Let’s try to describe matter in some more detail… Matter Pure substances: (water, salt, sugar) Mixtures: (soil, air) Compounds, Molecules & Elements can be broken down further into Molecules and Compounds 9 • Molecule - a single unit of a pure substance, chemically combined (bonded) in a defined ratio. • Compound - many molecules of the same pure substance. Example: a glass of water contains many millions of molecules of water. • Examples: water (H2O), hydrogen peroxide (H2O2), sodium chloride (NaCl)
  • 13. - elements can’t be broken down further and still keep their properties - 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. - 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. Elements 10 • Element - a pure substance consisting of a single type of atom
  • 14. 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 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)
  • 15. You are probably familiar with certain elements… Elements: Hydrogen & Oxygen 12
  • 16. Elements: Chlorine & Nitrogen 13
  • 17. Elements: Carbon & Sodium 14
  • 18. Adding other metals (Nickle, Tungsten) to steel gives different properties. Elements: Iron & Aluminum 15
  • 19. • 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? - brittle, dull, not magnetic, not malleable - have poor conductivity - good insulators - many are gases, tend to be reactive • Nonmetals: Hydrogen (H2), Oxygen (O2), Carbon (C ), Chlorine (Cl2) Properties of Elements 16
  • 20. are composed of Atoms: smallest building block of which matter is composed Matter Elements: pure substance with distinctive properties can’t be broken down further by physical or chemical means and retain their properties Pure substances: (water, salt, sugar) Mixtures: (soil, air) Compounds, Molecules & Elements can be broken down further into Describing Matter 17
  • 21. • 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 • Atoms: smallest building block of which matter is composed, when combined in specific ratios, they make the elements Structure of Atoms 18
  • 22. • 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 Na Sodium atom + Chlorine atom Cl • Atoms in molecules are held together by attractive forces called bonds. 1 Sodium chloride molecule Na Cl reaction Combining Atoms 19 Sodium - very reactive metal + Chlorine - toxic & reactive green gas Sodium chloride - inert (not reactive) colorless solid you can eat! Compounds often have different properties than the elements that make them up!
  • 23. • Atoms combining in defined ratios Combining Atoms 20 Hydrogen - very light, flammable gas 2 Hydrogen atoms H H + Oxygen atom O 1 Water molecule reaction HH O Oxygen - colorless gas, explosive + Water - needed by all life, can drink it Again, compounds often have different properties than the elements that make them up!
  • 24. • Physical properties: characteristic of a pure substance that can be observed without changing it into another substance. • Physical changes: changes to a substance that can be observed without changing its identity. Examples… - water always has a density of 1 g/mL at 25° C • Physical changes are sometimes hard to notice… Changes to Matter 21 Now that we have described matter and put it into different catagories, we can describe how matter changes… - at atmospheric pressure, water always melts at 0°C, and boils at 100°C - 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)
  • 25. • Chemical properties: a characteristic ability of a substance to change into another substance. • Chemical changes are often much more obvious than physical changes - Sodium metal is very reactive, never found alone in nature 1. Color change 2. Light, heat, or energy released (burning) 3. Gases or solids form where there were none before Chemical Changes 22 • Chemical changes: changes to a substance that results in a new substance forming. - Examples of chemical properties: flammablility, reactivity (the desire of a substance to combine with and form new susbtances
  • 26. Chemical Changes 23
  • 27. Atoms - smallest building blocks of matter (e.g. an atom of Oxygen contains 16 protons) 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) H O H Compounds - many molecules of the same pure substance Elements - many atoms of the same kind (e.g. Oxygen) O From Smallest to Largest 24
  • 28. Recall that all pure substances have characteristic properties that describe the way they behave, and can be used to identify the substance. • 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. H O H Electrons pulled here, more negative charge on this end (-) (+) Electrons pulled away, more positive charge on this end (+) • Polarity is a property of all substances resulting from the unequal sharing of electrons in the bonds holding the molecule together • So, one end of the moleule has a positive charge and one end has a negative charge. This gives rise to polarity! Polarity - a characteristic property 25
  • 29. • An example is Carbon Dioxide (CO2). OO C (+) (-) (-) • In some molecules, electrons are distributed over the molecule equally. Such a molecule is said to be non-polar. • We can list substances in order by polarity… Ok, Mr. Johnson… Why do we care about any of this? H2O Water CH3CH2OH Ethanol: the stuff in beer that makes you loopy (CH3)2O Acetone CH3CH2CH2CH2CH2CH2CH2CH3 Long chain hydrocarbons (waxes, oils, greasy stuff) very polar nonpolar Polarity - a characteristic property 26
  • 30. We care for a couple of reasons… - Water, Ethanol and Acetone can all dissolve or mix in each other (all polar) • Substances with similar polarities dissolve in each other • 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) Polarity - a characteristic property 27
  • 31. 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 Polarity - a characteristic property 28
  • 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. 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 • 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. 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. Write About It 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? Use information from the video or the article to answer the questions below in complete sentences.