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53 Cards in this Set
- Front
- Back
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What is a covalent bond?
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the sharing of electrons between atoms
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what type(s) of elements does it happen between?
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Non-metals
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why do the atoms decide to do covalent bonding?
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so they have a full outer shell and therefore, are more stable
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true or false: a covalent bond can form with enough electrons to almost fill up all the atoms' outer shells
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False: all atoms in the bond have to make enough bonds to fill up its outer shell completely
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How is hydrogen chloride written to show its covalent bonding?
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H --- Cl
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How is Carbon dioxide drawn to show its covalent bonding?
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O == C == O
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what are the 2 types of covalent substances?
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Simple Molecular covalent substances
Giant Molecular covalent substances |
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in simple molecular covalent substances, what do the atoms do?
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they form very strong covalent bonds of 2 or more atoms to form small molecules
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What are the forces between these small molecules like?
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very weak
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what are these bonds (the ones between the small molecules) called?
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inter-molecular forces
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what are the properties of these simple molecular covalent substances?
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very low melting and boiling points
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why?
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because it takes very little energy to separate the molecules from one another
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what state are most of the simple molecular covalent substances at room temperature?
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liquid or gas
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do these substances conduct electricity?
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no, because there are no ions
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give three examples of simple molecular covalent substances
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hydrogen, oxygen and water
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in giant molecular covalent substances, are there any ions?
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No.
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which of the atoms in giant molecular covalent substances are bonded together?
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all of them
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what are the strengths of the bonds?
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very strong
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owing to the strong bonds, what are the melting and boiling points like?
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very high
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do they ever conduct electricity?
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no, with the exception of graphite
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are the usually soluble or insoluble in water?
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insoluble in water
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what are the two main examples?
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diamond and graphite
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how many covalent bonds does each carbon atom have in diamond?
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4
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because of the 4 bonds, what is diamond like?
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very rigid and hard
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what is diamond used for owing to its hard property?
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cutting tools
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does it, or doesn't it conduct electricity and why?
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no, it does not because there are no free electrons
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how many covalent bonds does each carbon atom have in graphite?
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3
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what is the structure/formation of graphite like?
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sheets of carbon atoms
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what do these layers/sheets do?
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they slide over one another
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as a result of their free sliding ability, what is graphite good for?
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a lubricant and in pencils because the layers slide off each other onto the paper
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because only 3 of the four outer electrons of a carbon atom is covalently bonded, what happens?
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the 4th electron becomes delocalised and move through the layers freely
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what do the delocalised electrons cause?
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graphite to conduct electricity - it can be used in electrodes
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if a substance conducts electricity when dissolved in water, what structure is it?
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an ionic lattice
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if a substance does not conduct electricity at all and has a low melting/boiling point, what structure is it?
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a simple molecular structure
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if a substance does not conduct electricity at all but has a high melting/boiling point, what structure is it?
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a giant molecular structure
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if a substance does not conducts electricity at all but is soluble and has a low melting point, what structure is it?
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a simple molecular structure
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what is a miscible liquid?
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a liquid mixture that will mix together
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what is an immiscible liquid?
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a liquid mixture that will not mix together - one floats on top of the other
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how do you separate two immiscible liquids?
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using a separating funnel
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describe the process
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let the mixture stand. denser liquid sinks. less dense liquid floats. open the tap. drain bottom liquid into a beaker.
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how can miscible liquids be separated?
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using fractional distillation
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for fractional distillation to work, the different liquids must have different...
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boiling points
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what is fractionally distilled for industry and what are the 2 main products?
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air = nitrogen, oxygen
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what are the 6 steps in air distillation?
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1. air filtered to remove dust
2. cooled to a miscible liquid at -200 degrees C 3.water vapour condenses and removed 4. carbon dioxide freezes and removed 5. liquefied air enter fractionating column and slowly heated 6. nitrogen gas is separated and then oxygen and argon have to be separated |
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what is chromatography used for?
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to identify different substances in a mixture
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how does it work?
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different substances wash through wet filter paper at different rates
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what are the 4 steps to test a mixture?
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1. put spot of test mixture on pencil base line on filter paper
2. put paper into a beaker of solvent (ethanol/water) but keeping the baseline above the solvent 3. the solvent seeps up the paper, dragging substances with it 4. different chemicals separate out up the paper |
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what is the result of a chromatography analysis called?
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a chromatogram
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what does the number of spots in the chromatogram show?
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the number of substances within the mixture
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how can a chromatogram be used?
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you can compare the results of an unknown mixture to known mixtures to determine what the unknown mixture is.
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what is an Rf value?
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the ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent
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how can this be calculated?
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Rf = distance travelled by substance / distance travelled by solvent
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why is this useful?
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scientist keep Rf values to compare against unkown substances
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