Flashcards
Elements compounds and mixtures
Cards in this deck (27)
- 1What is an element?A substance made of only one type of atom
- 2What is a compound?A substance made by 2 or more types of elements chemically joined, in fixed proportions.
- 3What is a mixture?A substance made by 2 or more substances not chemically joined.
- 4Give examples of elementsCarbon, Oxygen, Gold
- 5Give examples of compoundsWater, Carbon Dioxide, Calcium Carbonate
- 6Give examples of mixturesSand, Air, Seawater
- 7How do we differentiate elements, compounds and mixtures using diagrams?-In a element, the molecules will often be the same colour
-In a compound, the molecules are identical, with the elements combining in equal proportions.
-In a mixture, the molecules will not be identical. Elements or co compounds will combine randomly. - 8Elements ad compounds are pure. What does this suggest?-They have a fixed melting or boiling points. (boils exactly at 100 degrees Celsius, or freezes as exactly 0 degrees Celsius.)
- 9Mixtures are impure. What does this suggest?-They melt or boil over a range of temperatures.
- 10What is the separation technique called when we separate a insoluble solid from a liquid.Filtration.
- 11Explain how filtration works.-Put a filter funnel over a beaker.
-Put filter paper on the filter funnel.
-The liquid that comes through is the filtrate.
-The insoluble solid left in the filter paper is called the residue. - 12Explain how crystallisation works.-Used to separate a solute from a solution.
-Heat solution in evaporating basin using Bunsen burner.
-This boils off water, forming a saturated solution.
-Bunsen burner is turned off and crystals form as more water evaporates. - 13How can we obtain pure salt from rock salt?-Crush rock salt, dissolve in hot water.
-Filter off the impurities as residue.
-The solid salt can be obtained using crystallisation on the salt solution (filtration) - 14-Explain how simple distillation works-Separates a soluble solid from a liquid, allowing us to collect both parts of the mixture.
-Mixture is heated, allowing the water in solution to boil.
-Water vapour will condense back to a liquid by the Liebig Condenser.
-Water is collected by the beaker. Salt remains in the flask. - 15What separating technique is used to separate ethanol and water?Fractional Distillation
- 16Explain how fractional distillation on ethanol and water works.-Used to separate a mixture of liquids, that have different boiling points.
-Fractionating column is set to boiling temperature of ethanol (78 degrees Celsius)
-Ethanol boils first, as it has a lower boiling point, and travels to the top of the fractionating column and out into the condenser.
-Water boils later, but condenses instantly in the column. It trickles back into the flask, where it is collected. - 17When is chromatography used?-Used to separate parts of a mixture with different solubilities. Mostly used to separate mixtures of coloured inks or food colourings.
- 18Why must a pencil be used to draw the line?-If a pen is used, the colours in the ink may dissolve in the solvent and move up the chromatography paper as well.
- 19Why must solvent level be below pencil line?So the ink spots don't dissolve in the solvent.
- 20What is the purpose of a lid?-Prevents solvent from evaporating from the surface of the paper.
- 21What is the solvent front?-The most soluble solvent (i.e. the spot that moved the furthest up from the pencil line)
- 22Suggest what it means if a spot has not moved up-It is insoluble in this specific solvent or experiment.
- 23If some spots are at the same height, what does this suggest?-They are the same components.
- 24What 2 factors suggest how far the spots in the mixture will move?-Its affinity with the paper. The higher the affinity, the more it sticks to the paper.
-How soluble they are in the solvent. - 25How do we find out the minimum number of components in the mixture?-Count the number of spots at different levels on the chromatogram.
- 26How do we calculate the Rf value?Distance the spot travels from pencil line/Solvent front
- 27—
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- GCSE Chemistry Flashcards on Elements compounds and mixtures, created by Ryan Wu on 27/10/2021.
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- Ryan Wu
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