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Measurements in Chemistry

Measurements in Chemistry. Science in Focus, Chemistry O’Level, 2 nd Edition, Chapter 1. http://www.raystoreylighting.com/chem/index.htm. What are we going to learn this Chapter?. Name appropriate apparatus for the measurement of time, temperature, mass and volume.

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Measurements in Chemistry

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  1. Measurements in Chemistry Science in Focus, Chemistry O’Level, 2nd Edition, Chapter 1 http://www.raystoreylighting.com/chem/index.htm

  2. What are we going to learn this Chapter? • Name appropriate apparatus for the measurement of time, temperature, mass and volume. • State the level of accuracy needed when using common measuring apparatus. • Suggest suitable apparatus for simple experiments • State the purpose of data logging and list examples of its uses.

  3. Apparatus for Measurement Stopwatch measures time Accuracy: Nearest second Electronic balance measures mass Accuracy: Up to 0.001 g Triple beam balance measures mass Accuracy: Nearest 0.1g

  4. Apparatus for Measurement Thermometer measures temperature Accuracy: Nearest 0.5 oC (either end with .0 or .5 oC) Gas Syringe measures volume of gas produced Accuracy: Nearest 1 cm3

  5. Apparatus for Measurement Measuring Volume of Solution Pipette Holds 10.0, 20.0 or 25.0 cm3 Only measures fixed volumes. Measuring Cylinder Holds either 100 or 250 cm3 Accuracy: Nearest 1 cm3 Burette Holds 50 cm3 Accuracy: Nearest 0.1 cm3

  6. Apparatus for Measurement • Is it correct to record a thermometer reading of 24.7 oC? • What apparatus can we use to measure 80 cm3 of solution? • What apparatus can we use to add 20.0 cm3 of acid solution drop by drop to an alkali solution? • What apparatus can we use to measure out 22.4 cm3 of solution?

  7. Apparatus for Experiments Heating of a Flammable Liquid Flammable liquid is heated using a water – bath. It can be used to find the boiling point of the flammable liquid. If the boiling point of the liquid is higher than water, then we use oil instead of water (oil-bath). (Learn how to draw)

  8. Apparatus for Experiments Titration Use a sulfuric acid of known concentration. Pipette a fixed volume of it. Add alkali solution bit by bit to it and find the volume needed to neutralized the acid completely Use the alkali volume measured to neutralize the acid and find the concentration of the alkali. (Important when you learn acid and base calculations)

  9. Apparatus for Experiments Change in Mass during a Reaction Used when gas is produced during a reaction. As gas escapes, the mass of the substances in the flask decreases. By measuring how fast the mass decreases, the speed of the reaction is determined.

  10. Apparatus for Experiments Volume of Gas during a Reaction Used when gas is produced during a reaction. As gas escapes, it fills the space in the gas syringe. By measuring how fast the syringe is filled, the speed of the reaction is determined.

  11. Apparatus for Experiments Stopper What are the two changes you would make to this set-up if you want to warm the flammable liquid? Explain. Flammable liquid Heat

  12. Volumetric flask To measure fixed volume of large amount of liquid accurately. (accurate to 0.1 ml) e.g. 100.0 ml, 250.0 ml

  13. Apparatus for Experiments Collection of Gas • Gases are collected for industrial and experimental uses after they are prepared. • Common gases are hydrogen, oxygen, ammonia, chlorine and carbon dioxide. • The method chosen to collect them depends on their solubility in water and density compared to air.

  14. Apparatus for Experiments Displacement of water (Learn how to draw) For gases insoluble in water, eg. oxygen, hydrogen, carbon dioxide

  15. Gas Deliverytube Gas jar Gas

  16. Apparatus for Experiments Upward delivery For gases soluble in water and less dense than air, eg. ammonia Special note: hydrogen (Learn how to draw)

  17. Gas Gas jar Delivery tube Gas

  18. Apparatus for Experiments Downward delivery For gases soluble in water and denser than air, eg. chlorine,hydrogen chloride, sulfur dioxide Special note: carbon dioxide (Learn how to draw)

  19. Gas Gas jar Gas Delivery tube

  20. Apparatus for Experiments Drying of gases (Removing water)

  21. Apparatus for Experiments • Hydrogen, carbon dioxide, ammonia and chlorine are produced from a factory. They are passed through a water tank and then concentrated sulfuric acid and lastly collected by downward delivery. • What is the use of the water tank? • What is the use of concentrated sulfuric acid? • What gas is collected at the end? Explain.

  22. Apparatus for Experiments Data logging is used for • Temperature changes • Change in volume of gas produced • Change in mass during reaction • Change in pH as acid reacts with alkali

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