1. Measurements in Chemistry
Science in Focus, Chemistry O’Level, 2nd Edition, Chapter 1

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 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
Measuring
Cylinder
Holds either 100 or 250 cm3
Accuracy: Nearest 1 cm3
Burette
Holds 50 cm3
Accuracy: Nearest 0.1 cm3
Pipette
Holds 10.0, 20.0 or 25.0 cm3
Only measures fixed volumes.

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?
wrong, because the thermometer can only record up to the nearest 0.5 oC
Measuring cylinder
Burette

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.
(Learn how to draw)
If the boiling point of the liquid is higher than water, then we use oil instead of water (oil-bath).

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.
Heat
Flammable liquid
1. Remove the stopper. This is to prevent pressure from building up in the tube and bursting the boiling tube.
2. Use a water-bath. This is to prevent the flammable liquid from catching fire as it is heated directly over a flame.

12. Volumetric flask To measure fixed volume of large amount of liquid
accurately.
(accurate to 0.1 ml)
e.g ml, 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. Delivery tube
Gas
Gas jar

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. Delivery tube
Gas jar
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. Delivery tube
Gas jar
Gas

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.
1a. Water tank is to remove the soluble chlorine.
b. Concentrated sulfuric acid is to remove water from the remaining gases and dry them.
c. Carbon dioxide is collected because it is denser than air. Hydrogen escapes as it is less dense than air.

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