Chemistry

1. Experimental Scale and Abilities
Dr Aung

2. ❖ Skills for scientific enquiry
❖ Safety
❖ Using and organising techniques, apparatus and materials
❖ Observing, measuring and recording
❖ Handling experimental observations and data
❖ Planning, carrying out and evaluating investigations

3. Safety

4. In the lab
1. Always wear the shoes - to protect your feet
2. Hot liquid and solid - set in safe position, handle with caution
3. Toxic materials – mercury (not allow), other toxic substances
(chlorine, bromine, lead) appropriate information will be given to
you on the work sheet and/ or by your teacher
4. Tie back long hair – to prevent it being caught in a flame.
5. Personal belongings – sensible place so that no one will trip over
there
6. Protect eyes and skin from contact with corrosive and harmful
chemicals
7. Bunsen flames and flammable liquids

5. International hazard waring symbols

6. Corrosive
These substances attack or destroy
living tissues including eye and skin
Harmful/noxious
These substances are similar to
toxic substances but less
dangerous
Harmful/noxious
These substances are not corrosive
but can cause reddening or
blistering of the skin.
Explosive
These substance, if treated
incorrectly, they may explode.
Oxidizing
These substances provide oxygen,
which allows other materials to burn
more fiercely.
Toxic
These substances can cause death
Highly flammable
These substances can easily catch
fire.

8. Check all chemical bottles and containers.
Special note to teachers.
Not to carry out a class practical.
substitute equipment
certain experiments are carried out in a fume cupboard

9. Using and organising techniques, apparatus
and materials

11. Balances
A balance is used to measure the mass of an object.
 Bean balance
 Leaver balance
 Digital top-pan balance
The unit of mass is the kilogram (kg)
The gram (g) is one-thousandth of a kilogram:
1g = 1/1000 kg = 10-3 kg = 0.001 kg
How accurately do your scales measure?
 A bean balance is accurate to the size of the smallest mass that tilts the
balanced beam.
 A digital top-pan balance is accurate to the size of the smallest mass that
can be measured on the scale setting your are using probably 0.01 g.
 When using an electronic balance you should wait until the reding is
steady before taking it.

12. Ruler and vernier scales
A ruler is often used to measure length in the centimetre range.
The unit of length is the metre (m)
 1 decimetre (dm) = 10-1 m
 1 centimetre (cm) = 10-2 m
 1 millimetre (mm) = 10-3 m
 1 micrometre (mm) = 10-6 m
 1 kilometre (km) = 1000 m
Correct way to measure

15. Clocks and timer
Clock, watch and timers  to measure time intervals
The unit of time is seconds (s)
Stopwatch + digital timer

16. Measuring cylinders
 The volume of a liquid can be obtained by pouring it
into a measuring cylinder.
 Measuring cylinder are often marked in milliliters (ml)
where
 1millilitere = 1 cm3
 The accuracy of the reading will be 1 cm3
 Note that 1 liter = 100 cm3 = 1 dm3

17. Degree of accuracy
The smallest division of the scale of each measuring device.
 For example, the smallest division on a meter rule is 1 mm, so the accuracy of any length measured with the
rule will be 1 mm.
 The degree of accuracy will be greater, the longer the length measured:
 For measured length of 1 m = 1000 mm, the degree of accuracy will be 1 part in 1000.
 For measured length of 1 cm = 10 mm, the degree of accuracy will be 1 part in 10.
 Similarly, if the gradations on a thermometer are at 1 C intervals, the accuracy of a temperature
reading will be 1 C

18. Significant figures
Indicates how accurate
Eg: 6.7 = two significant figure
0.235 = three significant figure
6.24 x 102 = three significant figures
 Your answer should have the same number of significant figure
 When rounding the least significant figure you look at the following figure. If that is less than 5, you round down
(1.23 become 1.2) but if it is 5 or above, you round up (1.235 become 1.24)

19. RULES FOR SIGNIFICANT FIGURES
1. All non-zero numbers ARE significant. The number 33.2 has THREE significant figures because all of the digits
present are non-zero.
2. Zeros between two non-zero digits ARE significant. 2051 has FOUR significant figures. The zero is between a 2
and a 5.
3. Leading zeros are NOT significant. They're nothing more than "place holders." The number 0.54 has only TWO
significant figures. 0.0032 also has TWO significant figures. All of the zeros are leading.
4. Trailing zeros to the right of the decimal ARE significant. There are FOUR significant figures in 92.00. 92.00 is
different from 92: a scientist who measures 92.00 milliliters knows his value to the nearest 1/100th milliliter;
meanwhile his colleague who measured 92 milliliters only knows his value to the nearest 1 milliliter. It's
important to understand that "zero" does not mean "nothing." Zero denotes actual information, just like any
other number. You cannot tag on zeros that aren't certain to belong there.

20. Other
 Systematic errors
 Tables
 Handling experimental observations and data
 Calculations
 Graphs
 Conclusions

21. 5/16/2023 Chemistry 21