1 Introducing science
1
Introducing science
1.1
Science and us
1
There are different branches of science such as biology, chemistry and physics.
2
Scientific discoveries and inventions have increased our understanding of the natural world
and improved our quality of life. However, they can be harmful if they are not used properly.
Leeuwenhoek discovered micro-organisms in 1674
Bell invented the telephone in 1876
3
Scientific knowledge is subject to change when there are new discoveries.
4
There are still many questions that cannot be answered using scientific knowledge.
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1.2
Working in the laboratory
1
Equipment in the laboratory
water tap and sink
gas tap
electric socket
fume cupboard
first aid box
eye wash bottle
fire extinguisher
fire blanket
sand bucket
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2
Laboratory apparatus
test tube
reagent bottle
boiling tube
dropping bottle
test tube rack
measuring cylinder
test tube holder
watch glass
test tube brush
evaporating dish
beaker
dropper
conical flask
spatula
glass rod
insulating mat
tongs
tripod
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Bunsen burner
3
wire gauze
stand and clamp
Some laboratory rules:
We should NOT …
We should ...
✓
keep all exits and passages clear.
✓
keep the laboratory clean and tidy.
✓
strictly follow the instructions given by
the teacher.
✓
✓
✓
4
✗
enter the laboratory without teacher’s
permission.
✗
do experiments without teacher’s
permission.
report all accidents to the teacher at once.
✗
wear safety goggles when heating or
mixing substances.
eat, drink, play or run about in the
laboratory.
✗
tie back long hair and fasten school ties
when doing experiments.
point the mouth of a test tube towards
anyone when heating.
✗
leave a lighted Bunsen burner
unattended.
✗
smell or taste any chemicals unless the
teacher allows us to do so.
✗
suck fingers or pencils because they may
be covered with chemicals or germs.
Some common hazard warning labels:
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1 .3
Basic skills in doing experiments
1
We can use a dropper to transfer a few drops of solution from one container to another.
2
We can use a Bunsen burner to heat substances in a laboratory.
chimney
air hole
collar
base
rubber tubing
3
The proper steps of using the Bunsen burner:

Make sure the rubber tubing of the Bunsen burner is connected to the gas tap.


Close the air hole before lighting the Bunsen burner.


Bring a lighted match over the chimney, then turn on the gas tap.


Slowly open the air hole until the flame turns blue.


Turn off the flame, close the air hole and turn off the gas tap.
4
Air hole
Colour of the
flame
Shape of the
flame
Brightness of
the flame
Temperature of
the flame
closed
yellow
irregular
luminous
lower
opened
blue
regular
non-luminous
higher
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We commonly use a blue Bunsen flame for heating.
hottest part of the
blue flame
6
Some instruments and common units for measurement:
Measurement
Instrument
Common unit
(symbol)
temperature
time
length
volume
weight
thermometer
stop-watch
metre rule,
half-metre rule
or measuring
tape
ruler or
measuring
cylinder
balance
degree Celsius
(°C )
second (s),
minute (min),
hour (h)
cubic centimeter
millimeter (mm),
(cm3),
milligram (mg),
centimeter (cm),
3
cubic metre (m ),
gram (g),
metre (m),
milliliter (mL),
kilogram (kg)
kilometer (km)
litre (L)
7
Volume of a rectangular block = length × breadth × height
8
When using the measuring cylinder to measure the volume of liquids, we should make sure
our eyes are at the same level as the bottom of the meniscus when taking readings.
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1.3
1 Introducing science
9
Volume of an
irregular object
1.4
1
2
3
=
Volume of water after
putting in the object
–
Volume of water before
putting in the object
Conducting a scientific investigation
A scientific investigation usually consists of the following basic steps:
making observations

setting questions

drawing conclusions

analyzing results

proposing hypotheses
designing and carrying out experiments
When designing a fair test, we should:

identify the dependent variable, which is to be measured;

identify the independent variable, changing this variable will affect the dependent
variable;

keep the controlled variables the same.
If the experimental results support the hypothesis, we can consider the hypothesis to be a
good explanation of the observed phenomenon.
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