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Chapter 1 Scientific Endeavor - Coggle Diagram
Chapter 1 Scientific Endeavor
1.1
Safety in conducting experiments
1.1.1 Safety Rules in Laboratory
General Safety Rules
Do not
enter the laboratory without the teacher's permission
Open all doors and windows unless otherwise instructed by your teacher
Do not
carry out any test or experiment without the teacher’s permission.
Read the instructions first and understand them before starting your experiment. If in doubt, always ask your teacher.
Handle all apparatus and chemicals carefully and correctly. Always check the label on the container before using the substance it contains.
Do not
pour any unused chemicals back into its container to avoid contamination.
Do not
taste any chemicals unless otherwise instructed by the teacher.
Do not
eat, drink or play in the laboratory.
Do not
tamper with the electrical mains and other fittings in the laboratory.
Work tidily. Wash up all used apparatus and dispose of the waste correctly.
Return the apparatus to their proper storage places after cleaning.
Do not
remove any apparatus or chemicals from the laboratory.
Wash your hands after all laboratory work.
Safety rules when heating or mixing chemicals
Wear goggles when mixing or heating chemicals.
Place flammable substances away from a naked flame.
Point the mouth of a test tube which is being heated away from yourself and people around you
When accidents occur
Report all accidents, injuries, breakage and spillage to your teacher immediately.
Should a chemical get into your mouth, spit it out into a basin and rinse your mouth with plenty of water. Similarly, if any chemical comes into contact with other parts of your body or clothing, wash thoroughly with plenty of water and report to your teacher
1.1.2 Hazard Symbols
Hazard Symbols
: Hazard symbols alert us to the presence of a hazardous chemical so that we know the precautions when handling these chemicals.
1.1.3 Handling of Bunsen Burner
Lighting a Bunsen Burner
Step 1
- Connect the Bunsen burner to the gas tap with a piece of rubber tubing.
Step 2
- Turn the collar to close the air-holes.
Step 3
- Hold the lighter over the top of the
barrel
and turn on the gas tap with your free hand. This produces a luminous flame.
Step 4
- To obtain a non-luminous flame, turn the collar to open the air-hole.
Step 5
- After completing the experiment,
turn off the gas tap
to put out the flame.
Luminous flame
:
Closed air-hole
Yellow/Orange outer flame and Dark blue inner flame
Can be seen easily
Has an unsteady flame
Has a less hot relative temperature of flame
Produces soot (carbon)
**Non-Luminous flame :
Open air-hole
Light blue outer flame and a dark blue inner flame
Cannot be seen easily
Has a steady flame
Has a hotter relative temperature of flame
Does not produce soot (carbon)
1.2
Planning and Designing Scientific Investigations
When designing scientific investigations, or experiments, the main components are the
aim
,
variables
and
hypothesis
.
The
aim
is the purpose of the investigation.
There are three types of variables in every investigation: the
independent variable
,
dependent variable
, and
controlled variables
.
The independent variable is the one factor that the researcher changes or controls
The dependent variable is the factor measured1 to determine the effect of the independent variable
Controlled variables are factors that are kept constant to ensure a fair test (i.e. to ensure that the change in the dependent variable is only caused by the change in independent variable).
The hypothesis is a specific and testable prediction of the relationship between the independent variable and the dependent variable.
1.3 Data Collection
1.3.1
Qualitative and Quantitative Data
Science is evidence-based. The evidence that we collect can be classified into
qualitative
or
quantitative
data.
Qualitative data (Observations) are made using our senses – sight, hearing, touch, smell and taste. Examples of qualitative data are colour and odour.
Quantitative data (Measurements) are actual values made using scientific instruments. Examples of quantitative data are weight and volume.
1.3.2
International System of Units
SI Units (Physical Quantity/SI Unit (symbol for SI Unit) :
length/metre (m)
volume/cubic metre (m3)
time/seconds (s)
temperature/Kelvin (K)
mass/kilogram (kg)
1.3.3
Common Equipment in the Laboratory
A) Measuring Length :
Apparatus = measuring tape/ metre rule/ digital calipers
S.I Units = metre (m)
Other units = centimeter (cm), kilometer (km), micrometer (μm)
Degree of Accuracy = metre rule & measuring tape: 0.1cm digital calipers: 0.01cm
B) Measuring Time :
Apparatus = digital stopwatch
S.I Units = second (s)
Other units = minute (min), hour (h)
Degree of Accuracy = 0.1s or 0.01s (depending on type of stopwatch)
C) Measuring Temperature : Apparatus = thermometer
S.I Unit = Kelvin (K)
Other units = degree Celsius (°C)
Degree of Accuracy = 0.5 °C
D) Measuring Mass :
Apparatus = electronic balance
S.I Units = kilogram (kg)
Other units = gram (g), milligram (mg)
Degree of Accuracy = 0.1 g or 0.01 g (depending on type of electronic balance)
E) Measuring Volume of Gas : Apparatus = gas syringe
S.I Unit = cubic metre (m3)
Other units = cubic centimetre (cm3)
F) Measuring Volume of Liquid :
Beaker = To measure an
approximate volume
of liquid. (e.g. 100 cm3)
Measuring Cylinder = To measure the volume of a liquid, to an accuracy of
0.5 cm3
Burette = To measure the volume of a liquid, to an accuracy of
0.05 cm3
. (e.g. 42.35 cm3
/ 23.70 cm3)
Pipette = To measure a
specific volume
of a liquid, to an accuracy of
0.1 cm3
. (e.g. 25.0 cm3) *volume depends on type
of pipette
G) Other Common Apparatus :
Test Tube = For heating or containing small amount of substances
Boiling tube = For heating, boiling or containing larger amounts of substances than the test tube
Tripod stand = To support apparatus (usually evaporating dish or round-bottomed flask) during heating
Retort stand = To support apparatus during experiments
Filter funnel =
For transferring liquids from one container to another.
For separating insoluble solids from a mixture (filtering) when used with filter paper
Flat-bottomed flask = For preparation of gases if the process does not require heating
Round-bottomed flask = For preparation of gases if the process does require heating
Evaporating dish = To evaporate a liquid from a solution to collect the dissolved solid
Conical flask = For containing chemicals or collecting liquid
Wire gauze = Placed on tripod stand to spread heat evenly over the apparatus during heating
1.3.4
Errors in Data Collection
There are two common types of errors that can arise when taking measurements: zero error and parallax error. Errors will cause measurements to be less accurate or less precise.
1.3.4.1
Zero Error
Zero error is a type of error which an instrument gives a non-zero reading when the measured quantity should be zero.
Instruments with zero error must be adjusted to remove the error, otherwise any readings taken with the instrument will be inaccurate. Some instruments e.g. electronic balance have the “tare” function that can reset the scale to remove the zero error.
If an electronic balance shows a reading of 0.1 g when it is tared and nothing is placed on it, it exhibits zero error. We will need to subtract 0.1 g from the reading that we obtain to accurately measure the mass of an object.
*Consistent Error and Unpredictable Error (optional for NA)
Zero error is a
consistent error
because the same error will occur repeatedly in different measurements (e.g. measuring different objects with an electronic balance with zero error).
Unpredictable errors
are errors that cannot be controlled and might change when experiments are repeated. Examples are errors caused by weather conditions, or human reaction time (it is unlikely that our reaction time is the same all the time).
1.3.4.2
Parallax Error
Parallax error is a type of error that is introduced when the marking of an instrument is viewed from the wrong angle.
For example, when recording volume of liquids, we take the reading at the
curved
surface (
meniscus
) of the liquid at eye-level. If the reading is taken from another angle, it will introduce parallax error.
Parallax error can be introduced into any measurements involving instruments with markings (e.g. ruler, thermometer).
1.4
Data Interpretation
1.4.1
Accuracy and Precision
Accuracy
refers to the closeness of agreement
between a measured value and the true value
of what is measured. If the reading is very close to or the same as the true value, measurement is said to be accurate.
Precision
refers to the closeness of agreement
between measured values obtained by repeated measurements
. If multiple readings taken are very close to one another or the same, measurements are said to be precise.