Science notes, chapter 1

Introduction to Scientific Investigation

Textbook Science Form 1 (DLP), pages 2–42

By the end of this chapter you can

Explain what science is and why it matters in daily life (1.1)
Name common laboratory apparatus, their functions and the hazard symbols (1.2)
Use base quantities, S.I. units and prefixes, and convert units (1.3)
Choose and read measuring instruments; explain accuracy, consistency, sensitivity and errors (1.4)
Calculate density and predict whether objects float or sink (1.5)
Follow the steps of a scientific investigation and identify variables (1.6)
Practise scientific attitudes and values (1.7)

1.1Science is Part of Daily Life

Science is a discipline that involves systematic observations and experiments of natural phenomena. The word comes from the Latin scientia, meaning "knowledge".

Natural phenomena are things that happen in nature, such as a rainbow, thunder, day and night, or a baby growing. Things made by people, such as tall buildings, are not natural phenomena.

Why science is important

Area	How science helps
Engineering	Construction of tall buildings and bridges
Communication	Satellites make communication faster and more effective
Agriculture	Fertilisers, pesticides and the hydroponic method increase crop yields
Medicine	Vaccines and antibiotics control infectious diseases and reduce the death rate

Fields of science and careers

Field	Study of	Examples of branches	Careers
Biology	Living things	Zoology, botany, microbiology, physiology	Doctor, zoologist, botanist, microbiologist
Physics	Energy and its influence on matter	Engineering	Physicist, engineer
Chemistry	Matter and its reactions	Pharmacology, forensics, toxicology	Pharmacist, chemist, forensic scientist
Geology	Rocks, soil and minerals	Geochemistry, geophysics	Geologist
Astronomy	Planets, stars and objects in the universe	Astrophysics	Astronomer
Meteorology	Weather and climate change	Hydrometeorology	Meteorologist

Inventions such as cars, telephones, computers and robots are innovations in technology that use science to solve problems in life.

The discovery of a new vaccine for dengue belongs to which field of science?

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Microbiology (a branch of biology) — vaccines act against microorganisms such as viruses.

1.2Your Science Laboratory

Common apparatus and their functions

Beaker
Holds larger amounts of chemicals

Conical flask
Holds larger amounts of chemicals

Flat-bottom flask
Holds larger amounts of chemicals

Measuring cylinder
Measures volume of liquid

Burette
Measures volume of liquid accurately

Pipette
Measures a fixed volume of liquid

Tripod stand
Supports apparatus during heating

Filter funnel
Separates insoluble solids from mixtures

Gas jar
Contains gas

Retort stand with clamp
Holds or supports apparatus

Evaporating dish
Evaporates excess solvent

Apparatus drawings: Science Form 1 (DLP) textbook, Table 1.1, pp. 10–11.

Boiling tube = heat small amounts of chemicals. Test tube = hold small amounts. Wire gauze = spreads heat evenly.

Mixing up the burette and the pipette. A burette has a tap and a scale, so it measures any volume accurately. A pipette has one mark, so it delivers one fixed volume.

Hazard symbols

Symbol	Meaning and precaution	Examples
	Irritant — vapour or fumes hurt the eyes, nose and throat. Do not inhale; use a fume chamber.	Chloroform, ammonia
	Radioactive — emits radioactive rays that can cause cancer.	Uranium, plutonium
	Corrosive — burns the skin. Do not touch; if it touches you, wash with lots of water.	Concentrated acid and alkali
	Poison / toxic — do not drink, eat, smell or taste.	Mercury, chlorine
	Explosive — use carefully according to instructions.	Hydrogen gas, butane gas
	Flammable — vaporises easily and catches fire. Keep away from fire and heat.	Alcohol, petrol

Hazard symbols: textbook Figure 1.7, p. 12.

Laboratory rules and safety

Do not enter the laboratory or start an experiment without the teacher's permission and instructions.
No eating, drinking or playing. Do not take apparatus or chemicals out of the laboratory.
Never point the mouth of a test tube at yourself or others. Wear safety goggles when mixing or heating chemicals.
Do not taste or smell anything unless the teacher allows it.
If an accident happens: do not panic, report to the teacher, switch off the electricity if there is a fire, and rinse chemicals off the skin with plenty of water.

Why are potassium and lithium kept in paraffin oil?

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They react when exposed to air. Paraffin oil keeps air away from them.

1.3Physical Quantities and Their Units

A physical quantity is a physical characteristic that can be measured. S.I. units (Système International d'Unités) are used worldwide so that measurements are consistent.

Base quantity	S.I. unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Electric current	ampere	A

Prefixes

Prefix	Symbol	Value	Standard form
giga	G	1 000 000 000	10⁹
mega	M	1 000 000	10⁶
kilo	k	1 000	10³
deci	d	0.1	10⁻¹
centi	c	0.01	10⁻²
milli	m	0.001	10⁻³
micro	µ	0.000 001	10⁻⁶
nano	n	0.000 000 001	10⁻⁹

Converting units

Mass: kg → g, × 1000. g → kg, ÷ 1000.
Length: km → m ×1000; m → cm ×100; cm → mm ×10 (divide to go the other way).
Time: hour → minute ×60; minute → second ×60 (divide to go the other way).

Worked examples

1.9 kg = 1.9 × 1000 = 1900 g
8200 g = 8200 ÷ 1000 = 8.2 kg
95 mm = 95 ÷ 1000 = 0.095 m
450 s = 450 ÷ 60 ÷ 60 = 0.125 hr

Going to a bigger unit makes the number smaller (divide). Going to a smaller unit makes the number bigger (multiply).

Why S.I. units matter: old measurements such as the span, fathom, pace and cubit depend on the size of the person's body, so two people get different answers. Standard units let everyone, everywhere, agree.

Convert 0.13 m to cm, and 24 000 g to kg.

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0.13 × 100 = 13 cm; 24 000 ÷ 1000 = 24 kg.

1.4Measuring Instruments, Accuracy, Consistency, Sensitivity and Errors

Accuracy — how close a reading is to the actual value.
Consistency — giving the same reading when a measurement is repeated.
Sensitivity — the ability to detect a small change in the quantity measured.

Quantity	Instrument	Smallest reading
Length	Ruler, measuring tape	0.1 cm (1 mm)
Length (thickness, diameter, depth)	Vernier calipers	0.01 cm (0.1 mm)
Length (very small: paper, hair, wire)	Micrometer screw gauge	0.001 cm (0.01 mm)
Mass	Lever balance, triple beam balance, digital electronic balance	—
Time	Stopwatch (0.1 s or 0.2 s); digital stopwatch (0.01 s)
Temperature	Laboratory thermometer (1 °C); clinical thermometer (0.1 °C); digital thermometer (0.1 °C)
Electric current	Ammeter; digital ammeter (0.01 A)
Volume of liquid	Measuring cylinder

To convert °C to kelvin, add 273: 0 °C = 273 K.

Eye positions when reading a ruler — Read with your eye directly above (perpendicular to) the scale to avoid parallax error. (Textbook Figure 1.9, p. 19)

Reading vernier calipers

Vernier calipers showing 3.22 cm — Main scale reading just before the vernier zero = 3.2 cm. The 2nd vernier line lines up with a main scale line → 0.02 cm.

Steps

1. Read the main scale just before the vernier "0": 3.2 cm.
2. Find the vernier line that lines up exactly with a main-scale line: line 2 → 2 × 0.01 = 0.02 cm.
3. Add: 3.2 + 0.02 = 3.22 cm.

Reading a micrometer screw gauge

Micrometer showing 3.88 mm — Sleeve: 3.5 mm is showing (3 mm + a half-mm mark). Thimble line on the centre line: 38 → 0.38 mm.

Steps

1. Sleeve reading: the last visible mark is 3.5 mm (the lower marks are half-millimetres).
2. Thimble reading: division on the centre line = 38 → 38 × 0.01 = 0.38 mm.
3. Add: 3.50 + 0.38 = 3.88 mm.

Zero error: close the jaws (or anvil) first. Actual reading = instrument reading − zero error. A negative zero error is subtracted as a negative, so it adds to the reading.

Errors

	Systematic error	Random error
What	Same error in every measurement, from the instrument	Uncertainty caused by the observer
Examples	Zero error; inaccurate instrument	Parallax error; carelessness; wrong technique
Reduce it by	Working carefully; repeating with a different instrument	Taking several readings and averaging; eye perpendicular to the scale

Estimating before measuring

Area of an irregular shape: trace it on 1 cm graph paper and count squares that are at least half covered.
Mass of something very light: weigh many and divide (100 sheets = 500 g → 1 sheet ≈ 5 g).
Volume of a regular solid: length × width × height. Irregular solid: water displacement (final volume − initial volume).

Bar measured with a ruler from 1.0 cm to 4.6 cm — The bar starts at 1.0 cm and ends at 4.6 cm, so its length is 4.6 − 1.0 = 3.6 cm.

Which instrument would you use to measure the thickness of one strand of hair? Why?

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A micrometer screw gauge — it is the most sensitive (smallest reading 0.01 mm), so it can measure very small thicknesses.

1.5Density

Density is the mass per unit volume of a material.
Density (g cm⁻³) = Mass (g) ÷ Volume (cm³)

Materials that are less dense float on materials that are denser. Ice (0.92 g cm⁻³) floats on water (1.00 g cm⁻³); copper (8.92 g cm⁻³) sinks.

Petrol, water and mercury layers with cork, ice and copper — Arrangement by density. (Textbook Figures 1.24 and 1.25, p. 30)

Liquids and solids arranged by density — Arrangement by density. (Textbook Figures 1.24 and 1.25, p. 30)

Worked example — formula

An empty measuring cylinder has a mass of 230 g. With 50 cm³ of liquid X its mass is 320 g.
Mass of X = 320 − 230 = 90 g. Density = 90 ÷ 50 = 1.8 g cm⁻³.

Worked example — water displacement

A stone of mass 24 g raises the water level from 15 cm³ to 23 cm³.
Volume = 23 − 15 = 8 cm³. Density = 24 ÷ 8 = 3 g cm⁻³ → denser than water, so it sinks.

Density in daily life: ice floats on water; helium balloons rise because helium is less dense than air; timber can be floated down rivers; layered drinks (e.g. three-layer tea) are made by pouring the densest liquid first.

Forgetting the unit. Density must be written with its unit, g cm⁻³ (or g/cm³).

1.6Steps in a Scientific Investigation

The 12 science process skills: observing, classifying, measuring and using numbers, making inferences, predicting, communicating, using time–space relationships, interpreting data, defining operationally, controlling variables, making a hypothesis, experimenting.

Identify a problem that can be tested.
Construct a hypothesis — a testable statement linking two variables.
Control variables — manipulated, responding and constant.
Plan the experiment — materials, apparatus and method.
Conduct the experiment — carefully and safely.
Collect data — at least three readings; record in a table.
Analyse and interpret data — use tables and graphs.
Make a conclusion — accept or reject the hypothesis.
Write a report.

Manipulated variable — what you change on purpose.
Responding variable — what changes as a result (what you measure).
Constant variable — what you keep the same.

Example: pendulum experiment (textbook p. 36)

Hypothesis: the longer the pendulum, the longer the time for 10 complete oscillations.
Manipulated: length of pendulum. Responding: time for 10 oscillations. Constant: mass of pendulum, angle of release.
Conclusion: hypothesis accepted.

A good hypothesis names both variables and the direction: "The larger the surface area, the more water evaporates."

1.7Scientific Attitudes and Values

Be interested and curious about your surroundings.
Be honest and accurate when recording and validating data.
Be responsible for your own and others' safety, and for the environment.
Appreciate a clean and healthy lifestyle and the balance of nature; be polite; be grateful for nature as a gift from God.

Practising these attitudes gives more accurate results and makes you a better problem solver and a responsible, creative researcher.

Summary

Remember	Key fact
Science	Systematic observations and experiments of natural phenomena
5 base quantities	Length (m), mass (kg), time (s), temperature (K), electric current (A)
Most sensitive length instrument	Micrometer screw gauge (0.01 mm) > vernier calipers (0.1 mm) > ruler (1 mm)
Actual reading	Reading − zero error
Density	Mass ÷ volume; less dense floats, denser sinks
Variables	Manipulated (change) → responding (measure); constant (keep same)