Scientific Learning

Science is a way of finding out how the world works. Why does a stone fall? Why does milk turn sour? Why do some seeds grow in a week and others in a month? Scientists do not guess the answers. They observe, ask questions, test their ideas and measure carefully. This unit shows you the steps of that method, how an investigation is planned, how we measure with correct units, and how you can do a small science project of your own. Every later unit in this book uses these skills.

1.1 Science and scientific method

What is science?

The word science comes from the Latin word scientia, meaning "knowledge". Science is the organised study of nature through observation and experiment.

Science has three connected parts:

Part	Meaning	Example
Knowledge	Facts, laws and theories already established	Water boils at 100 °C at sea level
Method	The way in which the knowledge is found	Heating water and recording the temperature
Attitude	The habits of mind of a scientist	Curiosity, honesty, patience

Scientific attitude

A person with a scientific attitude:

• is curious and asks "why" and "how";
• is honest and records what really happened, not what he or she wished to happen;
• is open-minded and changes an idea when new evidence appears;
• does not believe something only because someone said so; he or she asks for evidence;
• is patient and repeats an experiment to be sure;
• is careful and works with accuracy.

Branches of science

Science is divided into branches. In this book you meet Biology (living things), Physics (matter, energy, force, light, electricity), Chemistry (substances and their changes), Astronomy (stars, planets and the universe) and ICT (information and communication technology). A fuller list is given below.

Branch	What it studies
Botany	Plants
Zoology	Animals
Physics	Matter, energy and their interactions
Chemistry	Composition, properties and reactions of substances
Geology	Rocks, minerals and the structure of the Earth
Astronomy	Heavenly bodies and the universe
Ecology	Living things and their surroundings
Genetics	Heredity and variation

Science and technology

Science finds knowledge. Technology uses that knowledge to make useful things and to solve problems. Scientists found how electric current produces a magnetic field; engineers used it to build electric motors. Science is knowing; technology is doing. Each helps the other: a better microscope (technology) lets biologists see bacteria (science), and what they learn helps make new medicines (technology).

The scientific method

The scientific method is the step-by-step way in which scientists solve a problem. The steps are:

1. Identifying the problem – noticing something and asking a clear question.
2. Observation and collection of information – looking carefully and reading what is already known.
3. Forming a hypothesis – a possible answer that can be tested.
4. Experiment – a fair test to check the hypothesis.
5. Recording data and analysing it – tables, graphs, calculation.
6. Drawing a conclusion – decide whether the hypothesis is supported.
7. Reporting the result – so that others can check the work.

Hypothesis, theory and law

Term	Meaning	Example
Hypothesis	A testable guess made before the experiment	Plants grow faster with more sunlight
Theory	A well-tested explanation supported by much evidence	Cell theory
Law	A statement of a pattern found to be always true under given conditions	Ohm's law

1.2 Scientific investigation

A scientific investigation is a planned study to answer a question. It is more careful than casual observation, because it controls what changes.

Variables

A variable is anything that can change in an experiment.

Variable	Meaning	In the bean example
Independent (manipulated)	The one thing we change on purpose	Amount of light
Dependent (responding)	What we measure; it changes because of the independent variable	Colour or height of seedlings
Controlled (constant)	Everything we keep the same so the test is fair	Soil, water, seed type, temperature

A control group is the set that is kept in normal conditions (or without the treatment) for comparison. The pot kept in light is the control; the pot in the dark is the experimental group.

Steps of an investigation

1. State the question or aim.
2. Make a hypothesis and predict the result.
3. List the materials and apparatus.
4. Write the procedure so that someone else can repeat it.
5. Observe and collect data (measurements and notes).
6. Present the data in tables and graphs.
7. Analyse the data and find the pattern.
8. Conclude and discuss errors and improvements.

Observation and inference

An observation is what you see, hear, touch, smell or measure. An inference is the meaning you give to it. "The candle goes out under the jar" is an observation. "The candle needs air to burn" is an inference. Keep the two separate in your report.

Observation	Possible inference
Wet clothes dry faster in sunshine	Heat increases the rate of evaporation
A magnet attracts a nail but not a coin	The nail is magnetic material; the coin is not
Leaves of the plant in the shade are larger	Plants may make larger leaves to catch more light

Data and graphs

Data are the facts and measurements collected. Two kinds exist: qualitative (colour, smell, texture) and quantitative (numbers with units). Quantitative data are best shown in a table and then a graph. A graph shows the pattern at a glance.

Rules for a good graph:

• Put the independent variable on the horizontal (x) axis and the dependent variable on the vertical (y) axis.
• Give the graph a title and label each axis with the quantity and unit.
• Choose a suitable scale that uses most of the paper.
• Plot the points clearly and draw a smooth line or best-fit straight line.

Accuracy, precision and error

• Accuracy means how close a measurement is to the true value.
• Precision means how close repeated measurements are to each other.
• Error is the difference between the measured value and the true value.

Errors are of two main kinds. A systematic error is always in the same direction (for example, a ruler whose end is worn, or a balance that does not read zero at the start). A random error changes unpredictably (for example, reaction time in starting a stopwatch). We reduce random error by taking several readings and finding their mean.

Safety in the laboratory

• Wear an apron; tie long hair.
• Never taste or directly smell chemicals; waft the vapour gently towards the nose.
• Add acid to water, never water to acid.
• Handle glass, flames and electricity with care.
• Know where the first-aid box and the fire-extinguisher are.
• Wash hands after the experiment and dispose of waste properly.

1.3 Measurement and units

To measure is to compare an unknown quantity with a standard quantity of the same kind, called a unit. A measurement has two parts: a number and a unit. "5" alone is meaningless; "5 m" is a length.

Physical quantities

A physical quantity is anything that can be measured. Fundamental quantities do not depend on other quantities. Derived quantities are made by combining fundamental ones.

SI units

All countries use the International System of Units (SI), so that measurements are understood everywhere. The seven fundamental SI quantities are given in the table; you must know the first six.

Quantity	SI unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Electric current	ampere	A
Luminous intensity	candela	cd
Amount of substance	mole	mol

Some useful derived units:

Quantity	Formula	SI unit
Area	length × breadth	m²
Volume	length × breadth × height	m³
Density	mass / volume	kg m⁻³
Speed	distance / time	m s⁻¹
Force	mass × acceleration	newton (N)
Pressure	force / area	pascal (Pa)
Energy	force × distance	joule (J)
Power	work / time	watt (W)

Prefixes

To write very large or very small numbers we put a prefix before the unit.

Prefix	Symbol	Multiplies by
kilo	k	1000
centi	c	1/100 = 0.01
milli	m	1/1000 = 0.001
micro	μ	one millionth
mega	M	one million

Measuring instruments

Quantity	Instrument
Length	Metre rule, measuring tape, vernier calliper, screw gauge
Mass	Beam balance, electronic balance
Time	Stopwatch, clock
Volume of liquid	Measuring cylinder, burette, pipette
Temperature	Thermometer
Current	Ammeter

Least count

The least count of an instrument is the smallest value it can measure correctly.

• For a metre rule marked in millimetres, the least count is 1 mm = 0.1 cm.
• For a vernier calliper: least count = value of 1 main-scale division − value of 1 vernier-scale division. With 1 main division = 1 mm and 10 vernier divisions equal to 9 main divisions, the least count is 1 mm / 10 = 0.1 mm = 0.01 cm.
• For a screw gauge: least count = pitch / number of divisions on the circular scale. The pitch is the distance moved by the screw in one full turn. With pitch 1 mm and 100 divisions, the least count is 0.01 mm.

Measuring volume

To read a measuring cylinder, keep your eye level with the liquid surface and read the bottom of the curved surface (the meniscus) of water. Reading from above or below gives an error called parallax error. The volume of an irregular solid, such as a stone, is found by lowering it into water: volume of stone = new level − first level.

Significant figures and rounding

Digits that are known with certainty plus one uncertain digit are called significant figures. A reading of 1.36 cm has three. Never give an answer with more digits than the data allow. If a calculator gives 2.7142857 for data with two figures, write 2.7.

1.4 Project work

A project is a small investigation that you plan and carry out yourself, over some days or weeks, and then report. Project work trains you to solve real problems, to work in a team, and to present results. Under the Grade 10 curriculum it also earns internal marks.

Steps of a project

1. Select the topic. It should be interesting, small enough, safe, and possible with local materials. Examples: the effect of fertiliser on bean growth; types of waste in our school; water quality of the local tap; plants in my neighbourhood used as medicine; the energy used by a home in a month.
2. Plan. Write the aim, hypothesis, materials, methods, time table and who does what.
3. Collect data. Experiment, survey, interview or observe. Record in a notebook with dates.
4. Analyse data. Make tables, graphs, averages and percentages.
5. Draw conclusions. Answer the original question honestly.
6. Report and present. Write a report and show it to the class or school.

Parts of a project report

Part	Content
Title page	Title, name, class, school, date
Acknowledgement	Thanks to those who helped
Introduction and objectives	Why the work was done; what question it answers
Methodology	Materials, procedure, sample, place and time
Data and analysis	Tables, charts, calculations
Findings and conclusion	What was found; limits of the work
Recommendations	Suggestions for action
References	Books, websites, people consulted

Types of project work

• Experimental project: a fair test, such as growing plants with and without compost.
• Survey project: collecting information from many people or places, such as a study of the use of plastic bags in a bazaar.
• Model-making project: building a working model, such as a water filter or a model of the solar system.
• Collection project: gathering and identifying specimens, such as leaves or rocks (take only what you need and do not harm nature).

A sample project plan

Title: Effect of plastic mulch on the growth of tomato seedlings. Hypothesis: Seedlings with mulch will grow taller because the soil keeps more water. Independent variable: presence of mulch. Dependent variable: height in cm after 3 weeks. Controlled variables: soil, seed variety, water volume, sunlight.

Week	Height without mulch (cm)	Height with mulch (cm)
1	3.0	3.4
2	5.1	6.0
3	7.2	8.8

From the table, the seedlings with mulch grew 8.8 − 7.2 = 1.6 cm more in three weeks, so the hypothesis is supported for this small sample. A good report would also say that more plants and a longer time are needed to be sure.

Chapter summary

• Science is the organised study of nature through observation and experiment; technology applies scientific knowledge to solve problems.
• The scientific method: problem → observation → hypothesis → experiment → data analysis → conclusion → report.
• In an experiment there is one independent variable, a dependent variable that we measure, and controlled variables kept constant; a control group is used for comparison.
• Accuracy is closeness to the true value; precision is closeness of repeated readings. Taking the mean of several readings reduces random error.
• SI base units: metre (m), kilogram (kg), second (s), kelvin (K), ampere (A), candela (cd), mole (mol). Going to a smaller unit, multiply; to a bigger unit, divide.
• Least count of a vernier = 1 MSD − 1 VSD (usually 0.01 cm); of a screw gauge = pitch / number of circular divisions (usually 0.01 mm).
• Density = mass / volume; km/h to m/s: multiply by 5/18.
• A project follows these steps: topic, plan, data collection, analysis, conclusion, report. A report has an introduction, methods, analysis, conclusion and references.

Practice questions

Group A — Objective questions (1 mark each)

1. Which one is the correct order of the first three steps of the scientific method? [1]ahypothesis, problem, observationbproblem, observation, hypothesiscexperiment, hypothesis, problemdconclusion, problem, hypothesis
2. The SI unit of temperature is [1]adegree Celsiusbdegree Fahrenheitckelvindcalorie
3. The least count of a screw gauge with pitch 0.5 mm and 50 circular divisions is [1]a0.1 mmb0.01 mmc0.05 mmd0.001 mm
4. The variable that a scientist keeps the same in a fair test is called the [1]adependent variablebindependent variableccontrolled variabledrandom variable
5. Technology is best described as [1]aa guess about naturebapplication of scientific knowledgecthe study of starsda type of experiment
6. Fill in the blank: A testable guess made before an experiment is called a ______. [1]alawbtheorychypothesisdresult

Answers to Group A

1. (b) — we first state the problem, then observe, then form a hypothesis.

2. (c) — the kelvin is the SI unit of temperature.

3. (b) — 0.5 mm / 50 = 0.01 mm.

4. (c) — controlled variables are kept constant so that the test is fair.

5. (b) — technology uses knowledge to make useful things.

6. (c) — a hypothesis is tested by experiment.

Group B — Short answer (2 marks each)

1. Define science and technology. [2]
2. Differentiate between accuracy and precision. [2]
3. What is the least count of an instrument? Write the least count of a metre rule marked in millimetres. [2]
4. Convert 90 km/h into m/s. [2]
5. What is a control group? Why is it used? [2]

Answers to Group B

1. Science is the organised body of knowledge about nature obtained by observation and experiment. Technology is the application of scientific knowledge to make useful things and solve problems.

2. Accuracy is how close a measurement is to the true value. Precision is how close repeated measurements are to one another. A measurement can be precise but not accurate if there is a systematic error.

3. The least count is the smallest value that an instrument can measure correctly. For a metre rule marked in mm it is 1 mm (0.1 cm).

4. 90 × 5/18 = 25 m/s.

5. A control group is the set of subjects kept under normal conditions without the change being tested. It is used for comparison, so we can tell whether the change really caused the result.

Group C — Long answer (4 marks each)

1. Describe the steps of the scientific method with a suitable example. [4]
2. A vernier calliper has 10 vernier divisions equal to 9 main-scale divisions, each main division being 1 mm. The main-scale reading is 2.5 cm and the 7th vernier line coincides. Find the least count and the reading. If the instrument has a zero error of +0.02 cm, find the corrected reading. [4]
3. A stone of mass 150 g is lowered into a measuring cylinder. The water level rises from 40 mL to 100 mL. Find the volume and the density of the stone in g cm⁻³ and in kg m⁻³. [4]
4. You are asked to do a project on "waste produced in our school". Write the steps you would follow and the parts of the report. [4]

Answers to Group C

1. Steps: identify the problem, observe and collect information, form a hypothesis, experiment, record and analyse data, draw a conclusion, report. Example: if seeds are kept with and without water, the problem is "do seeds need water to germinate?", the hypothesis is "seeds need water", two sets are kept with the same conditions except water, germination is counted, and the conclusion is that seeds without water do not germinate.

2. Least count = 1 mm − 0.9 mm = 0.1 mm = 0.01 cm. Reading = 2.5 + 7 × 0.01 = 2.57 cm. Corrected reading = 2.57 − 0.02 = 2.55 cm.

3. Volume = 100 − 40 = 60 mL = 60 cm³. Density = 150 / 60 = 2.5 g cm⁻³ = 2500 kg m⁻³.

4. Steps: choose the topic and aim; plan the methods and time table; collect data by counting and weighing the waste from each class for a week; present the data in tables and bar graphs; analyse which waste is largest; conclude and recommend (for example separate bins and composting). Report parts: title page, acknowledgement, introduction and objectives, methods, data and analysis, findings and conclusion, recommendations, references.