DoAssignment study guide

A1.12 · Use suitable symbols, graphs, numbers, and units

Learn to use suitable symbols, graphs, numbers, and units through clear examples and targeted practice.

Ontario Grade 10 Science

Scientific Investigation and Careers

A practical guide to showing science information clearly

In science, information is easier to use when it is shown clearly. A number without a unit may be hard to understand. A graph without labelled axes may hide what the data show. A symbol can save space, but only if its meaning is clear. This lesson focuses on choosing suitable symbols, graphs, numbers, and units. The data used in the examples are hypothetical, not real measurements.

What you will learn

Choose symbols and labels that make scientific information clear.
Organize numerical data in a table and graph.
Write numbers with units that match what is being measured.
Check that a scientific representation communicates the evidence accurately.

Start with what you already know

In Grade 9, you may have recorded observations in a table or used a graph to compare results. The same basic idea applies here: organize information so another person can understand it without guessing.

A measurement has two important parts: a number and a unit. The number tells how much. The unit tells what scale or kind of measurement is being used. For example, a length of 12 centimetres is clearer than the number 12 by itself.

A symbol is a short mark or letter that stands for something. In science, a symbol may stand for a measured quantity, such as time or temperature. Define symbols when you use them, especially if readers may not know what they mean.

A measurement needs a suitable unit.
A symbol should have a clear, stated meaning.
Tables and graphs should make patterns easier to see.

Choose a clear representation

Imagine observing the temperature of water at regular time intervals. A table can keep each time and temperature reading together. A graph can help show whether the temperature rises, falls, or stays about the same.

For a graph, give it a title that says what is being shown. Label each axis with the quantity and its unit. The horizontal axis is usually used for the quantity that is set or recorded in sequence, such as time. The vertical axis can show the quantity that changes, such as temperature. Mark a sensible number scale so the plotted points can be read.

A graph is not automatically better than a table. A table is useful when exact values matter. A graph is useful when the pattern or change matters. Choose the format that best answers the question.

Use a familiar unit that fits the measurement. Time might be recorded in seconds or minutes. Temperature might be recorded in degrees Celsius. Length might be recorded in centimetres or metres. Do not attach a unit that describes a different quantity.

Use numbers that are supported by the information you have. Do not add extra decimal places that were not measured or provided. If data are hypothetical, say so. This keeps an example from being mistaken for an actual observation.

A graph needs a title, labelled axes, units, and a readable scale.
Use a table for exact values and a graph to make a pattern easier to see.
Match the unit to the quantity being described.

Use symbols and numbers consistently

Symbols make notes shorter, but consistency matters. If you use

t

for time in a table, use the same symbol in the graph label or explanation. State what each symbol means and include its unit where relevant.

Numbers should be easy to compare. In a table, put the same kind of quantity in the same column. In a graph, use equal spacing for equal steps on an axis. For example, if one grid interval represents two minutes, the next interval should also represent two minutes.

Check the meaning of the information from start to finish. Ask: Does the title match the data? Are the quantities labelled? Are units present? Can someone read the scale? Do the plotted points match the table? These checks help prevent unclear or misleading displays.

Keep the meaning of a symbol the same throughout your work.
Use equal scale intervals on graph axes.
Compare the graph with the table to catch plotting errors.

Evidence and careful presentation

A table or graph presents evidence: the observations or measurements used to support a description. The display should show the information as it was recorded, rather than changing values to make a pattern look stronger.

When working with real measurements in class, follow the teacher's directions and use the assigned equipment safely. Record only observations you actually made. Do not treat made-up example data as laboratory results.

Clear presentation is part of communicating science. A reader should be able to identify what was measured, how values are organized, and what units were used. If any of these details are missing, the reader may misunderstand the evidence.

Represent observations honestly.
Label hypothetical data as hypothetical.
Clear labels and units help readers interpret evidence.

Worked example

Add the missing measurement details

A student writes, “The liquid was 18.” Improve the statement so a reader knows what was measured. Assume the hypothetical observation was a temperature of 18 degrees Celsius.

Identify what the number describes
The number alone is not enough. The observation concerns temperature, so name that quantity.
Include a suitable unit
Degrees Celsius is the unit given for this hypothetical temperature. Including it prevents the value from being confused with a length, time, or another quantity.
Write the complete observation
The improved statement names the quantity and gives its value with the unit. The data are explicitly hypothetical.
$T = 18\ ^\circ\mathrm{C}$

Answer: The hypothetical liquid temperature was 18 degrees Celsius.

Check: The quantity and its unit are both stated.

Worked example

Choose a graph for changing temperature

These hypothetical values show water temperature recorded over time: at 0 minutes it is 20 degrees Celsius, at 2 minutes it is 24 degrees Celsius, at 4 minutes it is 27 degrees Celsius, and at 6 minutes it is 29 degrees Celsius. Describe a suitable graph and the pattern it would show.

Choose and label the axes
Time is recorded in sequence, so put time on the horizontal axis. Temperature goes on the vertical axis. Include the units in both labels.
$t\ (\mathrm{min}),\quad T\ (^\circ\mathrm{C})$
Set a readable scale
A horizontal scale that marks 0, 2, 4, and 6 minutes matches the recorded times. Choose a vertical scale that includes all four temperatures and spaces the values clearly.
Plot and describe the points
Plot each time-temperature pair from the hypothetical data. The points rise from left to right, so the recorded temperature increases over the time shown.
$(0,20),\ (2,24),\ (4,27),\ (6,29)$

Answer: Use a graph titled “Hypothetical water temperature over time.” Label the horizontal axis time in minutes and the vertical axis temperature in degrees Celsius. Plot the four supplied pairs. The plotted values show temperature increasing during the recorded interval.

Check: The axis labels include the matching units, and the plotted pairs agree with the supplied values.

Worked example

Select a suitable unit and symbol

A class records how far a toy car travels across a classroom floor. The distance is about 3 metres. Suggest a clear symbol and a suitable way to record the value.

Name the quantity
The class is measuring distance. A symbol can make a table heading shorter, but it must be defined so readers know what it means.
$d = \text{distance}$
Choose a unit that fits
Metres are suitable for a distance of about 3 metres across a classroom. The unit should be written in the heading or beside the value.
Record the value clearly
The symbol, number, and unit now work together. Since the value is described as approximate, the word “about” should remain in the written record.
$d \approx 3\ \mathrm{m}$

Answer: A clear record is: distance,

d

, was about 3 metres. A table heading could read “Distance,

d

(m).”

Check: The symbol is defined, and the unit matches the quantity.

Common mistakes and how to avoid them

Writing a number without saying what it measures or giving a unit.

Correction: Name the quantity and include a suitable unit, such as 18 degrees Celsius for a temperature.

Drawing a graph with no title or with unlabeled axes.

Correction: Add a clear title and label each axis with the quantity and unit.

Using the same symbol for different quantities in one piece of work.

Correction: Choose a symbol for each quantity, define it, and use it consistently.

Treating hypothetical values as if they were measured results.

Correction: Clearly label example values as hypothetical and record real observations only when they have actually been made.

Lesson summary

Use symbols only when their meanings are clear.
Include a suitable unit with a measured number.
Use tables to organize exact values and graphs to show patterns.
Give graphs a title, labelled axes, units, and readable scales.
Check that every displayed value matches the information it represents.

Check your understanding

Question 1

A graph shows distance recorded at different times. Which choice gives the clearest axis labels?

Horizontal: time (s); vertical: distance (m)
Horizontal: distance; vertical: time
Horizontal: seconds; vertical: metres, with no quantity names
No labels are needed if the points are clear

Show answer and explanation

Horizontal: time (s); vertical: distance (m)

The first choice names each quantity and gives its unit. The other choices omit useful information or reverse the chosen arrangement without clear labels.

Question 2

A table heading uses

T

for temperature. What should the student do to make the symbol clear?

Define $T$ as temperature and include the unit in the heading or table.
Use $T$ without explanation because all readers know what it means.
Replace the unit with a second symbol.
Use $T$ to mean both temperature and time.

Show answer and explanation

Define

T

as temperature and include the unit in the heading or table.

Defining the symbol and showing the unit makes the table understandable. A symbol should not have two meanings in the same work.

Question 3

A set of hypothetical readings rises from 12 to 16 to 19 degrees Celsius. What can a graph of these values show?

The recorded values increase across the listed observations.
The readings prove what will happen in every situation.
The data are real because they are written as numbers.
The units can be left out because the values rise.

Show answer and explanation

The recorded values increase across the listed observations.

The graph can show the pattern in the supplied hypothetical values. It cannot turn hypothetical data into measured evidence or make units unnecessary.

Key terms

Unit: A named scale used to describe a measurement, such as metres for distance or minutes for time.
Symbol: A letter or mark used to stand for a quantity or other scientific idea.
Axis: One of the reference lines on a graph where a quantity and its scale are shown.
Hypothetical data: Values created for an example rather than collected as real observations.

Continue through SNC2D

View the complete SNC2D Ontario Grade 10 Science curriculum and lessons

About this lesson and its review

Published by DoAssignment. This reviewed lesson follows Ontario Grade 10 Science (SNC2D), expectation A1.12. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

Official curriculum reference

Report a correction or ask a question