Taking careful measurements
Biology · Key Stage 1 · The School
Choosing the right equipment
A ruler measures length. Scales measure weight. A thermometer measures temperature. A measuring jug measures liquid. Using the wrong equipment gives a useless answer. Choosing the right tool is the first step.
Non-standard units
You can measure a table using hand-spans. Count how many hand-spans long it is. This works, but only for you. Someone with bigger hands gets a different number for the very same table.
Why standard units are better
A centimetre is always the same size. It does not matter who is measuring. Two people measuring the same table in centimetres get the same answer. That is what makes a standard unit fair to compare.
Measuring carefully
Line the ruler up at zero, not at the edge. Read the number at eye level, not from an angle. Write down the unit every time, not just the number. A number without a unit does not mean anything on its own.
One table, measured two ways
A table is measured in hand-spans: seven, using a child's hand. The same table is measured in hand-spans by an adult: five. Same table, two different answers, because hands are different sizes. Now measure it in centimetres: 140 cm, every single time, whoever measures it. That is why science uses standard units.