SI Units, Significant Figures, Precision vs Accuracy

Understanding SI Units

The International System of Units (SI) is the standard for measuring quantities. It ensures consistency in measurements worldwide. Here are some basic SI units:

• Length: meter (m)
• Mass: kilogram (kg)
• Time: second (s)
• Temperature: Kelvin (K)
• Amount of substance: mole (mol)

Significant Figures

Significant figures in a number are the digits that carry meaningful information about its precision. Here’s how to determine them:

• All non-zero digits are significant.
• Any zeros between significant digits are significant.
• Leading zeros are not significant.
• Trailing zeros in a decimal number are significant.

Example

In the number 0.004560, the significant figures are 4560.

Precision vs Accuracy

Precision and accuracy are terms used to describe the quality of measurements:

• Precision refers to how close multiple measurements are to each other.
• Accuracy refers to how close a measurement is to the true or accepted value.

Example

If you weigh a substance three times and get 5.0g, 5.1g, and 5.0g, your measurements are precise. If the actual weight is 5.0g, your measurements are also accurate.