Lesson Vocabulary • meniscus: The curved upper surface of a liquid in a tube. • estimate: A process of referencing a physical quantity in terms of a calibration or reference point. • uncertainty: All measurements have an uncertainty equal to one half of the smallest difference between reference marks. • accuracy: Describes how close an estimate is to a known standard. • precision: Describes how close estimates are to one another. • calibration: A method of setting or correcting a measuring device by matching it to known measurement standards. • percent uncertainty: The ratio of the uncertainty to the measured value, multiplied by one hundred. • percent error: An expression of the accuracy of a measurement, standardized to how large the measurement is. • significant figures: Consist of all the certain digits in that measurement plus one uncertain or estimated digit. • density: An expression of the mass of substance in terms of the volume occupied by the substance. • mass: The quantity of inertia possessed by an object. • weight: The gravitational force acting on a mass, as measured on a scale. • Fahrenheit scale: The most commonly used scale in the United States, it defines the normal freezing point and boiling point of water as 32°F and 212°F, respectively. • Celsius scale: The most commonly used scale around the world, it defines the normal freezing point and boiling point of water as 0°C and 100°C, respectively. • Kelvin scale: Referred to as the absolute temperature scale, it defines absolute zero as the lowest theoretically possible temperature.