Over the course of human history, people have developed many interconnected and validated ideas about the physical, biological, psychological, and social worlds. Those ideas have enabled successive generations to achieve an increasingly comprehensive and reliable understanding of the human species and its environment. The means used to develop these ideas are particular ways of observing, thinking, experimenting, and validating. These ways represent a fundamental aspect of the nature of science and reflect how science tends to differ from other modes of knowing.
In science, a model is a representation of an idea, an object or even a process or a system that is used to describe and explain phenomena that cannot be experienced directly. Models are central to what scientists do, both in their research as well as when communicating their explanations.
Models are a mentally visual way of linking theory with experiment, and they guide research by being simplified representations of an imagined reality that enable predictions to be developed and tested by experiment.
A theory presents a systematic way of understanding events or situations. It is a set of concepts, definitions, and propositions that explain or predict these events or situations by illustrating the relationships between variables.
A law in science is a generalized rule to explain a body of observations in the form of a verbal or mathematical statement.
Measurement is a process of detecting an unknown physical quantity by using standard quantity. For example: Take a book and use ruler (scale) to find its length. Suppose the length was 20 cm. You underwent through a process called Measurement where:
The unknown physical quantity was the length of book.
There are two types of measurement errors:
Random Errors
Systematic Errors
Random Errors
Random errors occur when measurements are being made; as a result, the measurements may vary in unpredictable ways, which could result in a significant deviation from the true value.
The ruler was the standard quantity.
20 was the magnitude.
cm was the unit of the book-length.
The interval in which the true value lies is called the uncertainty in the measurement.
Absolute Uncertainty or ± value
The absolute uncertainty in the mean value of measurements is half the range of the measurements.
E.g.
Suppose the measurements of the diameter of a pin by a Vernier Calliper are as follows:
0.25mm; 0.24mm;0.26mm; 0.23mm;0.27mm;
The mean = (0.25 + 0.24 + 0.26 + 0.23 + 0.27)/5 =125/5 = 0.25mm
The range = 0.27 - 0.23 = 0.04mm
Absolute Uncertainty = ± 0.04/2 = ± 0.02
So, the mean value = mean ± range/2 = 25 ± 0.04/2 = 25 ± 0.02
Accuracy:
This is the closeness of the measured values to the true value.
Precision:
This is the closeness of the measured values to each other: the closer they are to each other, the more precise they are.
Units provide specific meaning to the magnitude of a substance. Units of measurement provide standard to identify measurement of a physical quantify. For example: If you say that, the volume of your notebook is 25, it provides no exact meaning because it could be 25 mm3 or 25 cm3 or 25 dm3 and many more. But if you use units cm3, it provides accurate meaning that the volume of the notebook is 25 cm3.
