Issues in teaching and learning science

This is a post about my thoughts and reflections on the topics and issues that I have learnt in the lower secondary science curriculum. 
SI Units
Firstly, I have understood the importance of the SI units. The SI base units refer to the International System of Units and is made up of the following base units and their physical quantities,-
metres for length,
kilograms for mass,
seconds for time
amperes for electric currents,
kelvin for temperature,
candela for luminous intensity, and
mole for the amount of a certain substance.

The main importance of SI units is standardization. The idea is to use the same standard units all over the world. SI units form a coherent set, and they are the only form of units that are globally recognized. They have a clear advantage for establishing a worldwide dialogue, and therefore simplify the teaching of science and technology if everyone uses this system.
I feel that SI units are of significant importance to the study of Science, and I have understood their importance to our daily life.

Difference between weight and density

Density represents a physical property of matter. Every element has a unique density, and the weight of an object depends on gravitational force, which can vary between different objects.

Also, density is typically expressed in grams per milliliter or cubic centimeter, and it remains constant for any particular substance. 

However, the weight of an object varies according to its location in the universe, and the force that gravity exerts on it at that location. For example, an astronaut on the moon would weigh 1/6 of his weight on Earth, which shows that weight varies according to the object's location.