Give two examples of simple, complex substances and mixtures you know. Where are the named substances and mixtures used?

Simple substances: oxygen O2 (respiration), helium He (gel balls)
Complex substances: table salt NaCl (food industry), chalk CaCO3 (at school)
Mixtures: air (environment), sea water (sea)

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.