What is a abstact concepts?

A chair weighs 10 kilograms on Earth. How much does the chair weigh on Mercury? Tissue that forms nerves and the brain? What does overall impact mean? What is pencergrasp? Is it possible for someone to know absolutely nothing? What is contraction factor? What is a scientific explanation that can be tested by observations or experiments? What are the limitations of using a regular search engine such as Google or Bing when it comes to conducting research in a formal academic environment? How many meters are in 17 cm? Why is observation such an important quality in forensic science? Why does some friction occur with seemingly smoth surfaces? What branch of science does mold belong too? Can you briefly explain Torricelli's Experiment between mercury and atmospheric pressure? What is 39.2 C in Fahrenheit? What does 150X mean for a microscope? Why do sedimentary rocks have stripes? What does the fossil record gourmet say is needed to make a fossil? Why do density of a substance is wrong when some of the water splashes? What advances in technology made war more terrible than it had been in earlier years? Why are 17 inch wheels better than 16 inch?