The Role of Units Physicists, like other scientists, make observations and ask basic questions. For example: how big is an object? How much mass does it have? How far did it travel? To answer these questions, they make measurements with various instruments (e.g., meter stick, balance, stopwatch, etc.). The measurements of physical quantities are expressed in terms of units, which are standardized values. For example, the length of a race, which is a physical quantity, can be expressed in meters (for sprinters) or kilometers (for distance runners.) Without standardized units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way. Distances given in unknown units are maddeningly useless. All physical quantities in the SI system of units are expressed in terms of combinations of seven fundamental physical units, which are units for: length, mass, time, electric current, temperature, amount of a substance, and luminous intensit...
Chemistry / Matter and its Composition Matter : Anything that has weight and occupies space and can be perceived by our senses is called matter. States of matter: Solids: A solid has a definite shape and volume. Examples of solids include ice (solid water), a bar of steel, and dry ice (solid carbon dioxide). Liquids: A liquid has a definite volume, but takes the shape of its container. Examples of liquids include water and oil. Gases: A gas has neither a definite volume nor a definite shape. Examples of gases are air, oxygen, and helium. Plasma is recognized as fourth state of matter. Inter conversion of three states of matter: 1. Melting : Change of substance from solid state to liquid state. 2. Evaporation or boiling: Change of substance from liquid state to gaseous state. Transpiration is the evaporation of water into the atmosphere from the leaves and stems of plants 3. Condensation : change of substance from gaseous state to liquid state. ...
Comments
Post a Comment