Chapter 2: Measurement and Units  2.1 Space and Time  2.2 Mass, Matter, and Atoms  2.3 Experiments and Data

Inv 2.2 Time Investigation Key Question: How do we measure and describe time?

2.2 Mass, matter, and atoms  Mass —is the amount of “stuff” an object contains.  Two effects mass has on matter: —Weight  is the force of the Earth’s gravity pulling down.  Gravity acts on an object’s mass. —Inertia  is the tendency of an object to resist changes in motion.  Inertia comes from mass.

2.2 Measuring mass  Kilogram —is the mass of 1 liter of water or 1,000 cubic centimeters of water.

2.2 Very large and very small numbers  Because physics covers such a wide range of values for length, time, and mass you will need a method of working with large and small numbers.  In scientific notation, numbers are written as a value between 1 and 10, multiplied by a power of 10 called the exponent.

2.2 Matter and atoms  A single atom is about meters in diameter.  Aluminum foil is thin but still more than 200,000 atoms thick.  Whether matter is a solid, liquid, or gas depends on how the atoms are organized.

2.2 Matter and atoms  Solids - Atoms in a solid stay together because the energy per atom is too low to break the bonds between atoms.  Liquids - Liquids flow because atoms have enough energy to move around by temporarily breaking and reforming bonds with neighboring atoms.  Gases - Gas atoms have enough energy to completely break bonds with each other.  Plasma - In plasma, matter becomes ionized as electrons are broken loose from atoms.

2.2 The diversity of matter  There is an incredible diversity of matter around you.  This diversity comes from combining elements into compounds, then compounds into mixtures of compounds.

2.2 The diversity of matter  Each type of matter is called an element.  Each element has is own properties, such as mass and the ability to combine with other elements.  There are about 92 different types of atoms in ordinary matter.

2.2 The diversity of matter  A compound is a substance that contains two or more different elements bonded together.  Water is an example of a compound.  If you could look at water with a powerful atomic microscope you would find each particle of water is made from one oxygen atom and two hydrogen atoms.

2.2 The diversity of matter  Another compound, glucose, is a sugar in food.  A single glucose molecule is made of carbon, oxygen, and hydrogen atoms.

2.2 Matter and atoms  The matter you normally experience is made of mixtures of compounds.  Wood is a mixture that contains water and more than 100 other compounds.