Fundamentals of Physical Science : PSC1030. Week 2 Course Notes Properties of Matter

Transcription

1 Fundamentals of Physical Science : PSC1030 Week 2 Course Notes Properties of Matter

2 Microscopic Ma*er

3 Matter, how does it work? Atoms are the Legos of all matter. All matter is built from atoms. Atoms have different types like the Legos have different colors and shapes. Subatomic Particles in Atoms Atoms Protons Electrons Neutrons Atoms are different if they do not have the exact same numbers of subatomic particles.

4 Subatomic Particles Protons Positive electric charge Same size as neutrons Bigger than electrons Found in the nucleus (center of the atom) The number of protons in an atom determines the name of the atom. Example Atoms: 6 proton atom = Carbon atom 7 proton atom = Nitrogen atom 8 proton atom = Oxygen atom

5 Subatomic Particles Electrons Negative electric charge Smallest of the three particles Found in energy levels (shells) orbiting the nucleus The number of electrons relative to the number of protons gives the electric charge of the atom. Electrons > Protons è Negative Ion Electrons < Protons è Positive Ion Electrons = Protons è Neutral Atom

6 Subatomic Particles Neutrons No electric charge Same size as protons Much bigger than electrons Found in the nucleus The number of neutrons determines the isotope of an atom. Isotopes help determine the age of decaying organic compounds through carbon dating.

7 Building with Atoms Substances built with only one type of atom are elements. gold atoms gold (element) Substances built with multiple types of atoms are compounds. sodium & chlorine atoms salt (compound)

8 Types of Atoms The Periodic Table is a chart that organizes the elements by the configuration of electrons in an atom of that element. Metals are good conductors of heat and electricity, have high densities and melting points, easily lose electrons, and are shiny. Nonmetals are poor conductors of heat and electricity, have low melting points and densities, tend to gain electrons, and are dull and brittle. Metalloids have characteristics of both metals and nonmetals A column of elements is known as a group, and each element in a group has the same number of electrons in its highest energy level (outer shell) and react similarly. Examples: Alkali Metals Halogens Noble Gases Periodic Table

9 How the Pieces Fit Chemical bonds are formed between atoms by transferring or sharing electrons. Bonds where the electrons move Bonds where atoms share electrons freely around the atoms are called are called covalent. metallic. nucleus nucleus electron Shared Electrons C o v a l e n t b o n d s o c c u r between non-metal atoms. electron - Metallic bonds are formed between metal atoms. Transferred Electron nucleus electron Bonds where atoms transfer electrons from one atom to another are called ionic. Ionic bonds are found between metal and nonmetal atoms.

10 Material Properties

11 Molecules & Phase Molecules are individual groupings of atoms. The phase of a substance is defined by the relationship between molecules. Gases have widely spaced molecules that move relative to each other. Liquids have closely packed molecules that move relative to each other. Solids have closely packed molecules that stay in position.

12 Density Density is a material property and is the average amount of matter in a volume. Density can be thought of as a measure of a substance s heaviness. less dense = light more dense = heavy Density is calculated by dividing mass by volume. Density = Mass Volume

13 Pressure Pressure is force spread over a surface area. Force of the strike over the contact area determines if the sword pierces its target. The weight of a person over their contact area determines if they fall through the ice. Pressure is calculated by dividing force by area. Pressure = Force Area

14 Pressure & Area Pressure can determine whether one object pierces another. Pressure is inversely proportional to area. Less Area More Pressure More Area Less Pressure The same force (weight) distributed over more area creates less pressure. So, greater area lowers pressure. The professor s weight on the area of the nails does not generate enough pressure to pierce him.

15 Pressure in a Liquid Depth Increases Pressure Increases Pressure in a liquid increases as depth increases. Lower Pressure So, the bottom of a submerged object has greater pressure applied to it than the top because the bottom is deeper. Buoyancy Buoyancy is the force pushing on a submerged object from greater pressure to lower pressure. Greater Pressure

16 Pressure in a Gas Pressure in a gas is inversely proportional to the volume of the gas. When the volume of a gas decreases the pressure increases. (Temperature is held constant.) Volume Pressure Gas Pressure in a gas is directly proportional to the temperature of the gas. When the temperature of a gas increases the pressure increases. (Volume is held constant.) Temperature Pressure

17 Temperature & Heat The temperature of a substance is the measurement of the average energy of the molecular motion in that substance. lower temperature = lower molecular motion Add Heat higher temperature = higher molecular motion Heat is the molecular energy of motion transferred from one object to another. The temperature of an object in contact with a hotter object rises because heat flows from higher to lower temperatures.

18 Specific Heat Specific heat is a material property and is the rate at which a substance changes heat energy into temperature. A substance with a high specific heat requires more energy to raise its temperature compared to a substance with a low specific heat. Water has a higher specific heat than the ground, so it takes more heat to increase water to the same temperature as the ground.

19 Thermal Conductivity Heat travels through materials at a specific rate. A metal spoon in boiling water will eventually conduct the heat from the boiling water across the length of the spoon and into your hand. Thermal conductivity is a measure of how quickly heat is transmi*ed through a material. A material with high thermal conductivity will transmit heat quickly. A thermal infrared image of a coffee cup filled with a hot liquid. Notice the rings of color showing heat traveling from the hot liquid through the metal cup. A low thermal conductivity material will transmit heat at a much slower rate. These substances are classified as thermal insulators. The insulation material that fills the walls of your home has low thermal conductivity, slowing the rate of heat transfer into (and out of) your home.

20 Phase Transition When heat energy is added to a substance, that substance s temperature rises or that substance changes its phase. Phase changes occur at specific temperatures, and during a phase change the temperature stays constant.