Presentation on theme: "PHYSICAL SCIENCE What You Need to Know. Describe that matter is made of minute particles called atoms and atoms are comprised of even smaller components."— Presentation transcript:
PHYSICAL SCIENCE What You Need to Know
Describe that matter is made of minute particles called atoms and atoms are comprised of even smaller components. Explain the structure and properties of atoms. Atoms are made of three basic particles: protons (+), electrons (-), and neutrons (0). Atoms of the same element have the same number of protons (atomic number). Protons and neutrons make up the nucleus of atoms, where electrons are outside that nucleus. The reason the electron keeps traveling around the nucleus is the electric attraction between the electron (-) and the proton (+).
Isotopes Atoms of the same element may have different numbers of neutrons (which are neutral in charge). This causes different masses (atomic mass) BUT has no effect on charge. For example, all carbon atoms have 6 protons (atomic number is 6). The number of electrons depends on the charge and the number of neutrons depends on the atomic mass. C-14 has 6 protons and 8 neutrons.
Ions Each atom has the same number of electrons as protons IF neutral; they have more electrons than protons if negative; and they have more protons than electrons if positive. Protons are +, electrons are -. Charged atoms are called ions.
Periodic Table Atoms are listed in order by atomic number. Elements form “families” where the elements in a family (a vertical column on the table) have similar properties. Some of these properties are similarities in electron patterns, similarities in physical properties, and similarities in chemical properties.
Explain how atoms react with each other to form other substances and how molecules react with each other or other atoms to form even different substances. Atoms can “bond” to other atoms or molecules to form new substances with different properties. Hydrogen and oxygen, for instance, react to form water, a very different substance. During these reactions, nothing is gained or lost (conservation of matter). Equations showing reactions are “balanced.” For example, 2H 2 + O 2 = 2 H 2 O. There are 4 H atoms on left and right and 2 O atoms on left and right. Reactions involve sharing of electrons or trading of electrons. pH is used to tell if substances are acids (pH less than 7), bases (pH greater than 7), or neutral (pH = 7).
Chemical Reactions In some reactions, an ionic bond is formed. An IONIC BOND is a bond that holds together a positively charged ion and a negatively charged ion. One atom loses an electron to another atom, And, as everyone knows, opposites attract. In table salt, for example, an electron from a sodium atom is transferred to a chlorine atom, forming Na+ and Cl-. Because the ions have opposite charges, they are attracted to each other. Ionic bonds form most often between elements on opposite sides of the periodic table (metals and non-metals) and result in the formation of ions. Ionically bonded substances are held together with very strong bonds; this means that these substances are hard to melt, hard to boil, and hard to separate back into the elements which made up the compound. It is possible for more than one electron to be taken away from another atom, as in barium chloride (BaCl 2, a substance used in medicinal preparations). In barium chloride, two chlorine atoms each take one electron away from barium, leaving the barium ion Ba +2.
Chemical Reactions In some reactions, neither element is “strong” enough to take electrons from the other SO, the atoms share electrons. This is called a covalent bond. Covalent bonds most often form between similar types of elements (non- metals with other non-metals, etc). This type of bond results in the formation of molecules. Covalently bonded substances are held together with weaker bonds (generally speaking) than ionic substances, which makes them easier to boil, easier to melt, and easier to break back down into the original elements that made up the compound. In both these reactions, as in all chemical reactions, the number of protons and neutrons in each atom remains the same. This also means that the atoms do not change their identities. For instance, when sodium loses one electron to chlorine to make salt, sodium is still sodium because it still has 11 protons and that is true only for the element sodium. The number of protons establishes the identity of the element.
Describe the identifiable physical properties of substances. Explain how changes in these properties can occur without changing the chemical nature of the substance. Substances are often classified by their properties. They have physical properties (based on appearance, such as color, melting point, etc) and chemical properties (based on how they react and with what they react). Physical properties are color, MP, BP, conductivity, hardness, density (mass divided by volume), etc. If you investigate a substance’s physical properties, you do not change the substance. Chemical properties are ability to burn, inability to react, etc. If you investigate a substance’s chemical properties, you turn it into a new substance (or would, if it reacted). The ability to conduct heat and electricity is a physical property that depends on the substance’s electrons being able to move from place to place (most often found in metals).
Explain the movement of objects by applying Newton’s three laws of motion. Motion depends on the observer and where they are in relation to the moving object and can be described in terms of position, speed, velocity, acceleration, and time. Friction often affects motion, sometimes in a good way and sometimes in a bad way. Friction is a force that opposes the motion of an object when the object is in contact with another object or surface. What causes friction? How is friction bad and good?force
Newton’s Three Laws of Motion An object at rest stays at rest or an object in motion stays in motion unless acted on by an unbalanced force. (First law or Law of Inertia) If a force acts on an object, the affect on that object’s motion depends on its mass and the amount of force or F = m a. (Second law) For every action force, there is an equal and opposite reaction force. (Third law)
Examples of Newton’s Laws Seat belts are used to provide safety for passengers whose motion is governed by Newton's laws. The seat belt provides the unbalanced force which brings you from a state of motion to a state of rest safely. Picture a big car and a small car. The bigger car obviously has more mass than the small car. If you give them the same force (the same push or pull), won’t the big car move (accelerate) less? An unfortunate bug strikes the windshield of a bus. The bug hit the windshield and the windshield hit the bug. Which of the two forces is greater: the force on the bug or the force on the bus?
Friction The strength of a frictional force depends on the nature of the surfaces that are in contact and the force pushing them together. When friction affects a moving object, it turns the object’s kinetic energy, or energy of motion, into heat. People welcome the heat caused by friction when rubbing their hands together to stay warm. Frictional heat is not so welcome when it damages machine parts, such as car brakes. heatbrakes Objects moving through a fluid, like air or water, experience fluid friction, or drag. Teflon creates very little friction because it is so smooth. Teflon, along with Velcro and many other things, was developed as a result of our explorations in space.
Demonstrate that energy can be considered to be either kinetic (motion) or potential (stored). Kinetic energy can be calculated as KE = ½ m v 2. More mass and/or more velocity means more KE. Potential energy can be calculated as PE = m g h. More mass and/or more height means more PE. Give examples of objects with either kinetic or potential energy.
Conservation of Energy
Explain how energy may change form or be redistributed but the total quantity of energy is conserved. Thermal energy is the motion of atoms and molecules. The more energy and higher temperature, the faster the atoms and molecules move. Reactions are either endothermic or exothermic. In reactions, not only are elements the same (left and right), the total energy is the same (left and right). Energy can change form but there is no more or no less of it after it changes form. (Look at totals for the skier.)
Nuclear Reactions Radioactive substances decay naturally (remember from Earth science) and give off small particles and energy. Nuclear reactions involve LOTS of energy (very exothermic). This is because some mass is lost and turned into energy. Total mass and energy is the same, before and after. Unlike chemical reactions, the nucleus of the atom DOES change (in chemical reactions, only electrons are involved). Fission is when an atom splits into smaller ones; fusion is when smaller atoms become one larger atom, like H into He in stars (remember from Earth science).
Transfer of Thermal Energy There are three ways thermal energy can be transferred: Radiation - Radiation is the transfer of heat energy by electromagnetic radiation and can occur through mostly empty space. If you have stood in front of a fireplace or near a campfire, you have felt the heat transfer known as radiation. Conduction - Conduction is the transfer of heat energy from one substance to another or within a substance. These substances must be in direct contact with each other and heat flows through the materials by the collision of particles. Convection - Convection is the transfer of heat energy in a fluid. This type of heating is most commonly seen in the kitchen when you see liquid boiling. Convection is how heat is transferred within the liquid mantle which helps move the Earth’s plates.
Demonstrate that waves (e.g., sound, seismic, water and light) have energy and waves can transfer energy when they interact with matter. Electromagnetic radiation is a form of energy. There are many types as shown in this diagram: Visible light is a part of this, and like all electromagnetic waves, can travel through empty space.
Wave Properties Waves can sometimes: Bend around corners (diffract), like sound Reflect off surfaces Refract through new substances (the bending is due to the change in speed) Interact with each other in other ways.
Trace the historical development of scientific theories and ideas, and describe emerging issues in the study of physical sciences. The theory of atoms was only completely developed in the last 100 years after beginning with the Greeks, centuries ago. Einstein did a lot of work with changing our ideas of energy and matter. Newton and Galileo changed the thinking of people about forces and motion. Look at the changes in energy of many types, nanotechnology, plastics, computers, and other new technologies.