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…………………………………………………… carbon dioxide: CO2 (solid form is dry ice) 7th Grade Physical Science SLEs (Student Learning Expectations) 1 atom of carbon + 2 atoms of oxygen = 1 molecule of carbon dioxide PS.5.7.1 Explain how a small number of naturallyoccurring elements can result in the large variety of substances found in the world. O – C – O = CO2 Depending on the source of information, there are between 88-92 naturally occurring elements on Earth. These elements may combine to form o elemental molecules such as O2 and H2 o compounds such as H2O and CO2 o mixtures such as in the air (O2, Ar, and CO2 dissolved in N2) Substances found in the world include elements, compounds, and mixtures. 2 or more elements combine chemically to form compounds. Ex.: C + O + O = CO2 (carbon dioxide), H + H + O = H2O (water), Na + Cl = NaCl (sodium chloride – table salt), Fe + Fe+ O + O + O = Fe2O3 (iron oxide), N + H + H + H = NH3 (ammonia) 2 or more substances (elements, compounds, and mixtures) are physically combined to form mixtures. There are a huge number of possible combinations of elements in forming these compounds and mixtures. …………………………………………………… 1 atom of sodium + 1 atom of chlorine = 1 molecule of sodium chloride Na – Cl = NaCl Sodium Chloride (salt crystal) …………………………………………………… PS.5.7.2 Create models of common compounds: sodium chloride (table salt): NaCl iron II oxide: FeO or iron III oxide: Fe2O3 1 atom of iron + 1 atom of oxygen = iron II oxide water : H2O Fe – O = FeO 2 atoms of hydrogen + 1 atom of oxygen = 1 molecule of water 2 atoms of iron + 3 atoms of oxygen = iron III oxide H – O – H = H2O O – Fe – O – Fe – O = Fe2O3 Hematite: mineral form of iron oxide …………………………………………..……… 1 ammonia: NH3 The compound water is a clear, tasteless liquid that is safe to drink. The 2 elements that chemically combine to form water are: 1 atom of nitrogen + 3 atoms of hydrogen = 1 molecule of ammonia H = NH3 H–N–H o hydrogen: a colorless, odorless gas. Extremely flammable and explosive. Inhaling high concentrations of hydrogen gas will cause breathing to stop. o oxygen: a colorless, odorless gas. Oxygen gas is not flammable itself, but it does support combustion. …………………………………………..……… PS.5.7.3 Identify compounds as substances consisting of two or more elements chemically combined. Compounds are: made of 2 or more different elements the elements are chemically combined a chemical reaction is required to separate the elements back out of the compound carbon dioxide (CO2): is composed of the elements carbon and oxygen. The compound carbon dioxide is a colorless and odorless gas at room temperature. Inhaling large amounts may cause breathing to stop. The 2 elements that chemically combine to form carbon dioxide are: o carbon: a black, odorless solid that is combustible (will burn). PS.5.7.4 Compare and contrast properties of compounds to those of the elements that compose them: Water (H2O): is composed of the elements hydrogen and oxygen. o oxygen: a colorless, odorless gas. Oxygen gas is not flammable itself, but it does support combustion. salt (NaCl) : sodium chloride is composed of the elements sodium and chlorine. PS.5.7.5 Demonstrate techniques for forming and separating mixtures: The compound sodium chloride is common table salt. It is in the form of white cubic crystals that are safe to eat in small amounts. The 2 elements that chemically combine to form table salt are: Forming mixtures: mixing 2 or more substances together. Ex.: mixing chocolate in milk to form chocolate milk, stirring salt into water to form salt water, mixing soil in water to make muddy water o sodium (Na): a soft, silvery metal that explodes in water. It will burn skin, eyes, or internal tissues. o chlorine (Cl): a greenish-yellow gas which is toxic when excessive amounts are inhaled or ingested. 2 Separating mixtures: mechanically or physically separating the parts in a mixture. chromatography: used to separate the colors in a mixture of colors. Ex.: separating the colors that are contained in black ink settling: used to separate the substances in a suspension according to their different densities. Ex: allowing the suspended soil to settle out of a mixture of soil and water. The soil will settle to the bottom because it is denser than the water. magnetic attraction: used to separate a magnetic substance (iron, nickel, cobalt) from a nonmagnetic substance. Ex.: separating iron filings from a mixture of sulfur and iron filings. evaporation: used to separate a dissolved solute from a solution. Ex.: separating the salt from a solution of salt water soil water PS.5.7.6 Classify substances as elements: o Elements are pure substances that make up all matter. They cannot be separated by chemical or physical means. o Elements are organized in the periodic table of the elements. o Each element has its own symbol such as H for hydrogen. o Some elements and their symbols include; carbon C sodium Na hydrogen H argon Ar oxygen O helium He iron Fe copper Cu nitrogen N filtration: used to separate a solid (or suspension) from a liquid. Ex.: separating sand from a mixture of sand and water 3 carbon dioxide CO2 water H2O glucose C6H12O6 ammonia NH3 Solution salt water Kool-aid Solute(s) dissolved in salt flavor powder and sugar air oxygen, argon, and carbon dioxide sterling silver copper compounds: o Compounds are made of 2 or more different kinds of elements that are chemically combined. o Each molecule of a compound is exactly like every other molecule of that compound. o Each compound is represented by its own chemical formula. o Some compounds and their formulas include; iron oxide Fe2O3 or FeO table salt NaCl isopropyl alcohol C3H8O Colloids: milk, fog, cloud silly putty marshmallows shaving cream pudding nitrogen silver PS.5.7.8 Investigate the effect of variables on solubility rates size of the particles (surface area): breaking a solute into smaller pieces, increases the surface area on which the solvent can work to dissolve. (grind up sugar cubes to make smaller particles) stirring: stirring liquids and solids (such as salt into water) increases the rate of solubility (the salt dissolves faster when stirred) temperature: for solids and liquids, more solute dissolves when the temperature increases. The opposite happens with gases. amount of solute already dissolved: Solutes dissolve faster when only a little solute is already dissolved. As the solution becomes more concentrated, the rate of solubility decreases. Mixtures: o Mixtures are made of 2 or more substances that are physically combined. o Mixtures may vary in the amount of each substance that is present. o Some mixtures of different types and examples include; Solutions: salt water Kool-aid hairspray dry air sterling silver Solvent water water Suspensions: muddy water sand in water lake water PS.5.7.9 Interpret solubility graphs PS.5.7.7 Distinguish among solvent, solute, and solution A solution is a homogenous mixture (the solute is evenly mixed throughout the solvent.) The solute is the substance(s) that dissolves in the solvent. The solute is the substance that is in the smaller amount. There may be more than one solute in a solution. The solvent is the substance in which the solutes dissolve. It is the substance that is in the largest amount. Graph A: 4 Use the solubility graph A on the previous page to answer : 1. Which solute’s solubility is most affected by temperature change of the solvent? _________________________________ 2. Which solute’s solubility is least affected by temperature change of the solvent? _________________________________ 3. What can you say about the solubility of potassium nitrate as the temperature of the water increases? __________________________________ 4. What is the solubility of sodium nitrate in water at 60oC? ______ g/100mL PS.7.7.3 Conduct investigations to identify types of potential energy and kinetic energy potential energy – stored energy kinetic energy – energy of motion Graph B: Look at the diagram on the preceding page: Think about the pipe insulation roller coaster lab; Gravitational potential energy was highest at the highest point on the roller coaster. Kinetic energy is highest at the bottom where the marble is rolling the fastest. Use the solubility graph B to answer : 1. Which solute’s solubility is most affected by temperature change of the solvent? ___________________________________ 2. Which solute’s solubility is least affected by temperature change of the solvent? ___________________________________ 3. What can you say about the solubility of NaCl as the temperature of the water increases? __________________________ ___________________________________ 4. What is the solubility of KBr in water at 130oC? ______ g/100mL 5. Which solute has the greatest solubility in water at 60oC? ______________________ At 90oC? ___________________________ The rubber-band stores elastic potential energy. Hot molecules have more kinetic energy than cool molecules. Notice in the illustration how energy of motion is shown. 5 PS.7.7.2 Describe alternatives to the use of fossil fuels: solar energy, geothermal energy, wind, hydroelectric power, nuclear energy, biomass Energy is the ability to do work. Biomass is renewable energy from plants and animals. Hydropower plant changing the energy from moving water to electrical energy. ……………………………………………………. Solar energy is energy from the sun. ……………………………………………………. Geothermal energy is generated deep inside the Earth. Radiant energy from the sun has powered life on Earth for many millions of years. Solar energy can be used for heat & to generate electricity Photovoltaic (PV devices) or “solar cells” change sunlight directly into electricity. This photograph shows a vertical geothermal well test in the Nevada Desert. ……………………………………………………. Hydropower is energy from moving water. …………………………………………………… Beaver Dam 6 PS.6.7.1-6.7.5Compare and contrast Newton’s three laws of motion; Conduct investigations demonstrating Newton’s first law of motion; Demonstrate Newton’s second law of motion; Conduct investigations of Newton’s third law of motion; Explain how Newton’s three laws of motion apply to real world situations (e.g., sports, transportation) Wind energy is energy from moving air. Newton’s 1st Law of Motion: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Also sometimes called the law of inertia. Inertia is a property of matter. Matter wants to remain as it is (either resting or moving) How Uneven Heating of Water and Land Causes Wind Examples: Wind farm made up of wind turbines (windmills) used to generate electricity ……………………………………………………. Nuclear Energy is energy from atoms. It is energy in the nucleus (core) of an atom and is a nonrenewable energy resource. Tablecloth is removed (pulled by an unbalanced force) while dishes stay on the table. The dishes were at rest and an unbalanced force did not act on the dishes. The sun is basically a giant ball of hydrogen gas undergoing fusion (atoms nuclei fuse together) into helium gas and giving off vast amounts of energy in the process. Nuclear power at nuclear power plants comes from fission (splitting of the atom’s nucleus). Bicycle stops but the rider continues in motion over the handlebars. The bicycle was acted upon by an unbalanced force (uneven ground) but the rider was not acted on by that unbalanced force (until of course he lands). Nuclear Power Plant ……………………………………………………. 7 Newton’s 3rd Law of Motion: For every action there is an equal and opposite reaction. (action-reaction) Newton’s 2nd Law of Motion: Force = Mass X Acceleration (F=MA) "Forces always occur in pairs. If object A exerts a force F on object B, then object B exerts an equal and opposite force –F on object A" The change in velocity caused by a force depends on the mass and speed of the object. Acceleration is in the direction of the force. Pushing force to the right Pulling force to right object moves right object moves right If you push or pull with twice the force, the object accelerates to twice as fast. If an object is being acted on by a force of 2 N and then more force is added for a total of 4 N, the object will move twice as fast as it did at 2 N. (If a wagon is pulled with twice the force, the wagon will accelerate until it is traveling twice as fast.) This is a picture demonstrating Newton's third law. It has an action force pushing the skateboard forward and a reaction force pushing back with the same force in the opposite direction. As mass increases, acceleration slows. (If more children are added to the wagon and the force does not change, the wagon will slow down. 8