Chapter 16 chemistry grades 5-8


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Chapter 16 chemistry grades 5-8

  1. 1. 16-1 FUNDAMENTALS OF MATTER Objectives: Explain what a scientific model is Identify individuals who contributed to the advancement of chemistry
  2. 2. FUNDAMENTALS OF MATTER Scientist use models, but not always physical objects: instead they are explanations that improve scientists’ understanding of what is being studied.
  3. 3. MATTER Scientists have used many models in studying matter Matter is anything that has mass and takes up space. Aristotle, a Greek teacher who lived more than 2000 years ago, was one of the first to study matter. Aristotle’s model of matter was that everything was made from four elements: earth, air, fire, and water. wood was thought to be earth and fire. steam was thought to be a combination of water and fire
  4. 4. DEMOCRITUS Greek Scientist believed everything was made up of tiny unbreakable spheres. these spheres could not be made any smaller than they already were named these little units “atoms” because the Greek work atomos meant “cannot be divided” believed that an atom could connect with other atoms to form al kinds of matter
  5. 5. LATER SCIENTISTS John Dalton proved that matter was made of atoms and they did connect to form different types of matter J. J. Thompson discovered that atoms contained small particles with a negative charge he called them corpuscles and he believed that they floated randomly inside the atom. today we call them electrons Ernest Rutherford created a new model for explaining the structure of the atom atom not solid, but mostly empty space only the center was solid and he called it the nucleus Later scientists discovered positively charged particles in the center of the atom, these are called protons.
  6. 6. DID YOU KNOW? If all the space were taken out of the atoms that make up your body, and the electrons, protons, and neutrons were forced together, the total volume of your body would be less than that of a grain of sand!!! An atom is so empty that if it were the size of the Earth (13000km) its nucleus would be less than 2 km across.
  7. 7. MORE LATER SCIENTISTS In 1913, Neils Bohr proposed that the negatively charged electrons circle the nucleus in established orbits like planets revolve around the sun. This planetary model worked for some atoms but not for all. James Chadwick discovered another type of particle in the nucleus next to the protons. these particles lacked any electrical charge and were neutrons. Current thinking scientists believe that the atom is best explained by the electron-cloud model
  9. 9. 16-2: STATES OF MATTER Objectives: compare and contrast the states of matter describe how the kinetic-molecular theory relates to changes of matter
  10. 10. STATES OF MATTER Solids: keep the same shape and volume and when heated they change shapes Liquids: always keep the same volume but change shape depending on the container they are in. Gas: has no fixed shape or volume. It retains the shape and volume of its container. Plasma: consists of matter that has lost electrons. It usually exists at extremely high temperatures such as those found on the sun.
  11. 11. KINETIC Kinetic refers to the energy of motion. Kinetic-molecular theory deals with the motion of atoms. according to this theory, all atoms have energy: hence, all atoms move. atoms of solids have less kinetic energy than atoms of liquids and gases, making them move more slowly. the slower movement allows these atoms to hold tightly to surrounding atoms. in liquid state atoms have more energy, they move faster and bounce farther off each other in gaseous form, atoms have the highest energy and move the fastest and farthest apart.
  12. 12. SUBLIMATION At times, matter can change from a solid to a gas, or a gas to a solid, without becoming a liquid in a process called sublimation. Iodine crystals are heated, the atoms gain energy and move far apart and become a gas. Dry Ice is another example.
  13. 13. 16-3: PROPERTIES OF MATTER P H Y S I C A L P R O P E R T I E S Silver’s bright shiny luster Water boils at 100 C Chalk comes in many colors Lipstick is made in many shades Hard candies are sweet Aluminum can be hammered into thin sheets to form foil C H E M I C A L P R O P E R T I E S Statues of marble and bronze corroded by acids Hardness of diamonds Drain cleaner dissolves substances Starter fluid helps charcoal briquettes burn Silver compound in photographic film breaks down in light to form pictures
  14. 14. PHYSICAL PROPERTIES Physical properties can be observed by the senses They include: color shape odor taste form Other properties: density texture hardness
  15. 15. CHEMICAL PROPERTIES Describes how different types of matter combine or interact with each other to form new substances. Reaction with oxygen: if paper becomes warm enough, it will combine with oxygen in the air and burn Reaction with acid: iron will react with the oxygen in water to form rust. If baking soda combines with vinegar (an acid) bubbles of carbon dioxide gas are produced. If baking soda combines with water instead of vinegar, no bubbles are produced.
  16. 16. 16-4: CHANGES OF MATTER Objectives: Distinguish between physical and chemical changes.
  17. 17. CHANGES OF MATTER Matter has both physical and chemical properties and can go through physical and chemical changes. Physical changes: changes in which the properties of matter change but the identity of the matter does not. cutting wire grinding crystal melting a metal All of these physical changes make matter look different, but they don’t change what it is.
  18. 18. CHEMICAL CHANGES Chemical changes are those in which one type of matter is changes into another type of matter having different properties. While absolute proof of a chemical change is provided only by chemical analysis, certain easily observed changes provide strong evidence that chemical changes have occurred. production of heat or light production of a gas production of a precipitate, a solid substance that separates from solution