1 / 23

Chemical vs. Physical Change

Chemical vs. Physical Change. Physical Change. Any process involving a substance changing from one state of matter to another without altering the chemical composition. These changes are often considered ‘easy’ to undo. Ex. Ice melting, water boiling, sugar dissolving. PhysicalChange1_Part1.

kinsey
Download Presentation

Chemical vs. Physical Change

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical vs. Physical Change

  2. Physical Change • Any process involving a substance changing from one state of matter to another without altering the chemical composition. • These changes are often considered ‘easy’ to undo. • Ex. Ice melting, water boiling, sugar dissolving. PhysicalChange1_Part1 PhysicalChange1_Part2

  3. Chemical Change A change that occurs when one or more substances are changed into a new substance. These changes cannot be reversed. Some observations that occur during a chemical change are: color, fizzing, precipitate (solids forming), heat change (hot or cold). ChemicalChange1_Part1 ChemicalChange1_Part2

  4. Acids & Bases • Acids are compounds which produce hydrogen ions when combined with water. • Hydrogen ions have an overall positive charge (H+) • Bases are compounds that produce hydroxide ions when combined with water. • Hydroxide ions have an overall negative charge (OH-)

  5. The pH scale • Substances that are acids or bases can be measured on a scale from 0 to 14. • This scale is called the pH scale. • “pH” stands for ‘potential hydrogen’ • Acids have a pH less than 7 • Bases have a pH higher than 7.

  6. Turning Blue/Black • Iodine solution contains iodine, potassium iodide, water, and alcohol. • This is a good indicator for starch molecules. • When combined with starch molecules it will turn blue in color. • This is due to a chemical change between the starch and iodine atoms.

  7. Turning Pink/Orange/Green • This is also a chemical change. • Many fruits or vegetables contain pigments which will change color when added to an acid or base. • These pigments will change color as their molecules change.

  8. Bubbling/Fizzing • Bubbling or fizzing is also a chemical change. • Bubbles are a result of the formation of Carbon Dioxide. • Carbon Dioxide is formed when molecules recombine to form a new substance. Often times carbon dioxide is left over and given off as a gas.

  9. The Crystal Lab • You will be investigating several crystals by examining their physical properties. • You will utilize your results to try to identify an ‘unknown’ crystal.

  10. Crystal - Size • Crystal size is determined by many variables. These can include: • Time of formation • Amount of substance • Rate of evaporation (Typically, the more time, amount of substance, and slower rate….. The larger the crystals will be.)

  11. Crystal - Color • The color of a crystal is determined by the substance and the elements which are found in the substance. • Each crystal of the same substance should have a similar color although variations may exist.

  12. Crystal - Shape • The Shape of a crystal is determined by the atomic structure of the substance in the crystal. • There are some common crystalline structures that are often seen in the natural world. They include….. • Cubic/Hexagonal/Triclinic/Monoclinic/ Orthorhombic/Rhomobohedral/ Tetragonal

  13. Crystal - Luster • Luster describes how light reflects off the surface of a crystal. • Terms to describe luster: • Glossy • Metallic • Dull • Pearly • Silky

  14. Crystal – Light Transmission • Light Transmission is used to describe how light passes through a crystal. • Terms used to describe light transmission include: • Translucent/Transparent/Opaque

  15. Monosodium Glutamate

  16. Salt

  17. Epsom Salt

  18. Lab activity A Sense-ational Activity In the Sense-ational Activity you will be conducting an experiment to test your skills of observation. In the first part of this experiment, you will be observing 5 white powders with each of you senses. In the second part of this experiment, you will be observing how each of these powders reacts (chemically / physically) when mixed with various solutions. Your ability to observe with all of your senses will be tested.

  19. Powder ‘A’ • Powder A was cornstarch. • Corn starch is an agent used as a thickener. • It is composed of longer starch molecules and has a neutral pH.

  20. Powder ‘B’ • Powder B was Baking Soda (sodium bicarbonate) • Baking soda is used to generate bubbles in recipes that contain acidic ingredients. • This is a weak base.

  21. Powder ‘C’ • Powder C was Cream of Tartar • Cream of Tartar is used to prevent sugar from crystallizing during the making of candy. • It is acidic.

  22. Powder ‘D’ • Powder D was powdered sugar. • Powdered sugar is made of smaller sucrose molecules.

  23. Powder ‘E’ • Powder E was baking powder (combination of baking soda and calcium acid phosphate and corn starch) • This will cause bubbles whether or not other ingredients are acidic.

More Related