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Physical and Chemical Changes

Physical and Chemical Changes. 7 th Grade Science. Physical Changes. Matter is always changing form, size, shape, color, etc. There are 2 types of changes that matter undergoes. PHYSICAL OR CHEMICAL CHANGE

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Physical and Chemical Changes

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  1. Physical and Chemical Changes 7thGrade Science

  2. Physical Changes Matter is always changing form, size, shape, color, etc. There are 2 types of changes that matter undergoes. PHYSICAL OR CHEMICAL CHANGE I. Physical Changes:a change of matter without changing the identity of the substance. IN OTHER WORDS • A CHANGE IN STATE • A CHANGE IN SIZE, SHAPE, MASS • DOES NOT CHANGE THE CHEMICAL MAKE UP OF THE MATTER • YOU HAVE WHAT YOU STARTED WITH, JUST IN A DIFFERENT FORM

  3. Examples of Physical Changes • Verbs used to describe physical changes – grind, dissolve, erode, rip, tear, break, phase change (melt, freeze, condense, etc)

  4. Other Physical Change Examples • PAPER TORN INTO PIECES • SUGAR DISSOLVED INTO TEA • SALT DISSOLVED INTO WATER • NAILS OR HAIR CUT

  5. Chemical Changes The other way that matter can be changed is call a CHEMICAL CHANGE. II. CHEMICAL CHANGE –occurs when 2 or more substances are combined into entirely new substance with all new properties. CANNOTCHANGE IT BACK!!!!!

  6. Chemical Change Verbs • Chemical Change Verbs: rusting, rotting, curdling, burning, cooking, light sensitivity, digesting, tarnishing.

  7. Kinetic Theory of Matter THEORY OF KINETIC ENERGY A. ATOMS ARE ALWAYS MOVING B. THE MORE ENERGY ADDED TO THE ATOMS, THE FASTER & FARTHER APART THEY MOVE

  8. WHEN MOLECULES MOVE FASTER, THEY PRODUCE MORE FRICTION AND THEREFORE MORE HEAT. THEY SPREAD FARTHER APART & EXPAND • WHEN MOLECULES MOVE SLOWER, THEY CAUSE LESS FRICTION AND THEREFORE LESS HEAT & CLOSER TOGETHER & CONTRACT

  9. MATTER CHANGES FROM ONE STATE OF MATTER TO ANOTHER • WHEN HEAT (ENERGY) IS ADDED • WHEN HEAT (ENERGY IS TAKEN AWAY

  10. CHANGING STATES DOES NOT CHANGE THE CHEMICAL MAKE UP OF THE MATTER • YOU HAVE WHAT YOU STARTED WITH JUST IN A DIFFERENT FORM • ICE  WATER  WATER VAPOR • H2OH2OH2O

  11. Phase Changes are PHYSICAL PHYSICAL!!!!! • Types of Phase Changes: • 1. Melting • 2. Freezing • 3. Evaporation • 4. Boiling • 5. Condensation • 6. Sublimation • 7. Deposition • ALL phase changes are caused by ADDING or TAKING away energy!!!

  12. Melting 1. MELTING– matter changing FROM A SOLID TO A LIQUID. • Energy is added • When more heat (energy) is added to matter the particles move faster till the bonds break. • Decrease density except ice to water.

  13. Evaporation/Vaporization 2. EVAPORATION • Matter changing FROM A LIQUID TO A GAS AT THE SURFACE • ENERGY IS ADDED TO SURFACE OF LIQUID • THE PARTICLES AT THE SURFACE MOVE FASTER breaking bonds. • Decreases density. • VAPORIZATION- a general term for any substance changing to a gas.

  14. Boiling 3. BOILING • matter changing FROM A LIQUID TO A GAS ALL THROUGHOUT THE LIQUID • ENERGY IS ADDED TO ALL OF LIQUID • PARTICLES MOVE FASTER ALL THROUGH THE LIQUID • SOME PARTICLES MOVE FAST ENOUGH TO CHANGE TO GAS WHILE THEY ARE IN THE MIDDLE OF THE LIQUID • DENSITY DESCREASES • Water boils at 212 F, 100C. • EX: pan of liquid on the stove • VAPORIZATION- a general term for any substance changing to a gas.

  15. VAPORIZATION!!! • Remember that vaporization is a general word for any substance changing to a gas. • Boiling, evaporation, and sublimation are ALL examples of vaporization!!!

  16. Condensation 4. CONDENSATION • Matter CHANGING FROM A GAS TO A LIQUID • ENERGY IS REMOVED • THE PARTICLES MOVE SLOWER • THE ATTRACTION BETWEEN THE PARTICLES BEGAN TO PULL THE PARTICLES CLOSER TOGETHER & THE MATTER TURNS INTO A LIQUID • DENSTITY INCREASES • Ex: dew in the lawn, water running down mirror, ring on table under glass.

  17. Freezing 5) FREEZING • CHANGING FROM A LIQUID TO A SOLID • ENERGY IS REMOVED • THE PARTICLES MOVE EVEN SLOWER • THE ATTRACTION BETWEEN THE PARTICLES BEGAN TO PULL THE PARTICLES CLOSER TOGETHER & THE MATTER TURNS INTO A SOLID • Increase density. • Water freezes at 32 F, 0 C • EX: water to ice, wax or chocolate hardening

  18. SOLIDIFICATION!!!! • Solidification is a general word for any substance changing to a solid. • Freezing and deposition are examples of SOLIDIFICATION!

  19. Sublimation 6) Sublimation: matter changes straight from a solid to a gas!!!! • Heat added rapidly • Molecules speed up and spread out rapidly • decrease density • Examples of Sublimation: dry ice, shrinking ice in a freezer, air freshener.

  20. Deposition 7) Deposition- when matter changes from a gas directly to a solid. -Heat is taken away rapidly -Density increases -Molecules slow down and get closer together. Examples: Snowflakes, frost on a wind shield

  21. WHAT HAS TO HAPPEN FOR THESE CHANGES OF STATES TO OCCUR?

  22. DRAW THIS DIAGRAM IN YOUR NOTES!!!!

  23. Let’s Sing!!!! • Phase changes are physical, physical… • Melting is physical…. Freezing is physical. • BOYS: Let me see some condensation. • GIRLS: (in high pitch voice) It’s physical. • BOYS: Let me see some sublimation. • GIRLS: (in high pitch voice) It’s physical. • Phase changes are physical, physical… • Boiling is physical… Boiling is physical… • BOYS: Let me see some deposition. • GIRLS: (in high pitch voice) It’s physical • BOYS: Let me see some evaporation. • GIRLS: (in high pitch voice) It’s physical

  24. Chemical Changes The other way that matter can be changed is call a CHEMICAL CHANGE. II. CHEMICAL CHANGE –occurs when 2 or more substances are combined into entirely new substance with all new properties. CANNOTCHANGE IT BACK!!!!!

  25. Chemical Change Verbs • Chemical Change Verbs: rusting, rotting, curdling, burning, cooking, light sensitivity, digesting, tarnishing.

  26. Chemical Changes • SOME SIGNS OF A CHEMICAL CHANGE • FIZZES OR BUBBLES • COLOR CHANGE • HEAT GIVEN OFF • LIGHT GIVEN OFF • ODOR • HEAT REQUIRED FOR REACTION • NEW SUBSTANCE FORMED • Precipitate (solid) • Precipitate (gas bubbles)

  27. CHEMICAL CHANGE EXAMPLES • BAKING BREAD – NO LONGER HAVE FLOUR, EGGS, MILK, YEAST • ALKASELTER • BAKING SODA & VINEGAR • RUST • TARNISH

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