Chemical or Physical Change?

1. Chemical or Physical Change?

2. Physical Change Chemical before change is the same chemical afterwards. • Only its form has been altered. • Examples: • Big piece broken into smaller pieces • Phase changes • Shape change: bending a straw

3. Chemical Change Chemical before change is not the same chemical after. Change in Properties: • Melting point, boiling points, density, color, taste, texture, smell, etc. are now different. • Precipitation: solid forms when 2 liquids react when mixed • Gas production: Change in Energy: • Heat energy absorbed, heat energy released, light energy released

4. Chemical or Physical Change? Physical Cutting paper? Why? Paper before Paper after Only altered its form.

5. Chemical or Physical Change? Physical Ice melting? Why? Water before, water after. Just a phase change, solid -> liquid

6. Chemical or Physical Change? Chemical Toast burning? Why? Change in properties. Different smell, taste, color, texture.

7. Chemical or Physical Change? chemical Rocket fuel burning? Why? Heat and light energy released Gas production

8. Chemical or Physical Change? Physical Why? Sawing wood? Wood before, wood after, just smaller pieces.

9. Chemical or Physical Change? chemical Metal rusting? Why? Metal before, rust (iron oxide) after Color change (grey to red/orange), strength change (strong to weak) texture (smooth to powdery)

10. Chemical or Physical Change? Physical Disappearing puddle? Why? Water before, water after Just a phase change: Liquid water to gaseous water

11. Chemical or Physical Change? Chemical Why? Candle burning? Change in energy: release of light and heat energy Wax reacts with oxygen in air and produces carbon dioxide gas and water gas

12. Chemical or Physical Change? Physical Why? Dry ice? Carbon dioxide before, carbon dioxide after Phase change: Solid to gas (sublimation)