PROPERTIES AND CHANGES

What is Chemistry? Matter is anything that has mass and takes up space Chemistry is the study of matter and the changes it undergoes

Physical and Chemical Properties A physical property is a characteristic that can be observed without changing the identity of the substance Example: solid, liquid or gas; frozen water melts at 0°C A chemical property describes what happens to a substance when it reacts to produce a new substance Example: the ability to burn or ability to bleach

Examples of Physical Properties PropertyDescriptionQualitative or Quantitative? Example colour odour lustre malleability ductility conductivity melting/ freezing pt boiling point density what the substance looks like qualitative red, colourless what the substance smells like qualitative odourless, sharp how shiny a substance is shiny, dull the ability of a substance to be hammered into thin sheets malleable the ability of a substance to be drawn into thin wires qualitative ductile the ability of a substance to allow the flow of electricity qualitative high or low conductivity temp at which a solid becomes liquid or a liquid becomes solid quantitative0°C for water the temperature at which a liquid changes into a gas quantitative 100°C for water mass per unit volume of a substance quantitative g/mL

Describe the physical properties…

Physical Changes When a substance changes but no new substance is formed often they can be reversed Examples: In dissolving, molecules are spreading out and can no longer be seen but no new substance has been formed

Change of state: the substance stays the same but looks slightly different sublimation melting evaporation condensation solidification

Chemical Changes When a new substance(s) is created These changes are much more difficult or even impossible to reverse Example: When baking soda is added to vinegar, carbon dioxide gas forms

How do you know the difference? Physical ChangeChemical Change change of state dissolved substance can change back (sometimes!) a new colour appears heat or light is given off a solid (precipitate) forms in a liquid change is generally difficult to reverse bubbles of gas form (not from heating)

To Do: Complete questions 1-4 on page 170