Properties of Matter: Classifying Pure Substances & Mixtures

1. Chapter 2 – Properties of Matter Inquiry Activity pg 37

2. 2.1 Classifying Matter • Pure substance (substance) – matter that always has exactly the same composition • Ex. Table Salt, Table Sugar • Every sample has the same properties due to a fixed, uniform composition.

3. Element – substance that contains only one type of atom, cannot be broken into simpler substances • Atom – smallest particle of an element • Ex. – Carbon, Oxygen, Nitrogen, Gold, Silver, Calcium, etc.

4. Symbols for Elements • 1-3 letters • First letter is capital • May be first few letters of element name • C = Carbon Ca = Calcium He = Helium • May be derived from latin name • Fe = iron (from latin Ferrum) Au = gold (aurum)

5. Compound – made from two or more simpler substances, joined in a fixed proportion • Compounds AND Elements are PURE SUBSTANCES • Ex. Water – hydrogen and oxygen • Ex. Salt – sodium and chlorine

6. Mixtures – composition is not fixed, properties may vary • Ex. Salsa, spaghetti sauce, sand, salad dressing, salt water • Heterogeneous Mixtures – parts are noticeably different from one another • Homogenous Mixtures – substances are so evenly distributed that it appears to contain only one substance

7. Heterogeneous Homogeneous

8. Solutions, Suspensions, Colloids Solution – formed when substances dissolve and form a homogeneous mixture; particles are too small to settle Suspension – heterogeneous mixture that separates into layers over time; larger particles Colloids – contain intermediate sized particles; do not separate into layers; particles scatter light

9. 2.2 Physical Properties • Physical Property – any characteristic that can be observed or measured without changing the composition of a substance • Viscosity – a liquid’s resistance to flowing • The greater the viscosity, the slower the liquid flows and vice versa • Conductivity – a material’s ability to allow heat to flow • Malleability – ability of a solid to be hammered without shattering

10. Hardness – tested by seeing which of two materials can scratch the other • Melting and Boiling Points – Temperatures at which substances melt or boil

11. Density – mass/volume; can be used to test the purity of a substance • Most dense substances will sink; less dense will float

12. Other physical properties include the following: • Color • Shape • Texture • Mass • Volume • Weight

13. Using Physical Properties • Identify a material • Separate the substances in a mixture • Choose a material for a specific purpose

14. Separating Mixtures Filtration – separates mixture based on the size of the particles Distillation – separates substances based on their boiling points

15. Physical Changes • Some of the properties change; composition remains the same • Some physical changes can be reversed • Phase changes (change from solid to liquid to gas) are physical changes

16. Cutting hair is a phys. Change that is not reversible Braiding hair is a reversible phys. change

17. Pg 44 1-8

18. 2.3 Chemical Properties • Chemical properties – can only be observed when substances are changing into different substances • Flammability – ability to burn in the presence of oxygen

19. Reactivity – how readily a substance combines chemically with other substances Ex. Rust forms when iron reacts with oxygen and water

20. Recognizing Chemical Changes • Three types of evidence for chemical change • Change in color • Examples: • Jewelry tarnishing • Bananas turning black

21. Production of a Gas – bubbling, fizzing

22. Formation of a Precipitate • Precipitate – solid that forms and separates from a liquid mixture