Matter: Properties & Changes Chapter 2 notes

(2.1) Physical Properties of Matter can be observed or measured without changing the composition of the sample Examples: color, phase, melting or boiling point, density, hardness, odor, taste

States of Matter Solid (s) - definite volume and shape Liquid (l) - definite volume, but not shape Gas (g) - no definite volume or shape Plasma - highly ionized gas (s) (l) (g)

sToP & tHinK Which state or states of matter take(s) the shape of its container? Which state or states of matter can change in volume (without adding or subtracting from the sample)?

Physical Changes Physical changes alter a substance without changing its composition

sToP & tHinK Which of the following are physical properties? liquid at room temperature reacts with metals to form H2 gas acids and bases combine to form water and a ‘salt’ boils at 145 degrees Celsius

(2.2) Mixtures… Mixture - a combination of two or more pure substances, in which each substance retains its individual chemical properties Heterogeneous mixture - does not blend smoothly, individual substances are distinct Homogeneous mixture - solution; has a constant composition throughout

sToP & tHinK Heterogenous or Homogeneous? (1) (2)

Separating Mixtures Filtration - porous barrier separates solid from liquid Distillation - liquids separated by differences in boiling point Crystallization - forms pure solids from dissolved substances Chromatography - separation based on ability to travel or be drawn across a material

filtration

distillation

crystallization

chromatography

sToP & tHinK What separation technique is shown in the following pictures? B A

(2.3) Elements & Compounds Elements - pure substances that cannot be broken down into simpler substances on the Periodic Table! Compounds - two or more elements bonded together that can be broken down

sToP & tHinK In your own words, what is the difference between an element and a compound? Classify the following as being elements or compounds Sodium Sodium chloride Oxygen Carbon dioxide Copper

(2.4) Chemical Properties the ability of a substance to undergo chemical change Examples: “reacts with oxygen to form rust”, “forms a deep blue solution when in contact with ammonia”

Chemical Changes Chemical changes alter the composition so that a new substance forms Evidence of chemical change: formation of a gas or solid (precipitate), smoke, fire, an odor, temperature change, color change Law of Conservation of Mass: composition changes, but mass doesn’t

sToP & tHinK Substance A is a yellow liquid and substance B is a blue liquid. The two are mixed and form a green liquid and a white solid. What evidence suggests a chemical change occurred? What other things could you look for to determine if there was a chemical change?

sToP & tHinK - which shows physical change and which shows chemical change? link to change animation #1 link to change animation #2