Chemical and Physical Changes Notes and Lab

Warm - Up What is matter? How is a solid like a liquid? What is the Law of Conservation of Matter? What are crystalline solids? What causes matter to change states?

Objective Today I will be able to: ◦ Differentiate between a chemical and physical change ◦ Explore the properties of chemical and physical changes by completing a lab.

Homework STEM Fair Experimental Design due Monday ◦ First notebook check!!!!

Agenda Warm – Up STEM fair concerns? Chemical and Physical Changes Notes Lab Safety Lab Exit Ticket – Chemical and Physical Changes Practice

Chemical and Physical Changes

Physical Properties Description of a substance undergoing a physical change Intensive Properties – do not depend on the amount of matter present (density, boiling point, freezing point, color, odor) Extensive Properties – depend on the amount of matter that is present (mass, volume, pressure, length)

Chemical Properties Enables a substance to change into a brand new substance, and they describe how a substance reacts with other substances

Changes in Matter Through experimentation and natural occurrences, matter tends to change in either of two ways - Physical Changes - Chemical Changes

Physical Changes Only physical properties change The form of matter changes, but the identity of the matter remains the same Examples: change in state (phase change), breaking a pencil, tearing paper

Physical Changes Phase Change – physical process in which one state of matter is transformed into another

Physical Changes

During a change of state, the temperature remains constant, but energy must be continually transferred because the particles that make up the sample have different quantities of potential energy before and after the change

Physical Changes

Chemical Changes Properties of original substance disappear as new substances with different properties are formed Change in chemical composition Cannot return to original form Can be detected through – energy changes (temperature), change in color, emission of gas, solid formed Examples – wood burning, iron rusting, sour milk

Examples – Chemical or Physical Change? A match lights when struck Wood is placed into a chipper A lump of gold is pounded into a large, thin sheet Baking powder bubbles and gives off CO 2 when it is moistened A pan of water boils on the stove Hydrogen Sulfide gas causes silver to tarnish

Reactions Involving Energy Most chemical reactions, physical changes of state, and dissolving processes involve energy changes Energy can be released or absorbed Exothermic Reactions Endothermic Reactions

Reactions Involving Energy Exothermic Reactions – reactions that release energy into their surroundings - Results in a temperature increase - Feels warm to the touch Example Reaction – Combustion of Propane - C 3 H 8(g) + 5 O 2(g)  3 CO 2(g) + 4 H 2 O (g) kJ

Reactions Involving Energy Endothermic Reactions - reactions that absorb energy from their surroundings - Results in a temperature decrease - Feels cold to the touch Example Reaction – Photosynthesis - Sunlight + 6 CO 2(g) + H 2 O (l)  C 6 H 12 O 6(aq) + 6 O 2(g)

Lab Safety Closed toe shoes, goggles, aprons must be worn to participate Hair must be tied back Review Bunsen burner safety In step 3, DO NOT stare directly into the light HCl, sodium chromate and barium nitrate are in a low concentration, if you spill it just rinse it off of your skin in a sink Dispose of all chemicals in the waste container, DO NOT pour directly down the sink

Exit Ticket Complete the worksheet stating if each event is a chemical or physical change