Energy and Matter College Chemistry

Scientific Method Steps can be done in ANY order! State the problem clearly. Gather information. Form a hypothesis Test the hypothesis. Evaluate the data to form a conclusion. 6. Share the results.

Scientific Method Data that you observe can be qualitative or quantitative Qual – observations Quant – think “quantity”, numbers Theory vs. law Theory – principle that explains a set of facts, observations that describe something, explains what Law – statement (usually mathematical) that explains how something works, explains why

Energy The capacity to do work or to produce heat It does NOT have matter or volume – you cannot see it or touch it Two types of energy – kinetic and potential Kinetic energy – energy of motion Potential energy – energy of an object at rest

Energy Measured in Joules 1 Joule = 1/1000 of a food-calorie 1 J of energy: Required to lift an apple 1 meter Kinetic energy of a tennis ball moving 14 mph Energy released by a person sitting every 1/60 of a second

Law of Conservation of Energy Energy cannot be created or destroyed It can only transform from one form to another Ex: kinetic to potential, heat to electrical

Matter Anything that has mass and volume (exists and take up space) Solid – holds a particular shape and has a definite volume Liquid – does not hold its own shape, but does occupy a definite volume Gas – no definite shape or volume

Element An element is a substance that CANNOT be broken done into any simpler substances by a chemical change All on the periodic table All have abbreviations – chemical symbols

Compound A compound is two or more elements that have been combined chemically Chemists generally use symbols for a compound using the elements they came from Ex: magnesium oxide - MgO

Compounds and Elements Compounds and elements are pure substances Each element and compound has a unique set of chemical and physical properties

Molecules Simplest form of a compound Can contain just one element (a compound must have at least 2 different elements!!) Ex: N2 – molecule H2O - compound

Mixture A mixture is a blend of two or more pure substances Physically combined, NOT chemically

Types of Mixtures Mixtures may not appear to be of more than one type of matter (think of Kool-Aid) Heterogeneous mixture – mixture that has visibly different parts (choc. Chip cookie, granite) Homogeneous mixture – mixture that does NOT have visibly different parts AKA: solution

Substance Substance – form of matter that has a definite composition and distance properties (includes elements and compounds)

Physical vs. Chemical Changes Physical – can be observed and measured without changing the composition or identity of a substance Ex: melting ice Chemical – changes the entire chemical compound Ex: H2 + O2  H2O

Measurable Properties of Matter Extensive – Depends on how much matter is present Ex: mass, volume Intensive – Does not depend on how much matter is present Ex: density, temperature