Mr. Taglia Welcome to Chemistry

What is Chemistry? The official definition of Chemistry is listed as: “The study of matter and the changes it undergoes…”

What is matter? Matter is anything that has mass and takes up space. Mass is a measurement that reflects the amount of matter. (usually measured in grams) Volume is the amount of space matter takes up. (usually measured in Liters or milliliters)

Properties of Matter All different forms of matter possess a set of chemical and physical properties Physical- what we can observe with our senses alone… Chemical- how a type of matter might chemically interact with other types

What changes can matter undergo? Matter can change its structure and its composition Changes in the structure and composition of matter lead to changes in the properties of the matter. Two types of changes are: Chemical Changes – changes in composition Physical Changes – changes in form Highlight property changes of the burned match. It’s now brittle, color is different, etc… STOP Even the oxygen that was in the air has changed its structure, composition, and therefore its properties.

What observations can we make? Color change Temperature Presence of a new material Bubbles/Fizz Physical characteristics and changes Odor

Conservation of matter Mass is neither created nor destroyed during a chemical reaction…. ***~Law of Conservation of Mass~*** So where does it go if the starting and ending masses are different?

Scientific Method The scientific method is a systematic approach used in scientific study (chemistry, physics, biology, etc…)

Steps of the Scientific Method Observation Scientific study begins with an observation. It is simply the act of gathering information Qualitative information - color, odor, shape, and other physical characteristics Quantitative data - numerical information (temperature, pressure, volume, quantity, etc..)

Steps of the Scientific Method Create a Hypothesis A Hypothesis is a tentative explanation for what has been observed.

Steps of the Scientific Method Conduct an experiment to test the hypothesis… Independent variable - the variable that you plan to change and control Dependent variable - the variable whose value changes in response to a change in the independent variable (Usually a measurement) Record Data & Observations…

Steps of the Scientific Method Draw a Conclusion A conclusion is a judgment based on the information Go back to your hypothesis and see if you were right.

Building a Theory Theory A theory is an explanation that has been supported by many, many experiments

An Undisputed Law… Scientific Law - a relationship in nature that is supported by many experiments.

SI (System International) Base Units Fundamental units (also called base units) Length = meter (m) Mass = kilogram (kg) Time = seconds (s) Temperature = degrees Kelvin (K) Number of particles = moles (mol) Other fundamental units include Temperature (K), Electric current (A), Luminous Intensity (candela (cd)), Number of particles (mole) These are the seven fundamental properties upon which all measurements are based.

Derived Units Derived units - are combinations of fundamental units Density - a ratio that compares the mass of an object to its volume. Units are often grams per milliliter (g/mL)

Let’s Practice Density Reference Tables Table T (first equation) If a sample of wood has a mass of 125 g and a volume of 132 mL, what is its density? Solution Density = mass / volume =125 g / 132 cm3 = 0.947 g/cm3

Accuracy Reference Tables Table T Accuracy is the extent to which a measured value agrees with the standard or accepted value. Accuracy is measured using percent error % error = [(measured value - accepted value) / accepted value] x 100 Reference Tables Table T

Precision Precision is the degree of exactness (if that’s a word) to which the measurement of a quantity can be reproduced Precision is linked to significant figures Significant figures includes all known digits

Scientific Notation Numbers expressed as ? x 10? Where: M is the “mantissa”, a number between 1 and 10. The mantissa must contain the correct number of sig figs. n is the exponent, an integer

Let’s Practice Express 0.0000578 in scientific notation. In your calculator, type in the number 4.567x108.

One more thing… Use your calculator to perform the following calculation (3.45x1012 kg) x (4.3x10-2 m/s2) Express your answer with the correct units.

Temperature

Temperature Conversion… Going from degrees Celsius to Kelvin. Use the formula on Table T : K = °C + 273 Try These Conversions: a) 30°C to Kelvin… b) 180 K to Celsisus…