The study of Chemical & Physical Properties and Changes of Matter Chemistry The study of Chemical & Physical Properties and Changes of Matter

Chemistry What is Chemistry? What is Matter? The study of the of matter What is matter? How can/will matter change when you do something to it What is Matter? Anything that has mass and takes up space (volume) All “stuff” around you is matter All matter is made up of substances or mixtures

Substances v. Mixture Substance – All the same stuff (“pure”). No matter how much you have, it is all still the same stuff. Ex: a “pure” sample of water is only H20

Substances v. Mixture Substances consists of: Elements (single atoms) i.e. Carbon (C), Oxygen (O) 2. Molecules (combinations of elements) i.e. Water (H2O), Carbon Dioxide (CO2), Salt (NaCl) Molecules are simply a bunch of atoms “stuck” together! Water Carbon Dioxide Sodium Chloride (table salt)

Substances v. Mixture Mixture Made of two or more substances – (elements, molecules or both) that are together in the same place, but NOT chemically bonded. Salad Salt Water Sand/dirt

Filter: Pure Substance Leftover Substances v. Mixture If it’s a mixture, you can separate out the parts relatively easily. (i.e. filtering/distilling) Drain Fill Filter: Pure Substance Leftover Mixture Pure Substance Demo: filter Italian salad dressing

What are Properties? How do you identify a specific substance? -What atoms/molecules make it up! Problem: WE CAN’T SEE THEM! They are way too small! But we can use “Properties” to identify them Properties are “identifying characteristics” (clues) of elements/substances. All substances have their own properties unlike any other substance Can Identify elements, molecules and substances (combination of elements/molecules) if you know enough of the properties (clues) Demo: which student am I describing? So what if we have a substance that we need to identify?

Intro: Substance ID Try to Identify the 3 substances How do you know or can tell what it is? Demo: Three Cups: Salt, Sugar & Mystery Substance Before you are a sample of Sugar, Salt, and a mystery substance First just look at them and try to tell them apart Now smell them and try to tell them apart Now taste them and try to tell them apart The main point: If we know enough “properties” we can identify a substance from other substances.

2 Types of Properties: Chemical Physical -Describes generally how a substance appears, feels, etc... Can usually be easily observed without testing anything. Examples: Taste, Smell, Texture, Color, size, Solid/Liquid/Gas, mass, etc… Chemical -Describes how one substance changes into a new substance. Or how it will act under certain conditions. What can/will it do? Examples: Oxidation, +/- Charge, release of bubbles, causes a new smell/color, ALL REACTIONS!

Q: What if we try to do something to the substance? Change it somehow… Physical Change The substance simply changes shape, size, solid/liquid/gas, etc… The substance/element DOES NOT CHANGE!!! It only changes how it appears!!! EX: Freezing water Chemical Change The substance burns/reacts and can release some of it’s “parts” into the air. The substance completely changes to something brand new! EX: Iron Iron Oxide Demo: Burning Paper Demo: Breathing Fire

Identifying Matter Our Brains instinctively use physical properties to identify matter all the time – but can also be deceiving. Chemists also use chemical properties to help identify unknown substances. Physical Characteristics Chemical Characteristics a characteristic of a pure substance that can be observed without changing it into another substance. a characteristic of a pure substance that describers its ability to change into different substances. Ding! Ding! Ding! It’s …

Properties are used to solve crimes! Physical Characteristics Chemical Characteristics What do you observe at the crime scene? Perform some tests to see what chemicals are at the crime scene. List Physical Characteristics: List Chemical Characteristics: Ding! Ding! Ding! The answer to the mystery is…

Physical Review Chemical Review Describes how the substance or mixture appears, feels, dimensions, etc... Describes the substances ability to react with other substances. A change of the substance w/o changing the substance. Elements and molecules remain the same! Bend, twist, crush, tear, melt, boil, etc… An change of the substance by reacting it with another substance to make it a new substance. Burn (combust), rust, tarnish, light, new smell, fizzing, etc… Properties Change