Chapter 2 Section 1 Key Concepts: What are elements and how do they relate to compounds? What kinds of properties are used to describe matter? What are the properties of a mixture?

KEY TERMS – there be a lot so start a learnin’ em now. Molecule Matter Compound Chemistry Chemical formula Substance Mixture Physical property Heterogenous mixture Chemical property Homogeneous mixture Element Atom Solution Chemical bond

Matter matters. It does. What is matter? Matter has mass and takes up space. (all you need 2 kno) What is mass? – the amount of matter in an object Properties of matter Chemistry – the study of the properties of matter and how matter changes Say whaaat? It’s about the elements and how they interact with one another. Hydrogen oxygen neon etc, they all have certain properties and then they do certain stuff to one another that is specific to them when they interact with one another.

All matter has two kinds of properties (KNOW THEM): Physical property- characteristic of a pure substance that can be observed without changing it into another substance Chemical property – characteristic of a pure substance that describes its ability to change into different substances (substance: a single kind of matter that is pure; it has a specific set of properties and a specific makeup)

Physical vs. chemical properties Physical - The material itself is the same before and after a measurement. Hardness, texture, solid, liquid, gas, ability to conduct heat, luster, flexibility, examples: melting, freezing, condensing, breaking, crushing, bending. Chemical – To observe the chemical properties of a substance, you must try to change it to another substance. The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.“ example: the rust on a rusty nail; Flammability, reactivity, digestion, respiration, photosynthesis, burning, decomposition

Why did Ms. Fuentes.. Underline and bold and italicize those past descriptions for physical property and chemical property? They’re difficult concepts on the surface. You need to know those concepts 

More examples? Aluminum foil is cut in half Physical Clay is molded into a new shape Jewelry tarnishes Chemical Butter melts on warm toast A match is lit Water evaporates Bread becomes toast

Physical vs. Chemical When liquid freezes… it becomes frozen… liquid. It is still that substance. So this is physical. Example: ICE/water/steam are all H2O If you burn something, the chemical makeup changes. If iron rusts, the chemical makeup changes. It is different than before and cannot return to its original. It is a chemical property. QUEEESSSTIONS??? Learn to learn what you can’t understand…..

What is an element? An element is a substance that cannot be broken down into any other substances by chemical or physical means. Elements are the simplest substances. (remember: substance is a single kind of matter that is pure --- I know it’s vague. Just hang on, we’ll come back to it) Elements can be differentiated from one another by their specific chemical and physical properties Consists of one kind of atom (most important thing on the slide) Eventually this will all be very clear. But for now, write all this down.

Note: Matter does not need to be living 

Periodic table!

Atoms An atom is the basic particle from which all elements are made Different elements have different atoms Atoms can form chemical bonds to one another. Atoms chemically bonded to one another combine to form larger particles called molecules

Example: Hydrogen and oxygen are different elements. Meaning they can’t be broken down further into a different kind of material/matter. Their atoms, meaning one little oxygen atom runs into two little hydrogen atoms, interact with one another and become water (a whole new thing with new properties of its own). This new thing is a molecule. How do they interact???????? ?? -- ?????????? (I hope you can’t wait to find out…)

Oh, well, since you asked: They interact by chemical bonds. A chemical bond is an attraction between two atoms. The atoms can bond with members of the same element (O2 oxygen gas) or different elements (C3H8 – propane). Again, when bonded, atoms form molecules.

Molecules Molecules are groups of two or more atoms held together by chemical bonds Examples Water Oxygen CO2

Scientist Cat

Compounds A compound is a pure substance made of two or more elements chemically combined in a set ratio May be represented with a chemical formula When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements

Common questions What is the difference between a compound and a molecule? A molecule is formed when two or more atoms join together chemically (via chemical bond). A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds.

Difference continued… (don’t need to write this down, just read it) Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element. The smallest bit of each of these substances would be referred to as a molecule.

For example: In a water molecule, h2o, there are 2 hydrogen atoms (from the element hydrogen) and 1 oxygen atom (from the element oxygen). They form together in a chemical bond to make that molecule. Because they are different elements, they are also a compound.

Mixtures A mixture is made of two or more substances – elements, compounds, or both – that are together in the same place but are not chemically combined (i.e. no chemical reaction occurs). Mixtures are different from compounds in two ways: Each substance in a mixture keeps its individual properties (i.e. they don’t really mix, even if they appear to) Parts of a mixture are not combined in a set ratio (unlike molecules  )

More mixtures Heterogenous mixtures – you can see the different parts Salads, soil, lava lamps, tacos, (yes, tacos) Homogenous mixtures – so evenly mixed you cannot see the different parts Coffee, water with food coloring Solution – an example of a homogenous mixture. Does not have to be liquid Brass is an example of a solution. It is copper and zinc.

Four ways to separate mixtures Magnetic attraction (some atoms/compounds/molecules respond to magnets and will come out of a mixture) Filtration (some atoms/compounds/molecules are bigger and will come out of a mixture via limiting size) Distillation (boiling) Evaporation (some stuff floats off into the air and leaves other stuff behind) This will be clearer later. Just know these 4 things for now.

Mixtures Lava Lamp experiment REVIEW! 1. What is the question we are addressing? 2. What is the hypothesis? 3. What is the experiment we are performing? 4. What is the data we are collecting? 5. What is the conclusion?

Science Lab

Practice Questions… as you’ve now seen, these are sometimes on the exams… And eventually, you won’t get to use your notes for the exams… so learn how to utilize these questions now: KNOW ALL KEY TERMS! What‘s the difference between a compound and a molecule? Between an atom and a molecule? What is an element? What is a physical property? What is a chemical property? Your HWK is to review your notes for 15 minutes. SERIOUSLY. DO THIS. LEARN TO LEARN.