Unit 2: Physical Science - Chemical Reactions

What the heck is “Chemistry” anyway? The study of the composition, structure, and properties of matter The study of the composition, structure, and properties of matter Includes the study of the changes matter undergoes Includes the study of the changes matter undergoes Chemistry is incorporated into every aspect of life because everything in the world is made of matter! Chemistry is incorporated into every aspect of life because everything in the world is made of matter!

Properties of Matter Matter is anything that has a mass and takes up space Matter has a wide variety of chemical and physical Properties

Classification of Matter Matter can be classified by observing the following physical properties: Matter can be classified by observing the following physical properties: Appearance Appearance What it looks like What it looks like Composition Composition What it is made of What it is made of How it can be separated or broken down How it can be separated or broken down

Classification of Matter: Appearance Homogeneous: Homogeneous: It looks the same throughout It looks the same throughout Has a uniform appearance Has a uniform appearance Heterogeneous: Heterogeneous: You can see different parts or components You can see different parts or components Has a variable appearance Has a variable appearance

Classification of Matter: Composition Physical Separation Physical Separation Filtering or straining Boiling Chemical Separation Chemical Separation Chemical reactions are required Decomposition

Classification of Matter: Different Types All matter can be classified as an element, compound or a mixture All matter can be classified as an element, compound or a mixture Element: Element: Matter that is composed of only one type of atom Matter that is composed of only one type of atom Cannot be broken down into simpler substances Cannot be broken down into simpler substances Homogeneous appearance Homogeneous appearance Compound: Compound: Matter that is composed of more than one element Matter that is composed of more than one element Can only be broken down by chemical reactions Can only be broken down by chemical reactions Homogeneous appearance Homogeneous appearance Mixture: Mixture: Many elements or compounds together Many elements or compounds together Not pure substances Not pure substances Can easily be separated by physical processes Can easily be separated by physical processes Can be either homogeneous or heterogeneous based on their appearance Can be either homogeneous or heterogeneous based on their appearance

Matter can change in two ways: physical change & chemical change 1. Physical Change: - In a physical change there is only a change of state - For example: ice melting to water or water boiling - The new substance has the same properties as the old one. - No new substance is produced.

Physical Change continued… - A physical change may also involve changing the shape of the substance. - For example: paper cut into pieces is still paper, sloughing a field but the field still remains as soil, cutting wood into pieces is still wood, and molding a sculpture is still cement or marble!

Physical Change continued… The bottom line for a physical change is to always remember that… The bottom line for a physical change is to always remember that… THERE IS NO NEW SUBSTANCE FORMED! **In all of these changes, you can get the original materials back!**

Chemical Change 2. Chemical Change: In a chemical change one or more NEW substances are created. In a chemical change one or more NEW substances are created. The new substance is different from the original. The new substance is different from the original. It has properties that are different than those of the starting materials. It has properties that are different than those of the starting materials. Plus, you cannot get the original materials back easily (or at all) Plus, you cannot get the original materials back easily (or at all)

Chemical Change continued… For Example: Think about an ordinary box of matches. A single match in a box can remain unchanged forever. But if someone were to take the match and then light it...A flame lights up and then burns out. What remains will have changed forever. The match can never be lit again. The match has undergone a chemical reaction. For Example: Think about an ordinary box of matches. A single match in a box can remain unchanged forever. But if someone were to take the match and then light it...A flame lights up and then burns out. What remains will have changed forever. The match can never be lit again. The match has undergone a chemical reaction.

Signs that a Chemical Change has Occurred: 1. Color Change 2. Heat or light is given off 3. Gas is released 4. A solid precipitate is formed in a liquid 5. The change is difficult or impossible to reverse

Chemical Change continued… **Despite the 5 signs that a chemical change has occurred, the most important thing to remember is that one or more new substances must be formed!** Sometimes one or more of the signs of a chemical change are visible but with no new substance formed, so you have to be careful!

The Atom: Components The Atom is the fundamental building block of all of the stuff in the world (Remember, the scientific word for stuff is matter) The Atom is the fundamental building block of all of the stuff in the world (Remember, the scientific word for stuff is matter) Atoms are the smallest piece of any type of “stuff” you can think of Atoms are the smallest piece of any type of “stuff” you can think of Even though atoms are the smallest piece of any type of stuff, they are composed of smaller components Even though atoms are the smallest piece of any type of stuff, they are composed of smaller components There are 3 types of components in every atom: There are 3 types of components in every atom: 1. Proton 2. Neutron 3. Electron

The Atom Components - Protons Protons: Protons: Positive charge (+) Positive charge (+) Dense Dense Give an atom its identity Give an atom its identity The number of protons determines which element the atom is The number of protons determines which element the atom is Example: The only difference between a carbon atom and a nitrogen atom is one proton. Carbon has 6 and nitrogen has 7 Example: The only difference between a carbon atom and a nitrogen atom is one proton. Carbon has 6 and nitrogen has 7 Located in the nucleus of an atom Located in the nucleus of an atom

The Atom: Components - Neutrons Neutrons: Neutrons: Neutral, no charge, (0) Neutral, no charge, (0) Similar to protons: Similar to protons: Also very dense Also very dense Weigh the same as a proton Weigh the same as a proton Located in the nucleus of an atom Located in the nucleus of an atom Differ from protons: Differ from protons: Do not determine the identity of an atom, but they do contribute significantly to its mass Do not determine the identity of an atom, but they do contribute significantly to its mass

The Atom: Components - Electrons Electrons Electrons Negative charge, (-) Very light, not dense Do not contribute to the weight of an atom at all Very small in size compared to protons and neutrons Located in orbitals around the nucleus Orbitals: energy levels located outside of the nucleus Region where electrons are found

The Atom: Components – The Nucleus Nucleus: Nucleus: Structure located in the center of an atom Structure located in the center of an atom Consists of 2 components Consists of 2 components Protons Protons Neutrons Neutrons Very dense: protons and neutrons are packed together very tightly Very dense: protons and neutrons are packed together very tightly Positively charged Positively charged Why is it important? Why is it important? Gives an atom its identity Gives an atom its identity The number of protons in an atom’s nucleus determines which element it is The number of protons in an atom’s nucleus determines which element it is

Components of the Atom & the Periodic Table The periodic table of elements is a list of all the different types of atoms in the world The periodic table of elements is a list of all the different types of atoms in the world Each element is a different type of atom Each type of atom has its own properties and characteristics Gold is different from carbon, which is different from oxygen, etc. The differences in elements is based on the differences in the structure of the atoms The number of protons being the most important