The Particles of MatterMatter is anything that has mass and takes up space. The main particles of matter we will be concerned with are called atoms and molecules depending on the exact type of matter being discussed.

Atoms -

Molecules -

There are approximately 90 different types of atoms that naturally occur on Earth. These different types of atoms make up the different elements, which are the simplest forms of matter that have unique properties.

[Other types of atoms have been made by humans, bringing the current total number of elements to 118]

The Periodic Table of Elements

On The Periodic Table, each different element is represented with a one or two letter chemical symbol. The first letter is always capital and if there is second, it is always lowercase. This is important for communicating properly in chemistry!

Elements Compounds

Co - cobalt metal CO - carbon monoxide gas

Hf- Hafnium metal HF - Hydrogen Fluoride/ Hydrofluoric Acid

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Classifying Matter

Pure Substances

To begin with, we will look only at pure substances. The are types of matter that in their pure form always have the same composition and properties. This includes elements and compounds.

Elements are the simplest forms of matter. Each element is made of a single kind of atom. Each different element is made of a different kind of atom. Sometimes though, the most common form of an element is as molecules.

He O2

Cu H2

Fe N2

Compounds are a pure substance composed of 2 or more elements chemically bonded together, forming a new substance. Compounds have unique properties from the elements they came from. The smallest particle of a compound is usually called a molecule. A compound can be represented by a chemical formula that shows the chemical symbol of each element in the compound, along with small numbers ("subscripts") if there is more than one of that element in the compound. Elements can often combine in more than one ratio to form different compounds.

H2O H2O2 CO2 CO CH4 NaHCO3

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Carbon (C)

Hydrogen (H)

Oxygen (O)

Glucose (C6H12O6)

Water (H2O)

Vegetable Oil (C18H32O2)

Oil & Water

Glucose & Water

Examples of elements, compounds and different mixtures:

When elements combine to form a new compound, a chemical change (or a "chemical reaction") has taken place. Chemical changes also take place when compounds are broken apart into elements, or when compounds change into other compounds. In all cases, the atoms of the substances involved are rearranged.

The starting substances of a chemical reaction are referred to as reactants, or reagents, and the substances made in the reaction are called products. There can be one or more of either reactants or products, depending on the type of chemical reaction taking place.

After the reaction, the identity and the properties of the products are completely different than those of the reactants. The contrast can be especially stark in some examples (shown below).

Chemical equations are used to describe chemical reactions in a shorthand way. Chemical symbols and formulas are used to represent different substances. The reactants are shown on the left and the products on the right, separated by an arrow. The arrow stands in for the word "produces" or "makes" or "yields."

Examples:

Hydrogen gas + Oxygen gas --> Water

H2 (g) + O2 (g) --> H2O (g)

Sodium metal + Chlorine gas --> Sodium Chloride ("salt")

Na (s) + Cl2 (g) --> NaCl (s)

Balancing Chemical Equations

Another important rule about chemical equations ust obey the Law of Conservation of Mass. This states that matter is not created or destroyed. This means that the number and types of atoms in the reactants must be equal to the number and types of atoms ofthe reactants. In other words, the reaction must be balanced. Once the chemical formulas are correct, this is done by adding coefficients in front of each chemical formula, as needed, until the atoms are matched on each side of the equation.

Additional Practice Balancing Chemical Equations:

N2 (g) + H2 (g) --> NH3 (g)

CH4 (g) + O2 (g) --> CO2 (g) + H2O (g)

CuCO3 (s) --> CuO (s) + CO2 (g)

C3H8 (g) + O2 (g) --> CO2 (g) + H2O (g)

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Chemical Reactions and Chemical Equations

Kinetic Molecular Theory (KMT)1. Matter is made of tiny particles that are in constant, random motion.

2. There is empty space between particles. The amount of empty space depends on the state, or phase, of matter.

3. Attractive forces exist between particles when they are close enough together.

4. The temperature of a substance is a measure of the average kinetic energy (energy of motion, which is related to speed) of the particles in a substance.

States (Phases) of Matter

Particle Behavior & Properties

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Reaction RatesRate of Reaction: How quickly a reactant concentration decreases, or, how quickly a product concentration increases, per unit time.

Informally it is described as the speed at which, or how fast, a chemical reaction occurs.

Based on the above graph for a generic chemical reaction:

Why do the starting points for reactants (reagents) and products make sense? Explain.

When (on which part of the graph) is the reaction happening fastest? What makes you say that?

When (on which part of the graph) is the reaction finished? What makes you say that?

What value on a graph represents its rate of change?

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Common methods used to measured rate of reaction:

-Collect volume of gas produced over time

-Measure pressure of gas produced over time

-Measure mass change over time

-Measure color change over time

With all of these methods, the rate of reaction is determined using a trendline.

A trendline, or a line of best fit, is a line that matches a given set of data points as closely possible.

After matching a linear trendline to the data at a certain time, the equation of that line can be figured out either by data processing software (Capstone, Excel, etc.) or by finding two points on the line and calculating it (slope = rise/run).

The most important feature of the equation of the trendline is the slope, or gradient, which represents the rate of reaction for that time of the reaction.

Faster Reaction Rates = Steeper Slopes

Slower Reaction Rates = Less Steep Slopes

Usually, the trendline is made to fit the beginning of the data, as the slope there represents the initial rate of reaction. This is when the reaction rate is fastest and when the amounts and concentrations of reactants are known the best.

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Measuring Reaction RatesUsually, to determine a reaction rate, you need to determine a property that will measurably change over time as the reaction happens. This is easiest if the reaction involves the production of a gas, or involves a color change.

Reaction RatesPractice problem

The graph below shows the volume of carbon dioxide gas produced by a chemical reaction over time.

1.) What volume of carbon dioxide has been produced after 600 seconds?

2.) How long did it take the reaction to produce 100 cm3 of carbon dioxide?

3.) At what time does the reaction reach completion? Explain your reasoning.

4.) Determine the initial rate of reaction for time 0 - 200s, showing your work. Include units in your answer.

5.) Sketch a trendline on the graph for the time between 400 - 600s. Determine the equation of the line and state the rate of reaction during that time, with units.

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