Chemical Reactions - Observing Chemical Change

Properties and Changes in Matter

Matter can undergo both physical change and chemical change.

Chemical Reactions - Observing Chemical Change

Properties and Changes in Matter

Chemical changes occur when bonds break and new bonds form.

Chemical Reactions - Describing Chemical Reactions

Describing Chemical Reactions

Cellular phone messages make use of symbols and abbreviations to express ideas in shorter form. Similarly, chemists often use chemical equations in place of words.

Chemical Reactions - Describing Chemical Reactions

What Are Chemical Equations?

• A short, easy way to show a chemical reaction.• Chemical equations use chemical formulas and other

symbols instead of words to summarize a reaction.

Chemical Reactions - Describing Chemical Reactions

Chemical Formulas

The formula of a compound identifies the elements in the compound and the ratios in which their atoms are present.

Chemical Reactions - Describing Chemical Reactions

Conservation of Mass

The principle of conservation of mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products.

Chemical Reactions

Open System vs. Closed System

•Open System- A system that allows matter to enter from or escape to the surroundings.•Closed System- A system that does not allow for matter to enter from or escape to the surroundings.

•A chemical reaction taking place inside of a plastic, sealed bag.

Chemical Reactions - Describing Chemical Reactions

Balancing Chemical Equations

To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.

Chemical Reactions

Balancing Chemical Equations

Magnesium metal (Mg) reacts with oxygen gas (O2), forming magnesium oxide (MgO). To write a balanced equation for this reaction, first write the equation using the formulas of the reactants and products, then count the number of atoms of each element.

- Describing Chemical Reactions

Chemical Reactions

Balancing Chemical Equations

Balancing Chemical Equations:

Balance the equation for the reaction of sodium metal (Na) with oxygen gas (O2), forming sodium oxide (Na2O).

- Describing Chemical Reactions

Chemical Reactions

Balancing Chemical Equations

Balancing Chemical Equations:

Balance the equation for the reaction of tin (Sn) with chlorine gas (Cl2), forming tin chloride (SnCl2).

- Describing Chemical Reactions

Chemical Reactions - Describing Chemical Reactions

Classifying Chemical ReactionsMany chemical reactions can be classified in one of three categories: synthesis, decomposition, or replacement.

Chemical Reactions

Graphic Organizer

Endothermic reactions

Chemical reactions

Exothermic reactions Equations

Activation energy Chemical

symbolsArrows and plus signs

Coefficients

can be are written as

which require written using

balanced with