Section 1 – pg 214 Observing Chemical Change Chapter 6 Section 1 – pg 214 Observing Chemical Change

Review Matter: anything that has mass and takes up space Pg 214 Review Matter: anything that has mass and takes up space Chemistry: the study of matter and how matter changes

Pg 215 Matter and Change Changes in matter can be described in terms of physical changes and chemical changes

Pg 215 Matter and Change Physical Property: a characteristic of a substance that can be observed without changing the substance into another substance IE: Melting and boiling point, color, hardness, texture, shine, flexibility, ability to dissolve and conduct electricity or heat Chemical Property: a characteristic of a substance that describes its ability to change into other substances IE: flammability, ability to rust or tarnish

Pg 216 Changes of Matter Physical Change: any change that alters the form or appearance of a substance but does not make the substance into another substance

Changes of Matter (cont.) Pg 216 Changes of Matter (cont.) Chemical Change (chemical reaction): a change in matter that produces one or two new substances The atoms are rearranged to form new substances with different chemical and physical properties Reactants: the substances that undergo change in a chemical reaction Products: the new substances formed by the reaction

Bonding and Chemical Change Pg 217 Bonding and Chemical Change Chemical changes occur when bonds break and new bonds form - > new substance forms

Evidence for Chemical Reactions Pg 218 Evidence for Chemical Reactions Chemical reactions involve changes in properties and changes in energy that you can observe

Pg 218 Changes in Properties One way to detect chemical reactions is to observe changes in the properties of the materials involved IE: change in color, texture, or hardness Precipitate: a solid that forms from solution during a chemical reaction

Pg 220 Changes in Energy As matter changes, it can either absorb or release energy Chemical reactions usually absorb heat or liberate heat This is why an indicator that a chemical reaction occurs is temp. change Endothermic Reaction: the total making and breaking of bonds results in a heat absorption of energy Break bonds requires energy, making bonds releases energy B/c the reaction is taking in heat/energy the ending temp will be higher

Changes in Energy (cont.) Pg 221 Changes in Energy (cont.) Exothermic Reaction: the total making and breaking of bonds results in a net release of energy Energy is typically released as heat to surrounding area

Chapter 6 Section 1 Homework – pg 221

1A. What is the difference between physical properties and chemical properties of a substance?

1B. When silver coins are found in ancient shipwrecks, they are coated with a black crust. What question could you ask to help you decide whether the silver underwent a chemical change or a physical change?

1C. In terms of chemical bonds and electrons, what kinds of changes occur between atoms when substances undergo chemical reactions?

2A. What kinds of evidence can you use to determine if a chemical reaction has occurred?

2B. How do the properties of the cooked egg shown in Figure 5 differ from the properties of a raw egg?

2C. How are endothermic and exothermic reactions the same 2C. How are endothermic and exothermic reactions the same? How are they different?