Activity 12 Major Concepts: Graphing is used to analyze and clarify data People make important personal and social decisions based on perceptions of benefits and risks (trade-offs)

Activity 14 Major Concepts: Substances have characteristic properties, such as density and conductivity, that are independent of the amount of the sample Substances are often placed in categories or groups if they react in similar ways; metal is an example of such a group The properties of materials determine their uses

Activity 15 Title: Families of Elements

Read B-19 Problem: How can elements be grouped based on their physical and chemical properties? Hypothesis/Initial Thoughts: Procedure: Read and follow the procedure on pages B-20 and B-21.

Background: More than 2000 years ago, the Greeks introduced the idea that there were some basic building blocks of matter, called elements Today scientists know that there are 90 naturally occurring elements---substances that cannot be broken down by any normal chemical means, such as heating, reacting them with acids or other chemicals, or exposing them to electrical currents.

Background: Each visible sample of an element is made of many billions of small particles called atoms. Each kind of element is made of a particular kind of atom. From Activity 14: –Copper –Aluminum –Iron –carbon These 4 are elements and are among some of the first elements early scientists discovered

Background:

Element symbol (chemical symbol) Shown by one or two letter symbols A capitol letter (H, B, S, O) OR A capitol and a lower case letter (Br, Si, Zn)

Physical Properties Metal or non-metal Solid, liquid or gas The color of most common form(s) The atomic mass refers to the mass of one atom (the smallest bit of each element) as based on hydrogen. –Cant directly be weighed –Expressed as atomic mass units (amu)

Chemical Properties Reactivity refers to how likely the element is to interact chemically, or react, with other elements. –Oxygen is very reactive, so its reactivity is listed as high. Number of hydrogen bonds –Hydrogen is the simplest element and can form only one bond

Sort the element cards Form at least 3 categories Must have 2 similar characteristics within each category You might want to start with only one criterion to begin your categories

Data/Observation: Procedure #4 (My Classification) Group name If needed Common properties

Procedure #9 (Class Classification) Family Name Similar Properties Elements in order of increasing atomic mass

Follow-up: The cards in the activity show only 14 of over 100 known elements Scientists have taken a similar approach to classify and organize all the elements onto a table called the Periodic Table of Elements The categories for the Element Family Cards are four of the accepted scientific classifications

alkali metals alkaline earth metals halogens noble gases