Kean University Continuing Education

Implementing the Science Standards K-4


Properties of Rocks and Soils

Introduction

Rocks are important. They are the things that the Earth is made of so students need to learn about them. Geologists classify rocks into groups depending on how they are formed and what their major components are. Many rocks can be thought of in the same terms used when someone is baking cookies. You have the batter and maybe put pieces of chocolate or nuts in the batter to make cookies. Then they are baked in the oven.

Rocks are made in similar fashion. They are composed of various minerals which are in turn composed of chemical elements. These minerals form the rocks which generally are produced under tremendous heat and pressure conditions deep underground.

Rocks can be classified according to their properties. One suggestion is given in Key to Rocks. This lists properties of a variety of rocks and sorts the rocks according to their properties.

The Rock Cycle

Many natural phenomena occur in cycles. The rock cycle explains the relationship between the three major groupings of rocks.

Formation of rocks takes a long, long time. Many of the rocks in Northwest New Jersey are well over 200 million years old. Many others go back much longer than that--half a billion years or more. Scientists use the Geologic Time Scale to indicate the ages of rocks.

Activity: Properties of Rocks

Introduction

Rocks have a variety of properties that can be studied in the classroom. Among others, these include

Geologists also use several other properties in studying rocks. These include the density and specific gravity, reactivity with acid and the color of the streak that the rock leaves on a piece of unglazed tile.

Materials

Procedure

1. Students can work in groups or individually. They examine each of the rocks that are available and write the properties of each one in their Science Journals. They could make property tables such as the one below.

Type of Rock __________________________________

Property

Observation

color __________________________________
crystals __________________________________
particles __________________________________
holes __________________________________
layers __________________________________
reflectivity __________________________________
luster __________________________________
hardness __________________________________
magnetism __________________________________

2. Each rock is examined for its overall color, whether it is dark or light. They also observe if there are holes in the rock or if the rock has layers. Reflectivity and luster are also noted.

3. The rock should be examined carefully with magnifiers to determine if there are crystals present. If crystals are present, they should be studied to see if they are arranged at random or in layers and if they are uniform or different. Students write results in their Science Journals. If sand or pebbles are present in the rock they are included in the table.

4. Hardness is tested using the nail, penny and glass plate. On the Mohs scale, a penny is about 3, glass is about 5 and the nail is about 5 - 5 1/2. Therefore, if the rock scratches the penny it is greater than 3 in hardness. If it scratches the glass it is greater than 5 in hardness. Alternatively, if the nail scratches the rock, the rock is less than 5 in hardness.

5. The magnet tests if the rock is magnetic or not.

Results

1. At the end of the investigation, each student will have a set of observations made on the various specimens of rocks studied in the classroom. These will be written in their Science Journals as data.

2. Students use the data obtained from the investigation to make reference cards for the rocks they studied. These can be kept on file for future use.

Discussion

1. Students are each assigned a rock or mineral to research. They write about it in their Science Journals. Each student makes a presentation about their rock or mineral to the class.

2. Students research mining. Virtually everything we use in our daily lives is traceable back to the mining industry. There is almost no mining in New Jersey. Therefore all of our raw materials that are used in our New Jersey industries have to be obtained elsewhere. Students trace the source, processing and use of different minerals and rocks. They write about the sequence in their Science Journals. For example, copper is mined in the western United States in such states as Utah and Arizona. The copper is separated from the copper ore and is purified. Then it is made into products or coined into pennies.

3. Students learn about the different types of rocks found in New Jersey. They utilize the Internet and write their results in their Science Journals.

Activity: Properties of Soils

Introduction

Soil is a mixture. It contains organic material such as decayed leaves, often called humus. It also contains rock particles produced by weathering of rocks and rock formations. Different types of soils are recognized based on their contents.

Many times the properties of the soil are determined by the properties of the rocks below them. Much of the really good farm land in south central Pennsylvania has soil that is directly above limestone deposits. The limestone adds lime to the soil.

Materials

Procedure.

1. Students describe each of the three types of soils in their Science Journals. They make lists of the properties of the soils they are studying and compare and contrast them.

2. Students examine a sample of each type of soil with a magnifier. They carefully tease apart the soil particles with toothpicks to get a good close look at them. They write their observations in their Science Journals.

3. Students describe where each type of soil is found and what it may be used for.

Results

1. Students have examined the properties of several different types of soils. They have made lists of the components of the soils that they saw including mineral particles and organic material.

2. Students have written in their Science Journals about the ways in which soil samples can be distinguished on the basis of their properties.

Discussion

1. Students relate the different types of soils they have studied to different habitats in the environment. They make a list of habitats and the types of soils they might expect to find in each one.

2. Students relate the different types of soils they have studied to the growth of plants. They investigate whether certain types of soils are better for growth of plants than others.