Age: grades K-2
Subject: Earth Science
Skills: observation, classification
Duration: 60 minutes
Group size: any
Setting: indoors or outdoors
Key vocabulary: color, size, shape
Materials
Pebbles
Tall, plain glass jar(s)
Magnifying glasses
Masonry hammer
Dishtowel
Objectives:
Students will be able to:
1. Recognize differences between different pebbles.
2. Describe a pebble as to color, size or shape. -
3. Use a magnifier to examine rack Fragments and sand grains.
Method:
Students will observe and compare different pebbles in a jar filled with water and pebble fragments using a magnifier.
Overview
This activity can be used to introduce rocks to early elementary students. In many areas there is an interesting variety of rock pebbles; they can be found in graveled driveways and roads, along rivers and streams, or on the school playground. Students can become Familiar with them as an early step in learning about rocks. At this stage it is not important to identify the kind of rock the pebble came From. Let the students make up their own names For the pebbles, based an their own observations.
Procedure
1. Have each student bring several pebbles to class or provide a bucket of #67 washed gravel in class for them to choose From (#67 washed gravel consists of rocks From old river beds that range From almond to egg size. While it is usually sold by the ton, a building supply house or local quarry will usually donate a bucketful for school use.)
2. Have each student wash their pebbles and then carefully place them in the glass jar. If there is still room, let those whose pebbles cannot easily be seen add others, until the jar is full.
3. While the students watch, fill the jar with water.
Does the water seem to change the size of the pebbles?
4. Stand the jar near a window where the students can examine the pebbles in good light. Let the students use a magnifying glass for a closer look.
Do all the pebbles look alike?
Are they similar in shape and smoothness?
What colors do you see?
Do any shine or sparkle?
Can light shine through some?
5. Break up a few of the pebbles by wrapping them one at a time in the dishtowel, placing it on a hard surface, and hitting it squarely with a masonry hammer. Let the students examine the fragments with the magnifying glasses.
Are there grains of different colors?
Do they look like tiny pieces of broken rocks?
How might rocks get broken into sand naturally?
Extension
1. Have the students sort and arrange the pebbles according to color, size or shape. Use egg cartons, margarine tubs or old muffin tins for sorting containers.
2. When the students question the specks and streaks of color they see as they observe the pebbles, tell them that most rocks are mixtures of many kinds of material. The materials are called minerals. There are 20 main minerals which make up most of the rocks in the world. Sometimes the mineral mixtures are easy to see as specks, sparkles and stripes. Rocks may contain many different combinations of minerals.
Evaluation
Give the student two different pebbles and have them draw them with crayons.
Source
1. Rockcastle, N., & Schmidt, V. (1968) Teaching Science With Everyday Things. New York: McGraw-Hill Book Co.