Earth MaterialsInvestigation 2

Scratch Test

Part 2 – Testing for Hardness

Science Safety

Scientists follow safety procedures to protect themselves when performing observations and experiments

They wear goggles to protect their eyes They used the tools carefully so that they do not

harm themselves or others They do not put any scientific materials in their

mouths Spills are cleaned up quickly using the correct

procedure

Science Jobs

Manager – this person will make sure that all members are on task

Reporter – this person will report the results of their groups work, you may need to take notes

Materials getter – this person will get materials

Materials collector – this person will return materials

Content Review

Rocks are made of different ingredients called minerals.

Minerals are pure materials that can’t be separated into different kinds of ingredients.

Vocabulary Review

weight – how heavy something is crystal – the solid form of a material that can

be identified by its special shape or pattern property – something you can observe, such

as color, shape, texture, living/non-living

Vocabulary Review

dissolve – to disappear in a liquid. When salt mixes with water, it goes into solution and cannot be seen until the water dries up.

earth material – a substance that comes from the earth

depth – how thick an object is from top to bottom

geologist – a person who studies the earth and the materials of which it is made.

Vocabulary Review

diameter – the distance across a round object mineral – a basic earth material; a rock

ingredient that cannot be broken down evaporate – to dry up rock – an earth material composed of

different ingredients circumference – the distance around an

object

What We Will Learn

Some rocks can be identified by using a scratch test.

What We Will Do

Identify the four minerals by name. Perform a scratch test on the four minerals

we observed yesterday to determine their hardness.

First we will use the tools and practice on a piece of tile.

Then we will do the scratch test on the four minerals.

Materials

Material Getters will get the trays with Their FOSS tray with their minerals 4 pieces of chalk 4 tiles 4 tool kits

You will record your information in your Earth Materials Booklet.

Your work in your Earth Materials Booklet will be graded, so do your best work.

Procedure

You will use three tools to help determine the hardness of the minerals on the tray: a paper clip (a geologist would generally use a

pocketknife) a penny your fingernails You will also use hand lenses for close

observation.

Procedure

You will use the paper clip and some “pretend earth material” samples (chalk and tile) to learn the technique.

Try to scratch a piece of chalk and the tile with the paper clip.

Use your finger to rub away any dust or surface marks.

Use a hand lens to check for a scratch (altered surface.)

Discuss Chalk and Tile Results Which is harder, chalk or tile? How do you

know? The chalk is easily scratched by the paper

clip, but the tile is unscratchable. The paper clip leaves a black mark (metal

fragments) on the tile, but the mark rubs off, leaving no permanent mark.

Discuss Chalk and Tile Results Which tool is harder, the paper clip or the

penny? The penny is easily scratched by the paper

clip. The mark does not rub off. That is evidence that the paper clip is harder than the penny.

Return Materials

Return the chalk and the tiles to the materials center.

Quartz Clue

Quartz is the hardest of the common minerals on Earth.

Will that information help you identify the quartz sample in your set?

Identify the Quartz

Use your paper clip to test the four minerals. Decide which mineral is the hardest.

Share

Reporters, share your group’s conclusion about which mineral they think is quartz and why they think so.

Gypsum Clue

Gypsum is the softest of the four minerals. Use this clue to help you identify gypsum.

Share

Reporters, share your group’s conclusion about which mineral they think is gypsum and why they think so.

Earth Materials Booklet Page 9 Write the names of the minerals you have

identified so far. Fill in the tool columns with a no if the tool

does not scratch the mineral and yes if the tool does scratch the mineral.

Fluorite and Calcite Clue

Fluorite is harder than calcite. Use your tools to identify these last two

minerals. What do you already know about these

minerals from the test you have already done?

Identifying Fluorite and Calcite Which scratch tool might give you the best

information at this time? The penny. How could you find out which was harder if

you didn’t have any scratch tools? Scratch one rock against the other and find

out which one has a mark left on it; that is the softer mineral.

Share

Reporters show us the mineral that your group has identified as calcite.

What is your evidence? Show us the mineral that you group has

identified as fluorite. What is your evidence?

Seriate the Minerals’ Hardness Tally the tools that would scratch each

mineral. Then number the minerals in order from

softest to hardest. Why did you seriate them this way?

Return Materials

Return materials to the Materials Center.

Content/Inquiry

What do we mean when we say a mineral has a certain hardness?

Hardness is a mineral property that refers to the resistance of a mineral t being scratched; minerals can be ordered by hardness.

If you did have any tools, how could you learn if one mineral was harder than another?

The harder one will always scratch the softer one.

Response Sheet – Scratch Test We will go over this sheet and then you will

complete it for a grade.

Science Stories

Read Science Stories “Digging It Up: Mining for Minerals” and “Birthstones: A Mineral for Each Month” after completing this part.