Activity 5 - Weathering – rocks changing. adapted from Kids Geozone.
Similar experiments can be found in Weathering and Erosion. The shaping of our landscape.
Building Science Concepts 2
Science Understandings:
 Over time the interaction of air, water, temperature change, radiation and
living things causes the outer layer of the earth’s surface to break down
and crumble. This process is called weathering.
 There are two main types of weathering, mechanical and chemical.
o Mechanical weathering (scouring, battering, cracking, levering)
break up rock into smaller pieces.
o Chemical weathering transforms rocks and minerals exposed to
water and atmospheric gases into new chemical compounds and
forms different rocks and minerals, some of which can be dissolved
away (think of limestone caves).
o In nature, mechanical and chemical weathering typically occur
together.
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Weathering is a long, slow process, which is why we think rocks last
forever.
As rock is destroyed, valuable products are created.
The major component of soil is weathered rock.
The growth of plants and the production of food is dependent on
weathering as it releases the minerals needed for these processes to take
place.
Resources:
lemon juice, white vinegar, water
water dropper bottles,
pieces each of limestone, lime fertiliser, greywacke and quartz.
Method:
1. Put a few drops of water on one of each of the samples.
2. Put a few drops of lemon juice and vinegar on one of each of the
samples.
3. Look and listen carefully each time you add the water, lemon juice or the
vinegar.
4. Record your observations on the chart below.
Questions:
What happens when you put water on each rock?
What happens when you put lemon juice or vinegar on each rock?
Did the lemon juice and vinegar act the same way on each rock?
What about the water?
Why did some of the rocks react differently? What does this experiment have to
do with weathering?
Water
I saw
Water
I heard
Lemon
I saw
Lemon
I heard
Vinegar
I saw
Vinegar
I heard
Greywacke
Limestone
Quartz
Lime
What should have happened:
Lemon juice and vinegar are both weak acids and distilled water is neutral (not sour).
The lemon juice contains citric acid and the vinegar contains acetic acid. These mild
acids can dissolve rocks that contain calcium carbonate. The lemon juice and vinegar
should have bubbled or fizzed on the limestone, and lime fertiliser, which all contain
calcium carbonate.
The lime fertiliser bubbles more, because this is ground up fine allowing the limejuice or
vinegar to have more place to react.
There should not have been a reaction on the greywacke or quartz, which do not contain
calcium carbonate.
Explain that rainwater commonly contains weak acids that dissolve rocks containing
calcium carbonate and other minerals.
You can google pictures of statues affected by acid rain.