Rate of Weathering

Weathering

Chemical Weathering

Chemical weathering changes the materials that are part of a rock into new materials. A chemically weathered piece of granite is no longer granite. 

Water is important in chemical weathering because water dissolves minerals in rock! The minerals that make up most rocks dissolve very slowly in water

Multiple Choice

________Dissolves minerals in rock

• Acid

• water

• chemicals

• none

Dissolving by Acids

Acids cause chemical weathering to occur at a faster rate than rain or water does. As acid rain rains on rock, it dissolves the minerals and causes chemical weathering

Scientists use pH, a property of solutions, to classify chemical liquids as acidic, basic, or neutral. They measure the pH of a solution on a scale from 0 to 14.

Normal Rain and Acid Rain

 Acid rain, which has a pH of 4.5 or less, dissolves rocks. It is caused by pollutants in the air reacting with rain water. For example, these pollutants can come from volcanoes. It can also come from burning coal that releases sulfur oxides into the atmosphere. Sulfur oxides dissolve in rain and produce acid rain

Normal rain on the other hand has a PH of 5.6 and can cause some chemical weathering, although at a SLOWER rate than acid rain

Multiple Choice

Which type of rain causes faster chemical weathering

• normal rain

• acid rain

• diluted rain

Oxidation

Oxidation is another process that causes chemical weathering. Oxidation combines oxygen with other elements or molecules. Most of the oxygen needed for oxidation comes from the air.

Oxidation, is short, is another name for RUST!

The outside of the rock is in contact with the air so when the rock contains iron and comes into contact with air, it forms rust as a layer on the outside surface

Multiple Choice

What does iron react with in the process of oxidation

• sulfer

• dioxide

• oxygen

Multiple Choice

In short, the process of oxidation in chemical weathering, is the formation or what?

• rocks

• minerals

• rust

• dirt

Rate of Weathering

The same rock can weather at different rates or speeds. The environment in which weathering happens is one things that helps determine the rate of weathering

The type of rock being weathered also affects the rate of weathering

Multiple Choice

What are the two things that affect how fast or how slow something is weathered?

• speed and time

• type of rock and environment

• environment and minerals

• temperature and pressure

Mechanical Weathering and Chemical Weathering

 Mechanical weathering requires frequent temperature changes. Repeated cycles of freezing and thawing will cause rocks to break(still the same rock, just broken into smaller pieces)

 Chemical weathering occurs most rapidly in warm, wet climates such as regions near the equator. 

Multiple Choice

Which type of weathering is more likely to occur in warm, wet climates

• chemical

• mechanical

Rock Hardness and weathering

When rocks are being weathered, soft rocks are going to be weathered more easily and broken down by mechanical and chemical weathering than hard rocks

This is because hard rocks are stronger and more resistant to breaking

Rain and weathering

When it rains on a rock, is can cause both chemical and mechanical weathering!

In a cold place, it can cause freezing and thawing and cause rocks to break mechanically

In a warm place, it can cause minerals to dissolves and rocks to change chemical. This can cause a rock to discolor!

Multiple Choice

Does rain cause more or less weathering?

• more

• less