Are you teaching your students the difference between porosity and permeability? While these two properties of soils and rocks are related, they are not the same! And what better way to understand the difference between porosity and permeability than a hands-on lab activity!?
In this lab experiment, compare the porosity and permeability of three sediments: gravel, sand, and clay/silt. These activities are easy to complete with common household items.
In this post, you will learn how to set up a porosity and permeability activity in your classroom. You can also get print-formatted versions of these directions, worksheets, handouts, and classroom posters to use during this lab in mySoil Science Unit!
Pre-lab Activity
Place a small amount of each sediment on three trays. Allow students to examine and touch the sediments. Ask students to consider:
Rub the material between your fingers. Describe how it feels. Coarse? Gritty? Fine? Sticky? Stiff? Loose?
Describe the material. Can you see individual grains? How large are they? What color(s) do you see?
Make a prediction: Which soil sill have the highest porosity? Which will have the lowest porosity?
Make a prediction: Which soil sill have the highest permeability? Which will have the lowest permeability?
Gather Your Materials
Gather the following materials for the demo. You will need:
Porosity Lab Activity Materials:
Dry gravel (~100 mL)
Dry sand (~100 mL)
Dry silt or clay (~100 mL)
3 small containers of equal size (e.g., 150 mL beakers)
Demonstrate the method with the gravel: Measure ~100 mL of gravel into a container and gently shake the container so that the surface of the gravel is flat.
Record the total volume of the gravel on thelab worksheet.
Fill a beaker with 100 mL of water.
Slowly and gently, pour the water into the gravel, until the water level reaches the surface of the gravel.
It may take some time for the water to “soak through” to the bottom of the beaker. You may need to pour a little water at a time and then wait before pouring some more.
Record the volume of the pore space. This is equal to the volume of water you poured into the gravel.
Students will repeat the procedure with the sand and the silt/clay.
After students collect their measurements, show the students how to calculate the porosity:
Permeability Directions:
Pass out the materials.
Demonstrate the method with the gravel: Balance the funnel on top of the graduated cylinder and place a filter paper into the funnel to cover the stem hole.
Fill the funnel approximately half way up with gravel. Do not fill the funnel all the way up to the top.
Tap the funnel lightly to make the surface of the gravel flat.
Use the marker to mark the level of the surface of the gravel on the funnel.
Put 200 mL of water in the beaker or measuring cup.
Start the stopwatch as you pour all 200 mL of water over the gravel.
At regular intervals, record the time and the volume of water in the graduated cylinder.
The water may pass through some sediments very rapidly. You may only have time to record a few volume measurements before the water is done passing through.
After students finish the procedure with the gravel, they will repeat the procedure with the sand and the silt/clay. Fill the funnel to your previous mark with the other sediments.
Look at the recorded data. Which sediment did the water pass through most quickly? This soil has the highest permeability.
In your own words: what is the difference between porosity and permeability?
What are some possible sources of error in the porosity lab?
What are some possible sources of error in the permeability lab?
During rain, water seeps down into the soil through its pores. Which soil will water pool on top of first: a soil with high permeability or a soil with low permeability. Which size grains would this soil likely have a lot of?
You are potting a plant that needs a soil with high porosity. What size grains might help give a soil a high porosity?
This lab comes from my Soil Science Unit!
Your students will love the illustrated learning materials, plus you’ll support Wild Earth Lab with your curriculum purchase!
Are you studying soil science, gardening, or agriculture with your students? If so, you have probably learned that soil is a mixture of sediments and organic matter. But different soils have different amounts of these two ingredients. A soil’s organic matter content is important, especially when considering a soil’s ability to support plants.
In this demo, qualitatively compare the organic matter content of two soils. You can test the soil samples for organic matter by putting hydrogen peroxide on the soils and watching for a reaction (bubbling). More bubbles = more organic matter!
In this post, you will learn how to set up a soil organic matter demo in your classroom. You can also get print-formatted versions of these directions, worksheets, handouts, and classroom posters to use during this lab in my Soil Science Unit!
Read and comply with all safety information and warnings on the hydrogen peroxide bottle. Before starting this demo, ensure all participants are prepared to safely handle hydrogen peroxide.
Ensure all participants and observers wear the appropriate personal protective equipment (gloves, lab coat, safety goggles).
Adult supervision is required at all times during this activity.
Directions
Do not tell students where soil samples A and B came from until after the lab. Explain that the two soil samples contain different amounts of organic matter. Hydrogen peroxide reacts with the organic matter in the soil, making bubbles or fizzing sounds.
Place ~2 Tbsp (15 mL) of soil A into a beaker
Place ~2 Tbsp (15 mL) of soil B into another beaker
Pass around the soils. Students should observe each soil and describe it.
Put on personal protective equipment.
Ask your students to gather around and watch as you squeeze an eyedropper full of hydrogen peroxide onto soil A and watch/listen for bubbles and fizzing.
Repeat the previous step with soil B. Which soil reacted more?
Finally, reveal that one of these samples came from a compost pile. Can students guess which one?
In this classroom demo, observe how soil organic matter reacts with hydrogen peroxide.
Reflection Questions
Describe soil A (color, texture, feel)
Describe soil B (color, texture feel)
What happened when your instructor added hydrogen peroxide to soil?
Did one soil react more than the other? Which soil reacted the most?
Hydrogen peroxide reacts with organic matter. What does this tell you about soils A and B?
This lab comes from my Soil Science Unit!
Your students will love the illustrated learning materials, plus you’ll support Wild Earth Lab with your curriculum purchase!
Are you studying soil science, gardening, or agriculture with your students? If so, there is nothing quite like a soil textures jar lab to learn about sand, silt, and clay in soils! In this lab activity, students observe the distribution of grain sizes in soil samples, then classify the soils using the soil textures triangle.
If a scientist wants to know a soil’s texture, then they need to figure out the proportion of sand, silt, and clay in the sediment part of the soil. But this can be a challenge. How do you separate and measure all those tiny grains? Soil scientists use a few different methods for doing this.
This most basic method, the “jar test”, is easy to do in a classroom setting. Shake up soil and water in a jar. Then, watch the grains settle over time. Larger grains settle faster than smaller ones.
In this post, you will learn how to set up a soil textures jar test lab in your classroom. You can also get print-formatted versions of these directions, worksheets, handouts, and classroom posters to use during this lab in my Soil Textures Mini Study!
Gather Your Materials
Gather the following materials for the lab. Each lab group will need:
2 or 3 soil samples: collect different soils from 2 or 3 places. Avoid soils with a very high organic matter content, such as compost. Bring at least 300 mL of each soil per lab group so that you have some extra in case mistakes are made.
Sieve
Tray
2 or 3 straight-sided, tall bottles (~ 500 mL)
Water
Dispersing agent: borax or dish detergent (optional)
This lab involves lots of waiting. You must collect certain measurements hours and days apart – make sure to plan accordingly.
Before starting, it may help to sieve your soil samples to remove any large gravel, cobbles and roots. To do this, place the soil into a sieve. Select a sieve with openings no smaller than 2 mm. Gently shake the sieve over the tray. The soil will fall through while the larger gravel, cobbles, and roots will remain in the sieve. If you do not have a sieve, you can also spread the soil out on a tray and pick out any especially large gravel, cobbles, and roots by hand.
Borax will help the clay settle. If you do not have any, dish detergent can be used as a substitute.
Once students begin the procedure, the bottles should not be moved. Select an area for this lab where the bottles can sit undisturbed for a few days.
Demonstrate the method with the first soil. Fill a bottle about one third of the way with a soil sample.
Gently tap or shake the bottle until the surface of the soil is flat. Then, use a permanent marker to mark the level of the soil on the outside of the bottle. Label the mark “initial”.
Fill the rest of the bottle with water.
Optional: add 1 tsp (5 mL) of the dispersing agent.
Tightly cap the bottle.
Shake the bottle vigorously for 5 minutes.
The instant you stop shaking the bottle, set it on the counter and start a stopwatch. Do not move or disturb the bottle once the stopwatch starts.
Sand takes about 1 minute to settle. After 1 minute, mark the top of the sand layer on the bottle with a marker. Label this mark “sand”. Measure the thickness of the sand layer with the ruler and record it on the student handout.
Silt takes 2 hours to settle and clay takes at least 48 hours to settle. Students should write the times these measurements should be taken on a sticky note and place it on the bottle. Depending on the length of your class period, you may need to measure and record the thickness of the silt layer for your students in 2 hours.
Students should then set up their second (and third) bottle(s) with the other soil sample(s) by repeating all the above steps.
Students will measure and record the thickness of the clay layer at least 48 hours later. The water may still look murky above the settled sediment. This is because a small amount of very fine clay is still in suspension. The final soil level may be somewhat less than the initial soil level. This is because shaking and settling changes a soil’s structure and amount of pore space.
Once students collect all of the measurements, show the students how to calculate the percentages of sand, silt, and clay in each soil sample. For example:
Find each of your soil samples on the soil textures triangle (external link). What is the name of each of your soils?
In your own words, define soil texture.
A soil is made of 35% clay, 40% silt, an 25% sand. What type of soil is it?
A soil is made of 10% clay, 5% silt, and 85% sand. What type of soil is it?
You are selecting a soil to plant a cactus in. The cactus needs a fast-draining soil, so you are looking for a soil with plenty of coarse sediments. Which soil is a better choice: a sandy loam or a silt loam? Why? (See the soil texture triangle).
You are choosing a place to dig a hole in your yard to build a fish pond. You do not want the water to drain out of the pond into the soil, so you are looking for a soil with plenty of fine sediments. The left side of your yard is a silty clay and the right side of your yard is a loamy sand. Where would you build the pond? Why? (See the soil texture triangle).
Public domain image courtesy of: USDA Natural Resources Conservation Service
This lab comes from my Soil Science Unit!
Your students will love the illustrated learning materials, plus you’ll support Wild Earth Lab with your curriculum purchase!
With the first signs of spring appearing, many of us are looking forward to spending more time enjoying our outdoor living spaces. Spring also means the beginning of yardwork season and time to start new projects in the yard or garden. Maybe you are looking to add more native plants, reduce your water usage, or just change things up to create a more enjoyable outdoor living space. No matter what your goal is or where you live, it is important to remember that we are not the only ones using our backyards. We share the outdoors with all kinds of animals and insects! Whether you are actively trying to attract more wildlife to your backyard, or just aiming to be a little more environmentally conscious, there are some steps that you can take to be more kind to the wildlife that visits and lives in your backyard! For me, I noticed a big difference in the wildlife I saw in my yard a few years ago when I moved to a rental house with a yard that was a bit more wildlife friendly. This spring, as I move into a new house again, I’m excited to use some of the things I learned to make my new yard a bit better for the animals and insects that live there!
My xeriscape backyard in early spring
A few years ago, I moved into a rental house near the edge of town with a yard that contained a variety of native bushes, trees, and flowers rather than being entirely grass. This type of yard is called a xeriscape, a style of landscaping designed to use little to no irrigation. Usually, xeriscapes involve a mixture of native or low water use plants, and non-living features such as rocks, gravel, pavers, and woodchips. While I knew xeriscaping was becoming more popular in my area for water saving purposes, I quickly learned about some other awesome benefits of having a xeriscape yard.
The first summer, I quickly became acquainted with the yard’s resident garter snake. I would often see this small snake on sunny afternoons, slithering through our vegetable garden, hiding amongst the rocks and shrubs, or prowling around the mint and raspberry bushes hunting grasshoppers. My scaly co inhabitant was not the only critter in my backyard. I also saw rabbits, squirrels, frogs, birds, and a variety of insects and invertebrates. From time to time, I would see hawks swoop over my house, returning from hunting at nearby farm fields to nest in the massive elm trees scattered throughout my neighborhood. Occasionally, I would see a hawk carrying a snake, and I would wait with anticipation until the next time I saw my garter snake pal.
My backyard garter snake pal
Prior to moving into my xeriscaped rental, I lived in several other houses, usually along busy roads, with bluegrass and dirt yards that had little variety. I imagine how these monotonous expanses must look to an animal. I would think they must feel very exposed out on a grass lawn – with no places to hide, build dens, or forage. Certainly, I had never seen a snake prowling through the short, uniform grass in my old backyard.
Comparatively, it seemed like there was a whole ecosystem in my new backyard. Through the seasons, I witnessed the small-scale ecosystem interactions happening in my own backyard, such as predation when my garter snake hunted insects (or when the local hawks hunted snakes!). I watched mutualism occur between my flower bushes and the visiting pollinators like hummingbirds and bees, who drank the sweet nectar in exchange for transporting the plants’ genetic material to other flowers. I observed competition too, mainly between the grasshoppers, the rabbits, and myself as we all competed for the limited amount of dwarf kale in my vegetable garden!
A northern goshawk – one of the many raptors you might see living near human-dominated areas
In addition to the joy of watching the day-to-day activity of my mini backyard ecosystem, I realized there might be other benefits to the presence of some of the animals that were attracted to my yard. After several months living in my house, I realized I almost never saw insects like ants and boxelder bugs inside of my house. It was also the only place I’ve lived where I’ve never seen a mouse inside or outside the house! I give credit to my snake friend – hunting its meals of insects and rodents while unknowingly defending the perimeter of my house from unwanted guests!
My lack of house pests was not the only perk of my mini-backyard ecosystem. The yard’s assortment of native flowering shrubs and plant species attracted a variety of hummingbirds, butterflies, bumblebees, and honeybees. In return, my summer vegetable garden reaped the benefits of these pollinators’ presence in my yard. I was grateful for an excellent harvest of squash, cucumbers, peppers, and tomatoes, thanks to the services these creatures provided.
As exciting as it is to witness the behaviors of my backyard wildlife, I sometimes feel a little guilty, knowing that many of these animals would have fared better decades ago, before my neighborhood was built and the land there was semi-arid shrublands. I think about how larger species like coyotes and pronghorn, which require larger swatches of land than snakes or honeybees, are pushed out of areas with humans. As we build roads and buildings, their natural habitat becomes fragmented, or divided into smaller, unusable units. My little backyard ecosystem is far from being like the natural habitat that occurred here long ago. Ultimately, any yard is going to be less desirable than an animal’s natural habitat. That said, there are things we can do to make our yards a little better for local wildlife:
1. Consider alternatives to chemicals
Using chemicals on the garden and lawn can help keep garden pests at bay and decrease the amount of time spent pulling weeds. But chemicals also have harmful impacts on backyard wildlife. Amphibians like frogs and salamanders are particularly sensitive to a variety of pesticides, herbicides, and fungicides, which may be contributing to their shrinking population sizes. Chemicals can also harm helpful garden insects like pollinators. If chemicals must be used, try to pick options that target specific pests and are not toxic to bees. Better yet, try chemical-free alternatives, like pulling weeds early and often before they get a chance to grow and spread. Or try using mesh netting to keep the grasshoppers out of the garden. These are just two examples – there are lots of ways to protect your garden from weeds and herbivores other than chemicals, although some methods may be more effective than others. Do some research, get creative, and find out what works best for your garden. For example, my great grandma insisted on painting pebbles with red nail polish and placing them around the bottom of her strawberry plants, as an unappetizing decoy for the birds and insects trying to eat the tasty berries!
The leopard frog, like many amphibians in impacted by pesticides and herbicides.
2. Reduce your pet’s impact
We all love our cats and dogs, but they are not a natural part of the ecosystem. Many pets will instinctually hunt or harass wildlife. Leaving a dog or cat outdoors unsupervised is like introducing an unnatural predator into an ecosystem – which can increase stress in wild animals and change their natural behavior. You can help by always supervising your pets when they are outside to make sure they do not bother wildlife. Cats especially may cause problems for wildlife. Outdoor domesticated cats kill a significant number of birds each year! Consider keeping your cat indoors to protect songbirds. If you must have an outdoor cat, add a jingle bell to its collar to increase the chance that birds will be able to hear your kitty sneaking up on them.
A ruby-throated hummingbird is one of many birds species impacted by outdoor cats
3. Create variety
Regardless of where you live, the natural environment in your area is likely not a monotonous expanse of grass, pebbles, or wood chips. Animals and insects are used to more complex environments that include places to hide. Adding a variety of trees, shrubs, groundcover plants, and rock features to your yard can provide critters with places to hide and build their nests. A more complex habitat allows for a greater diversity of species: simply put, a variety animals need a variety places in their environment to live, hide, and forage.
The swallowtail is a butterfly that overwinters as a chrysalis
4. Leave your yard waste
Raking leaves keeps lawns looking tidy. But leaves may actually provide important winter habitat for spiders and some insects. Spiders are a predator of many pest insects and can help decrease the number of insect invaders to your home. Additionally, yard waste like plant stalks and leaves may contain hibernating caterpillars or the cocoons and chrysalises of certain overwintering moth and butterfly species. Cocoons and chrysalises are the non-moving, intermediate life stages of moths and butterflies, respectively. In the spring, overwintering moth and butterfly species will emerge in their adult form, at which time they may pollinate plants in your garden! By removing yard waste, you may be unknowingly removing some of your pollinators! Raking leaves and cleaning up yard waste is a pain, so I know I am glad to hear there is a great excuse to put it off until after the spring!
Attracting pollinators to your yard is as easy as planting their favorite flowers! It is fun to watch butterflies and bees in your yard, and they can help pollinate your vegetable garden. It is important to select the right plants: choose native species that provide the necessary nutrients for the pollinators native to your local area. Visit a local plant nursery or research online to find out what native plant species can attract pollinators in your area!
A honeybee is one pollinator you might see in your yard!
This spring, I’m moving into a new house again. I’m looking forward to xeriscaping a few areas of my yard by adding native, pollinator-friendly plants – both to make my household more sustainable and to attract backyard wildlife. Maintaining xeriscape, especially a xeriscape with many plants and shrubs, can be hard work. I’m planning on writing another piece sometime soon weighing the pros and cons of xeriscape, as well as keeping everyone updated on my various sustainability projects in my yard and garden this summer.
If you enjoyed reading about my backyard wildlife experiences and learning about some of the ways you can make your backyard better wildlife habitat, please leave a comment below and subscribe to Wild Earth Lab for more posts like this one! You can also follow Wild Earth Lab using the links below, to get sneak previews of new learning resources in the works!
Finally, I created a free Backyard Wildlife Bingo game and a poster summarizing the tips in this post, linked below or available on the learning resources page! Check off the boxes in Backyard Wildlife Bingo while you and your family spend more time outside this spring!
Kawahara, A. Y., Reeves, L. E., Barber, J. R., & Black, S. H. (2021). Opinion: Eight simple actions that individuals can take to save insects from global declines. Proceedings of the National Academy of Sciences, 118(2). Available: https://www.pnas.org/content/118/2/e2002547117.short
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