For the months of September and October my 4th grade science club students have been working on engineering projects. We start by learning about the strongest shapes, then I usually discuss different types of materials and move to building bridges, towers, and simple machines. It is probably one of the favorite of all our club units. Kids LOVE building stuff!
I love teaching engineering because it is an amalgam of so many other scientific branches… physics, chemistry, technology, sometimes biology. It’s been an incredibly fun unit! This year, I changed the order of the lessons because The American Chemical Society’s (ACS) 2026 National Chemistry Week takes place October 18–24, with the theme “Chemistry Under Construction.” It is a great opportunity to explore how the substances in everyday building materials influence their strength, durability, and response to weather. I thought my students could celebrate ACS National Chemistry Week by learning about how materials science plays into engineering.
Imagine designing a school near the ocean, a library in a snowy mountain town, and a science center in a hot desert. Each building needs to support its own weight and protect the people inside while also withstanding the elements in their particular environment. How do engineers decide which materials will work best? Chemistry helps them answer that question. In fact, there is an entire branch of chemistry dedicated to materials science.
What is materials science?
Materials science connects what a material is made of, how it is structured, how it is processed, and how it behaves. Its chemical composition dictates the attributes of the material that we may not be able to see but will determine how it reacts in certain environments. This is where chemistry and engineering meet: understanding matter helps us design useful things.
First, the design team identifies what the structure must do. How much weight will it support? What wind, snow, or earthquake forces must it withstand? How long should it last? Then they consider the environment:
- Water and humidity: Will materials stay damp, encounter heavy rain, or repeatedly get wet and dry?
- Temperature: Will the site experience freezing weather, extreme heat, or large temperature changes?
- Chemical exposure: Will ocean spray, road salt, or chemicals in the soil contact the structure?
- Sunlight: How much ultraviolet radiation will outdoor surfaces receive?
Engineers compare material specifications, test results, and experience with similar conditions. They also consider cost, availability, maintenance, environmental impact, and building requirements. The goal is a suitable combination of materials for that project.
Common building materials: strengths and tradeoffs
Two important concepts in engineering are compression and tension. Compression means squeezing; tension means pulling. A material’s ability to resist these forces helps engineers decide where and how to use it. Its long-term behavior in the environment matters, too.
Concrete forms when cement reacts with water, binding sand and gravel together. It is strong in compression and can be cast into many shapes, making it useful for foundations, walls, and other structures. However, concrete is heavy and weak in tension, so it often needs reinforcement. When concrete becomes saturated with water, repeated freezing and thawing can cause damage.
Steel is an alloy made from iron combined with carbon and other elements. It provides high strength, and many structural grades are ductile, meaning they can bend or stretch before breaking. These properties make steel useful for supporting buildings and reinforcing concrete. However, unprotected carbon steel can rust, and its ability to resist cracking at low temperatures depends on the grade used.
Wood is a cellular material containing cellulose, hemicelluloses, and lignin. Many building woods provide useful strength at a relatively low weight and are easy to cut and join. Wood also responds to its surroundings: changes in moisture can cause it to swell or shrink, fungi and insects can damage it, and it can burn. These characteristics influence how builders protect and use it.
Fired clay brick is made by heating clay or shale until it becomes a ceramic material. Brick is durable, strong in compression, and does not burn. However, it is brittle and absorbs some water. Its composition and firing process affect its durability, while brick masonry needs drainage and movement joints to accommodate expansion and contraction.
Glass used in windows is usually made from silica and other oxides. It lets light into buildings, and coatings can help control heat transfer. Glass is brittle, however, and a window’s performance depends on the whole assembly. An unsuitable combination of glass, frame, and installation can allow excessive heat to enter or escape.
Plastics and other polymers consist of molecular chains, often combined with additives or fillers. Many are lightweight, easy to shape, or flexible, making them useful for pipes, insulation, and seals. Their resistance to heat and ultraviolet light varies by formulation. Over time, weathering can change their chemistry and reduce useful properties.
These are broad patterns rather than guarantees. The exact product, how it is manufactured, and how it is installed can make a substantial difference in how well it performs.
Concrete: a chemical reaction at the construction site
Concrete contains cement, water, and aggregates such as sand and gravel. When cement reacts with water, a process called hydration produces substances that bind the aggregate together. One important product is calcium-silicate hydrate, which helps give hardened concrete its strength.
Temperature affects the speed of these reactions. Cold conditions slow hydration; warmer conditions generally speed it up. Faster early strength development does not guarantee greater strength later. Builders manage moisture and temperature during curing so the concrete can develop its intended properties.
This gives students a useful example of chemistry in a familiar setting: the weather can influence a reaction happening inside a sidewalk, foundation, or bridge.
Concrete also shows why engineers combine materials. It handles compression well but is comparatively weak in tension. Steel reinforcement helps carry pulling forces, allowing the two materials to work together.
How weather changes material choices
Cold climates: water, pores, and freezing
Water can enter tiny pores in concrete. When sufficiently saturated concrete freezes, pressure from the freezing water can damage it. Repeated freezing and thawing can make the damage worse.
For these exposures, engineers can specify air-entrained concrete. Special additives create closely spaced microscopic air bubbles that provide space for pressure relief. Controlling this internal structure helps protect the concrete.
Freezing is a physical change. Hydration is a chemical reaction. Materials science uses both kinds of knowledge to explain how a structure develops strength and how it can deteriorate.
Wet and coastal climates: corrosion and moisture
Steel is an alloy made primarily from iron, with carbon and other elements. Adjusting its composition and processing changes properties such as strength, toughness, and ductility—the ability to deform without immediately breaking. Engineers can select grades with suitable toughness for cold service conditions.
Ordinary carbon steel can react with oxygen and water to form rust. Rust is porous and flaky, allowing corrosion to continue. Salt exposure adds to the challenge near coastlines or salted roads. Protective coatings, galvanizing, and suitable alloy choices help engineers manage corrosion.
Stainless steel provides a chemistry example: its chromium helps form a thin protective oxide layer. Its resistance still depends on the grade and exposure conditions.
Wood has a different relationship with moisture. Its cell walls contain natural polymers, including cellulose, hemicelluloses, and lignin. Changes in moisture content can cause swelling and shrinking. Persistent dampness can also allow decay fungi to grow. Material selection, moisture control, and protection therefore work together in wood construction.
Hot and sunny climates: polymers and windows
Plastics used in pipes, siding, and other building products contain polymers: long chains of repeating molecular units. The chains and additives influence flexibility, strength, and resistance to heat or sunlight. Ultraviolet exposure can drive chemical changes that make some polymers more brittle over time. Engineers look for formulations tested for their intended outdoor conditions.
Glass offers another connection between chemistry and climate. Ordinary window glass is largely silica-based. Thin coatings on the glass can change how much solar energy enters a building. In a hot location, limiting unwanted solar heat gain can help keep indoor spaces comfortable. In colder locations, reducing heat loss is a major consideration. The complete window—including its panes, frame, and seals—affects performance.
Temperature changes also cause materials to expand and contract. Different materials move by different amounts, so engineers design connections and joints to accommodate that movement. Brick masonry, for example, needs appropriate provisions for temperature and moisture-related changes.
You can explore how environmental conditions affect building materials using small, matching pieces of fully set and dried plaster. Compare pieces exposed to plain water at room temperature with pieces exposed to repeated freezing and thawing, diluted vinegar as a simplified model of acidic rain, or saltwater to represent salty coastal exposure. Diluted vinegar models acidity, but it does not reproduce the chemistry of actual acid rain. For a coastal model, try repeated wetting and drying rather than continuous soaking. Keep a dry, untreated piece for comparison, change one condition at a time, and photograph any cracks, flaking, or surface changes over several days. Include a plain-water comparison because water alone can weaken plaster. Plaster responds differently from concrete and other building materials, so this investigation helps students explore weathering and the limits of scientific models rather than predict exactly how a real building will deteriorate. Have an adult prepare the plaster according to the product’s directions, using the recommended eye and respiratory protection.
Does shape matter?
Choosing a building material also means deciding how to use it. A structure’s shape and the arrangement of its parts affect how forces travel through it to its supports. Engineers consider geometry alongside material properties to design structures that can carry weight and withstand forces such as wind.
Triangles offer a familiar example. A triangular frame made from fixed-length pieces cannot change shape without a piece bending, stretching, or a connection failing. A square with movable joints, however, can tilt into a diamond shape without its sides changing length. Adding a diagonal brace divides the square into triangles and helps resist that movement. This is why triangular patterns appear in many bridge trusses and roof supports.
Students can explore this by building a triangle and a square in a few different ways. You can either make these shapes from craft sticks joined with binder clips, poster board strips joined with brass fasteners, or short pieces of straw threaded through pipe cleaners. Gently push sideways and/or top down on each frame, and notice how it moves. Then add a diagonal brace to the square and test it again. What changed? Encourage students to notice both the arrangement of the pieces and what happens at the connections.
This brings us back to chemistry and weather. A well-designed frame still depends on materials and connections that retain their useful properties over time. If steel supports corrode or wooden members decay, the structure’s ability to carry forces can change. Engineers therefore ask several questions together: What shape will work? Which materials suit the job? How will those materials respond to the environment? A successful design brings these answers together.
Engineering: a field of many disciplines
A building project brings several disciplines together. Chemistry explains reactions such as cement hydration, corrosion, and polymer degradation. Physics helps explain heat transfer and forces. Mathematics supports calculations, geometry, and design. Biology contributes both an understanding of how materials change and inspiration for creating new ones. Many useful materials come from living things, including natural polymers such as cellulose in wood, silk proteins, and chitin in insect exoskeletons. Engineers bring this knowledge together to choose materials, develop designs, and test how well they meet a project’s needs.
That testing matters because a material must perform beyond the day a structure is built. Researchers expose materials to controlled heat, moisture, and ultraviolet light, then compare their findings with outdoor exposure to better understand long-term performance. Students can begin exploring these same questions through simple investigations of shapes and weathering: What happened when we changed the design? How did water or freezing affect our material? What might we choose differently if our structure had to survive another climate?
The next time you pass a bridge, a brick wall, or a concrete sidewalk, take a closer look. Why were those materials chosen? How are the parts arranged? What signs of weathering can you find? National Chemistry Week is an invitation to notice the science in familiar places—and to discover how understanding the materials around us can help us build something better.
Explore “Chemistry Under Construction” with ACS
I have long loved celebrating The ACS National Chemistry Week. ACS does such an incredible job at providing tons of resources to get students engaged and learning. To bring these ideas into a classroom, homeschool, or science club, explore these resources from ACS and the American Association of Chemistry Teachers (AACT):
- ACS National Chemistry Week educational resources: Find theme-related readings and activities, including Celebrating Chemistry for students ages 9–12.
- AACT: Chemical Weathering of Rocks: This elementary-level lab compares the effects of vinegar and lemon juice on different rock and mineral samples. It offers a starting point for discussing how composition affects a material’s response to its surroundings.
- AACT: Corrosion in Motion: This middle- and high-school lab has students observe metal samples exposed to different solutions over time and connect corrosion to real-world examples.
Me at National Chemistry Week at the Denver Convention Center in 2010