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Excerpted from how2SCIENCE Science Essentials

Connecting Content With Six Key Concepts

While there are hundreds of different topics that can be explored with young children, the approach you use to explore these can be connected through KEY CONCEPTS, including:  diversity, change, cycle, growth, patterns, and energy-related transformations.  From birds to butterflies, solids to liquids, or from the frozen tundra to the tropical rainforests, these themes are ubiquitous throughout nature and can be connected to every science exploration. Key concepts are big ideas! Key Concepts can be viewed as approaches or perspectives that you can take on your topic/subject and which can be used, in part or whole, to create content-rich science experiences.

Thematic Relationships

While concepts can be applied independently of one another, there is a natural content flow connecting multiple concepts and which can be used to add richness and depth to your content. The concepts can be used to help you create an organizational framework on which to organize, build and elaborate your content. For some subjects, you may decide to apply just one of the concepts; while, in other situations you may decide to apply several of the concepts to your topic.

The following example shows how these thematic threads apply to water and water-related content. 

·    The various states (solid, liquid and gas) of water (diversity).

·    Saltwater versus freshwater in oceans versus the rivers, respectively (diversity).

·    How snowflakes are unique (diversity).

·    How ice crystals (snowflakes) form a hexagonal pattern (growth & patterns).

·    How water has a very specific structure, a pattern of two hydrogen molecules and one oxygen molecule (patterns).

·    How water changes in the water cycle through the processes of evaporation, condensation and precipitation (cycles).

·    The state of water depends on the temperature (change & energy-related transformations).

As noted above, these six key concepts represent approaches you can take to your subject; the actual content and focus of your exploration will, of course, depend on your particular lesson plan.  The following webbing diagram shows the myriad of content areas that can be derived from or connected to water with very few degrees of separation. 

In approaching these key concepts, think about which ones may apply to topics or subjects you routinely teach in your classes.  Each of the six concepts is described below and applied to various subjects/topics routinely taught in most preschool settings. 


Diversity is reflected in both our sameness and differences. Diversity provides us with the opportunity to describe, compare and sort (categorize) based on similarities as well as differences. Within a given collection of plants, animals or non-living matter we can look at how each member species or representative is the same and how it differs (same, but different). In comparing butterflies and moths…we can identify similarities and differences by comparing body design, shape, size, coloration, and sort them accordingly. Through diversity we can ultimately apply order and organization to a given system, across systems, or to a group of organisms or objects.

One way of defining diversity is in terms of variety.  There are millions of different plant and animal species on Earth.  Within each class of organisms you can find tremendous diversity and differences.  These differences can be discerned in the plant or animal’s physical features and characteristics, as well as habitat.  In the animal world, there are more than 150,000 different species of butterflies and moths. As members of the insect world -a several million plus member community-butterflies and moths share certain features in common.  There are, however, fundamental differences between moths and butterflies, and between different butterflies. Similarly, amongst the millions of different insect species you will find tremendous variation when comparing one to another, but each insect will display certain basic features in common, namely, six jointed legs, antennae, wings (sometimes) and three body segments (head, thorax and abdomen).

Some differences between species may be subtle, others dramatic.  Birds, for example, differ with respect to their body size, beak size and shape, body and contour feather coloration and length, wingspan, leg length, claw type and flight capabilities.  All birds have beaks, but beak size and shape differs significantly between species.  These differences represent adaptations to a particular habitat, to a particular function, or use.  For example, all birds of prey have hooked beaks, but there is tremendous variation between hawks, owls and eagles, as well as between a barn owl and a snowy owl.

While species variation relates specifically to living creatures, diversity (variation) can also be applied to non-living matter and inorganic substances.  There are many different types of gemstones, soil types or rock/sand; clouds can be categorized based on their shape, composition and height; and, while every snowflake is comprised of ice crystals, the six-branched pattern each forms is unique. 

Diversity is often applied to describing and categorizing living organisms, objects and materials, but it can also be viewed as a type of variation on a given theme or feature.  For example, eyespots are a type of adaptation.  Butterflies, butterfly fish and the four-eyed frog all have eyespots.  Despite the obvious differences between these organisms, we can, nonetheless, compare eyespots based on the similar purpose these serve, i.e. eyespots are designed to fool predators, and sometimes prey in the case of the tiger's back of the ear eyespots!  Eyespots are an advantageous adaptation that helps the organism, whatever it is, survive.

Observing/describing differences and similarities in a system
is central to scientific inquiry and investigation.

Pick a topic and identify how DIVERSITY may be applied. 

·    There are approximately 150,000 different moth and butterfly species in the world.  For every butterfly or moth there is a unique caterpillar.  Butterflies differ from moths in distinct ways.  Butterflies tend to be more active during the day, while moths are active at dusk or at night.  Butterflies rest with their wings closed, while moths rest with their wings open.  Butterflies tend to be more colorful than moths.  The coloration on a butterfly or moth’s wings is generally related to its habitat.

·    There are many different types of trees.  Trees are used for many different things.  Trees produce different types of fruit and wood types.  Some trees produce hardwoods.  Some trees as well as other plant parts are used to make medicines. 

·    Trees grow in different habitats.  Trees have developed special adaptations to thrive in different environments, such as the rainforest, desert or near the oceans. 

·    Trees produce seeds, which are used to make new plants.  Some trees produce fruit with many seeds; while, some trees produce fruit that only has a few seeds.  Some trees produce fruit we eat, while others produce fruit that may be poisonous or can make us sick. 

·    Not all bird’s nests are the same.  Some nests are built into the hollow of a tree, other nests are cup or bowl-shaped, and still other nests hang from a tree branch like a basket. 

·    Spiders spin webs, but not all webs are the same.  Webs differ in their size and shape, and also where the spider spins its web. 

·    There are many different types of solids.  Different solids have different properties.  Some solids are hard, while others can be reshaped (malleable).  Solids melt at different temperatures to become liquids.  Some solids melt at room temperature, while others need the heat from a fire to melt them.

·    Water, like all matter, can exist in at least three different states.  Depending on the temperature, water may be found in its solid, liquid or gaseous form. 

·    People don’t look the same, but all people share certain traits and features in common…two eyes, two ears, a nose.


Patterns provide us with a means of identifying and discerning subtle differences between species, and a means of organizing a collection of diverse objects, materials or organisms. Patterns can be discerned based on an analysis of particular attributes:shape, color, kind, number, arrangement or organization (symmetry). Patterns can be both obvious and subtle.  Some patterns can be observed directly, while other types of patterns can be viewed as components or parts of a cycle or a process. 

For example, the number of seeds in an apple and their organization in the apple’s core reflects 5-fold symmetry.  Relative to an apple, the seed organization and number of seeds is profoundly different in pumpkins and squashes, but these fruits also show a 5-fold pattern of symmetry.  Examine a butternut squash or a small pumpkin, and count the number of sections on the rind.  You will find that the sections are organized in multiples of five.  The extensive network of hexagonal cells in a honeycomb forms a regular repeating tessellation.  Three soap bubbles will form a “Y’ shaped wall between them, sharing bubble solution and as more bubbles are added to the system, the “Y” monomers form a hexagonal pattern.  The pattern of colors, spots or stripes on an insect’s wings is symmetrical.   We recognize a tiger because of its stripes or a leopard by its spots.  That pattern is invariant and provides us with a means of differentiating between the big cats.

Observing/describing patterns in a system or an individual is the basis
for making comparisons and is central to scientific inquiry and investigation.

Pick a topic and identify what types of PATTERNS may occur. 

·    Certain types of solids form crystals.  Crystals form regular, repeating patterns.  A salt crystal of any size is cubic (square) and contains a discernible “X” mark at its center.  

·    The Earth’s movement around the Sun and its cyclical rotation on its own axis can be viewed as a type of pattern. 

·    A tree’s leaves grow in a particular manner (shape, number and arrangement).  That pattern helps us to distinguish one type of tree from another.

·    The wings of a butterfly have a defined pattern that distinguishes it from another butterfly. 

·    The white stripe on a skunk’s back and tail are a distinguishing feature-an unmistakable pattern.

·    A young animal, such as a tapir, has a pattern of spots and stripes that differs from the adult’s fur pattern. 


Changes can occur naturally or because of the conditions we introduce. The results or outcomes of the changes we introduce are often predictable, though sometimes surprising. A seed sitting on a counter doesn’t appear to change, but if given a little water or planted in the ground, the seed undergoes tremendous changes. The leaves on a deciduous tree change colors because of the cooler nights and shorter days. A copper penny will tarnish slowly over time. The Statue of Liberty naturally developed its lovely blue patina because of oxidation. We can place a tarnished copper penny in vinegar, or another acidic solution, mix in a little salt, and the penny will become shiny again. But if we don't wash off the salt and vinegar, the penny will again develop a lovely blue patina when exposed to air.

Things change.  Things change over time.  Change can occur naturally or because of artificially introduced conditions.  In an experiment we might choose to introduce variables, changing the conditions that might ultimately affect the outcome.  Some changes are irreversible; others can be viewed as part of another process, such as a lifecycle or a pattern of growth.  Some changes can be beneficial, others harmful.  A mutation is a type of change, which may be beneficial or harmful depending on why and where it occurs, and how it affects the organism, positively or negatively.

Think about how we change.  We grow taller.  We grow older.  We grow fatter or thinner.  Our bones grow longer as we get taller.  Our muscles grow stronger, and sometimes bigger, with exercise.  Our hair and nails grow, but if we cut them we can change their length.  The texture of our skin changes over time.  If we play outside in the hot sun, the surface of our skin gets warmer or damp with sweat.  When we are sick with a fever our internal body temperature rises, but it will eventually return to normal. 

Some changes are permanent; others are only temporary-a response to a given set of conditions.  A grape left out in the sun (or even kept in the fridge for a long time) will eventually dry out and become a raisin.  We can plump up the raisin by putting it in water, but it will never be a grape again.  Not all temporary changes are the same...stroking an iron nail with a magnet will temporarily magnetize the nail but it will lose its magnetic capacity over time. In contrast, an electromagnetic can temporarily become a magnet when an electric charge is applied and as long as the charge is introduced the electromagnet will function accordingly. 

Observing/describing how a system changes through a process
is central to scientific inquiry and investigations.

Pick a topic and identify what types of CHANGE(S) may occur. 

·    Butterflies change during their lifecycle. 

·    Caterpillars change, growing larger before they become pupae. 

·    A young animal, such as a tapir, will have a pattern of spots and stripes on its fur, but the pattern changes as it matures. 

·    Trees change in appearance, losing their leaves during the year.  This phenomenon applies to both deciduous trees, which lose their leaves en masse, as well as to evergreen trees which lose their leaves (needles) sporadically throughout the year. 

·    Water can change its state depending on the temperature. 

·    The reactants in a chemical reaction combine, often changing their color, appearance or properties, to yield a new and different product. 

·    The appearance of the moon changes throughout the lunar cycle.

·    The position of the sun appears to change during the course of a day.

·    The types of clouds in the sky changes from day to day.

·    The surface of the Earth changes, coastlines may erode and the sands shift with the changing tides.

·    We change over time, growing taller and bigger. 


Growth is a type of change that occurs in animal, plant and inorganic systems.  You can view growth as a type of snapshot that provides us with insight into a particular phase or portion of an animal’s lifecycle.  Growth is often reflected in physical changes that can generally be observed both during a process and/or at the end of a process. Growth results in observable changes to a system that can be documented. The concepts of change, growth and cycles are obviously related to one another.  For example, plant growth can be described in terms of how a seed changes, the growth of a seedling’s root system or its emerging leaf pattern.  Animals and plants change and grow during their lifecycle, following a defined sequence of events or stages of development. 

By affecting conditions, we can often influence the rate of growth.  A young bean plant kept in the shade and given only small amounts of water will not grow as well as a plant given generous amounts of water and sunlight.  We grow and change over time.  Our muscles, bones and skin grow as we grow older, taller, and stronger.  Ice crystals grow into snowflakes, adding more ice crystals as they fall through the atmosphere.  The age of a tree can be determined by counting its annual rings.  These rings form a distinct pattern that reflects the amount of growth in a given year.  Butterfly larvae, a.k.a. caterpillars, grow larger before entering their next stage of development (pupae).  As a baby tapir grows it loses the pattern of spots and stripes on its fur.  Fungus and bacteria are constantly growing on surfaces all around us.  While generally microscopic in nature, fungi can become visible if their growth is not controlled. 

Most types of growth are coincident with a concomitant loss or change to another system.  A salt crystal will form in a saturated salt solution, but only as the water in the container evaporates.  The size of the salt crystal will depend on how much salt is used initially and it will continue to grow in size as long as there is salt available in the remaining solution.  During the early stages of a seedling’s growth, prior to leaf development and photosynthesis, the seedling utilizes its stored carbohydrate as an energy source (food).  The “spent” endosperm will eventually shrivel up as the first true leaves emerge and the plant becomes capable of making its own food (autotrophic).

We change over time, growing taller and bigger. Every day our hair and nails grow a little longer or thicker. Our bones and teeth grow and change over time. Our lifecycle may span many years. Like many other organisms, we begin our lives as eggs and eventually grow into adults. How do we change? Have each student bring in an article of their baby clothing or a picture from when they were babies. How have they changed? Alternatively, snap pictures of your class at the beginning of the school year, and compare it to pictures taken at the end of the year.

Observing/describing growth-related changes that occur as a function of time
and the conditions is central to scientific inquiry and investigations.

Pick a topic and identify what types of GROWTH(S) may occur. 

·    Butterflies change dramatically during their lifecycle.  At first, a caterpillar is very small, but then it grows bigger as it continues to eat.  The caterpillar must be a certain size before it continues on to the next stage of its development. 

·    A butterfly grows inside a chrysalis, changing from a crawling caterpillar to a four-winged butterfly.  Similarly, a moth grows inside a cocoon, changing from a crawling caterpillar to a four-winged moth.

·    Trees not only grow new leaves to replace the ones they have lost, but trees (and other plants) also grow taller and wider.  You can tell the age of a tree and how much water was available during its growth period by examining the annual rings.   

·    Evergreen type trees produce seeds inside cones.  The cones grow at the ends of the branches.  At first, the cones are very small, but eventually these can grow to be five or six inches long depending on the tree.

·    For a new tree to grow, its seeds must travel some distance away from the parent tree and then take root in the ground.  If conditions are right, the seed will grow and eventually become a tree. 


Cycles are repeating, recurring and returning events or sequences of events that occur in nature.  The cycle may be repeated from year to year in a single long-living species (perennial plant, people, animals), or be continued in the next generation of that species.  Just as change can be described in terms of growth or patterns of growth, cycles can be viewed as a reflection of growth and/or change and, sometimes, as a sequence of events-a type of pattern.  Nearly every organic and inorganic system operates within a cycle.  Humans, animals and plants have lifecycles-some short; some long.  An animal or plant has a lifecycle, growing and changing at each stage of development, from birth (germination) to death. 

Gases such as carbon dioxide and oxygen are cycled between plants and animals.  Water is cycled and recycled through its various states through the processes of evaporation, transpiration, condensation and precipitation.  Carbon, the basis of life on Earth, is recycled again and again.  Some cycles occur naturally…the changing tides, the change from day to night and day again, or the changing seasons.  Cycles can also occur in inorganic systems, as in the water cycle-a dynamic (changing) system. 

Cycles can not only be interrupted, but also influenced by outside factors or a change in conditions.  Deciduous trees will lose their leaves when daylight hours become shorter and nights become cooler.  A seed will not germinate until it imbibes water.  Cutting off a plant’s roots will interrupt its growth cycle.  Many insects will over winter in their larval stages until conditions are right to continue their lifecycles in the spring. 

Observing/describing cyclical events and the coincident changes at each
stage of a cycle is central to scientific inquiry and investigations.

Pick a topic and identify where CYCLE(S) may apply. 

·    Butterflies change during their lifecycle.  Adult butterflies lay eggs and the eggs eventually becoming adults themselves and the females will lay eggs. 

·    The larval pahse (caterpillar) of a butterfly’s lifecycle can last for several weeks; during that time the caterpillar grows larger before pupating. 

·    Trees bear seeds in order to reproduce.  A tree does not produce fruit or seeds year round, but only at certain times of the year. 

·    As the days get shorter, deciduous trees lose their leaves in the fall.  In the spring, deciduous trees once again grow new leaves, surviving for many years and repeating the same process throughout their lifecycle.

·    The constancy of the water cycle is critical to our survival.  Water is cycled between its liquid, solid and gaseous states through the process of evaporation, condensation and precipitation.

·    The movement of the moon around the Earth is cyclical, as is the orbit of the Earth around the Sun and the Earth’s rotation about its own axis. 

·    Everyday the oceans experience high and low tides. 

·    We change over time, growing taller and bigger.  Our lifecycle can span many years.  Like many other organisms, we begin our lives as eggs and eventually grow into adults. 

Energy-mediated Transformations

All processes in a given system are ultimately energy-mediated, utilizing, generating, or transforming energy.  This particular theme includes potentially complex examples that may not be suitable for younger children, but can be described and discussed with older children. 

For example, the process of photosynthesis is a light-dependent process that requires energy from the Sun.  Evaporation occurs naturally because of the air pressure, but can be accelerated by increasing the temperature naturally by the Sun’s energy (heat) or by the application of heat.  Chemical reactions either produce energy or utilize energy; these reactions are classified as being exothermic or endothermic, respectively.  Friction produces heat (energy) when two surfaces come into contact with one another.  A vortex builds as the system is agitated and the energy of the system increases.  Enzymes and catalysts speed up reaction rates by decreasing the amount of energy the system requires to drive the reaction. 

Observing/describing energy-mediated processes and the coincident changes to the system is central to scientific inquiry and investigations.

Pick a topic and identify where ENERGY-MEDIATED PROCESSES may apply. 

·    Parts of the water cycle depend on the transformation of water between its solid, liquid and gaseous states.  These processes require temperature changes.

·    When water vapor in the atmosphere condenses clouds may form. 

·    Photosynthesis is a light-dependent process that occurs in a plant’s leaves. 

·    Deciduous trees lose their leaves in the fall when the days grow shorter (less sunlight is available) and the nights grow cooler.

·    All metabolic processes that occur in our bodies produce and/or use energy.