Grade by Grade
C. Matter and Energy · Properties of and Changes in Matter

Changes of State at Home, in the Community and in Nature

C2.3 C2.6 A3.1 A3.3 A1.1About 40 minutes
Learning goals
  • I can describe changes of state I observe at home, in my community and in nature.
  • I can explain whether thermal energy is absorbed or released in each one.
  • I can explain how making maple syrup uses evaporation, and describe how First Nations knowledge of maple sap continues today.

Words to know

water vapour
Water as a gas. It is invisible.
dew
Drops of water that condense on grass and other surfaces, often on cool mornings.
frost
Ice crystals that form when water vapour turns straight into a solid (deposition).
sap
The watery liquid that flows inside a tree. Maple sap is mostly water with a little sugar.
sugar bush
A forest of maple trees where people collect sap to make maple syrup and sugar.

Changes of state are everywhere

You have now learned all six changes of state. In this lesson you will become a change-of-state spotter. You will find them in your home, your community and nature, and say whether thermal energy is being absorbed or released.

At home

  • Freezing: water in an ice cube tray turns to ice in the freezer (releases thermal energy).
  • Melting: butter or chocolate melts in a warm pan (absorbs). Only a grown-up uses the stove.
  • Boiling and condensation: water boils in a kettle (absorbs). The little cloud you see above the spout is not the gas itself. Water vapour is invisible. The cloud is tiny drops of water that formed when the vapour condensed in the cooler air (releases).
  • Condensation: the bathroom mirror fogs up after a hot shower (releases).
  • Evaporation: wet hair and wet laundry dry (absorbs).
  • Deposition: frost builds up on the walls of some freezers (releases).
A steel kettle heats on a gas stove while a white cloud drifts away from its spout.
The water inside is boiling. The white cloud is not the gas itself: it is tiny drops of water that formed when the invisible water vapour cooled and condensed in the air. AI-generated image

In the community

  • Skating rinks: to make or smooth the ice, workers spread a thin layer of water over the rink. It freezes into smooth new ice (releases).
  • Winter roads: road salt helps ice and snow melt even when it is a little below 0 °C (absorbs). When it is very cold, salt doesn't work as well.
  • Factories and workshops: metal, glass and plastic are melted and poured or moulded into shapes, then cooled until they freeze (become solid) again. Candles and chocolate bars are made this way too.
  • Sugar shacks: maple sap is boiled to evaporate water (absorbs).

In nature

  • Spring melt: snow and lake ice melt in March and April (absorb).
  • Freeze-up: lakes and rivers freeze in late fall and winter (release).
  • Dew: on a cool summer morning, water vapour condenses into drops on grass (releases).
  • Frost: on a cold fall morning, water vapour turns straight into ice crystals on leaves and windows by deposition (releases).
  • Clouds and fog: water vapour condenses into tiny drops high in the sky or near the ground (releases).
  • Puddles drying: after a rain, water evaporates (absorbs).
  • Icicles: snow on a roof melts in the sun, drips, and freezes again in the cold air at the edge of the roof.
snow on the roof1. Snow melts in the Sun(absorbs thermal energy)2. Water drips downto the roof edge3. At the cold edge it freezesinto icicles (releases)
How an icicle forms: snow melts in the Sun (absorbs thermal energy), the water drips to the cold roof edge, and there it freezes (releases thermal energy). Not to scale.
WhereWhat I seeChange of stateThermal energy
homefog on the bathroom mirrorcondensationreleased
homeice pops hardening in the freezerfreezingreleased
communitynew ice on the arena rinkfreezingreleased
communitywet sidewalk drying after rainevaporationabsorbed
naturedew on a spider webcondensationreleased
natureriver ice melting in springmeltingabsorbed
A change-of-state spotter's log.

Maple syrup: a change of state with a long history

When the maple sap runs in early spring, the nights are below freezing and the days are above freezing. Sap is mostly water with only a little sugar. To make syrup, the sap is boiled so that most of the water evaporates. What is left is thick, sweet syrup. It takes about 40 litres of sap to make about 1 litre of syrup.

First Nations peoples in the Great Lakes and eastern woodlands, including Anishinaabe and Haudenosaunee peoples, were making maple syrup and sugar long before Europeans arrived, and they taught newcomers how to do it. Today, many First Nations families and communities in Ontario still go to the sugar bush each spring. For many, it is a time to harvest together, share teachings about respect for the trees, and give thanks. Maple syrup is a gift of First Nations knowledge that is now part of life all across Canada.

40 L of sap40 L of sap40 L of sapboil3 L of syrup120 L of sap = 3 groups of 40 L (each small square is 1 L)Most of the water evaporates as the sap boils.
Sugar bush math: every 40 L of sap boils down to about 1 L of syrup. So 120 L of sap, which is 3 groups of 40 L, makes about 3 L of syrup.
Worked example

Let's identify a change of state

On a cool June morning, Nadia sees drops of water all over the grass, even though it didn't rain. What change of state is this, and is thermal energy absorbed or released?

  1. What was there before? Water vapour (an invisible gas) in the air.
  2. What is there now? Liquid water drops.
  3. Gas → liquid is condensation.
  4. During the night the grass cooled down. The water vapour that touched the cool grass released thermal energy and condensed.

It is dew, made by condensation. Thermal energy is released.

Worked example

Let's do some sugar bush math

A family collects 120 L of maple sap. About how much syrup can they make, if 40 L of sap makes about 1 L of syrup? Where does the rest go?

  1. Find how many groups of 40 L are in 120 L: 120 ÷ 40 = 3.
  2. Each group makes about 1 L of syrup, so 3 groups make about 3 L.
  3. The rest, about 117 L, was mostly water that evaporated into the air as water vapour.

About 3 L of syrup. Most of the water evaporated while the sap boiled.

Just for fun

Why should you keep your fingers away from Jack Frost?

Because Frost bites! (Real frost is a change of state: water vapour turns straight into ice crystals by deposition.)

Hands-on activity

Change-of-state spotter

You need: a notebook or a copy of the table above, a pencil. Optional: a clean, empty metal can with no sharp edges (a grown-up checks), crushed ice, about 2 tablespoons of salt, a spoon.

  1. For one whole day, look for changes of state at home, on the way to school or the store (community), and outdoors (nature).
  2. Record at least 6 in your table: where, what you saw, the change of state, and whether thermal energy was absorbed or released.
  3. Research (with a grown-up): find out about a sugar bush in your area, or a First Nations community in Ontario that holds a maple harvest. What do they do with the sap?
  4. Optional frost can: fill the can with crushed ice, add the salt and stir for a minute. Wait 5 to 10 minutes and look at the outside of the can. You may see drops (condensation) or a thin layer of frost (deposition). The salt makes the ice mixture colder than 0 °C.
  5. Share your three favourite finds with your family.

What to look for: a correct log has the right change for each observation, for example fog on mirror → condensation → released.

Safety: stay away from stoves, kettles and steam: steam can burn badly. Only a grown-up opens and checks the can for sharp edges. Don't hold the salty ice mixture or the can for a long time: it is cold enough to hurt skin. Never taste the salty ice.

Your turn

1

Name one change of state you could see at home and say whether thermal energy is absorbed or released.

2

How is a rink's ice smoothed?

3

What change of state makes dew?

4

What change of state makes frost?

5

Is the cloud above a boiling kettle a gas? Explain.

6

Why is maple sap boiled to make syrup?

More practice: warm-up

1

Snow melting in April: which change?

2

A lake freezing in December: which change?

3

A puddle drying up: which change?

4

Fog on the bathroom mirror: which change?

5

Is thermal energy absorbed or released when snow melts?

More practice: on your own

1

How do icicles form? Name both changes of state.

2

About how much syrup can be made from 200 L of sap?

3

Describe how a factory might make a chocolate bar using changes of state.

4

Why do people salt sidewalks in winter?

5

Name two ways First Nations knowledge about maple trees is still part of life today.

Challenge

1

Why does maple sap run in early spring, when nights are below freezing and days are above freezing?

2

Clothes dry faster on a warm, windy day than on a cool, still day. Explain using thermal energy.

3

Explain the frost can: what made the frost, and where did the water come from?

Check your understanding

Quiz

1.

Dew on the grass is made by...

2.

Which is an example of freezing in the community?

3.

To make maple syrup, sap is boiled so that most of the water...

4.

About how many litres of sap make 1 L of maple syrup?

5.

Frost on a window in the morning is made by...

6.

The cloud you see above a boiling kettle is...

For parents and teachers

Big idea: Ontario Grade 5 expectation C2.3 asks children to describe changes of state observed at home, in the community or in the natural environment; this lesson also revisits C2.6 (thermal energy absorbed or released). The maple syrup section shows a practical application of a change of state (A3.1) and the contribution of First Nations knowledge (A3.3). The research step practises A1.1.

How to help: Go on a change-of-state walk. If you can, visit a local sugar bush in March or April; many conservation areas and some First Nations communities welcome visitors. Talk about First Nations peoples as living communities who continue this practice today.

Common difficulties:

  • Calling the kettle's cloud "steam gas". The visible part is condensed droplets.
  • Mixing up dew (condensation) and frost (deposition).
  • Forgetting that factories use changes of state too.

Safety: steam and boiling water are for grown-ups only. A grown-up checks the can for sharp edges. Salt-ice mixtures can hurt skin with long contact.