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A Parent's Guide to Teaching the Phase Changes in Matter To Your Kids


As a family life and child development expert, JP has devoted years in nurturing students and strengthening family relations.

Water exists as solid, liquid or gas.

Water exists as solid, liquid or gas.

How much do you know about what your child is studying at school? Chances are, phase changes in matter is one of the topics. As parents we can help our kids learn more when we know what they are studying. Here's a crush course in the phase changes of matter.

We know that matter comes in different states or forms and we see this on a daily basis. The common states of matter we interact with are solid, liquid and gas. What’s even more amazing is that matter can change from one state or phase to another (for simplicity, we’ll interchange the word state and phase in this resource). We are so used to seeing these state changes that we barely think about them. However, they are fascinating processes fundamental to the world around us. And phase changes of water is one of the best examples we can use. After all, water exists in all three forms - solid liquid and gas.

Heat is a form of energy that is responsible for the phase changes in matter. Heat affects the molecules and particles of matter two important ways. First, adding heat makes the particles move faster. Second, heat increases the distance between particles. These two basic effects of heat allows for these phase changes to occur.

You can discuss melting in a delicious way.

You can discuss melting in a delicious way.

Melting and Solidification

Melting is the process where a solid turns into a liquid. On the other hand, solidification is the process when liquid turns into solid. Let’s see what happens in these two processes. First, melting occurs when we add heat to solid and it changes into a liquid. As we know, heat will increase the speed of its molecules or particles. Second, it will make the solid particles move farther apart. As the molecules move faster and spread farther apart, the structure of the solid starts to fall apart. This is why ice turns to liquid water or why butter melts when we put it on our hot pancakes.

Examples of melting:

  • Ice turns to liquid water
  • Butter turns liquid when heated
  • Candle melts when it is lit
  • Ice cream turn from solid to liquid when it is removed from the freezer

On the other hand, solidification happens when we remove heat from a liquid. As the molecules cool down, they loose heat and energy. This draws the molecules closer together and move slower. As such, it begins to solidify. Placing water in the freezer removes the heat in the water and thus, slows down the molecules and make the molecules move closer to one another.

Examples of Solidification:

  • Candle wax hardens after it drips on a surface
  • Lava hardens to form metamorphic rocks
  • Molten glass is is blown and shaped and is left to cool and set

Important Reminders When Teaching Melting and Solidification To Your Child:

  • Use actual objects when showing melting and solidification - show them a candle melting when lit then let them observe what happens as the melted wax moves away from the heat source.
  • Melting and solidification are the opposite processes
  • Generally, the liquid phase has a higher energy level compared to the solid phase
  • We can say that the molecules of liquids are at a higher state of energy and motion compared to the molecules of solids.
You can teach evaporation when you are cooking.

You can teach evaporation when you are cooking.

Evaporation/Vaporization and Condensation

Evaporation is the process where liquid turns into gas. Conversely, when a gas turns into a liquid we call it condensation. Again, by adding or removing heat, these processes take place. Obviously, when we add heat to a liquid it increases its energy and molecular movement. Likewise, it increases the spaces between the molecules increase. When we heat water, the spaces get farther apart and when there is enough heat, air is released as bubbles.

Examples of Evaporation:

  • Drying clothes in the sun
  • Rubbing alcohol dries up in your hand
  • Evaporation of sweat on the surface of your skin

In contrast, condensation occurs when gas loses its heat. This can happen in many ways. For example, when gas comes into contact with a cold surface, it decreases its energy and condenses. This is the reason why droplets of water appear on the surface of your cold glass. Water vapor in the air gets cooled down and condenses on the surface of your glass.

Examples of Condensation:

  • Clouds form in the sky
  • Water droplets form on the a cold surface
  • Fog in the air
  • Dew forms on the leaves of plants and grass in the morning
  • Eye glasses clouds up when you breathe on it.

Important Reminders When Teaching Evaporation and Condensation To Your Child:

  • You really don't need to boil water for it to evaporate but it speeds up the process. Water evaporates naturally like when you leave spilled water on your table.
  • There are liquid that evaporates faster than others. For example, rubbing alcohol evaporates faster then water
  • Remember to use protective tools such as eye-wear and/or gloves when handling hot objects
  • Ice in a glass can show different phase changes of matter - melting of the ice, condensation forming on the surface of the glass, droplets of water eventually evaporates.
Soot from fires is a good example for the process of deposition.

Soot from fires is a good example for the process of deposition.

Sublimation and Deposition

The classic examples of phase changes in matter happen with a familiar substance -water. Ice turns into liquid (melting process) then liquid water turns into water vapor (evaporation process). And in reverse a gas condenses into liquid and liquid solidifies as ice. We may think that the solid must go through the liquid phase before it turns to gas and gas needs to turn into liquid before it becomes solid. However, there are cases when solid can directly turn into gas without going through the liquid phase. This process is called sublimation, while gas turning directly into solid is called deposition.

Examples of sublimation:

  • Dry ice turns to gas at room temperature
  • Mothballs slowly turns into gas when they are left in cabinets
  • Solid air fresheners (car and toilet) will slowly turn into gas to give off peasant odors
  • Sublimation ink in t-Shirt printing. Special sublimation inks in T-shirt printing use sublimation as a method of printing on shirts and fabrics. Ink pigments sublimates and are affixed to the surface of the fabric.

Examples of deposition:

  • Frost forms on cold surfaces during cold weather
  • Soot forms on objects near a fire
  • Carbon Dioxide gas turns solid when pressure is applied. This solid state of carbon dioxide is called dry ice.

Important Reminders when Teaching Sublimation and Deposition To Your Child:

  • Handling dry ice is dangerous since it extremely cold, use gloves and protective gear when possible
  • Since sublimation is solid turning into gas, make sure your place is well-ventilated when showing your sublimation to your child
  • Placing a spoon over a lit candle is an excellent way to show the deposition of soot on the surface of the spoon. Remember to use gloves for protection.

Phase changes in matter are physical changes that occur due to the addition or removal of heat. Moreover, heat affects matter in different ways. Some require tremendous amount of heat and energy in order to change its phase while others require little. Without a doubt, heat is a critical ingredient in the behavior of matter. These fundamental processes of matter allow us to interact and utilize numerous resources. As we learn more about the universe, we continue to unlock the mysteries of matter.

Let's test what you can remember:

For each question, choose the best answer. The answer key is below.

  1. Which one is an example of sublimation?
    • Water turns into ice
    • Dry ice turns to gas
    • Heat turns to cold
    • Dew forms on leaves
  2. What type of energy influences phase changes in matter?
    • Water
    • Gravity
    • LIght
    • Heat
  3. What phase change occurs when soot forms on surfaces near a fire?
    • Evaporation or Vaporization
    • Solidification
    • Deposition
    • Sublimation
  4. What happens to the particles of matter when heat is added?
    • The molecules move slower and closer to each other.
    • The molecules move faster and farther apart.
    • The molecules radiate light and start pulsating.
    • the molecules form a line while spinning around.
  5. What phase change occurs when you boil water?
    • Solidification
    • Melting
    • Deformation
    • Evaporation or Vaporization
  6. Which one is an example of condensation?
    • Drying clothes in the sun
    • Gravy becomes thicker as you heat it up in a sauce pan.
    • Dew rolls down the side of a stem.
    • Droplets of water form on the surface of your cold glass.
  7. What phase change occurs when ice turns to liquid water?
    • Melting
    • Evaporating
    • Solidifying
    • Condensing
  8. Which one is an example of solidification?
    • Candle wax becomes softer when it is lit.
    • Lava cools down and turns into rock
    • Cold dry ice turns into gas
    • Water droplets form on the cold surface of your glass.
  9. Which statement is true?
    • Some matter can change from solid to gas without going through the liquid phase.
    • Liquid matter needs heat in order to turn into ice.
    • Fog in the air is an example of solidification of water vapor.
    • Boiling water is an example of deposition.

Answer Key

  1. Dry ice turns to gas
  2. Water
  3. Deposition
  4. The molecules move faster and farther apart.
  5. Evaporation or Vaporization
  6. Droplets of water form on the surface of your cold glass.
  7. Melting
  8. Lava cools down and turns into rock
  9. Some matter can change from solid to gas without going through the liquid phase.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2021 JP Carlos

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