Elect a spokesperson. Plenary 1 In a plenary: Invite reports from each group. Lead students towards a scientifically correct viewpoint using molecular models of water. Ask them to correct their worksheet, if they need to. Demonstration and activity: stage 3 Introduce the next task, which is to look at the liquid—solid state change. Place a beaker of ice cubes in front of the class. This can be warmed gently, but may also be left at room temperature.
Invite students to work individually on completing the second page of the worksheet. Activity: stage 4 Reform the groups, or create different groups of four students.
Plenary 2 In a plenary: Invite reports from each group. Use a model of ice to support the development of the concept that bonds exist between water molecules in ice.
Reinforce that these terms apply to all substances. Feedback Provide written feedback commenting on the extent to which students have demonstrated learning of the scientific viewpoints about state changes.
Commentary Discussing personal viewpoints with others allows students to review each other and feed back. Wear eye protection. It is the responsibility of the teacher to carry out appropriate risk assessments for the demonstrations. Boil the water in one beaker. Place the water molecule models in the second beaker, to use in explaining the state change. Answers What happens when water boils? What happens when ice melts? Skill development Children will develop their working scientifically skills by: Drawing conclusions and raising further questions that could be investigated, based on their data and observations.
Using appropriate scientific language and ideas to explain, evaluate and communicate their methods and findings. Learning outcomes Children will: Compare and group materials together according to whether they are solids, liquids or gases. Observe that some materials change state when they are heated or cooled. This means that a plasma has very different properties from those of an ordinary gas. Plasmas occur naturally in flames, lightning and auroras.
Other, more exotic states of matter can occur at extremely high energy levels or at extremely low temperatures, where atoms and molecules or their components arrange in unusual ways. Scientists also sometimes distinguish between crystalline solids where the atoms and molecules are lined up in a regular pattern and glassy solids where the atoms and molecules are attached in a random fashion.
Elements and compounds can move from one phase to another phase if energy is added or taken away. The state of matter can change when the temperature changes. Generally, as the temperature rises, matter moves to a more active state. For example, water vapour gas can condense and become a drop of water. If you put that drop in the freezer, it would become a solid. No matter what phase it is in, it is always water — two atoms of hydrogen attached to one atom of oxygen H 2 0.
In a liquid, the atoms and molecules are loosely bonded. When a substance is cooled, its internal energy decreases:. The particles in a substance stay the same when it changes state - only their closeness, arrangement or motion change. This means that:. For example, 10 g of water boils to form 10 g of steam, or freezes to form 10 g of ice. For example, liquid water turns into steam when it is heated enough, and it turns into ice when it is cooled enough.
The closeness, arrangement and motion of the particles in a substance change when it changes state. Simple diagrams of particles in a solid, liquid and a gas are shown like this:.
The table summarises what happens to the particles in a substance when it gains energy, and it melts or boils ie changes state :.
Evaporation happens below the boiling point of a liquid. When the liquid reaches its boiling point, evaporation happens very quickly and the liquid boils. The table summarises what happens to the particles in a substance when it loses energy, and it freezes or condenses ie changes state :.
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