what is the difference between melting and dissolving

This central idea is explored through:

Contrast between student’s point of view and science

Contents

Students experience everyday

For many students at this level, melting and dissolving are considered indistinguishable. Although two materials are required for the dissolution process, students tend to focus only on solids and they consider the process to be similar to ‘melting’. They often assume that the freezing of all ingredients takes place only at cold temperatures such as in a refrigerator or freezer. Usually melts are considered to be substances that convert to water. This is reinforced because children see heat involved in both processes – they know if you want to dissolve more sugar, you warm the water. water-soluble sugar), students often consider salt/sugar just gone. Typically, students will make comments such as:

  • solute (solute) in a solution that does not take up any space
  • only the taste and/or color left when something dissolves, not the substance itself
  • Substances change into new substances when they dissolve.

Scientific point of view

Read more: 15mm in inches The adhesion and freezing of materials depends on their temperature. When something melts then that liquid is a solid like substance. Not all solids melt when heated (they can burn or decompose). Dissolution may involve chemical changes (eg, antacid tablets mixed with water or metal dissolved in acid).

Critical Teaching Ideas

  • Melting and dissolution are not the same.
  • In melting only one substance is involved and liquid and solid are the same substance. Heat is required for melting to occur.
  • Dissolution involves two materials; The resulting solution is a mixture of both.
  • The solute is still present in the solution even though it cannot be seen.
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globeExplore the relationship between ideas about matter in Concept Development Map – States of Matter to clarify the difference between melting and dissolving. These are concepts familiar to students that are built from everyday experiences. Teaching should be directed at turning their often unscientific explanations into more scientific ones. and dissolving a range of materials with which students are familiar, such as chocolate, cooking fats, and candle wax, and the use of common solvents such as turpentine, eucalyptus oil, and acetone may be beneficial. . Change and teaching should include a multi-step process. Students need time to articulate their preconceptions about melting and dissolution in activities like Predict-Observe-Explain. Opportunities should be provided to explore their own and others’ ideas – this may involve teamwork and role-playing.

Teaching activities

Opens discussion through shared experiences and promotes reflection and clarification of existing ideas

This image shows an egg poacher being used to melt four different substances.Allow students to experience substances other than water and melting ice. Place fat, butter, wax, and chocolate in four places in the whisk. Gently warm the poaching tool and note when each substance melts. Students can be asked to predict which substance will dissolve first. Then place the flask in ice to cool and ask students to predict and observe the order in which the substances solidify. Use analogy to explain melting; for example, talk about building a house out of Lego and pulling the bricks apart to form a block of loose bricks. Students will have the opportunity to observe dissolution and distinguish it from melting. Dissolve colored materials such as copper sulphate (available from the nursery) and Condy’s crystals (purple potassium) in the water. Both of these substances give a bold color, which helps students to monitor changes when observing these substances dissolve. Students should compare how this process differs from the melting observation above. Students can then dissolve substances in solvents other than water, such as eucalyptus oil and acetone (nail polish remover). This may involve using cleaning products around the house, designed to dissolve fats and oils. To see the downside of dissolving, pour a small amount of concentrated solutions such as copper sulphate, salt water or shellac in the form of methylated alcohol into the dish and allow to evaporate. Students can observe changes over time. Using the Predict-Observation-Explain technique ask students to predict what will happen to the mass of water when the sugar dissolves. Record the changes in weight when the sugar is added to the water and stir until dissolved. (You can show that the resulting solution has the same mass as the sugar and water separately).

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Clarifies and reinforces ideas to/by communicating to others

Students can build PowerPoint posters/slides to identify examples of melting, solidifying, and dissolving changes they’ve seen around their homes. This will help them identify some of the differences between molten and dissolve. Some other projects students can explore include glass blowing and silver jewelry manufacturing. Read more: what does com.samsung.android.app.dressroom mean.

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