In this unit, students expand their understanding of solids, liquids, and gases and how they change. Through their experiences, students are introduced to the following concepts, skills, and attitudes.

• Changes occur all the time in the world around us.
• Some changes happen quickly, and others take place over a period of time.
• Substances can be classified as solids, liquids, or gases.
• Solids, liquids, and gases can be described by their properties. These properties include color, size, shape, odor, texture, and weight.
• Water can freeze into a solid and then melt into a liquid again.
• Water can evaporate into a gas and then condense into a liquid again.
• Mixtures can be made by combining solids, liquids, or gases, or a combination of these.
• A substance can change in appearance yet remain the same substance.
• Some mixtures can be separated using a sieve, a filter, or the processes of evaporation and chromatography.
• When some solids—such as salt and sugar—are added to water, they dissolve and seem to disappear.
• Some dissolved solids can be recovered as crystals through evaporation.
• When a solid is dissolving in a liquid, the size of the solid particles, the temperature of the liquid, and stirring can affect the speed at which the solid dissolves.
• When two or more substances are mixed, a chemical reaction may occur. Indicators of a chemical reaction can include a change in color, a change in temperature, or the production of a new substance, such as rust or gas.

Skills

• Observing and describing changes that occur in everyday experiences.
• Observing and describing the properties of solids, liquids, and gases.
• Observing and describing changes that result from mixing substances.
• Observing and describing water as it freezes, melts, evaporates, and condenses.
• Comparing mixtures.
• Separating mixtures with a sieve, a filter, and the processes of evaporation and chromatography.
• Performing tests to investigate a mystery mixture.
• Communicating ideas, observations, and experiences through writing, drawing, discussion, and presentation.
• Predicting, observing, classifying, and recording results in a journal and on record sheets, class charts, and brainstorming lists.
• Designing and testing a recipe in which substances are mixed to create a chemical reaction.

Attitudes

• Becoming curious about the changes that occur in the world around us.
• Developing an interest in investigating changes in the properties of solids and liquids.
• Developing an appreciation for the importance of recording and organizing information on record sheets, science journals, and class charts.