Physical & Chemical changes Review & reinforcement How does one determine the difference between chemical and physical changes?

Physical & chemical changes Matter can undergo 2 types of changes: physical changes and chemical changes. Do you remember what the main differences are between physical and chemical changes? Can you give any examples of a physical change or a chemical change? It is important to note that all matter can go through changes!

Goal for today: While we have a pretty good understanding of the difference between physical and chemical changes, we have to learn a little bit more about how to determine the difference between these two types of changes to matter in everyday situations.

Physical & chemical changes Demonstration Experiment #1: Vinegar and Sugar Experiment #2: Vinegar and Baking Soda So what clues can we use to determine if a chemical reaction has taken place? [Brainstorm & be ready to share out!]

Physical changes A substance has characteristic properties such as density, a boiling point, melting point & solubility.

Physical changes Physical changes DO NOT change the structure of the matter when it is observed or described. Structure refers to how the atoms are put together. A substance has characteristic properties such as density, a boiling point, melting point & solubility. Physical properties involve things that can be measured without changing the chemical properties. Matter can undergo physical changes which affect only physical properties. Physical changes can involve changes in energy.

Solubility A substance has characteristic properties such as density, a boiling point, melting point & solubility. Physical properties involve things that can be measured without changing the chemical properties. Matter can undergo physical changes which affect only physical properties. Physical changes can involve changes in energy. Solubility means the amount of solute that can be dissolved in a specific volume of solvent under certain conditions. A solute’s solubility depends on the chemical nature of the solvent. Another important factor influencing solubility is temperature. The most common solvent is water.

Physical Changes: Solubility A substance has characteristic properties such as density, a boiling point, melting point & solubility. Physical properties involve things that can be measured without changing the chemical properties. Matter can undergo physical changes which affect only physical properties. Physical changes can involve changes in energy. Solubility means the amount of solute that can be dissolved in a specific volume of solvent under certain conditions. A solute’s solubility depends on the chemical nature of the solvent. Another important factor influencing solubility is temperature. The most common solvent is water.

Physical Changes Changes in the state of matter: only the state of the matter changes, the substance does not. Matter can undergo physical changes which affect only physical properties. Physical changes can involve changes in energy. Investigate the physical properties of pure substances in terms of unique temperatures at which each substance undergoes state changes.

Structure of water Structure of ice Structure of steam Miss Lamb, Are you sure that when matter changes from one state to the next that it is only going through a physical change? I mean, can you really prove it to me scientifically? -Skeptical in Linglestown Structure of ice Matter can undergo physical changes which affect only physical properties. Physical changes can involve changes in energy. Investigate the physical properties of pure substances in terms of unique temperatures at which each substance undergoes state changes. Structure of steam

Chemical Properties Our NC standard does not include chemical properties, but I still like to go over them, so this section would be considered extension in the state of NC

Chemical Properties Chemical properties describe a change in structure. The substance is forever changed, it can not be changed back. extension

Chemical Properties: During the demonstration of the baking soda and vinegar, we saw bubbles form, signaling a chemical reaction. What other clues might signal a chemical reaction? extension Found in the first column of the periodic table of elements, the alkali metals react readily with many substances in the environment, even with relatively inert substances, such as water. Because of their extreme reactivity, alkali metals rely on special containment to prevent inadvertent reactions that tarnish the purity of the sample. Alkali metals share certain identifying characteristics: extreme reactivity, pliability, silvery color and low density

Signs of chemical changes Clue Example Changes in color [be careful here] green tomato turns red cake browns in oven apple in the air browns fried egg Changes in odor burning wood spoiled food Changes in temperature without being heated/cooled rotting leaves in compost pile become warm hand warmer packs Bubbles form Baking soda & vinegar Yeast & water Gives off gas/gases Burning wood gives off carbon dioxide and water vapor Yeast & water releases carbon dioxide gas New solids form Rust is created

Let’s check & make sure we understand!

“Name that change!” challenge You will now be given the opportunity to travel around to different stations around the room. Visit each station and follow the directions. Determine whether the station represents a physical or a chemical change. Justify and explain your answer.