Think about it: 1. What’s the difference between cutting and burning a piece of wood? 2. How should the mass of the products (results of each process) compare to the original piece of wood?

Physical and Chemical Changes AGENDA: Distinguishing and identifying changes Steel wool demonstration (this will get started early in the lesson, but we will revisit it several times. Guided practice to distinguish changes. Independent practice And how to tell the difference

Physical Change Chemical Change Substance may seem different, but the way the atoms combine is the same. Changes the way the atoms combine to form substances (new substances will have different physical properties)

Steel Wool Demonstration We will be taking observations every 5 minutes for this demonstrations Teachers: assign a time keeper for the demonstrations and have students assist with recording observations

It’s a physical change if It’s a chemical change if It’s a physical change if It changes shape or size It dissolves. It changes phase (freezes, boils, evaporates, condenses) It burns Temperature changes without heating/cooling It bubbles (makes a gas) It changes color It forms any new materials How are these different? Students should distinguish boiling (phase change) from creating of a new gas. Boiling water and the bubbles (carbon dioxide) released from mixing vinegar and baking soda can be used as a reference for students.

What kind of change is it if someone... Tears up paper? Physical change Mixes salt and water? The following examples can be used as think-alouds to model how students should justify answer. Use of individual or group whiteboards or another type of response system can be used to check for understanding.

What kind of change is it if someone... Burns paper? Chemical change Evaporates salt water? Physical change

What kind of change is it if someone... Mixing vinegar and baking soda? Chemical change

Guided Practice (Left Side): For each of the following examples Decide whether the changes is chemical or physical Justify your answer.

This is the only slide from the guided practice that has a modeled justification. All other examples only state whether to the processes is a physical or chemical change. Boiling water is a physical change because the liquid water changes state to become water vapor when enough heat is added.

Rusting (oxidation) Chemcal

Physical or Chemical Change? Painting Wood PHYSICAL

Physical or Chemical Change? Burning Paper CHEMICAL

Physical or Chemical Change? Digestion of food CHEMICAL

Physical or Chemical Change? Sugar dissolving in water PHYSICAL

Physical or Chemical Change? A pond freezing in winter PHYSICAL

Physical or Chemical Change? Cutting wire PHYSICAL

Law of Conservation of Mass Matter can never be created or destroyed. This means: During any physical or chemical change, the total mass of all substances before and after the change remains the same. Sometimes, measuring all the components of a change is difficult. Example: if you boiled water, it would be difficult to measure the mass of all the water vapor.

Temperatures influence on chemical changes As with the steel wool demonstration, adding energy in the form of heat typically speeds up the change. This means: During any physical or chemical change, the total mass of all substances before and after the change remains the same.

Time (min) Mass (g) Color Other Observations   Room temp. Hot Room temp.