Physical and Chemical Properties and Changes
Objective and essential question Objectives: SWBAT distinguish between physical and chemical changes and properties. Essential Question: What are the properties that classify a physical or chemical change? In what ways is a chemical change different from a physical one?
Physical Properties Describes how the substance looks/feels, etc Examples: melting point, color, mass, luster (shine), hardness, temperature
Particle Picture: Physical Changes Definition: Change the appearance, not the substance or chemical composition Examples: Hair cut, state change (melting), sugar cube dissolving
Particle Picture: chemical Changes Definition: Produces a new substance (changes chemical composition) Involves a chemical reaction Examples: fireworks, rust, burning coal, baking bread
Chemical Properties and changes Examples: Describes how a substance reacts Substance has to chemically change to observe it Examples: chemical stability, flammability, ability to oxidize or react
Observable factors of a chemical Change Precipitate Formation Light or Heat Released Gas Formation Color Change
Summary: Physical vs. chemical changes Physical Change Chemical Change Does not involve changes in identity of a substance Change the (chemical) identity of the substance Cause a change in state or shape Involves a chemical reaction, Causes a change on a particle level
Sample Test Question Which process involves a chemical change? melting of ice boiling of water freezing of water decomposing of water (H2O) into H and O
Which process involves only (a) physical change(s)? Sample Test Question Which process involves only (a) physical change(s)? Burning gasoline Reacting hydrochloric acid with ammonia Combining hydrogen and oxygen to form water (H2O) Melting barium
Mixing two kinds of paint produces a physical change because: Sample Test Question Mixing two kinds of paint produces a physical change because: A new substance is formed and the color changes The color may change, but no new substance is formed A new liquid is formed (different color paint) This is not a physical change. It is a chemical change.
Which of the following always takes place in a chemical reaction? Sample Test Question Which of the following always takes place in a chemical reaction? A new product (substance) forms The temperature increases The mass of the product changes A gas forms
Sample Test Question Given the particle diagram: Which particle diagram best represents this same substance after a physical change has taken place?
Extra Practice
Identify whether the following are physical or chemical changes or properties and explain why A sheet of copper can be pounded into a bowl Digesting food Two cans of paint mixed together Potassium Burns when placed in water Acid in tomato sauce can corrode aluminum foil Barium melts at 725 C Mixing baking soda and vinegar Water freezing and forming ice Gasoline is flammable An apple will turn brown if left in oxygen
Chemical or physical change? Karla broke her pencil and she can’t put it back together. She thinks it’s a chemical change. Is she correct? Why?
Chemical or physical change? If Ms. Hagan puts food coloring in water, the water color changes so it must be a chemical change right?
HOT Question 1 Trey made the following statement when speaking to his lab partners: "Breaking a rock into several pieces is an example of a chemical change. When I started, I had one substance (a rock). At the end, I had several different substances (the different sized pebbles).“ Assess the validity of his claim and justify your reasoning.
HOT Question 2 Water (H2O) is made of Hydrogen (a gas) and Oxygen (also a gas). Water is a liquid at room temperature. Based on this, it seems like hydrogen and oxygen combining to form water is a physical change (gases turning into solids). Do you agree with this assessment? Why or why not?
HOT Question 4 The diagram below shows particles at the molecular level undergoing a change of some type. Assess the diagram and explain what type of change you believe to be taking place. Give one example of the type of change this might be. Be sure to justify your answer.
HoT Question 5 The image shows the decomposition of Mercury Oxide: Mercury oxide Oxygen + Mercury Mercury oxide is undergoing a chemical change. Prove this using at least three pieces of evidence.