Physical Properties (Chapter 3-Section 2)

Identifying Physical Properties A physical property of matter is a characteristic that can be observed or measured without changing the matter’s identity. Examples of physical properties are melting temperature, density, hardness, thermal conductivity, and electrical conductivity.

Physical Changes: No New Substances A physical change is a change of matter from one form to another without a change in chemical properties. Physical changes include dissolving, cutting, bending, freezing, and melting. Physical changes do not change the identity of the matter.

Chemical Properties (Chapter 3-Section 3)

Identifying Chemical Properties Chemical properties describe matter based on its ability to change to new matter – or matter whose identity is different than the original matter Reactivity – it is the ability of a substance to change into one or more substance. Flammability – it is the ability of a substance to burn

Differences Between Physical & Chemical Properties Physical properties are easy to observe without changing the identity of the substance Chemical properties are not as easy to observe – Example: you only see wood that is flammable only when it is actually burning. Even though it is harder to observe, substances always have chemical properties

Characteristic Properties Used to identify a substance – may be physical or chemical. The properties are the same for all samples of the given substance (even if the sample size changes) Examples: density, reactivity, flammability, melting point, boiling point

Chemical Changes When one or more substances change into new substances that have new and different properties. You can learn about a substance’s chemical properties by observing the chemical changes it undergoes. Example: Alka-Seltzer tablets (citric acid and baking soda) react with water and begin to bubble and fizz (CO2 produced)

Signs of a Chemical Change The signs of a chemical change include a change in… color Smell/odor gas production (bubbles, fizzing and foaming) changes in temperature (heat produced -gets warmer or heat absorbed - gets colder) sound or light being given off formation of a precipitate (solid from liquids)

Physical vs. Chemical Changes How do you know if a substance has undergone a physical change or a chemical change? Ask… did the composition of the substance change? Which are physical, which are chemical changes? a) water boiling b) vinegar poured over baking soda c) soda can crushed d) green fireworks e) salt dissolved in water f) soured milk a,c,e are physical changes; b,d,f are chemical changes

Conservation of Matter The law of conservation of matter states that matter is neither created nor destroyed. Your type of matter may change, but all parts before (reactants) and after (products) can be accounted for.