Presentation on theme: "Bok! Do Now: Pick up your stampsheet and take out your HW draw three pictures to represent: solid liquid gas Agenda: introduce matter HW: Ch 3 #1,2,5,8,11-14,19,20."— Presentation transcript:
Bok! Do Now: Pick up your stampsheet and take out your HW draw three pictures to represent: solid liquid gas Agenda: introduce matter HW: Ch 3 #1,2,5,8,11-14,19,20
What is Matter? Matter is anything that takes up space and has mass. Mass- amount of material or “stuff” in an object Weight is due to gravity, and changes from location to location; mass is always constant.
Why isn’t matter classified according to its physical characteristics, such as color? Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.
Why isn’t it a good idea to classify matter by its phases? Because one kind of substance can exist in more than one phase – such as H 2 0. And matter changes phases rather easily.
Types of Properties Extensive- depend on the amount of matter Examples: volume, mass, amount of energy Intensive- do not depend on the amount Examples: density, boiling point, ability to conduct
Types of Properties Physical properties- characteristics that can be observed or measured without changing the identity of a substance (adjectives) Observed with your five senses Chemical properties- relates to a substances ability to undergo changes that transform it into a different substance Easiest to see when a chemical is reacting
Physical vs. Chemical Change Physical change will change the visible appearance, without changing the composition of the material. Boil, melt, cut, bend, split, crack Is boiled water still water? Can be reversible, or irreversible Chemical change - a change where a new form of matter is formed. Rust, burn, decompose, ferment
States of matter 1. Solid- matter that can not flow (definite shape) and has definite volume. 2. Liquid- definite volume but takes the shape of its container (flows). 3. Gas- a substance without definite volume or shape and can flow. 4. Vapor- a substance that is currently a gas, but normally is a liquid or solid at room temperature. (water vapor?)
Solid Liquid Gas Melt Evaporate Condense Freeze
Recognizing Chemical Changes 1) Energy is absorbed or released (temperature changes hotter or colder) 2) Color – it changes 3) Gas production (bubbling, fizzing, or odor change; smoke) 4)formation of a precipitate - a solid that separates from solution (won’t dissolve) 5) Irreversibility - not easily reversed But, there are examples of these that are not chemical – boiling water bubbles, etc.
Chemical Change A change in which one or more substances are converted into different substances. Heat and light are often evidence of a chemical change.
Types of Matter Substance- a particular kind of matter - pure; is uniform (all the same) and has a definite composition (examples are elements & compounds) water; gold Mixture- more than one kind of matter; has a variable composition
Mixtures: Heterogeneous – the mixture is not uniform in composition Chocolate chip cookie, gravel, soil. Homogeneous - same composition throughout; called “solutions” Kool-aid, air, salt water Every part keeps it’s own properties.
Solutions = Homogenous Mixed molecule by molecule Can occur between any state of matter: Air, vinegar, stainless steel (Fe, Cr, Ni) Some can be separated easily by physical means: or salt and water Other methods: distillation- takes advantage of different boiling points
Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. They are also colloids.
Example: Separate iron filings from sulfur using a magnet.
Filtration: separates a solid from a liquid in a heterogeneous mixture
Separation of a Mixture Distillation: takes advantage of different boiling points. NaCl boils at 1415 o C
Distillation of Crude Oil (Refining) Crude Oil is a mixture of Hydrocarbons
Substances: How are elements and compounds different?
Element: the simplest form of matter that has a unique set of properties. Cannot be broken down into a simpler form (that retains its unique properties) (All of them are listed on the periodic table!) Ex: carbon, helium, barium, nitrogen, zirconium, phosphorus…
Compound: substances that can be broken down only by chemical methods Ex: magnesium oxide (MgO), water (H 2 O), sodium chloride (NaCl) … Made of two or more atoms, chemically combined (not physical blend!)
Properties of Compounds In general, the properties of compounds are quite different from those of their component elements. When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties.
Compound or Mixture CompoundMixture Made of one kind of material Made of more than one kind of material Made by a chemical change Made by a physical change Definite composition Variable composition
2.3 REVIEW: Substances vs. Mixtures How can substances and mixtures be distinguished? If the composition of a material is fixed, the material is a substance. If the composition of a material may vary, the material is a mixture.