What do I need to know for Chapter 1-3 Exam? 1. Scientific law vs. Theory vs. Hypothesis Scientific law is a statement that summarizes a pattern found in nature. Theory is an explanation for a pattern found in nature. Hypothesis is a proposed answer to a question.

2. Scientific notation Remember if the number is greater than 10 the exponent will be positive. If the number is less than 1 the exponent will be negative. (I would rather have $10 than $1 so 10 is a positive thing and 1 is a negative thing.) Write in scientific notation x 10 2

3. SI unit conversion How many meters are in mm? K H D Bu D C M First place the decimal point to the right of the mm and put the other digits under the units in order Then move the decimal point to the right of the Bu (because you are looking for meters which is a base unit) and write your answer Then move the decimal point to the right of the Bu (because you are looking for meters which is a base unit) and write your answer m

4. SI temperature scale for water FreezingBoiling (Melting)(Condensation)Point 0⁰C100⁰C

5. Which graph to use? to show a comparison between variables to show a part of the whole To show how one variable relates to another variable Bar graph Circle (pie) graph Line graph

6. Matter Classifications What is a pure substance? Examples: A material that always has exactly the same chemical composition. It is not a mixture. elements or compounds What is the difference between an element and a compound? Elements have only one type of atom and cannot be broken down. Ex: Elements have only one type of atom and cannot be broken down. Ex: Au, C, O, Mg Compounds are two or more elements chemically combined. Their atoms always combine in the same ratio. Ex: H 2 0, CO, CO 2, C 6 H 12 O 6

6. Matter Classifications (cont.) What is a mixture? Examples: A material that has a variable composition. It is not a pure substance. Homogeneous and Heterogeneous What is the difference between a homogeneous and a heterogeneous mixture? Homogeneous mixtures have particles so small that they look the same throughout. Ex: air, stainless steel, coffee, tap water, salt water. These last three examples are also known as solutions because they are liquid mixtures.

6. Matter Classifications (cont.) Heterogeneous mixtures have particles that are noticeably different from one another. Ex. pizza, chocolate chip cookies. When the heterogeneous mixture is a liquid, they are classified as colloids or suspensions. Colloids have particle sizes that range between a solution and a suspension. Ex: fog, milk, gels Suspensions have larger particles that will settle out upon standing. They need to be shaken. Ex: ocean water, salad dressing, chocolate milk

7. Physical Properties can be observed or measured without changing the chemical composition of the substance. Ex. malleability - the ability of a material to be hammered without shattering. Ex. metals, modeling clay, wax hardness - the resistance to being scratched Ex. Diamonds are the hardest substance. They will scratch all other substances. Chalk has a hardness of 1. It will be scratched by most other materials.

7. Physical Properties (cont.) viscosity - a material’s resistance to flowing Ex. water has a low viscosity and motor oil has a high viscosity density - the ratio between a material’s mass and its volume. It does not change no matter what size the sample is. other physical properties include: size, shape, volume, mass, color, boiling and melting points.

7.Physical Properties (cont.) Using Melting Point and Boiling Point Which substances would be a solid at 0⁰C? S S L L G G O ⁰C Which substances would be a solid at 0⁰C? Acetic Acid and Gold Which substance would be a liquid at -200⁰C? -20O ⁰C Which substance would be a liquid at -200⁰C? Nitrogen

8. Separating mixtures using physical properties: size of particles and boiling point Filtration uses the size of the particles to separate a mixture. Screens, sieves, and filter paper all have holes that allow only particles smaller that their holes to pass through, leaving larger particle behind.

8. Separating mixtures using physical properties: size of particles and boiling point (cont.) Distillation uses the boiling points of the substances in the mixture to separate them. Each substance has its own unique boiling point. As the temperature is increased, the substance with the lowest boiling point will change to a gas first, while the other substances will still be a liquid.

9. Chemical Properties any property that produces a change in the chemical composition of a material Ex flammability - the ability of a material to burn in the presence of oxygen reactivity - how readily a substance combined chemically with other substances Evidence of a chemical change change of color Ex. leaves in the fall, rust, tarnish production of a gas Ex. fizzing, bread rising formation of a precipitate Ex. cottage cheese

10. Physical Changes vs. Chemical Changes During physical changes, the composition of the materials do not change Ex cutting hair, crumbling paper, melting ice During chemical changes, new substances are formed. Ex. - breaking down water into hydrogen and oxygen, rusting (iron combines with oxygen to form iron oxide), baking a cake

11. 5 States of matter Solids Liquids - definite shape, definite volume, strong attraction of particles so they packed close together and arranged in a pattern - no definite shape, definite volume, weaker attraction of particles than in a solid so they packed farther apart and are randomly arranged, shape determined by its container

11. 5 States of matter (cont.) Gases Plasmas BEC’s - no definite shape nor volume, attraction of particles so weak it can be ignored, volume and shape determined by its container - form under extremely high temperatures (like in the sun) or high frequency electricity, makes up 99% of all the matter in the universe - forms under extremely low temperatures (0 K), causes atoms to act as one large particle

12.Gas Laws Factors that affect gas pressure Boyle’s Law Charles’ Law –increase pressure-decrease volume (temperature and number of particles remain constant) P 1 V 1 =P 2 V 2 - temperature, volume and number of particles - increase temperature-increase pressure (volume and number of particles remain constant)

13.Phase Changes 6 Phase Changes 1. solid to liquid 2. liquid to solid 3. liquid to gas a. occurs at the boiling point b. occurs below the boiling point (at the surface of the material) 4. gas to liquid 5. gas to solid 6. solid to gas Melting - Freezing - Vaporization - Condensation - Deposition - Sublimation - Boiling - Evaporation -

14. Energy Transfers During Phase Changes During a phase change the temperature of the substance ______________ the energy needed to change a solid to a liquid (melt) the energy needed to change a liquid to a gas Heat of Fusion - DOES NOT CHANGE. Heat of Vaporization -

14. Energy Transfers During Phase Changes (cont.) Types of energy transfers Endothermic Exothermic - energy is absorbed from its surroundings (substance gets warmer) Ex: melting, vaporization, sublimation - energy is released to the surroundings (substance gets cooler) Ex: freezing, condensation, deposition