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Chapter 2: Matter and Change

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1 Chapter 2: Matter and Change
CP Chemistry THHS

2 Section 2.1 Matter Objectives
Identify the characteristics of matter and substances Differentiate among the three states of matter Define physical property and list several common physical properties of substances

3 Properties of Matter Matter anything that has mass and takes up space.
The amount of matter the object contains. Note mass ≠ weight. Substance Pure substances contain only one kind of matter. Question – is lemonade a substance?

4 Physical Properties Physical Property – a quality or condition of a substance that can be observed without changing the substance’s composition. Examples of physical properties are color, solubility, odor, hardness, density, melting point, and boiling point.

5 Properties of Solids, Liquids, Gases
Has a definite shape and volume Does not depend on the shape of its container Almost incompressible Liquid Particles are in close contact but not rigidly packed Can flow and take the shape of the container it is in A fixed volume can take a variety of shapes

6 Properties of Solids, Liquids, Gases
Gas or vapor “Gas” is limited to those substances who are in a gaseous state at room temperature. “Vapor” describes the gaseous state of a substance that is a liquid or a solid at room temperature. An example is steam. Gases take the shape of the container they are in. Particles are spaced far apart. Gases expand without limit to fill any space, so its volume changes with the container, unlike liquids. Gases tend to expand when heated.

7 Physical Changes A change which alters a given material without changing its composition is called a physical change Examples are cutting, grinding, bending Melting a metal, melting ice, boiling water Boil, freeze, dissolve, melt, condense, break, split, crack – all examples of physical changes

8 Section 2.2 - Mixtures Objectives
Categorize a sample of matter as a substance or a mixture Distinguish between homogeneous and heterogeneous samples of matter

9 Classifying Mixtures Salad with lettuce, tomatoes, carrots
A mixture is a physical blend of two or more substances. Salad with lettuce, tomatoes, carrots Blood – with water, cells, chemicals Each of these mixtures can vary in composition Heterogeneous mixture – if you were to sample the mixture in two different places the composition wouldn’t be the same (salad) Homogeneous mixture – if you were to sample the mixtures in two different places, the composition would be the same (salt water) Homogeneous mixtures are called solutions.

10 Phases in Mixtures System Examples Gas- gas Carbon dioxide and oxygen in nitrogen (air) Liquid – gas Water vapor in air (moist air) Gas – liquid Carbon dioxide in water (soda water) Liquid- liquid Acetic acid in water (vinegar) Solid – liquid Sodium chloride in water (salt water or brine) Solid – solid Copper in silver (sterling silver, an alloy) Phase – any part of a system with uniform composition and properties is a phase. Homogeneous mixtures are one phase. Heterogeneous mixtures are two or more phases. Oil and vinegar separates into two phases

11 Separating Mixtures Some mixtures can be separated by physical methods. Magnet to separate iron filings from sulfur. Distillation can be used to separate pure water from impurities.

12 Section 2.3 – Elements and Compounds
Objectives Explain the difference between an element and a compound. Identify the chemical symbols of common elements, and name common elements given their symbols

13 Elements vs. Compounds Elements are the simplest forms of matter that can exist under normal laboratory conditions. This statement does not include the subatomic level (protons, neutrons, etc.) Elements cannot be separated into simpler substances by chemical means . Examples: Oxygen, carbon, nitrogen Compounds are made when two or more elements combine chemically, like H2O or CO2 . Compounds can be separated into simpler substances by chemical means.

14 Compounds Example: Sodium chloride NaCl (table salt) Composed of Chlorine (which is the gas Cl2 as an element) and Sodium (which is the solid Na as an element) Anyone know why sodium (solid) is normally stored in oil?

15 Chemical Symbols Some chemical symbols are easy to remember
Carbon = C, Oxygen = O, Nitrogen = N Others are not so easy, and come from Latin or other sources Sodium = Na (from Natrium) Potassium = K (from Kalium) Gold = Au (from Aurum) Lead = Pb (from Plumbum) A list of more unusual symbols is on page 40 and on my website for you to review! You will need to know at least the top 4 rows of the periodic table - name and symbol

16 Section 2.4 – Chemical Reactions
Objectives Differentiate between physical and chemical changes in matter Apply the law of conservation of mass

17 Changing reactants to products
Chemical reactions - one or more substances react and change into a new substance Example: iron + oxygen = rust (iron oxide) The starting substances are called reactants The ending substances are called products Words that convey that a chemical change has occurred include: burn, rot, rust, decompose, ferment, explode, corrode, etc.

18 Chemical Properties Chemical properties tell you something about the ability of a substance to undergo a chemical reaction to form new substances Rusting is a chemical property of iron Rotting is a chemical property of waste organic material Burning is a chemical property of wood

19 Examples of chemical reactions

20 Chemical reactions How can you tell if a reaction has taken place?
Energy is always given off or absorbed during a reaction Change in color or odor – silver chromate forms when yellow sodium chromate is added to clear silver nitrate (above right) Production of gas or solid from a liquid zinc + hydrochloric acid releases H2 gas >>> Most chemical changes are not easily reversed, like many physical changes are.

21 Conservation of Mass – Key concept
When you burn wood at a beach bonfire, the reaction produces carbon dioxide gas (CO2), water vapor (H2O) and some ash. It may seem that the amount of matter has been reduced when you look at the ash pile. However, if you could carefully measure the mass of the reactants and the mass of the products, you would find they are the same. This is the law of conservation of mass – mass is neither created or destroyed in a chemical reaction.

22 Conservation of Mass Let’s say you have 32 grams of methane(CH4) that combine with 128 grams of oxygen gas to form 88 grams of carbon dioxide and an unknown number of grams of water. How much water is formed? 𝐶 𝐻 4 +2 𝑂 𝐶 𝑂 2 + 𝐻 2 𝑂 = x grams Solve for x x = = 72 g This is because mass of total reactants must equal mass of total products.

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