Matter – Properties & Changes

1. Matter – Properties & Changes Honors Chemistry Chapter 3

2. Section 3.1 – Properties of Matter 1. Substances • Matter is anything that has mass and takes up space. • Matter is everything around us. • Matter with a uniform and unchanging composition is a substance.

3. 2. Physical Properties of Matter • A physical propertyis a characteristic that can be observed or measured without changing the sample’s composition. • Extensive propertiesare dependent on the amount of substance present, such as mass, length, or volume. • Intensive propertiesare independent of the amount of substance present, such as density.

4. 3. Chemical Properties of Matter • The ability of a substance to combine with or change into one or more other substances is called a chemical property. • The ability of Iron to form rust • The inability of a substance to change into another substance • Copper turning green in the air

5. A substance can change form–an important concept in chemistry. • Chemical properties can change with specific environmental conditions, such as temperature and pressure. • Observations of properties may vary depending on the conditions of the immediate environment. 4. Observing Properties of Matter

6. 5. States of Matter • The physical forms of matter, either solid, liquid, or gas, are called the states of matter. • Solidsare a form of matter that have their own definite shape and volume. • The particles of matter in a solid are very tightly packed.

7. States of Matter (cont.) • Liquidsare a form of matter that have a definite volume but take the shape of the container. • The particles in a liquid are not rigidly held in place and are less closely packed than are the particles in a solid: liquid particles are able to move past each other. • Gaseshave no definite shape or volume. They expand to fill their container. • Compared to solids and liquids, the particles of gases are very far apart. • Vaporrefers to the gaseous state of a substance that is a solid or liquid at room temperature.

8. End of Section 3.1

9. Section 3.2 – Changes in Matter 6. Physical Changes • A change that alters a substance without changing its composition is known as a physical change. • A phase changeis a transition of matter from one state to another. • Boiling, freezing, melting, and condensing all describe phase changes in chemistry.

10. 7. Chemical Changes • A change that involves one or more substances turning into new substances is called a chemical change. • Decomposing, rusting, exploding, burning, or oxidizing are all terms that describe chemical changes.

11. The law of conservation of massstates that mass is neither created nor destroyed in a chemical reaction, it is conserved. • The mass of the reactants equals the mass of the products. massreactants = massproducts 8. Conservation of Mass

12. End of Section 3.2

13. Section 3.3 – Mixtures of Matter 9. Mixtures • A mixtureis a combination of two or more pure substances in which each pure substance retains its individual chemical properties. • A homogeneous mixtureis a mixture where the composition is constant throughout. • Homogeneous mixtures are also called solutions. • A heterogeneous mixtureis a mixture where the individual substances remain distinct.

14. Filtrationis a technique that uses a porous barrier to separate a solid from a liquid in a heterogeneous mixture. • Distillationis a separation technique for homogeneous mixtures that is based on the differences in boiling points of substances. • Crystallizationis a separation technique for homogenous mixtures that results in the formation of pure solid particles from a solution containing the dissolved substance. • Sublimationis the process of a solid changing directly to a gas, which can be used to separate mixtures of solids when one sublimates and the other does not. • Chromatographyis a technique that separates the components of a mixture on the basis of tendency of each to travel across the surface of another material. 10. Separating Mixtures

15. End of Section 3.3

16. Section 3.4 - Elements & Compounds 11. Elements • An elementis a pure substance that cannot be separated into simpler substances by physical or chemical means. • 92 elements occur naturally on Earth. • Each element has a unique name and a one, two, or three-letter symbol. • The periodic tableorganizes the elements into a grid of horizontal rows called periods and vertical columns called groups. • Elements in the same group have similar chemical and physical properties • The table is called “periodic” because the pattern of similar properties repeats

17. 12. Compounds • A compound is a made up of two or more elements combined chemically. • Most of the matter in the universe exists as compounds. • Table salt, NaCl, and water, H2O, are compounds. • Elements can never be separated. • Compounds can be broken into components by chemical means. • The properties of a compound are different from its component elements. This figure shows electrolysis of water to form hydrogen and oxygen.

18. The law of definite proportionsstates that a compound is always composed of the same elements in the same proportion by mass, no matter how large or small the sample. • Joseph Proust (France 1799) • The relative amounts are expressed as percent by mass, the ratio of the mass of each element to the total mass of the compound expressed as a percentage. • Example: H2O is always made up of 2 atoms of H and one atom of O. • The ratio of O to H in water is always 16:2 or 8:1. 13. Law of Definite Proportions This table demonstrates that the percentages of elements in sucrose remain the same despite differences in sample amount.

19. The law of multiple proportions states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in whole number ratios. • H2O2 and H2O • Copper(I) chloride and copper(II) chloride 14. Law of Multiple Proportions

20. Law of Multiple Proportions (cont.) • Practice Problem 1: • In the carbon compounds ethane (C2H6) and ethane (C2H4), what is the lowest whole number ratio of H atoms that react with the same number of C atoms? • Answer: 3:2 • Practice Problem 2: • Carbon reacts with oxygen to form two compounds as shown: • Compound A: 2.41 g C, 3.22 g O • Compound B: 6.71 g C, 17.9 g O • Find the lowest whole number ratio of C that reacts with an equal mass of O • Answer: 2:1

21. Law of Multiple Proportions (cont.) • Practice Problem 3: • Lead forms two compounds with oxygen as shown: • Compound A: 2.98 g Pb, 0.461 g O • Compound B: 9.89 g Pb, 0.763 g O • For a given mass of oxygen, what is the lowest whole number mass ratio of lead in the two compounds? • Answer: 1:2

22. End of Section 3-4

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