1.2 Properties and Changes of Matter

1. 1.2 Properties and Changes of Matter Objectives: Distinguish between physical and chemical properties. Contrast chemical and physical changes. Apply the law of conservation of matter to chemical changes.

2. Identifying Matter by Its Properties • Physical properties are those that do not change the composition • They can be quantitative or qualitative. • Qualitative: • The solid is hard. • The liquid boils at a low temperature. • Quantitative: • Ice freezes at 0°C • Iron has a density of 7.86 g/mL

3. States of Matter • Three common states of matter: • Solid • Liquid • Gas • Fourth less familiar type: • Plasma: an ionized gas

4. Solid • Solid- a substance in which the particles occupy fixed positions in a well-defined, three-dimensional arrangement. • Definite shape and volume. • Examples: • Iron • Ice

5. Liquid • Liquid - a flowing substance with a definite volume but an indefinite shape. • Definite volume and takes shape of container • Examples: • Water • Mercury • Bromine

6. Gas • Gas – a flowing, compressible substance with no definite shape or volume. • Takes shape and volume of container • Examples • Oxygen • Hydrogen • Helium

7. States of Matter • The state in which matter is found depends on the temperature and pressure. • When you discuss the physical state of matter you are discussing the state at room temperature (20-25°C) • What is the physical state of neon at room temperature?

8. States of Matter – Disc 2

9. States of Matter – Disc 2

10. Physical States • the temperature at which matter changes from one state to another is closely related to its physical state • Water freezes (and melts) at 0°C • Salt melts (and freezes) at 804°C • Oxygen freezes (and melts) at -218°C • The melting points and freezing point are the same for substances

11. Volatile • Volatile – describes a substance that easily change to a gas at room temperature • Alcohol and gasoline are more volatile then water. • Naphthalene (mothballs) is a solid that is volatile. • You can easily smell alcohol, gasoline and mothballs because since they are volatile the molecules are present in the air.

12. Density • Density- the amount of matter (mass) in a given unit volume. • The units for density are usually g/mL

13. Density • You fill two beakers; one with cotton balls and one with marbles. • The beaker with the marbles is heavier than the one with the cotton balls, but they both occupy the same volume (the beaker). • The marbles have a larger mass than the cotton balls. • Therefore, the marbles have a larger density than the cotton balls

14. Densities of Some Common Materials

15. Determining Density • One way you can determine density is by using water displacing • Weigh you object. (10 g) • Fill a graduated cylinder with water to a particular mark. Such as, 10mL. • Carefully add you object to the graduated cylinder. • Record the level of the water. ( maybe 15mL) • Next you use the weigh of you object and the level of the water to determine the density. • Your water level started at 10mL and ended at 15mL. • 15mL – 10mL = 5mL • Next you take your mass and divide it by your volume. • 10g/5mL = 2 g/mL

16. Let’s Try It • Determine the density of the objects provided by your teacher.

17. The Composition of Pennies • Read over this lab on page 38 & 39 of your packet. • Make a flow chart of the procedure for this lab, using only pictures. We may use this technique for more complicated labs in the future.

18. It’s a Liquid, It’s a Solid…It’s Slime • Lab is on page 40 of your packet. • You must wear safety glasses for this lab. • Please, be very careful with the chemicals. • You may work in groups of three.

19. Chemical Properties and Changes • Chemical Properties- can be observed only when there is a change in the composition of the substance. • Describes the ability of a substance to react with another substance or to decompose • Examples: • Rusting • Reactivity

20. Hydrogen Peroxide (H2O2) • Is always stored in brown bottles because it will break down to hydrogen and water gas when exposed to light.

21. Chemical Change • Chemical Change – the change of one or more substance into other substances. • Also called a Chemical Reaction • The sulfuric acid and the sugar • If you add vinegar to baking soda

22. Atoms and Chemical Change • All matter is made up of atoms. • Any chemical change involves the rearrangement of atoms. • When water breaks down it is the rearrangement of the hydrogen and oxygen atoms. Oxygen molecules Hydrogen molecules Water molecules

23. Law of Conservation of Mass • Law of Conservation of Mass – in a chemical change, matter is neither created nor destroyed. • Example: Water molecules • 2 H2O  O2 + 2H2

24. Law of Conservation of Mass

25. Chemical Reactions and Energy • Chemical changes involve some sort of energy change. • Energy – the capacity to do work • Many reactions give off energy and some absorb energy. • Exothermic – gives off heat • Endothermic - absorbs heat

26. Chemistry and Chemical Reactions • Are all around you and are in everything that you do.

27. Properties

28. Review • Distinguish between a liquid, solid, and a gas. • Give an example of a physical change and a chemical change. • What are two substances that would be considered volatile?