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Physical and Chemical Changes

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Presentation on theme: "Physical and Chemical Changes"— Presentation transcript:

1 Physical and Chemical Changes
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2 What kind of changes does matter undergo?
All matter, regardless of state, undergoes physical and chemical changes. These changes can be microscopic or macroscopic.

3 Properties of Matter

4 Intensive and Extensive Properties
Physical and chemical properties may be intensive or extensive.

5 What are intensive properties?
Intensive properties such as density, color, and boiling point do not depend on the size of the sample of matter and can be used to identify substances.

6 What are extensive properties?
Extensive properties such as mass and volume do depend on the quantity of the sample.

7 How can we identify physical properties?
Physical properties are those that we can determine without changing the identity of the substance we are studying.

8 Examples of physical properties:
The physical properties of sodium metal can be observed or measured. It is a soft, lustrous, silver-colored metal with a relatively low melting point and low density. Hardness, color, melting point and density are all physical properties.

9 What is a physical change?
A physical change occurs when the substance changes state but does not change its chemical composition. For example: water freezing into ice, cutting a piece of wood into smaller pieces, etc. The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.) Definition of physical changes.

10 Characteristics of Physical Changes
Density Electrical conductivity Solubility Adsorption to a surface Hardness Melting point Boiling point Vapor pressure Color State of matter Physical changes are characterized by the following:

11 What are chemical properties?
Chemical properties describe the way a substance can change or react to form other substances. These properties, then, must be determined using a process that changes the identity of the substance of interest.

12 CHEMICAL PROPERTIES A chemical property must describe how some substance REACTS or DOES NOT REACT with other substances. In other words, they describe how a substance will be changed or will not be changed when it interacts with other substances.

13 How can chemical properties be identified?
One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens. In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

14 What are chemical changes?
A chemical change occurs when a substance changes into something new. This occurs due to heating, chemical reaction, etc. You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (change in color, change in temperature, formation of a gas, emission of light, formation of a precipitate). Definition of chemical change.

15 Characteristics of Chemical Changes
Reaction with acids Reaction with bases (alkalis) Reaction with oxygen (combustion) Ability to act as oxidizing agent Ability to act as reducing agent Reaction with other elements Decomposition into simpler substances Corrosion Chemical Changes are characterized by the following:

16 Evidence of Chemical Change
Bubbles of gas appear A precipitate forms A color change occurs The temperature changes Light is emitted Evidence of Chemical Change

17 Comparison of Physical and Chemical Properties
Create a Venn diagram to compare and contrast physical and chemical properties

18 Two Important Physical Properties
States of Matter Density of Matter Two Important Physical Properties

19 (And how the Kinetic Molecular Theory affects each)
States of Matter (And how the Kinetic Molecular Theory affects each) Solids Liquids Gases Plasma

20 States of Matter

21 Kinetic Molecular Theory
Solids Have a definite shape Have a definite volume Kinetic Molecular Theory Molecules are held close together and there is very little movement between them.

22 Liquids Have an indefinite shape Have a definite volume Kinetic Molecular Theory: Atoms and molecules have more space between them than a solid does, but less than a gas (ie. It is more “fluid”.)

23 Gases Have an indefinite shape Have an indefinite volume Kinetic Molecular Theory: Molecules are moving in random patterns with varying amounts of distance between the particles.

24 Kinetic Molecular Model of Water
At 100°C, water becomes water vapor, a gas. Molecules can move randomly over large distances. Between 0°C and 100 °C, water is a liquid. In the liquid state, water molecules are close together, but can move about freely. Below 0°C, water solidifies to become ice. In the solid state, water molecules are held together in a rigid structure.

25 Phases of Matter Concept Map

26 On earth we live upon an island of "ordinary" matter
On earth we live upon an island of "ordinary" matter. The different states of matter generally found on earth are solid, liquid, and gas. We have learned to work, play, and rest using these familiar states of matter. Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma, in 1879.

27 Plasma Plasma is by far the most common form of matter. Plasma in the stars and in the tenuous space between them makes up over 99% of the visible universe and perhaps most of that which is not visible.

28 EXAMPLES: Computer chips and integrated circuits Computer hard drives Electronics Machine tools Medical implants and prosthetics Audio and video tapes Aircraft and automobile engine parts Printing on plastic food containers Energy-efficient window coatings High-efficiency window coatings Safe drinking water Voice and data communications components Anti-scratch and anti-glare coatings on eyeglasses and other optics

29 Density Note ml = cm3 Density = mass (g) D = g or g volume (ml) ml cm3

30 Learning Check D1 Osmium is a very dense metal. What is its density in g/cm3 if g of the metal occupies a volume of 2.22cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3 lecturePLUS Timberlake

31 Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = g = volume 2.22 cm3 = g/cm3 = 22.5 g/cm3 lecturePLUS Timberlake

32 Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL lecturePLUS Timberlake

33 Learning Check 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3
What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm ) 6 g/m ) g/cm3 33 mL 25 mL lecturePLUS Timberlake

34 Solution 2) 6 g/cm3 Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL Volume of metal (cm3) = 8 mL x 1 cm3 = 8 cm3 1 mL Density of metal = mass = 48 g = 6 g/cm3 volume 8 cm3 lecturePLUS Timberlake

35 Learning Check3 K V W V K W W V K 1) 2) 3)
Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K V W K V W W V K lecturePLUS Timberlake

36 Solution (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) V W K lecturePLUS Timberlake

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