Physical Science: Unit 5

1. What do you think the difference is between a physical change and a chemical change?

Physical Change Chemical Change

▪Anything that can be observed without change the fundamental properties/appearance

▪No change in structure and properties

▪Change in structure

▪Producing a new substance

▪Different properties

Physical Chemical

▪ State of matter at given temp (solid, liquid, gas)

▪ Boiling/melting point

▪ Grinding/Cutting

▪ Color

▪ Dissolving

▪ Conductivity

▪ Malleability

▪ Ductility

▪ Burning

▪ Rusting

▪ Addition of products that change composition (ex. Yeast)

1. Define: Physical Change. Give an example.

2. Define: Chemical Change. Give an example.

1. Classify the following as a physical or chemical change:

a) Tearing a piece of paper

b) Burning a piece of paper

c) Metal rusting

d) Dissolving salt in water

e) Using yeast to make bread

Pure substance Mixture

▪ A substance with definite physical and chemical properties

▪ Made up of just one type of particle

▪ Example: Elements and compounds are pure substances

▪ A combination of two or more pure substances that are not chemically combined▪ Held together by physical forces, not

chemical

▪ No chemical change; can be physically separated

▪ Each retains properties in the mixture

▪ Example: Salad

Element Compound

▪ A pure substance that cannot be separated into simpler substance by physical or chemical means

▪ Pure substance composed of two or more different elements joined by chemical bonds

▪ Ex. Water (H2O)Ex: Lead

Homogeneous Mixture Heterogeneous Mixture

▪ “Homo” means “same”

▪ Same throughout (molecules cannot be easily distinguished from one another)

▪ Ex. Vinegar, soda in sealed bottle

▪ “Hetero” means “different”

▪ Materials that can be easily separated

▪ Ex. Pizza

1. Define: Pure Substance. Give an example.

2. Define: Mixture. Give an example.

3. Which of the following is an element? A compound? How do you know?

a) O

b) H2O

▪The Tyndall effect is the scattering of light as a light beam passes through a colloid

▪The Tyndall effect can help distinguish between solutions and colloids

▪ Based on particle size, settling out, and light (Tyndall Effect)

▪ Solution-Do not separate in layers over time, can be poured through filter, light passes through▪ Ex. Sweet Tea

▪ Suspension-Separate into layers over time, filters can separate, scatter light▪ Ex. Flour in water, muddy swamp water (“shake well before using”)

▪ Colloid-intermediate between solution and suspension (does not separate, filters can’t separate, scatter light)▪ Ex. Peanut butter, whipped cream

https://www.youtube.com/watch?v=V7eqD-Jw6m4

https://www.youtube.com/watch?v=r4MVEpS0tvk

1. What is the Tyndall Effect? Describe it and give an example.

2. What is the difference between homogeneous and heterogeneous mixtures? Give an example of each.

▪Density is the state of being compact; how packed together the molecules are

▪Density can be found with the volume and mass of a substance

▪Density Differences of Substances can be calculated with the formula D=m/v

▪ D=Density

▪ m=mass

▪ v=volume

Given

▪M = 45 g

▪V = 15 cm3

▪D = ?

Solution

▪D = m/v

▪D = 45/15

▪D = 3 g/cm3

▪Placing an object in water displaces the water a set amount; this amount is the volume of the object

▪For example, below the water is at 80mL. After adding the ball, it is at 100mL. Therefore, the volume of the ball must be 20mL (100mL-80mL=20mL)

1. What is the definition of density?

2. How do you calculate it? What are the units involved?

▪Tiny, constantly moving particles make up all matter.

▪The kinetic energy (motion) of these particles increases as temperature increases.

▪Solid

▪Liquid

▪Gas

▪Plasma

▪Low KE - particles vibrate but can’t move around

▪Definite shape & volume

▪Crystalline - repeating geometric pattern

▪Amorphous - no pattern (e.g. glass, wax)

▪Higher KE - particles can move around but are still close together

▪Indefinite shape

▪Definite volume

▪High KE - particles can separate and move throughout container

▪Indefinite shape & volume

▪Very high KE - particles collide with enough energy to break into charged particles (+/-)

▪Gas-like, indefiniteshape & volume

▪Stars, fluorescentlight bulbs, TV tubes

▪Most matter expands when heated & contracts when cooled.

▪ Temp causes KE. Particles collide with more force & spread out.

▪EX: thermostats (bimetallic strip)

▪Amorphous solids and liquids do not act as you think they should.

▪Amorphous Solids

▪Glass

▪Plastic

▪Chainlike structures that get jumbled and twisted (not orderly)

▪Liquid Crystals (LCD)

▪Clock, watch, calculator displays

▪Responsive to temp changes and electric fields

1. What are the four phases of matter?

2. Describe what the matter looks like within a gas vs. a liquid vs. a solid.

▪Parts of a solution▪ Solvent

▪ Major component of a solution

▪ Dissolves the solute (usually water)

▪ Solute(s)▪ Minor componets of a solution

▪ Active ingredients (ex. Salt in salt water)

▪ The part being dissolved

▪ Solution = Solvent + Solute(s)

▪Not all substances dissolve in water

▪Polarity-”Like dissolves Like”

▪Polar molecules are molecules in which charge is not distributed symmetrically among the atoms making up the molecule

▪Polar solutes tend to dissolve more in polar solvents

▪Nonpolar solutes tend to dissolve more in non-polar solvents

▪Saturated-A solution with solute that dissolves until it is unable to dissolve anymore, leaving the undissolvedsubstances at the bottom.

▪Unsaturated-A solution (with less solute than the saturated solution) that completely dissolves, leaving no remaining substances.

▪Supersaturated-A solution (with more solute than the saturated solution) that contains more undissolved solute than the saturated solution because of its tendency to crystallize and precipitate.

Concentrated Dilute

▪More concentrated=less water

▪“strong”

▪Ex. Frozen Orange juice

▪Less concentrated=more water

▪“weak”

▪Ex. Orange juice after mixing

▪Compares the solubilitiesof several compounds in water as a function of temperature

▪For example, at 70oC, 135g of KNO3 will dissolve in 100g of water

▪Explain the difference between a saturated, unsaturated, and supersaturated solution. Give an example of each.

▪Elements are classified as metals, nonmetals, or metalloids

▪The periodic table helps to classify elements with similar properties

▪Metals-shiny, malleable, good conductors of heat and electricity

▪Nonmetals-Dull, brittle, poor conductors

▪Metalloids-Some properties of metals, some of nonmetals (all solid at room temp, brittle, hard, somewhat reactive, conductive)

Element Compound

▪ A pure substance that cannot be separated into simpler substance by physical or chemical means

▪ Pure substance composed of two or more different elements joined by chemical bonds▪ Elements in specific ratio

▪ Has a chemical formula

▪ Can only be separated chemically, not physically

Ex: Lead; used for

many things,

including

reducing radiation

exposure in X-rays

1. Use the periodic table to determine if the following are metal, nonmetal, or metalloid.

a) Si (Silicon)

b) Mt (Meitnerium)

c) He (Helium)

▪Define the following:▪Homogeneous

▪Heterogeneous

▪Element

▪Compound