Chemical properties and changes of matter
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Chemical properties and changes of matter. 8 th grade. Physical and chemical changes (page 303). PHYSICAL CHANGE. EXAMPLES. Dissolving Bending Breaking cutting Changing state of matter. Appearance or form of a substance changes No new substance is produced.

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Chemical properties and changes of matter

Chemical properties and changes of matter


Physical and chemical changes page 303

Physical and chemical changes(page 303)







Changing state of matter

  • Appearance or form of a substance changes

  • No new substance is produced

Physical and chemical changes

Physical and chemical changes








  • A change in matter that produces one or more new substances

Chemical changes

Chemical changes

  • Combustion- Combining a fuel with oxygen produces new substances

    • Ex: burning natural gas on a gas stove.

      • When it burns, the methane in the natural gas combines with oxygen in the air to form carbon dioxide and water vapor.

  • Electrolysis-Using electricity to break a compound into elements

    • Ex: Breaking water into hydrogen and oxygen

Chemical changes1

Chemical changes

  • Oxidation-Combining a substance with oxygen

    • Ex: Rusting (combining iron with oxygen)

  • Tarnishing-Combining a bright metal with sulfur, (or another substance), which produces a dark coating on the metal

    • Ex: brass tarnishing



Reactants and products

Reactants and products

  • In a chemical change, there are reactants and products

  • Example: (Reactants) H+OH → H₂O (products)

Law of conservation of mass

Law of conservation of mass

  • The law of conservation of mass states that mass is neither created nor destroyed during a chemical of physical change.

    • Ex: evaporation of water-does water disappear?

    • Ex: Does a piece of paper weigh less when it is shredded into pieces?

Law of conservation of mass pg 418 chemical change

Law of conservation of mass –(pg. 418)(chemical change)

  • Fill it in…

How do you know a chemical change has taken place pg 419

How do you know a chemical change has taken place??? (pg. 419)

  • Some signs that a chemical change has taken place:

    • 1. Release of energy- chemical changes occur when bonds between atoms break.

      • Breaking a bond requires energy

      • Forming a bond releases energy

  • Exothermic reaction-energy is released (as heat)

  • Endothermic reaction-energy is absorbed

Chemical properties and changes of matter

  • 2. Color change (brown apple)

  • 3. Smell/odor (rotten food)

  • 4. Release of gas (bubbles)

  • 5. formation of a precipitate

    • A precipitate is a solid that forms from a liquid during a chemical reaction.

      • Ex: curdled milk

Class work

Class work

  • Identify the following as a physical or chemical change:

    • Ripping a piece of paper

    • Burning a piece of paper

    • Painting a house

    • Rusting

    • Dissolving salt in boiling water

    • Cutting you hair

How do elements combine

How do elements combine?

  • An element is the simplest substance. It cannot be broken down.

    • Ex: Carbon (C), Oxygen, (O), Hydrogen, (H)

  • Elements combine to form compounds

  • A compound is a substance made of two or more elements

    • Ex: water (H₂O), carbon dioxide (CO₂)

Pure substances mixtures and solutions pg 391

Pure substances, mixtures and solutions (pg. 391)

  • A pure substance is a single kind of mater with a specific make-up

    • EX: water, sugar, salt

    • Ex: elements and compounds are pure substances

  • A mixture is two or more substances that are together in the same place, but their atoms are not chemically bonded

    • Ex: salt water, cookie dough

    • Ex: air (mixture of nitrogen, oxygen and other gases)



  • Pure substances: cannot be separated easily

    • Sometimes not at all

  • Mixtures: can be physically separated

  • Let s look at an example

    Let’s look at an example

    • To make cookies you would need the following ingredients: salt, water, sugar, and baking soda.

    • Salt, water, sugar and baking soda are all _____________.

    • When you combine the salt, water, sugar and baking soda to make cookie dough, you get a _____________.

    Chemical properties and changes of matter

    • The cookie dough, (mixture), could be separated back into water, salt, baking soda and sugar.

    • The pure substances, however cannot be separated….only by a chemical reaction.

    Class work1

    Class Work

    • Identify the following as a mixture or a pure substance

      • Sand

      • Trail mix

      • Carbon dioxide

      • Flour

      • Gold

      • soil

      • Lemonade

      • rock



    • Two types of mixtures are:

      • Heterogeneous

      • Homogeneous



    • A heterogeneous mixture is a mixture in which you can see the different parts and easily separate them.

      • Example: trail mix (peanuts, pretzels, raisins)



    • A Homogeneous mixture is a mixture in which you cannot easily see the parts so separating the mixture is more difficult.

      • Ex: sugar in lemonade

    Class work2

    Class work

    • Identify the following mixtures as homogeneous or heterogeneous:

      • Chicken noodle soup

      • Coffee

      • Blood

      • Orange juice with pulp

      • Creamy peanut butter

    Classification of mixtures page 397

    Classification of mixtures(page 397)

    • Mixtures are classified based on the size of their largest particles:

    • They can be:

      • 1.Solutions

      • 2.Colloid

      • 3.particles

    S olution


    • A solution is a mixture containing a solventand at least one solute.

    • Solvent:does the dissolving

    • Solute: gets dissolved by the solvent

      • Solute can be a liquid, solid or gas

    Examples of solutions solvent and solutes

    Examples of solutions/solvent and solutes

    • Grape juice is a solution

      • The water is the solvent

      • The sugar and other ingredients are the solutes

    • Blood is a solution

      • Water is the solvent

      • Platelets, plasma, red and white blood cells are the solute

    Blood is a solution water is the solvent


    Acids bases and salts page 378

    Acids, bases and salts(page 378)

    • Acids-

      • React with metals

        • They are corrosive because they wear away the metal

      • Taste sour

        • Citrus fruit contains citric acid (lemons and grapefruit)

      • Turn blue litmus paper red

        • Litmus paper is an indicator. Indicators is a compound that changes color when it comes in contact with an acid.

    • Common examples: hydrochloric acid, citric acid, sulfuric acid



    • Bases

    • Common bases: ammonia, baking soda, sodium bicarbonate

      • Taste bitter

        • Tonic water contains the base quinine

      • Do not react with metals

      • Feel slippery

        • Shampoo and soap

      • Turn red litmus paper blue

    Litmus paper

    Litmus paper

    Chemical properties and changes of matter


    • When you mix and acid and a base together, a reaction occurs called neutralization.

      • The result of this reaction is the formation of a SALT

        • Many types of salt exist

    Ph scale

    pH Scale

    • Acids and bases can be measured using the pH scale.

    • We can tell how acidic or how basic a substance is

    • The pH scale ranges from 0 to 14

      • The lower the pH, the more acidic

      • The higher the pH, the more basic

      • pH 7 is neutral

        • so a pH lower then 7 is acidic and a pH higher then 7 is basic

        • Water is neutral

        • Salt is neutral

    Ph of common substances

    pH of common substances

    • Battery acid pH = 1.0

    • Lemon juice pH= 2.0

    • Vinegar pH = 2.2

    • Apples pH = 3.0

    • Baking soda pH = 8.3

    • Blood pH = 7.4

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