* Substance: Matter That Has a Uniform and Unchanging Composition, Aka Pure Substance

Chemistry Notes
Physical and Chemical Properties
Law of Conservation of Mass

What is Matter?

*  Matter =

*  Substance: matter that has a uniform and unchanging composition, aka pure substance

*  Mixture: two or more substances that have been combined and each substance retains its own chemical identity (sugar + flour)

Physical Properties

*  Substance – matter that has a uniform and unchanging composition

Example: salt – NaCl

*  Physical properties – characteristics that can be observed or measured without changing the composition of the sample

Examples:

2 Types of Physical Properties

1.  Extensive properties – dependent on the amount of substance present

2.  Intensive properties – independent of the amount of substance present

Recognizing Physical Changes

*  Some of the properties of a material change, but the substances in the material remain the same; chemical composition remains the same; some are reversible

Examples:

Physical Separation of substances

*  magnetic properties

*  crystallization/evaporation

*  filtration

*  chromatography

*  distillation

*  manual separation

Phases of Matter

*  Materials can be classified as solids, liquids, gases, or plasma based on whether their shapes and volumes are definite or variable

*  Shape and volume are clues to how the particles within a material are arranged

Solids

*  Definite shape and volume

*  Atoms are packed close together and have an orderly arrangement of particles

*  Changing the container doesn’t change the shape or volume of a solid

*  Examples: pencil, cafeteria tray, book, quarter

Examples:

Liquids

*  Definite volume and take the shape of its container

*  Can be poured, will take on a new shape

*  Atoms are close together, but their arrangement is more random than those of a solid

Examples:

Gases

*  Does not have a definite shape nor a definite volume

*  Takes the shape and volume of its container

*  Atoms are not arranged in a regular pattern and can have a big space between them

*  COMPRESSIBLE

Examples:

Plasma

*  Ionized gas with enough energy to have free electrons

Examples:

Kinetic Energy of Phases of Matter:

Particles / Shape / Volume / Compressible?
Solid
Liquid
Gas

Chemical Properties

*  Chemical properties – the ability of a substance to combine with or change into another substance

*  Iron + O2 -> Rust (FeO)

*  Burning

*  Cooking

*  CO2 + H2O -> C6H12O6 + O2

*  EVERY SUBSTANCE HAS A UNIQUE SET OF PHYSICAL AND CHEMICAL PROPERTIES

Chemical Equations

*  A useful description of a chemical reaction tells you the substances present before and after the reaction

*  Reactants undergo the change and the new substances that are formed are the products

*  Reactants Products

*  Recognizing Chemical Changes

Evidence of chemical changes include:

*  Change in color – leaves on trees, banana peel, copper, silver

*  Production of gas (bubbles) – vinegar and baking soda, cake baking

*  Formation of a precipitant – acid + milk (protein goes through chemical change), cottage cheese

*  Production of light

*  Temperature Change – reaction causes heat to be given off or absorbed (gets cold)

*  Endothermic

*  Exothermic

Law of Conservation of Mass

Steps to Solve Law of Conservation of Mass Problems

1.  Write what you know

•  chemical reaction

•  reactants and their masses

•  products and their masses

2.  What are you solving for?

3.  Solve for your unknown

Practice!

1.  From a laboratory experiment designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was initially involved in the process?

2.  A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted?

3.  In a flask, 10.3 g of aluminum reacted with 100 g of liquid bromine to form aluminum bromide. After the reaction, no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of compound were formed?

4.  A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted?

5.  If 50 grams of sodium reacts with chlorine to form 126 grams of salt, how many grams of chlorine reacted?

6.  If 20 grams of aluminum reacts with 200 grams of bromide to form aluminum bromide, and no aluminum is left after the reaction, but 23 grams of bromine remained unreacted how any grams of aluminum bromide were formed?

7.  If 178.8 g of water is separated into hydrogen and oxygen gas, and the hydrogen gas has a mass of 20.0 g, what is the mass of the oxygen gas produced?

8.  From a laboratory process, a student collects 28.0 g of hydrogen and 224.0 g of oxygen. How much water was originally involved in the process?

9.  A student carefully placed 23.0 g of sodium in a reactor with an excess quantity of chlorine gas. When the reaction is complete, the student obtained 58 grams of salt. How many grams of chlorine reacted?

10.  A 10 gram sample of iron reacts with oxygen to form 18.2 grams of ferric oxide. How many grams of oxygen reacted?

Conservation of Mass Practice Problems I

1)  50 grams of sodium reacts with chlorine to form 126 grams of salt. How many grams of chlorine reacted?

2)  20 grams of aluminum reacts with 200 grams of bromide to form aluminum bromide. No aluminum is left after the reaction, but 23 grams of bromine remained unreacted. How many grams of aluminum bromide were formed?

3)  178.8 g of water is separated into hydrogen and oxygen gas, and the hydrogen gas has a mass of 20.0 g. What is the mass of the oxygen gas produced?

4)  From a laboratory process, a student collects 28.0 g of hydrogen and 224.0 g of oxygen. How much water was originally involved in the process?

5)  A student carefully placed 23.0 g of sodium in a reactor with an excess quantity of chlorine gas. When the reaction is complete the student obtained 58 grams of salt. How many grams of chlorine gas reacted?

6)  A 10 gram sample of iron reacts with oxygen to form 18.2 grams of ferric oxide. How many grams of oxygen reacted?

1)  76 g 3) 158.8 g 5) 35 g

2)  197 g 4) 252 g 6) 8.2 g

Conservation of Mass Practice Problems II

Solve the following problems by writing the chemical equation and showing work for calculations.

1.)  From a laboratory experiment designed to separate water into hydrogen and oxygen gas, a student collected 10.0 grams of hydrogen and 79.4 grams of oxygen. How much water was initially involved in the process?

2.)  A student carefully placed 15.6 grams of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete the student obtained 39.7 grams of sodium chloride. How many grams of chlorine gas reacted?

3.)  In a flask, 10.3 grams of aluminum reacted with 100 grams of liquid bromine to form aluminum bromide. After the reaction no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of compound were formed?

4.)  A 10.0 gram sample of magnesium reacts with oxygen to form 16.6 grams of magnesium oxide. How many grams of oxygen reacted?

5.)  If 50 grams of sodium reacts with chlorine to form 126 grams of salt, how many grams of chlorine reacted?

6.)  Twenty grams of aluminum reacts with 200 grams of bromide to form aluminum bromide. No aluminum is left after the reaction, but 23 grams of bromine remain unreacted. How many grams of aluminum bromide were formed?

7.)  178.8 grams of water is separated into hydrogen and oxygen gas. The hydrogen gas has a mass of 20.0 grams. What is the mass of the oxygen gas produced?

8.)  From a laboratory experiment a student collects 28.0 grams of hydrogen and 224.0 grams of oxygen. How much water was originally involved in the process?

9.)  A student carefully placed 23.0 grams of sodium in a reactor with an excess quantity of chlorine gas. When the reaction is complete, the student obtained 58 grams of salt. How many grams of chlorine reacted?

10.)  A 10 gram sample of iron reacts with oxygen to form 18.2 grams of ferric oxide. How many grams of oxygen reacted?

Intensive & Extensive Properties

Introduction: Intensive and extensive properties are both physical properties. Even though they are both physical properties, they have differences. Intensive properties are independent of the amount of the substance present. On the other hand, extensive properties depend on the amount of the substance present.

Instructions:

1.  Observe the pieces of wood. Measure the length of the two pieces of wood and record them in centimeters below.

2.  What type of physical property is length? Explain how you know in the chart below.

3.  Place the two pieces of wood in a beaker of water. Record your observations in the chart below.

4.  What type of property is density? Explain how you know in the chart below.

Observation Table

Length of wood (cm) / Type of Property and Explanation / Observations of wood in beaker of H20 / Type of Property and Explanation
Wood Sample 1
Wood Sample 2