CHE 100 Lecture Notes - Lecture 2: Reagent, Chemical Formula, Chemical Reaction

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pinkotter981

8 Sep 2017

School

University at Buffalo

Department

Chemistry

Course

CHE 100

Professor

Clarke Priscilla

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Document Summary

Chemical formula = provides the number of each type of atom that makes up the smallest unit of a compound. Gives the composition of each substance by letters and numbers. Ex) the chemical formula for water is h2o. Physical properties = observed without changing a compound or element into another compound or element; describes appearance. Chemical properties = how a substance changes and reacts to form a new substance. Physical transformation = the same substance, but a different state of matter after transformation. Changes in matter that change appearance, but does not change the composition of a substance, such as changes of the physical state. Chemical transformation = starting substance changes that result in new substances. Usually associated with bubbles, flame, or color change. Reactant = the starting substance(s); on the left side of a chemical reaction. Product = the newly formed substance(s); to the right of the chemical reaction.

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I need help doing my lab homework, I missed lab that day because, I was sick and it's due.

Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.

1) Classify each of the following as a mixture, a compound, or an element?

table sugar, propane, bronze, tea, vinegar, dry ice, oxygen, aluminum

2) Select the statements that pertain to elements. Select all the statements that apply.
a) These can be broken down by physical means.
b) These cannot be broken down by chemical means.
c) These combine chemically to form new substances; they are building blocks of matter.
d) These are chemical combinations of simpler forms of matter.
e) These are pure substances.

3) Which of the following are chemical changes? Check all that apply.
a) sugar is dissolved in water
b) a warm coke bottle fizzes when opened
c) the copper roof turns green over time
d) baking soda is dissolved in vinegar and bubbles appear
e) a fog appears on your windshield in cold weather

4) Classify each property as physical or chemical.

a)susceptibility to rust

b) flammability

c) boiling point

d) melting point

e) conductivity

f) color

5) Which of these substances are elements? Check all that apply.

a) silicon

b) iodine

c) lead

d) quartz

e) silicone

f) water

CHE 100 Lecture Notes - Lecture 2: Reagent, Chemical Formula, Chemical Reaction

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