CHEM 1406 Concept Review: Matter and Energy

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Matter: Anything that has mass and takes up space. Matter can be in the form of a pure substance or a mixture.

Pure Substance: Matter composed of only one type of molecule or one type of atom. The two types of pure substances are elements and compounds.

Element: A pure substance composed of only one type of atom (i.e.-only oxygen or only iron)

Compound: A pure substance composed of only one type of molecule (i.e.-only H₂O molecules or only CO₂)

Mixture: Matter composed of two or more pure substances that are physically mixed but NOT chemically combined. (Examples: a tossed salad, cookie batter, or even a computer is a mixture of components.)

Homogenous Mixture: A mixture that is so completely and evenly mixed that there is no difference between one part of the mixture and another part. (Example: Maple syrup, salt water, air, and even metal alloys)

Heterogeneous Mixture: A mixture that is not evenly mixed and where the different components can be distinguished. (Example: Pulpy orange juice, chunky spaghetti sauce, and even this piece of paper which has an ink part and a paper part.)

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States of Matter Comparison

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Physical Properties: Characteristics that can be observed or measured without changing what the substance is.

Physical Change: A change in state or appearance that does not affect the composition or change what it is.

Chemical Property: the ability of a substance to react with other things or itself and become a different substance.

Chemical Change: a change where one substance reacts and becomes one or more different substances, each with different chemical and physical properties.

Energy

Energy: the ability to do work or transfer heat

Kinetic Energy: the energy of motion Equation: $LaTeX: E_k=\frac{1}{2}mv^2$ $E_k=\frac{1}{2}mv^2$ (m is mass, v is velocity)

Heat Energy: the energy of the motion of particles. Heat energy is a type of kinetic energy.

Potential Energy: any type of energy that is in a “stored” form, which includes gravitational potential energy, electrostatic potential energy, chemical potential energy, and more.

Chemical Potential Energy: the energy stored in the structure of atoms and molecules.

Joule: the SI unit of energy which is defined as $LaTeX: 1\:J=\frac{1\:kg\cdot m^2}{s^2}$ $1\:J=\frac{1\:kg\cdot m^2}{s^2}$ 4.184 J = 1 calorie (cal) 1kJ = 1000 J

Temperature Conversion

The Celsius scale is based upon the freezing (0˚C) and boiling (100˚C) points of water divided into 100 equal increments. The Kelvin scale is identical to the Celsius scale with regards to the size of increment but starts with its zero value (0 K) at absolute zero (the lowest temperature theoretically possible) instead of the freezing point of water. The equation for changing between the two scales is as follows:

$LaTeX: K=^{\circ}C+273.15$ $K=^{\circ}C+273.15$

The Fahrenheit scale is based on the same two temperature reference points of the freezing and boiling points of water, though those reference points are given different values (32˚F for freezing and 212˚F for boiling). Between the two points, there are exactly 180 increments, hence the use of the term “degrees”. The equations for changing between the Celsius and Fahrenheit scales are as follows:

$LaTeX: ^{\circ}C=\frac{\left(^{\circ}F-32\right)}{1.8}$ $^{\circ}C=\frac{\left(^{\circ}F-32\right)}{1.8}$ or $LaTeX: ^{\circ}F=1.8\left(^{\circ}C\right)+32$ $^{\circ}F=1.8\left(^{\circ}C\right)+32$

Calculations with Specific Heat

$LaTeX: q=m\times C_s\times\Delta T$ $q=m\times C_s\times\Delta T$

Where q is heat energy, m is mass, C_s is specific heat, and ∆T is change in temperature ( $LaTeX: \Delta T=T_F-T_I$ $\Delta T=T_F-T_I$ ).

This same equation is written in your book slightly different but says the same thing:

$LaTeX: Heat=mass\times SH\times\Delta T$ $Heat=mass\times SH\times\Delta T$

The units for each variable are as follows: J(Heat), g(mass), $LaTeX: \frac{J}{g^{\circ}C}$ $\frac{J}{g^{\circ}C}$ (SH), and ˚C(∆T).

Phase Changes and the Heating Curve

Heating Curve

What it tells us

Melting is changing from a solid to a liquid.

Freezing is changing from a liquid to a solid.

Boiling is changing from a liquid to a gas.

Condensing is changing from a gas to a liquid.

The melting point and the freezing point are both at the same temperature. Likewise, the boiling point and condensation point are also at the same temperature

Heat can either increase temperature or change the phase but not both at the same time.