Science Study Guide

Physical and Chemical Properties

• Physical Property- Characteristic that can be observed without changing matter into another type of matter.
• Chemical Property- Characteristics that describe something's ability to become something else.

Physical and Chemical Changes

• Physical Changes- Doesn't change the type of matter; nothing new or different is formed.
• Chemical Changes- Composition of the substance changes; substances present at the beginning of the change are now not present at the end; new substances are formed. Change can't be undone.

Classifying Matter

• Can be physically separated; mixture.
• Can't be physically separated; pure substance.
• If composition is uniform (mixture) then it is homogenous (solution) . If not it is heterogenous.
• Pure substance can be chemically decomposed; its a compound. If not it is an element.

Law of Conservation of Mass/Matter

• Mass/Matter can't be created or destroyed, only rearranged

Collision Theory

• All substances are made of atoms or neurons. For a reaction to take place, the particles of different substances must collide with enough activation energy and correct orientation.

Collision Theory

• Concentration;
• As you increase the concentration, there are more particles in the same volume so there is a higher chance of a collision.
• Surface Area;
• As we increase the surface area, we increase the rate of reaction.
• Bigger the surface area, the more particles are exposed and can react.
• Temperature;
• Increased temperature increases kinetic energy, therefore makeing the particles faster, making the chance of collision higher.
• There is an optimum temperature for every chemical react.
• Catalysts;
• Speeds up a chemical reaction. At end of the reaction the catalysts unchanged.
• Volume of a Container;
• As you shrink the volume of the space that particles are in, the particles have less space to move, increasing the chance of them bumping into each other.

States of Matter

• Solids; definite shape and volume, particles are packed together closely. Can only vibrate in place.
• Types of Solids;
• Crystalline Solids; Lattice pattern in particle structure. Melts at a distinct temperature.
• Amorphous Solids; Particles aren't arranged in a regular pattern. Doesn't melt at a distinct temperature. Useful in manufacturing; can
• Liquids; doesn't have definite shape, but has a constant volume. No shape of its own. Are almost always in contact with one another, less packed together then solids.
• Physical Properties;
• Surface tension, viscosity (resistance to flowing)
• Gas;
• No definite shape or volume, particles are widely spaces and collide with one another as they fly about.
• Physical Properties;
• Gas particles move and fill all of the spaces available, making the volume of the gas the same as its container.

Definitions

• Boiling; Below the surface.
• Evaporating; Top layer.
• Condensation; Gas to liquid (particles slow down)
• Thermal Energy; total kinetic and potential energy of all the particles in a object or substance.
• Temperature; measure of the average kinetic energy of the particles in an object or a substance.
• Melting; When the temperature of most solids increase enough, they change into a liquid.
• Freezing; Liquid to Solid; particles are slowed down absolute.
• Vaporization; Boiling and Evaporation are collectively known as.
• Sublimation; Solid goes straight to a gas; dry ice to carbon dioxide.
• Deposition; Gas goes straight to a solid.
• 2 Examples in change of state; mass same, density change.

Acids, Bases, pH Scale and Neutralizers

• Acids; chemicals with pH less than 7. They are sour. Contain many Hydrogen ions. Some are corrosive, some aren't (acid in our food)
• Bases; chemicals with pH more then 7. Contain hydroxide ions, and have a bitter taste. (OH-) React violently with acids. Soapy, slimy feeling.
• Indicator; change color in presence of an acid or a base. Red litmus- acid no change, changes to blue with base. Blue litmus- acid changes it to red, bases don't change it. Measures the number of hydrogen ions. It doesn't show strength though.
• Universal Indicators; indicates the pH of a substance in a more complex than pH indicators. Changes to color that is calibrated to indicated pH level.
• High= strong alkali
• Low= strong acid.

pH

• Ranges form 1-14. Way of testing to see if a substance is acidic basic or neutral.
• pH stands for potential hydrogen. Refers to the ability of a chemical to donate or accept H+ (hydrogen ions) to other chemicals.
• Each pH unit is 10 times as large as the previous one.

Reaction

• Acid+Base= salt and water.
• Neutralization;
• Neutral chemicals have a pH 7.
• Occurs when hydrogen ions and hydroxide ions are equal. Means they combine to form water. Pure water is neutral.

Energy Changes During Chem. Reactions

• Exothermic reactions; releases heat to the surroundings; temp of the surroundings increases. Thermal equilibrium puts the temperature back to normal. Reactants have more chem. energy than the products. Delta H is negative.
• Endothermic reactions; takes in heat energy from the surroundings. Temperature of surroundings decrease. Thermal equilibrium brings the temperature back to normal. Delta H is positive. Reactants have less energy than the products.
• Endothermic (energy must be supplied to break bonds)
• Exothermic (energy is released when new bonds are made)
• Hydrogen peroxide= deadly to cells.
• Enzymes- Bio catalyst.