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Atom
Atom
Atom = The smallest unit of matter; The basic unit of a chemical element. For example, Water (H2O) is made up of three atoms.
Boiling is a form of vaporization.
Consider water. When heat is added to water, the molecules vibrate with so much energy that they turn from liquid to gas. The bubbles are water vapor! Boiling is when phase change happens within the water.
Phase change also occurs at the surface of water. This is a physical change. The formula for water is not changed.
It may interest you to know that water can boil sooner when the air pressure is lower. Water at high altitudes boils faster and at lower temperatures (95 degrees, Celsius) than water at sea level. The water can change phase from liquid to gas more readily because the pressure is less.
Carbon Dioxide - You are exhaling this gas as you read this. It is one product of cellular respiration; the other is water. Carbon dioxide is also a product of combustion.
If you burn a log in the fire carbon dioxide as well as water are products of the reaction. Carbon dioxide is denser than air. It can displace oxygen. Watch this video about killer lakes.
A chemical property is the characteristic of a substance to undergo chemical reactions and to form new compounds. Some examples of chemical properties of matter are the ability to rust, corrode, decompose, or react.
Flammability is a chemical property that you are familiar with. As you may know, alcohol burns with oxygen. Other substances like gasoline or methane also burn with oxygen.
In contrast, helium is inert. Its chemical property is that it does not react.
Chemical Change: When one substance transforms into other substances via chemical reaction. Signs of chemical change include:
Color Change
(Ripening bananas, for example)
Temperature Change
(Heat is given off or taken in)
Gas Production
(Fizzing, bubbling, etc.)
Precipitate Formation
Cohesion
Cohesion
Molecules that stick together are cohesive. For example, water cohesive. Water sticks to itself. The cohesive nature of water causes rain to fall as drops. It also allows water bugs to walk on the surface of water.
Colloid = Milk, Jell-O, glue, and fog are colloids. The particles in a colloid are larger than ones found in solutions but smaller than ones found in suspensions. A Colloid is a homogeneous solution with an intermediate particle size between a solution and a suspension.
The colloid looks homogeneous to the naked eye. Colloids frequently appear "murky" or "opaque". The particles are large enough to scatter light.
Fog is a colloid. You have experience with the way fog interacts with the light from car headlights.
Colloids generally do not separate on standing. They are not separated by filtration. Many familiar substances, including butter, milk, cream, aerosols (fog, smog, and smoke), asphalt, inks, paints, glues, and seafoam are colloids.
Combustion
Combustion
Combustion - Anytime anything burns (in the usual sense), it is undergoing a combustion reaction. Oxygen gas, O2, is necessary for combustion to proceed. Fuel is also required.
When oxygen gas combines with organic material (something that contains C, H, and O from an organism) the products of the reaction are carbon dioxide and water.
The matter is conserved; atoms are neither created nor destroyed during chemical reactions. This concept is known as the Law of Conservation of Matter.
Here is the equation for the combustion of Ethyl Alcohol:
CH3CH2OH + 3O2 => 2CO2 + 3H2O
CH3CH2OH + 3O2 => 2CO2 + 3H2O
After the reaction, the fuel and oxygen are no longer available; they have been converted to carbon dioxide and water.
Conservation of Mass Law - In chemical reactions, matter is conserved; atoms are neither created nor destroyed during chemical reactions. The father of modern chemistry, Antoine Lavoisier discovered this in the year 1789. He discovered that the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction.
Atoms are recycled and new products are made, but the number of atoms does not change. This concept is known as the Law of Conservation of Mass (or Matter).
Chemists balance chemical equations to show that mass is conserved.
Compound = a chemical substance that is formed from two or more elements, that bond in a fixed ratio. For example, water (H2O) is a compound that is composed of two hydrogen atoms for every oxygen atom.
NH3, HCl, H2O2, SiO2, CH4, C2H2, and C2H4, are compounds. In contrast, O2 is not a compound because it is only made of one element. A compound is a pure substance.
Covalent Bonding is where 2 or more atoms bond by sharing their outer electrons.
Generally, covalent bonds are made between nonmetal atoms. The result of this bond is a molecule. Covalent means, "Sharing outer electrons". The nucleus of an atom is never changed or altered after bonding. Covalent bonding allows atoms to complete their outer shells.
Density = mass/volume. It is the amount of matter in a given amount of space.
Water has a density of 1 g/cm^3. Water is one of the few compounds that become less dense when it freezes. As the water molecules slow down, hydrogen bonds help the molecules to form crystalline structures. The ice takes up more volume, the density decreases, and the ice floats.
Diffusion: is a process where molecules at higher concentrations randomly move to areas with lower concentrations.
The molecules bounce around until they are evenly spread throughout a fluid.
Dissolve: When one substance is mixed into and absorbed by another. For example, oxygen gas is dissolved in water. This dissolved oxygen is breathed in by fish.
Lemonade mix is dissolved in water. Delicious. Fish are not delicious, imho.
Electrons are stable subatomic particles that have a negative charge. They can be found in the shells of atoms outside the nucleus. A pair of electrons form a covalent bond between atoms. They are responsible for bonding atoms.
An element is composed of one kind of atom. An element is a pure substance. An element cannot be broken down by physical or chemical means. 90 elements occur naturally on Earth. The other 19 or so are made in the lab. This means that in the universe, there are only 90 different types of atoms that make everything. C, H, O, N and P are the primary elements that make up living organisms.
Evaporation is a form of vaporization. Consider water.
Evaporation occurs at the surface of the water. It happens when molecules heat up and vibrate away from the liquid. The water molecules leave as a gas. This is a physical change.
Formula - A chemical formula shows what elements make up a compound.
For instance, the formula for water is H2 O.
The formula for carbon dioxide gas is CO2 .
The formula for oxygen gas is O2 .
The formula for methanol is CH3OH.
Freezing - The point at which liquids become solid.
Water freezes at 0 degrees Celsius. This is a physical change.
As heat leaves and as temperatures decrease, the water molecules move slower. At 0 degrees Celsius, hydrogen bonds cause the molecules to form a crystalline structure that we call ice! This structure takes up more volume and the density of the ice is less than that of water. The ice floats on water.
Heterogeneous Mixture – is made up of visibly different substances or phases.
Sand is a heterogeneous mixture. Beach sand is heterogeneous since you can see different colored particles.
Heterogeneous mixtures are not uniform. There are pockets of one substance surrounded by pockets of different substances.
A mixture of soil in water to make "mud" is heterogeneous. Likewise, a mixture of oil and water in salad dressing is heterogeneous.
Homogeneous Mixture – appears uniform and consistent throughout. Solutions and colloids are homogeneous mixtures.
A lemonade drink is a homogeneous mixture, known as a solution. So is air. Both brass and glass are homogeneous mixtures/solutions.
Hydrogen bonding is a special type of attraction between molecules. It is a temporary bond that results from the attractive force between a hydrogen atom and a very electronegative atom such as a N, O, or F.
Hydrogen bonding is what causes water to be so sticky and cohesive.
Ion: a charged particle formed when an atom (or molecule) gains or loses one or more electrons.
Ionic Bonding: is a type of bonding in which ions are held together by the strong attraction of their opposite charges.
The nucleus of an atom is never changed or altered after bonding.
Isotope: An isotope is an atom that has a different number of neutrons in its nucleus. Thus, an isotope has a different mass when compared to other atoms of the same element.
The octet rule states that after bonding...
1) 8 electrons surround all atoms in columns 4-7. (After bonding)
2) Hydrogen's outer ring is completed with 2 electrons. (After bonding)
3) All atoms have a complete outer ring. All electrons are paired up. (After bonding)
4) All atoms have a complete outer ring like noble gasses. (After bonding)
In summary: Atoms share or transfer their electrons with other atoms to complete their outer ring and be like the noble gasses.
Matter
Matter
You are made of matter. Matter is defined as anything that has mass and takes up space (volume).
Everything around you is matter. Atoms and compounds are matter. In addition, atoms are made of smaller parts of matter like protons, neutrons and electrons.
Melting = the point at which solids become liquid. For example, ice melts at 0 Degrees Celsius. This is a physical change.
Melting occurs due to the addition of heat. The heat causes the atoms and molecules to bounce more which results in the molecules leaving the solid as a liquid.
Methanol - is the simplest form alcohol. It is also known as methyl alcohol. Its formula is CH3OH.
Mixture = a physical combination of 2 or more substances. Each substance maintains its own properties. The substances can be physically separated.
A molecule consists of two or more atoms that bond by sharing their outer electrons.
Hydrogen gas (H2) and water (H20) are examples of molecules.
Neutrons are a type of subatomic particle of about the same mass as a proton but without an electric charge. They are present in all atomic nuclei except those of ordinary hydrogen. Neutrons are like glue. They help to keep the nucleus stable.
Noble gasses are elements found in column 8 of the periodic table. Each element in this family (Helium, Neon, Argon, etc…) has a complete outer ring of electrons. All of their electrons are paired up. This is why noble gasses do not interact with other atoms.
An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen.
Glycine - A type of Amino Acid
Phase Change = States of matter. Consider water. As one heats ice it turns to liquid. As one heats liquid it turns to gas.
We will consider 4 phases of matter: Solid, Liquid, Gas, and Plasma.
All changes in state are physical changes. The matter is not chemically altered.
Polar
Polar
A molecule is said to be polar if it has regions with different charges. For example, water is polar. The oxygen atom within the molecule is negative and the hydron atoms are positive. Polar molecules love to stick together. Water is cohesive because of its polarity.
Physical Change: A change in form that does not change the chemistry of the substance.
Physical properties are used to describe matter. Physical properties include: color, texture, magnetism, hardness, melting point, boiling point, density, solubility, polarity, appearance, odor etc...
Physical properties can help to identify a substance. Consider water. It freezes or melts at 0 degrees Celcius. It boils at 100 degrees Celcius. Its density is 1 gram/cubic centimeter. It is clear, polar and odorless.
A Precipitate is solid that comes out from a solution during a chemical reaction.
Protons are stable subatomic particles that are found in the nucleus of all atoms. Protons have a positive charge and counteract the charge of electrons. The number of protons in the nucleus determines what the element is. For instance, atoms with one proton are the element hydrogen. Atoms with 8 protons are the element of Oxygen.
Reactions: The nucleus of is never changed or altered after a chemical reaction. For instance, 2H2O can be broken back down to 2H2 and O2. Alcohol can combust with oxygen gas to create carbon dioxide and water vapor.
Solute – this is the substance that gets dissolved. For example, lemonade drink mix is the solute that gets added to the water (solvent).
Solvent – the substance the does the dissolving. For example, water is the solvent when you mix in lemonade drink mix. Water is known as the universal solvent.
Solution: a substance consisting of two or more substances mixed together and uniformly dispersed, most commonly the result of dissolving a solid, fluid, or gas in a liquid. A solution is a homogeneous mixture of two or more substances. Hydrogen Peroxide when mixed with water is a solution. Air is a solution. An example of a liquid solution is aqueous hydrochloric acid (HCl in water). A solution may exist in any phase or state of matter. An example of a solid solution is brass. Glass is another solid solution.
States of matter can also be referred to as Phases of Matter.
We will consider 4 phases of matter: Solid, Liquid, Gas, and Plasma.
All changes in state are physical changes. The matter is not chemically altered.
Subatomic Particles = particles smaller than an atom. Protons, neutrons and electrons are subatomic particles. In other words, they are particles that are smaller than the atom.
A suspension is a heterogeneous mixture of larger visible particles that will settle out over time. Muddy water is a suspension.
Symbol: Elements have been given a symbol. The symbol consists of one, two or three letters. If there is more than one letter for the symbol, only the first letter is capitalized.
The symbols for some elements have been known since ancient times and are derived from their Latin names. Ex: Potassium (K) is Kalium in Latin. Sodium (Na) is Natrium in Latin.
Temperature is a measure of the average kinetic energy of the molecules. Temperature measures the bounciness of matter. Atoms in hot matter vibrate quickly. In contrast, atoms in cold matter vibrate slowly.
Valence
Valence
Outer electrons are called valence electrons. Column number in the periodic table tells the valence number.
Lithium has 1 valence electron.
Valence electrons are electrons outside filled rings or shells. They are the outer electrons. Lithium has 1 valence electron.
Vaporization = When liquid changes from a liquid to a gas. Evaporation and boiling are forms of vaporization.
Boiling = is when a liquid like water turns to gas under and at the surface. In the case of water, the bubbles are water vapor.
Evaporation = occurs at the surface of a liquid. It happens when molecules vibrate away from the liquid and leave as a gas.
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