States of Matter, Mixtures, and Elements: A Chemistry Guide
States of Matter
Which state of matter has a definite volume and a definite shape?
Solid
Which state of matter has a definite volume but not a definite shape?
Liquid
Which state of matter does not have a definite volume nor a definite shape?
Gas
Mixtures
Homogeneous Mixtures
Can homogeneous mixtures be filtered? Cannot
When in liquid form, homogeneous mixtures can also be called: Solutions
Heterogeneous Mixtures
All heterogeneous mixtures can be filtered. True
The process used to separate heterogeneous mixtures of solids and liquids is called… Filtration
General Properties of Mixtures
In a mixture, are the substances chemically combined? Not chemically combined
In a mixture, can the substances be separated by chemical or physical processes? Physical
Examples of Mixtures
State an example of a solution: Mixing salt (solute) with water (solvent)
State an example of a suspension: Oil and Water
Methods to Separate Mixtures
List the different methods to separate a mixture: Filtration, Evaporation, Distillation, Sifting, Centrifugation, Extraction, Magnetic Separation
Filtration
When is it appropriate to separate a mixture by filtration? To separate a mixture by filtration, the mixture must be heterogeneous and must be a mixture of a solid and a liquid. This is because in the process of filtration, you pour the liquid with the solid through a sieve or filter paper; the solid gets stuck in the filter paper and the liquid goes through.
Distillation
What is the technique that uses the differences in boiling points of various substances to separate mixtures? Distillation
Crystallization
The formation of pure solid particles of a substance from a solution is called… Crystallization
Magnetic Separation
One of the processes used to separate mixtures: Magnetic Separation: Separates materials that are drawn to a magnetic field
Sulfur and Iron Filings Mixture: The Sulfur and Iron Filings are mixed together. When exposed to a magnetic field, the iron, being a metal, immediately binds to the magnetic field. Therefore, the two components have been classified separately by Magnetic separation.
Types of Mixtures and Their Differences
Solutions vs. Suspensions
Difference between a solution and a suspension: The difference is that a solution is a special type of homogeneous mixture where the particles dissolve and it cannot be filtered, while a suspension is a special type of heterogeneous mixture where particles will never dissolve and it can be filtered.
Sand and Water vs. Salt and Water
Difference between a mixture of sand and water and a mixture of salt and water: Salt and water are a homogeneous mixture; the salt dissolves completely into the water, and the different components are not visible. Sand and water are a heterogeneous mixture and a suspension; the sand will never dissolve into the water and will eventually settle on the bottom (different components are visible).
Tap Water vs. Distilled Water
Difference between Tap Water and Distilled Water: Tap Water comes out of the sink; it has contaminants (bacteria, dirt, rust, etc.) which make it non-pure and a homogeneous mixture. Distilled Water is purified water, which means it contains only H2O, meaning that it is a pure substance and a compound.
Elements and Compounds
Elements
An element can or cannot be broken down into a simpler substance? Cannot
Compounds
Compounds can be separated by chemical or physical means? Chemical
Compounds have the same or different characteristics as the elements that they are made of? Different
…Cannot be separated by physical means: Alloys
Elements, Compounds, and Mixtures
Difference between an element, a compound, and a mixture: Elements and compounds are pure substances, while a mixture is not. Mixtures can be separated by physical processes, elements and compounds can’t (compounds can only be separated by chemical processes). Elements are the pure form of an element from the periodic table. Compounds are when two or more elements chemically bond together. In mixtures, components are only together by physical means and can be separated.
Colloids
Colloids are homogeneous or heterogeneous at the macroscopic level? Homogeneous
Separating a Mixture of Sand, Water, and Alcohol
How to separate a mixture of sand, water, and alcohol:
- Step 1: The mixture is already in liquid form (H2O and Alcohol), so in order to separate the sand, you need to use the process of filtration. For filtration, you will need filter paper. You pour the mixture of sand, water, and alcohol through the filter paper. The water and alcohol will pass through the filter paper and go into the beaker below, and the sand will be trapped in the filter paper. You can set the sand aside.
- Step 2: To separate the water and alcohol, do NOT use boiling. This would cause the alcohol to evaporate into the air and only the water to remain. Instead, use distillation. For this, use the distillation apparatus. On one side, there is the water and the alcohol carefully heating with a flame. Alcohol has a lower boiling point, so it will begin to boil off first.
Physical and Chemical Changes
Physical Changes
When a physical change occurs, the composition of the components is changed: False – the components stay the same
Freezing occurs when a liquid substance changes into a gas: False – this is describing evaporation; freezing occurs when a liquid substance changes into a solid
When ice cream melts, a physical change occurs: True – melting is a physical change (changes in state of matter are physical changes)
Evaporating water from a mixture of salt and water is a physical change: True – evaporation is a physical change
Cutting a brownie is a chemical change: False – it is a physical change
Pouring milk in your cereal is a physical change: True – the components stay the same, just mixed together
Sublimation occurs when a solid substance changes directly into a gas (without first turning to a liquid): True
Chemical Changes
Exploding fireworks is a chemical change: True – this is combustion (chemical change)
Cooking pancakes is a physical change: False – cooking chemically changes food
Examples of Physical and Chemical Changes
Examples of a physical change: Boiling water and Shredding Paper
Examples of chemical change: Digesting Food, Baking a cake
Signs of a Chemical Change
4 signs that indicate that a chemical change has taken place: Color changes, odor changes, temperature changes, and formation of bubbles
Physical and Chemical Properties
What is an example of a chemical property of an object?: The flammability of gasoline
What makes physical properties different from chemical properties?: Physical properties can be observed without changing the composition of the substance
Examples of Physical and Chemical Properties
Physical properties include: color, odor, hardness, boiling point, density, solubility
Chemical properties include: flammability, reactivity, combustion
Physical Properties of Metals and Non-metals
Physical property that is true for all metals: Good conductor of heat, good conductor of electricity, ductile, malleable, lustrous, all solids except for mercury.
Physical property that is true for all non-metals: Not lustrous
The Periodic Table
Arrangement and Trends
Why do elements in the same group have similar properties?: Because they have the same number of valence electrons
Which scientist is responsible for the current arrangement of the Periodic Table?: Dimitri Mendeleev
Periodic Trends
- Atomic Radius & Reactivity: increases going down and decreases from left to right
- Electronegativity, Electron Affinity & Ionization Energy: decreases going down and increases from left to right
Metals and Non-metals
Only metal that exists as a liquid at room temperature and standard pressure: Mercury
Only nonmetal that exists as a liquid at room temperature and standard pressure: Bromine
One physical property of all metals: Good conductors of heat
Naturally Occurring and Man-made Elements
How many naturally occurring elements exist?: 92
One man-made element: Neptunium
Transition Metals
Why is it “surprising” that the Transition Metals are so similar to each other with their physical and chemical properties?: It is surprising they all have similar properties when they have different numbers of valence electrons.
Information from the Periodic Table
10 things you can determine from the Periodic Table: Number of protons, Number of electrons, Atomic number, Atomic Mass, Number of neutrons, Number of valence electrons, Group, Metals or nonmetals, Atomic symbol, Electronegativity
Atomic Structure
Subatomic Particles
Which subatomic particle defines the identity of the atom? Describe where it is located: Proton, Neutron, Electron. Protons and Neutrons inside the Nucleus and Electrons outside of it
Charges of Subatomic Particles
What is the charge of a proton? +
What is the charge of an electron? –
What is the charge of a neutron? No charge
Atomic Mass and Charge
Location where the mass of the atom concentrates: Nucleus
Why isn’t the mass of an electron included in the overall mass of the atom?: Because their mass is much smaller, not enough to significantly contribute to the overall mass.
Why is the overall charge of the atom neutral?: The overall charge of an atom is neutral because it consists of an equal number of protons and electrons. Since the protons have a positive charge and the electrons a negative one, their charges cancel each other out. Neutrons don’t have a charge, therefore they do not change the charge of the atom.
Valence Electrons
What are valence electrons?: The electrons in the outermost shell of an atom
Elements and Compounds
Difference between an element and a compound: An element is a pure substance while a compound is a chemically combined substance
Atomic Mass and Mass Number
Difference between the Atomic Mass and the Mass Number: Atomic Mass is the number we see on the periodic table, and the mass number is that number rounded.
Nucleons
What are the nucleons of an atom? Where are they located?: The nucleons refer to the protons and neutrons of an atom. They are located in the nucleus.
Mass Number
What term is used to describe the sum of the protons and neutrons in an atom?: Mass Number
Periodic Trends in Detail
Electron Affinity (EA)
Electron affinity: The ability of an atom to accept an electron. How much it wants to GAIN an electron.
Describe the trend (EA) and state which element has the highest and the lowest value: Decreases going down a group and increases from left to right in a period. As you go up a group, electronegativity increases since the valence shell of electrons are closer to the nucleus, and when you go from left to right, it gets higher because you are increasing the number of valence electrons, causing the atom to want to GAIN electrons to fill its outer shell. Fluorine has the highest and Francium the lowest.
Which group does not have an electron affinity? Why?: Noble gasses because they have a full outer shell, therefore do not need more electrons.
Ionization Energy (IE)
Ionization energy: The energy required to completely remove an electron from a neutral atom.
Describe the trend (IE) and state which element has the highest and the lowest value: Ionization energy decreases moving down a group and increases moving from left to right in a period. As you go up a group, electronegativity increases since the valence shell of electrons are closer to the nucleus, and when you go from left to right, it gets higher because you are increasing the number of valence electrons; most likely, the atom will want to gain electrons to fill the outer shell, making it harder to remove an electron (increasing ionization energy). Highest = Helium Lowest = Francium
Which group has the highest ionization energy?: Noble Gasses since they have 8 valence electrons in their shell. By having the perfect shell, they do not want to lose any electrons, therefore it becomes hard for one to be removed (requires a lot of ionization energy).
Which group has the lowest ionization energy?: The Alkali Metals because they have only one valence shell electron, making it easier to take it away, which requires less ionization energy.
How is it possible that Ionization Energy and Electron Affinity have the same trend, but they are opposites to each other?: Because if an atom has high ionization energy, it means that it does NOT want to lose an electron, mostly meaning that it wants to gain one. Atoms that want to gain electrons have high electron affinity.
Electronegativity (EN)
Electronegativity: The atom’s ability to attract and bind with electrons (hold on to its electrons tightly).
Describe the trend (EN) and state which element has the highest/lowest value: Electronegativity DECREASES moving down a group and INCREASES from left to right in a period. It’s easier this way for the atom to hold on to its electrons (the closer the valence shell electrons are to the nucleus, the easier it is to hold on to them). From left to right, they gain electrons; the atom will most likely want to gain them and fill the outer shell, making the electrons it already has very important & to hold them tightly. Highest = Helium Lowest = Francium
Which group has the highest electronegativity?: Noble Gasses since they already have their perfect valence shell of 8 electrons. They don’t want to either gain or lose electrons, making them use high electronegativity to hold on tightly to their 8 electrons.
Which group has the lowest electronegativity?: The Alkali Metals because they have only one valence shell electron and want to lose it, requiring less electronegativity since they don’t want to hold on to it.
Atomic Radius
Describe the trend and state which element has the smallest and the biggest radius: Atomic Radius INCREASES moving down a group and DECREASES from left to right in a period. Smallest = Helium Biggest = Francium
Ions
Cations
Which group is likely to become a cation with a +1 charge?: Alkali metals since they have 1 electron to lose in order to have a full valence shell, they will lose it easily. Once they lose a negative charge, the positive charge takes over, and the atom will have a positive charge. Positively charged ions are called cations.
Anions
Why do atoms become ions?: Atoms become ions so that they can have a full valence shell of electrons.
Cations vs. Anions
Difference between a cation and an anion: The difference between a cation and an anion is that a cation is formed when an ion loses electrons and is positively charged; on the other hand, an anion is formed when an ion gains electrons and is negatively charged.
Lewis Dot Diagram
Why was the Lewis Dot Diagram created?: Created in order to show the total number of valence electrons for atoms, paired electrons, and lone pair (unpaired) electrons in an atom.