Physical Science Midterm
What is a chemical reaction?
A chemical reaction is when one or more substances is combined with a reactant to form one or more different substances.
What is a group in the periodic table? What do all of these elements have in common?
A group of elements is a column in the periodic table. These elements all have the same number of valence electrons. Group 1 has 1, group 2, skip the transition metals, group 13, 3, so on.
What does a high temperature tell us about the molecules in the substance?
A high temperature means the molecules are moving quickly and are far apart, they're bumping into each other and transferring thermal energy
Silver Selenide
Ag2Se I
What are the three types of radioactive decay? Describe what is emitted for each type of decay.
Alpha, Beta and Gamma Decay. Alpha shoots off a Helium atom and it's large. Beta is smaller cause it just shoots off an electron and it's smaller. And Gamma decay is just energy
Give an example of something that can shield you from each type of decay.
Alpha: because helium is so big, something like paper can stop it's radiation. Beta decay can go through paper but needs something more solid like aluminum to stop it. And Gamma needs to be stopped by something very thick and dense like lead.
Give a brief description of what happens in fission. What particle is required to start a fission reaction?
An electron is shot into a uranium atom and it splits creating more electrons that shoot off as well as a ton of energy.
If the density of water is 1 g/mL (1 g/cm3), which of your objects do you think would float? Explain.
Any objects with a density less than 1. Styrofoam would be an example of something that would float because it's density is less than 1.
How does adding/removing heat affect what state of matter a substance is in?
As those molecules get further apart, they start to change to state of matter because the major difference between the 3 main states of matter are the space between the molecules. Think about boiling something, as you heat those molecules they get so far apart that they become a gas, steam.
Why do atoms form bonds with other atoms? What are they trying to achieve? #goals
Atoms form chemical bonds to reach stability. Atoms are trying to share electrons with other atoms in order to have a full outer shell of electrons (8e-)
Food is digested
C
Mentos in coke causing foam
C
Wood rotting
C
ability to catch fire
C
reacts to water
C
What are chemical bonds?
Chemical bonds are bonds between atoms to create compounds. These bonds include ionic and covalent bonds.
Synthesis -
Combining two or more substances into one substance
What type of reaction is the following? CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
Combustion
What is the difference between covalent and ionic bonds?
Covalent bonds are between 2 nonmetals and ionic bonds are between a metal and a nonmetal. Also how you name them is different. With covalent bonds you use prefixes.
The density of aluminum is 2.7 g/cm3. An unknown sample has a mass of 45g and a volume of 13.5 cm3. Could the unknown sample be aluminum? Why or why not? Make sure you show your math calculation.
D = M/V | 45g / 13.5cm3 = 3.33g/cm3. Probably not aluminum, because it doesn't have the density of aluminum.
What is density and how do you calculate it (units too)?
Density is how close or far apart the molecules in a substance are. D(g/m3) = Mass(g)/Volume(m3)
How can density be used to identify an unknown substance? Be specific.
Density is specific to a substance, every substance will only have one density. Therefore, if you know the density of a substance, you can identify that substance.
How do you determine the number of valence electrons an atom has?
Depending on what group it's in. group 1 - 2 have said many electrons skip the transition metals, 13 has 3, 14 has 4, so on.
What type of reaction is the following? 2KI(aq) + Pb(NO3)2(aq)→2KNO3(aq) + PbI2(s)
Double Replacement
What method can you use to determine the volume of an irregular shaped object and what is a unit it could be in? Be specific.
Drop it in water and find how many milliliters of water it displaces by measuring the water before and after the object is dropped in it.
What are elements? What are some examples?
Elements are what everything is made out of. They come in various forms and states of matter, most commonly metals and carbon. Ex: Carbon, Silicon, Iron, Magnesium, Potassium.
Which periodic families are the most reactive? Why?
Families closer to the left side are more reactive and families closer to the right are non reactive.
How does heat energy flow/move? (ie. low to high concentration, ect.) What is the overall goal of heat transfer?
Heat always moves from high concentration to low concentration. The overall goal is to real equilibrium.
What is the most important factor in determining an element's place in the periodic table?
How many protons it has.
How do you determine the number of protons an atom has?
If it's a neutral atom it will have as many electrons as protons and if it's an Ion you have to know the element and its atomic number.
How do molecules move when they are in a solid, liquid and gas? Discuss their speed, space between molecules, etc.
In a solid they vibrate but for most part are stationary, they're packed very tightly together and don't have a ton of speed. In a liquid, they have much more space between the molecules and they all move fast but not super fast. In a gas, there is a lot of space between all the molecules and they're traveling really fast.
Give a brief description of what happens in fusion.
In fusion, two atoms combine to create a larger nucleus in which it releases a ton of energy
How do you determine the volume of a cube and what is a unit it could be in? Be specific.
Length x Width x Height. It's in m3.
What are Lewis dot structures? What do they show?
Lewis dot structures are a way of displaying how many valence electrons are in the element.
What is the law of conservation of matter?
Matter can not be created or destroyed. Matter is just redistributed.
BeSe
Metal Nonmetal Ionic
SnO
Metal Nonmetal Ionic
Which types of elements conduct electricity/heat and are malleable?
Metals
Where are the metals on the periodic table? Non-metals? Give examples of each.
Metals are all to the left of the metalloids which is a staircase on the right side of the periodic table. Non-metals are on the right of the staircase. A metal would be Radium, and a nonmetal would be oxygen.
How are elements/atoms different from molecules/compounds?
Molecules/Compounds are made up of elements/atoms. Elements are found naturally in the world somehow and can be combined with each other to form new compounds. These combinations can occur naturally or artificially.
C2H6
Nonmetal Nonmetal Covalent
PCl3
Nonmetal Nonmetal Covalent
Identify the following as a chemical (C) or physical (P) property: luster
P
Label the following examples as a physical or chemical change: Alcohol evaporates
P
Salt dissolving in water
P
Squeezing the water out of a sponge
P
boiling point
P
malleability
P
smell
P
What is the difference between physical and chemical changes? Give an example of each.
Physical changes are changes in matter that can be observed without actually altering the substance, ex: density, color. Chemical changes are changes that alter the substance into a new substance somehow, ex: flammability, rusting.
How do you determine the mass number of an atom?
Protons and neutrons are 1 AMU each but electrons are negligible in weight. Add Protons + Neutrons.
What are the three parts that make up an atom? What are the charges of these parts? Where are they located in the atom? Include a model.
Protons, Neutrons, and Electrons, positive, neutral, and negative. Neutrons and Protons are in the nucleus and electrons' orbit.
Sulfur hexafluoride
SF6 C
What should you look for to determine science vs pseudoscience?
Science has scientific backing with evidence. You can prove science over and over again. One of the key factors of science is if it's repeatable. pseudoscience, on the other hand, are claims without evidence to back up the claim. typically not repeatable by following and SOP.
Trisilicon tetranitride
Si3N5 C
Is Carbon most like Silicon or Aluminum? Why?
Silicon because it's in the same group and it makes the same amount of bond.
What are some elements in period 3?
Sodium, Magnesium, Aluminum
Strontium fluoride
Sr2Fl I
What type of reaction is the following? 2 CO(g) + O2(g) → 2CO2(g)
Synthesis
What is temperature/how is it measured?
Temperature is a measure of the average kinetic energy in a substance, which basically means a measure of how fast the molecules are moving. It is measured with a thermometer and in units called degrees. There are two systems of measurement, Fahrenheit and Celsius. Occasionally Kelvin is also used.
Where are the alkaline earth and alkali metals? Give examples of each.
The Alkaline earth metals are the second column. Very reactive. Magnesium, Calcium.
Which elements are in group 2?
The Alkaline-Earth metals. Elements with 2 valence electrons
Where is the halogen family? Give examples.
The halogens are the second to last column in the periodic table. Iodine, Chlorine.
Where are the noble gases? Give examples.
The noble gases are all the way to the right, very last column. They are not reactive because they have a full outter shell. Helium, Argon.
How do you determine the charge on an atom?
The number of protons and electrons. Whatever there's more of is the charge of the atom.
What happens to the kinetic energy of molecules when heat is added? What happens to the kinetic energy of molecules when heat is removed?
The particles move faster and expand (get further apart) when they're introduced to heat and vice versa when heat is taken away. The particles get closer and they condense.
What is a period on the periodic table? What do all of these elements have in common?
The rows are called periods. As you go down the periods all elements in a row have the same number of electron shells.
Where are the transition metals? Give examples.
The transition metals are between groups 3 and 12 and they are all metals. Iron, Aluminum
What is wrong with this formula (Ca2I) for Calcium Iodide? Fix it.
The values for the elements are switched. It should be CaI2
Decomposition -
Turning 1 substance into two or more substances.
List the important parts of a graph and describe why they are important?
Two axises comparing two things against each other (to know how to distinguish what you're comparing); Labels of each graph including units, numbers (to know how to define and interpret the data correctly); Title of the graph to know what you're comparing; The graph itself with data (to come to scientific conclusions).
A lead cylinder has a mass of 540 grams and a density of 2.70 g/mL. What is the volume?
V = M/D, 540g / 2.7g/mL = 200mL
Combustion -
When a substance combines with oxygen gas to produce a large amount of energy.
Double Replacement -
When ions from two compounds exchange place to form new compounds
Single replacement -
When one element replaces another similar element in a compound
How can you determine the formula for an ionic compound?
●Step 1-identify the metal and non-metal ●Step 2- write the symbols ●Step 3- write the charges ●Step 4- cross over the charges ●Step 5- remove the charge (+ -) ●Step 6- simplify the numbers and get rid of 1's Mg & Cl ⇒ MgCl2 Na & O ⇒ Na2O
