Atomic Stucture
What subatomic particle has a positive charge and is located in the nucleus of an atom?
Define a pure substance and give one example.
A pure substance has the same chemical composition throughout (give example of an element or a compound)
Give one physical property and one chemical property of water.
Physical - liquid at room temp, clear, tasteless, etc.
Chemical - reacts with metals like iron to form rust, reacts with lithium to explode, is not combustible
Name the three most common states of matter found on Earth.
Solid, liquid, and gas
State the law of conservation of matter in one sentence.
Matter can never be created or destroyed, it can only change forms
Draw or describe an atomic model for an atom with 6 protons, 6 neutrons, and 6 electrons. What element is this?
Carbon (draw Bohr Model)
Explain the difference between an element and a compound, with one example of each.
An element is made of only one type of atom, and a compound is multiple different types of atoms bonded together. (give examples)
Identify whether boiling water is a physical or chemical change and explain your answer with evidence
Physical change, because it did not change the chemical makeup and can be reversed easily.
Describe how particle arrangement and movement differ between a solid and a liquid.
A solid has particles that are very close together and barely moving, but a liquid has particles a little farther apart and moving a little faster
In a sealed container, a chemical reaction produces a gas that later re-dissolves into solution with no mass loss measured. How does this observation support the law of conservation of matter?
The reaction ended with the same amount of mass that it started with (products mass = reactants mass)
Explain how the number of protons determines an atom’s identity (its element). Give an example.
The number of protons is the atomic number, and no two elements have the same atomic number
Describe two ways to separate a mixture (physical method) and name a sample mixture that could be separated that way.
We could evaporate water off to leave a solute (like in salt water), we could pick out different pieces (like in trail mix), we could pour it through a filter (like sand and water), etc.
Describe an investigation (brief procedure) to compare the density of two liquids and explain how density is a physical property useful for classification.
Pour the two liquids together and observe which one sinks vs. floats. Density is physical because we can observe it without changing what the matter is made of.
Explain what happens to particle motion and spacing when thermal energy is added to a gas.
The particles in the gas speed up and get farther apart.
A reaction before mixing: reactants mass = 25.0 g. After reaction (sealed), products mass = 25.0 g. Explain, using particle/atomic-level reasoning, why the masses are the same even though appearance changed.
The particles rearranged to form new substances, but no new particles were created and none were destroyed
Describe how we can determine the number of neutrons in an atom, using its tile from the periodic table.
We can subtract the atomic number from the mass number
A sample shows two substances mixed uniformly at the particle level and cannot be separated by filtration. Is it a homogeneous mixture, heterogeneous mixture, compound, or element? Explain your reasoning.
Homogeneous mixture. It said that they are mixed uniformly, but not bonded. We cannot separate a homogenous mixture by a filter alone.
A piece of aluminum metal is heated and begins to glow; later it forms a white powder on the surface when left in air. Which observations represent physical changes and which represent chemical change? Explain using evidence
When it was heated, this is a physical change. It is still aluminum, and only changed its temperature.
When it formed a white powder, this was a chemical change. This created a new substance that wasn't there before.
Define plasma and give one example where plasma naturally occurs or is created by humans
Plasma is a gas that has been heated until it gains an electrical charge. We use plasma in neon signs and it is also in the Sun
Design a short classroom lab (materials and steps) to demonstrate conservation of matter during a chemical reaction that produces a gas. (Include how to measure or show conservation.)
Using baking soda and vinegar with a balloon, we can observe the reaction and trap the gas in a balloon so that it can still be measured.
Using patterns in the periodic table, predict whether an element with 1 valence electron is likely to be a metal or nonmetal and explain why in terms of electron arrangement.
It is a metal because it is in group 1 of the periodic table, and metals are to the left of the "staircase"
You are given three samples: (A) salt (NaCl) crystals, (B) saltwater, and (C) an iron nail. Classify each as element, compound, homogeneous mixture, or heterogeneous mixture and justify each classification using particle-level reasoning.
A) compound
B) homogeneous mixture
C) element
Two clear solutions are mixed and form a solid precipitate and release heat. List at least three pieces of observational evidence that support the claim this is a chemical change.
There was a color change, a solid formed, and heat was produced.
Draw or describe a particle-level model (words are fine) showing what happens during evaporation and condensation. Explain how thermal energy transfer causes the changes in particle motion.
During evaporation, liquid particles speed up and spread apart to become a gas. (thermal energy added)
During condensation, gas particles slow down and come together to form a liquid. (thermal energy removed)
A student claims that mass can be lost during a chemical reaction, because when they went camping this summer and build a fire, they noticed that the ashes left over weighed less than the firewood they burned. Explain why this student's claim is incorrect. What happened to the mass that was "destroyed"
The mass still exists, it just became smoke and other gases and escaped into the atmosphere.