Classifying Matter
This type of matter is made of only one kind of atom and cannot be broken down into a simpler substance by chemical means.
An Element
Identify the error in a model showing a neutral atom that has 3 protons and 4 electrons.
It has an extra electron, electrons must equal the number of protons.
The subatomic particle that determines the atomic number of an element.
A Proton
A student observes a substance changing from a solid directly into a gas. Physical or chemical change and why?
Physical change. Change in state.
In a chemical reaction, if you start with 50 grams of reactants in a closed container, how many grams of product will you have after the reaction?
50 grams. Closed system means no matter has escaped.
If a student stirs salt into a glass of water until it disappears, which classification of matter has been created?
A mixture. (*Homogenous Mixture)
A subatomic particle has no charge. Identify the particle and its specific location within the atom.
Neutron, located in the nucleus.
Where are the elements located that are typically dull, brittle, and poor conductors of electricity?
The far right side of the Periodic Table (Non-metals).
A silver spoon tarnishing. Physical or Chemical and why?
Chemical change (evidence: color change and formation of a new substance).
If a piece of wood is burned and the remaining ash weighs less than the original wood, where did the missing mass go?
It was released into the air as smoke and gas. Open system.
Methane exists as a pure gas. It is composed of one carbon atom and four hydrogen atoms bonded together. How is methane classified as?
A compound
Describe the location and the electric charge of the subatomic particles that orbit the nucleus in an atom.
These are electrons, which are located in the electron cloud and carry a negative charge.
Which family on the Periodic Table has elements that are the most stable? *Bonus points if you can name that family.
Group 18, Noble Gases.
When two clear liquid solutions are mixed together in a beaker, a solid substance forms and settles at the bottom. What is this solid called?
The solid is a precipitate, it settles during a chemical change.
In a chemical reaction, the reactants are CH4+2O2 and the products are CO2+2H2O. Is this chemical equation balanced and explain using numbers.
-One carbon atom, four hydrogen atoms, and four oxygen atoms on the reactants side
-One carbon atom, four oxygen atoms, and four hydrogen atoms on the products side
A student argues that air is a compound because it has a uniform appearance and every particle contains oxygen. Disprove this claim.
Air is a mixture. It's made from gases that are physically mixed but not chemically bonded, their ratios can change depending on the environment without creating a new substance.
A neutral atom has 8 protons. How would adding 2 neutrons affect the nucleus and the atom?
The charge remains +8, neutrons have no charge and do not change the positive nature of the nucleus/atom.
Describe the physical properties of the elements found on the left side of the Periodic Table and identify which category they belong to.
These elements are metals, shiny (luster), malleable, and excellent conductors of heat/electricity.
A copper rod is freezed until it shrinks in size, then dropped it into a beaker with liquid where it fizzes and turns the liquid green. Identify the two types of changes that occurred and name the specific evidence for each.
The shrinking was a physical change (change in size/volume due to temperature). The reaction with the liquid was a chemical change, by the fizzing (new gas) and color change.
Look at the following unbalanced equation for the reaction of Aluminum and Oxygen: Al+O2→Al2O3. What coefficients are needed for both reactants and the product to balance this equation?
4 in front of Al, 3 in front of O2, and 2 in front of Al2O3.
A liquid's boiling point rises from 78°C to 100°C while heating. Classify it.
It is a mixture, the changing temperature shows different substances evaporating
Why an atom is described as being mostly empty space. Compare the physical size and location of the subatomic particles to prove this.
The protons/neutrons are the same mass in the nucleus, however the electrons are in the orbitals/shells/cloud, meaning they don't contribute to the mass of an atom that much.
Explain how an element's reactivity relates to its position on the Periodic Table, specifically comparing Group 1 to Group 18.
Reactivity is determined by the number of valence electrons, Group 1 elements are highly reactive because they easily lose one electron, while Group 18 elements are unreactive because they have a complete outer shell.
Explain why the presence of bubbles when boiling water is a physical change, but the presence of bubbles when mixing baking soda and vinegar is a chemical change.
-Boiling water is a change of state, evaporation
-The baking soda+vinegar create bubbles due to a new gas forming from the chemical reaction.
Balance the following equation for the production of ammonia and explain how this balanced version supports the Law of Conservation of Mass.
N2+H2→NH3.
N2+3H2→2NH3. There are exactly 2 nitrogen atoms and 6 hydrogen atoms on both the reactant and product sides, proving no atoms were created or destroyed.