WorksheetsUnit #2 Chemistry Review
Total questions: 40
Worksheet time: 21mins
What is a chemical reaction?
Two or more substances interact to make one or more new substances
A single substance changes temperature without forming anything new
Mixing substances where no chemical change occurs
Separating substances using a filter
What is the Law of Conservation of Mass?
In a chemical reaction, the number of atoms of each type stays the same on both reactant and product sides
Mass can be created when energy is added to a system
Atoms are lost during chemical reactions because they turn into energy
Products always weigh less than reactants because gases escape
What is a mixture?
A substance made by combining two or more different materials without a chemical reaction, which can be separated
A new substance formed when materials chemically react
A pure substance with a fixed composition
A material that cannot be separated by any method
What is density?
How tightly packed the molecules are in a substance
The temperature at which a substance melts
How easily a substance dissolves in water
The mass of a substance per mole
What is melting point?
The temperature at which a solid substance melts into a liquid
The temperature at which a liquid freezes
How much heat a substance can absorb
The point where a gas condenses
What is solubility?
The ability for one substance to dissolve into another substance
The ability of a solid to melt when heated
The tendency of a substance to float in water
The measure of how hard a substance is
What are synthetic materials?
Materials made from natural resources by chemically changing the starting substances to create a material with different characteristics
Materials found directly in nature without any processing
Mixtures formed without chemical reactions
Substances that cannot be used by living things
Which list best shows physical properties mentioned in the study guide?
Color, density, odor, hardness, melting point, boiling point
Flammability, toxicity, reactivity to acid
Solubility, conservation of mass, mixture
Synthetic, natural, matter
Which examples match chemical properties we've talked about
Flammability, toxicity, reactivity to acid
Color, odor, hardness
Density, melting point, boiling point
Solubility and mixture
What is the first step in balancing a chemical equation?
Identify your reactants (left side) and your products (right side)
Start by adding coefficients to products only
Remove any atoms that appear more than once
Change formulas so the numbers of atoms match
density
chemical property
physical property
flammability (burns)
chemical property
physical property
reacts with acid
chemical property
physical property
supports combustion
chemical property
physical property
melting point
chemical property
physical property
reacts with water
chemical property
physical property
hardness
chemical property
physical property
boiling point
chemical property
physical property
luster
chemical property
physical property
reacts with air
chemical property
physical property
What is the law of conservation of mass?
Matter cannot be created or destroyed; total mass stays the same even when parts rearrange.
Mass is always lost as heat in reactions.
Atoms change into energy so mass is not conserved.
Mass can be created if enough energy is added.
Explain a time when the mass of something in a chemical reaction would appear to increase? (Hint...think about the statue of liberty)
When rust or oxidation forms on the surface of a metal, it seems heavier even though total mass is conserved.
When water boils and turns to steam, mass actually increases.
When a log is split into pieces, mass increases.
When salt dissolves in water, mass increases because salt disappears.
When 14 grams of Hydrogen reacts with 7 grams of Oxygen, what is the mass of the water? Explain why.
21 grams, because the total mass of reactants equals the total mass of products.
14 grams, because hydrogen is lighter.
7 grams, because oxygen is consumed.
28 grams, because mass doubles in reactions.
List some things that may indicate a chemical reaction happened. In other words, what might you observe? Select all observations that indicate a chemical reaction.
Change in smell or taste
Increase in mass without adding material
Object changes shape when cut
Movement of air due to a fan
Can I create platinum from aluminum? Choose the best answer.
No, because elements are pure substances and one element cannot be changed into another
Yes, by mixing aluminum with other metals to form platinum
Yes, through a chemical reaction that converts aluminum into platinum
No, but it can be done by physically separating aluminum into platinum
Be able to examine a table of properties of 2 substances and determine whether they are the same or different and explain why or why not. Which statement best describes how to decide using characteristic properties?
If melting points are different, the substances are different; if all characteristic properties match, they are the same.
If densities are different, the substances are still the same because density can change without forming a new substance.
If solubility changes, the substances must be the same because solubility is not a characteristic property.
Only color matters; other properties do not help identify substances.
Using the chemical equation C6H12O6 + 6O2 → 6H2O + 6 CO2, determine the number of carbon atoms on each side of the equation.
4
6
8
12
Using the chemical equation C6H12O6 + 6O2 → 6H2O + 6 CO2, determine the number of hydrogen atoms on each side of the equation.
6
10
12
18
Using the chemical equation C6H12O6 + 6O2 → 6H2O + 6 CO2, determine the number of oxygen atoms on each side of the equation.
12
16
18
24
A model shows circles labeled H and O before and after a change; the same total number of H atoms (4) and O atoms (2) appear on both sides, but they are arranged into new molecules. Is this a chemical reaction? Choose the best reason.
Yes, two materials chemically combined to create a new substance with different properties.
No, some atoms disappeared so it cannot be a reaction.
No, it is only a physical change because the molecules did not recombine.
Yes, because atoms were destroyed and new ones appeared.
How does the model relate to the conservation of mass? The image shows the same total of H atoms (4) and O atoms (2) on both sides before and after the change.
The number of each type of atom is the same on both sides, so mass is conserved.
More atoms are present after the change, so mass increases.
Fewer atoms are present after the change, so mass decreases.
Atoms change into different elements, so mass is not conserved.
Where do all synthetic materials come from? Use soap as an example.
They are made from natural resources that are chemically changed; for example, soap is made from fat.
They are created from nothing without any starting materials.
They come only from laboratory glassware, not from natural substances.
They are produced directly from sunlight without using matter.
Be able to explain the difference between a chemical and a physical property and give examples of each. Which option best states the correct difference and provides appropriate examples?
A physical property can be observed without changing a substance’s identity (examples: color, density); a chemical property is observed when the substance undergoes a chemical change (examples: flammability, reactivity to acid).
A physical property requires changing the chemical identity (examples: flammability, toxicity); a chemical property is observed without any change (examples: color, hardness).
Both physical and chemical properties require changing the substance’s identity; examples for both include mass and volume.
Physical properties always depend on the amount of substance (examples: mass, volume); chemical properties do not depend on amount (examples: boiling point, hardness).
Are mass and volume properties? Why or why not?
No, because they change with the amount of substance and properties do not depend on amount.
Yes, because any measurement of matter is a property regardless of amount.
No, because they are chemical properties that require a chemical change to be observed.
Yes, because they describe identity and remain the same no matter how much substance you have.
Is density a property? Why or why not?
Yes, because it is the ratio of mass to volume and does not depend on how much of the substance you have.
No, because it changes with the amount of substance just like mass and volume.
Yes, because it is simply how heavy an object feels when you hold it.
No, because it requires a chemical change to measure.
If a substance has a mass of 50 grams and a volume of 25 mL, what is the density of the substance?
D = M/V
2 g/mL
25 g/mL
0.5 g/mL
75 g/mL
