What Happened?
What is a substance made of only one type of atom?
Answer: Element
What is the smallest unit of an element that still has the properties of that element?
Atom
Crushing a can is what type of change?
Physical change
Which statement is incorrect?
A. An atom is one particle.
B. An element contains only one type of atom.
C. A compound contains two or more different elements.
D. A molecule contains only one atom.
Answer: D
A student says, “A chemical change only happens when a substance changes color.”
Is the student correct? Explain your answer and give an example of another type of evidence.
Answer: No. Other evidence can include gas production, light, precipitate formation, unexpected temperature change, or a new odor.
Which chemical formula has more oxygen atoms?
A. Fe(NO₃)₃
B. Ca₃(PO₄)₂
Answer: A
Which chemical formula has more oxygen atoms?
A. Ca(NO₃)₂
B. Al₂O₃
Explain your answer.
Answer: A
You have to multiply the subscript out side the parentheses with everything included in the parentheses. 3 X 2 = 6
How many elements are in C2HO2H?
List them
3
Carbon
Hydrogen
Oxygen
Why can't burning paper easily be changed back into paper?
A new substance called ash forms during the chemical change.
How many elements and atoms are in Mg(C₂H₃O₂)₂?
Answer: 4 Elements and 15 atoms
In Fe₂(SO₄)₃, how many sulfur atoms are there?
How many N atoms are in N₂HNO₃?
3
How many elements and total atoms are in Cl3H2ON4S2Fe3 ?
Answer: 6 Elements 15 Atoms
Which chemical formula has more oxygen atoms?
A. (NH₄)₂SO₄
B. Ca(NO₃)₂
B.
Compare O₂ and CO₂. How are they different even though both contain two oxygen atoms in their formulas?
Answer: O₂ contains only oxygen, so it is an element. CO₂ contains carbon and oxygen, so it is a compound.
How many elements and atoms in this chemical formula: MgCl₂Na₂SO₄
Answer: 5 Elements and 10 atoms
How many total atoms are in Na₂(SO₄)₃?
17
3. A student mixes two solutions. A white solid suddenly appears at the bottom of the container. The student did not add any solid to the mixture. What happened?
You must use the sciencetific word.
Precipitate
A student eats an apple. First, the student chews the apple into smaller pieces. Later, enzymes in the digestive system break down the substances in the apple. Which statement correctly identifies the changes?
A. Both are physical changes because the apple is only being broken apart.
B. Chewing is a physical change, while enzyme digestion is a chemical change.
C. Chewing is a chemical change, while enzyme digestion is a physical change.
D. Both are chemical changes because the apple changes.
Answer: B.
A student sees NaCl and says, "There are two molecules because there are two element symbols." What is wrong with this reasoning?
Answer: The two symbols represent two different elements, not two molecules. NaCl is a compound made from sodium and chlorine
A student sees the formula HO(N2H)₃. They say there are 2 nitrogen atoms and 4 hydrogen atoms. What is wrong with their answer?
Answer: The student forgot to multiply the Nitrogen atoms inside the parentheses by the subscript 3. So the formula contains 6 nitrogen atoms and 4 hydrogen atoms.
True or False: Elements and Compounds are essential to life and pure substances found on earth.
Give an Example of an element and a compound.
True.
Element: Oxygen (O₂)
Compound: Water (H₂O)
Compound: Salt (NaCl)
Element: Iron (Fe)
Compound: Water (H₂O)
Element: Carbon (C)
Compound: Carbon dioxide (CO₂)
Element: Oxygen (O)
Compound: Sugar (C₆H₁₂O₆)
How many total atoms are in 3H₂O? How many hydrogen atoms and oxygen atoms are there?
Answer:
A piece of metal is cut into smaller pieces. Another piece of metal is heated until it glows and then cools back down. Are these changes physical or chemical? Explain.
Answer: Both are physical changes. Cutting changes the size/shape, and heating changes the temperature/state, but neither creates a new substance.
What is the common name of this compound (NaCl) ?
A. Water
B. Salt
C. Sugar
D. Sand
Answer: B