PS.8.1.1 Element, Compounds, Mixtures
What type of substance is made up of only one kind of atom?
Element
What is the center of the atom called?
The nucleus
What are the columns on the periodic table called?
Groups or families
Cutting paper is what type of change?
Physical change
What does the Law of Conservation of Mass say?
Matter cannot be created or destroyed.
Two or more different atoms chemically combined form what type of substance?
Compound
Which subatomic particle has a negative charge?
Electron
Which side of the periodic table are metals found on?
The left side
Rust forming on metal is what type of change?
Chemical change
If 10 g of hydrogen reacts with 5 g of oxygen, what is the total mass of the products?
15 g
What is the big difference between mixtures and compounds?
Mixtures are physically combined; compounds are chemically bonded.
Where are protons and neutrons found in an atom?
In the nucleus
Elements in the same group have what in common?
Similar properties and the same number of valence electrons
Name one sign of a chemical change.
Color change, gas production, temperature change, or new substance forms.
If 10 grams of hydrogen react with 40 grams of oxygen to make water, what is the total mass of the water produced?
50 grams — mass of products equals mass of reactants.
A student heats iron filings and sulfur together. After heating, a solid forms that cannot be separated by a magnet. What type of substance was created- an element, compound or mixture?
A compound — the elements chemically reacted to form a new substance.
A model shows 8 protons, 8 neutrons, and 8 electrons. What element does this model represent?
The element is oxygen because it has 8 protons — the atomic number equals the number of protons.
If an element has one valence electron, which group does it belong to? Remember: #of valence electron=group #
Group 1 (Alkali Metals)
A student observes that a piece of metal turns reddish-brown after sitting outside for several days. The metal’s surface also becomes rough and flaky. Is this a physical or chemical change?
Chemical change — the color change and new substance (rust) show a chemical reaction occurred.
Which equation is balanced?
A. H₂ + O₂ → H₂O
B. 2H₂ + O₂ → 2H₂O
B. 2H₂ + O₂ → 2H₂O
Salt water contains both salt (NaCl) and water (H₂O). Explain why it’s a mixture, not a compound.
The salt and water are physically combined and can be separated by evaporation.
A student says electrons are found inside the nucleus because they are part of the atom. Is this student correct or incorrect? Why?
Incorrect; Electrons are outside the nucleus in the electron cloud; only protons and neutrons are inside the nucleus.
Which group is more reactive: Group 1 or Group 18 elements? Why?
Group 1 is highly reactive; Group 18 (noble gases) are nonreactive because they have full outer shells.
Two clear liquids are mixed together. The beaker becomes warm, and a white solid forms at the bottom. What type of change occurred, and how do you know?
A chemical change — the temperature increase shows an energy change, and the new solid (precipitate) proves a new substance formed.
A model shows 4 hydrogen atoms (H4) and 2 oxygen atoms (O2) before a reaction and 2 water (2H2O) molecules after.
Does the model follow the Law of Conservation of Mass? Explain.
Yes — there are still 4 H and 2 O atoms after the reaction, just rearranged into new molecules.