Physical & Chemical Properties
Flattening a block of gold into a sheet
Malleability
Physical Property
What are the signs of a physical change?
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Change in size, shape, and state WITHOUT changing the identity
What is a chemical formula?
The ratio of elements in a compound
Hydrogen-1 gains a neutron. Is it still hydrogen? What is its mass number?
Yes, it is still hydrogen.
Its mass number is 2.
What’s the difference between the atomic number and mass number of an atom?
Atomic number = # of protons
Mass number = # of protons + # of neutrons
Sodium metal ignites and explodes when coming in contact with water
Reactivity
Chemical Property
What are the five signs of a chemical change?
Energy Change
Color Change
Gas Formation
Odor/Taste Change
New Substance Formed
How many elements are in: 4 H3PO4?
3 elements
How many electrons are in a neutral atom of Bromine?
35 electrons
What determines the charge of an atom?
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Comparing the numbers of protons and electrons
Mixing sugar in water until you can’t see the sugar crystals
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Solubility
Physical Property
Are all physical changes reversible? Are all chemical changes irreversible?
No, physical changes are MOSTLY reversible
No, chemical changes are RARELY reversible
What does a coefficient tell you?
The number of molecules of a compound
Oxygen gains 1 proton and 1 electron. What element is it? What is its mass number?
Fluorine
17
Is the mass of an atom affected by electrons? Explain.
No
The electron has a mass that is much smaller compared to the protons and neutrons.
Explain conductivity
The ability to transfer energy (i.e. heat, electricity)
What is the difference between a physical change and a chemical change?
Chemical changes result in the change of the identity of the substance while physical changes will not.
What does a subscript tell you?
The number of atoms of an element in a compound
What is the charge of an ion with 29 protons, 35 neutrons, and 31 electrons?
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What’s the difference between atomic mass and mass number?
Atomic mass = average mass of one atom of an element
Mass number = # of protons + # of neutrons in a specific isotope of an element
Explain the difference between physical and chemical properties.
Physical properties: observed without changing the matter’s identity
Chemical properties: the matter’s identity changes when observing them
Will chemical changes result in physical changes? Why or why not?
Yes, chemical changes will change the physical properties of a substance, which means there is a physical change.
How many atoms are in:
3 (NH4)2Cr2O7?
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57 atoms
Carbon-14
How many protons, electrons, and neutrons does it have?
6 protons
6 electrons
8 neutrons
One atom has 23 protons, 26 neutrons, and 32 electrons. A different atom has 23 electrons, 24 protons, and 25 neutrons. Are they the same element? Why or why not?
No, they have different numbers of protons which would make them different elements.