Chemistry unit 1 test Flashcards
What is a pure substance + give an example.
-a substance that is made up of only one type of particle.
-ex. distilled water is only made of water particles, whereas tap water contains other minerals
What is a mixture + give an example.
-a substance that is made up of 2 or more particles
-ex. air, juice, cellphones.
What are the 2 kinds of mixtures?
Mechanical mixtures and solutions.
What is a mechanical mixture + give an example.
-a mixture in which you can see the different types of matter.
-ex. cereal
What is a solution + give an example.
-a mixture that looks like a pure substance because you can not visually see the different types of matter.
-ex. apple juice
How can you tell if a liquid or gas is a solution or mechanical mixture?
All solutions are clear, so if a liquid or gas mixture appears to be murky or opaque it is a mechanical mixture.
ex. fog, milk, orange juice
What are physical properties?
Observations of properties of a substance using our 5 senses (qualitative) or measurements (quantitative).
What is a physical change? What are the evidence of a physical change?
A change to a substance where the composition remains the same.
-change of state
-cutting
-ripping
-breaking
-dissolving
What are chemical properties?
Describes a substance ability to undergo chemical changes which produce new substances. ex. fire works
What are chemical changes? What are evidence of a physical change?
Change in the starting substance to create a new substance.
-change in color
-gas forms (bubbles/odor)
-change in temperature/energy
-irreversible
-new solid is seen
What is density?
A measure of how much mass is contained in a given unit volume of a substance.
What is freezing point, melting point, and boiling point?
Freezing point & melting point - 0 degrees
Boiling point - 100 degrees
As you know, water freezes at 0 degrees. How does salt melt snow and ice?
Adding any dissolved impurity such as salt interferes/lowers the freezing point of water.
What is the unusual behavior of water?
Its solid form is less dense than its liquid form, which is why ice floats on water.
Why can fish survive in lakes during the winter?
The water only freezes at the top since solid water is less dense and floats on the liquid surface. Also, the ice acts as insulation for the fish underneath.
