Chemical composition Flashcards
What are elements?
Elements are substances that contains only one type of atom. They cannot be broken down into simpler substances.
What are the horizontal rows and vertical columns known as in the Periodic Table?
Periods and Groups respectively.
What is an atom?
The smallest possible unit of a substance that still has its chemical properties and cannot be divided further.
What are molecules?
Multiple atoms combined.
What are the differences between metals and non-metals?
usually shiny; usually dull
good conductors of h&e; poor conductors of h&e
malleable and ductile; brittle
What does malleable mean?
Can be beaten into different shapes.
What does ductile mean?
Can be pulled into different shapes.
What is a compound?
Made up of two or more atoms chemically combined together.
(It may be made up of molecules or ions.)
How are compounds formed?
By a chemical change. A new substance is formed and the process is irreversible.
What are the properties of compounds?
- Elements combined in a fixed proportion by mass
- Pure; fixed melting and boiling points
- Different properties from their constituent elements
- Cannot be separated into their elements by physical methods
What is a mixture?
Made up of two or more elements and/or compounds that are not chemically combined.
Examples of mixtures
Steel, seawater, air
Properties of mixtures
- Have a variable proportion of elements and/or compounds
- Impure; no fixed melting or boiling points
- Elements and/or compounds in a mixture retain their respective properties
- Can be separated by physical methods into their constituent elements and/or compounds
What types of mixtures are there?
Solution and suspension.
What is a solution?
Mixture of two or more substances that are homogeneously mixed, usually dissolved.
What is a solution made of?
A solute and a solvent.
How is a solution formed?
By dissolving a solute into a solvent.
What is a suspension?
Mixtures that have some solid or liquid that is insoluble in a liquid or gas. They are know as heterogenous mixtures.
Describe a suspension
The insoluble particles inside are big enough to prevent light from passing through the suspension. The suspended particles will settle to the bottom when the suspension is left to stand for some time.
Differences between solutions and suspensions.
Particles of solute cannot be seen; insoluble substances can be seen
Solute does not settle to form solid deposits; insoluble substances can settle to form solid deposits
Light can pass through fully; light cannot pass through fully
What is the rate of dissolving?
The mass of a solute that can dissolve in a fixed volume of solvent in a fixed amount of time.
What factors affect rate of dissolving?
Temperature of solvent, size of solute particles, rate of stirring.
What is solubility?
The maximum mass of a solute that can dissolve in a fixed volume of a solvent at a certain temperature.
What factors affect solubility?
Type of solute, type of solvent, temperature of solvent.
