Pure substances, mixtures, changes, properties, pH & indicators
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What is a pure substance?
Made up of only one type of particle (atom or molecule) that possesses its own properties. A pure substance can be an element or a compound.
What is an element?
A pure substance made up of only one type of atom.
What are some examples of elements?
• Au (gold) • Fe (iron) • H (hydrogen)
What is a compound?
A pure substance made up of two or more types of atoms combined.
What is a mixture?
A substance that contains more than one type of element. A mixture can be homogeneous or heterogeneous.
What is a homogenous mixture?
Made of at least two pure substances whose particles are uniformly distributed. A solute is dissolved into the solvent and cannot be seen in the naked eye. (Coffee, vinegar,etc)
What is a heterogeneous mixture?
Made of at least two pure substances whose particles are not uniformly distributed, these substances can be seen with the naked eye. (Salad, soups,etc)
What are the types of transformations matter can go through?
Physical & chemical changes
What is a physical change?
A change that occurs when the appearance of a substance is changed without changing its nature.
What are some examples of physical changes?
• Change in shape • Phase change • Separation of a mixture • Dilution
What is a chemical change?
A change that takes place when two or more substances, called reactants, interact to create new substances called products.
What are some examples of chemical changes?
• Colour change • Gas, heat, light, electricity • Precipitate • create a new substance
What is a characteristic property?
Special or unique properties that help identify and classify a given substance.
What are some examples of characteristic properties?
• Melting point • Boiling point • Solubility • Density
What is density?
The measurement of how tightly a material is packed together in an object/substance.
How do you find density?
D = M/V
What does Cobalt chloride paper determine?
If a substance contains water or not.
What is an indicator?
Substances that react chemically in the presence of acids, bases, or neutral solutions by changing colours.
What are some examples of indicators?
• Litmus paper • Phenolphthalein • Bromothymol Blue
What is the pH scale?
Determines whether a solution is acidic, basic, or neutral.
Solutions from what numbers on the pH scale are acidic?
pH of 0-6
Solutions from what numbers on the pH scale are bases?
pH of 8-14
Solutions from what numbers on the pH scale are neutral?
pH of 7
What is Decomposition?
Breaks apart a substance into multiple components. 2H2O —–> 2H2 + O2