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Questions and Answers
Which type of mixture has particles that do not settle at the bottom?
A saturated solution can dissolve more solute without changing the temperature.
False
What is the process of forming a solution called?
Dissolution
When grinding solids into smaller pieces, the ______ increases, leading to faster dissolution.
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Match the following terms with their definitions:
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Which of the following is an example of a pure substance?
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Metalloids are excellent conductors of heat and electricity.
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What are the two parts of measuring?
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The periodic table currently has ______ elements.
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Match the following terms with their correct definitions:
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What property do pure substances have concerning their boiling point?
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Inorganic compounds contain both hydrogen and carbon atoms.
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List one characteristic of metals.
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Study Notes
Qualitative and Quantitative Observations
- Qualitative observations use our senses to describe something.
- Quantitative observations use numbers and measurements.
Inferring and Classifying
- Inferring is drawing conclusions based on evidence.
- Classifying is grouping objects based on similarities, differences, and relationships.
Measuring
- Measuring uses numbers and involves two parts: magnitude and unit.
Observing
- We use our senses to observe objects.
Communicating
- We communicate observations and findings to inform others.
Pure Substances
- A pure substance consists of only one type of substance or particle.
- Pure substances cannot be separated by physical means.
- Examples: salt, hydrogen gas, gold metal, copper wire, diamonds.
Mixtures
- Mixtures are formed by physically combining two or more substances.
Properties of Pure Substances
- Boiling Point: Pure substances have a constant and lower boiling point.
- Melting/Freezing Point: Pure substances have a constant and higher melting/freezing point.
Elements
- Elements cannot be broken down into simpler substances.
- The periodic table contains 118 elements.
- 90 elements occur naturally, while 28 are created in labs.
- Elements have chemical symbols, usually one or two letters.
- Symbols can be capital letters or a capital letter followed by a small letter.
- Elements have English or Latin names.
Classification of Elements
- Metals: hard, shiny (lustrous), malleable (thin sheets), ductile (thin wire), good conductors of heat and electricity, extracted from ores.
- Nonmetals: mostly gases at room temperature, dull, brittle, poor conductors of heat and electricity.
- Metalloids: have properties of both metals and nonmetals.
Compounds
- Compounds are formed by chemically combining two or more elements or molecules.
- They have a fixed ratio or composition.
- Compounds are represented by chemical names or formulas.
Molecules
- Molecules are formed by chemically combining two or more atoms.
- Molecules are the smallest particle of a compound.
Classifying Compounds
-
Organic Compounds: contain hydrogen and carbon atoms bonded together.
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
-
Inorganic Compounds: do not contain hydrogen and carbon.
- Examples: salt, soap, toothpaste.
Mixtures
-
Heterogeneous Mixtures: particles are not evenly spread, sizes vary, and components are easily identified.
- Suspension: Particles are large enough to be seen by the naked eye.
- Colloids: Particles do not settle at the bottom.
- Coarse: Particles can be easily recognized and picked apart by hand.
Properties of Solutions
- Solutions are formed by combining two or more substances.
- Solute + Solvent = Solution
- Solutions appear to be in one phase.
Solute, Solvent, and Dissolution
- Solute: The substance that dissolves in a solvent. The amount of solute affects concentration.
- Solvent: The substance that dissolves the solute. It is usually a liquid.
- Dissolution: The process of making a solution.
Soluble/Insoluble and Miscible/Immiscible
- Soluble/Insoluble: Refers to the dissolving ability of a substance in a specific amount.
- Miscible/Immiscible: Refers to the ability of substances to mix in any amount.
Unsaturated, Saturated, and Supersaturated Solutions
- Unsaturated Solution: More solute can be dissolved.
- Saturated Solution: No more solute can be dissolved.
- Supersaturated Solution: Excess solute cannot be dissolved, requiring additional solvent or heat to dissolve.
Factors Affecting Solubility
- Temperature: Solubility varies with temperature.
- Surface Area: Grinding solids into smaller pieces increases surface area, increasing solubility.
- Stirring: Speeding up the dissolution process.
- Pressure: Higher pressure increases the amount of gas dissolved in a liquid.
- Nature of Solute and Solvent: Inherent chemical properties of the substances being mixed.
Studying That Suits You
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Description
Test your knowledge on qualitative and quantitative observations, inferring, classifying, and the properties of pure substances. This quiz will help reinforce key concepts related to measuring and communicating scientific findings. Challenge yourself to identify pure substances and mixtures.
