Introduction to Matter

Vocabulary

Lesson 1

1. matter – Anything that has mass and takes up space.
2. chemistry – The study of the properties of matter and how matter changes.
3. substance – A single kind of matter that is pure and has a specific set of properties.
4. physical property – A characteristic of a pure substance that can be observed without changing it into another substance.
5. chemical property – A characteristic of a substance that describes its ability to change into different substances.

Lesson 2

6. element – A substance that cannot be broken down into any other substances by chemical or physical means.
7. atom – The basic particle from which all elements are made; the smallest particle of an element that has the properties of that element.
8. chemical bond – The force of attraction that holds two atoms together.
9. molecule – A neutral group of two or more atoms held together by covalent bonds.
10. compound – A substance made of two or more elements chemically combined in a specific ratio, or proportion.
11. chemical formula – Symbols that show the elements in a compound and the ratio of atoms.
12. mixture – Two or more substances that are together in the same place but their atoms are not chemically bonded.

Lesson 3

13. weight – A measure of the force of gravity acting on an object.
14. mass – The amount of matter in an object.
15. International System of Units – A system of measurement based on multiples of ten and on established measures of mass, length, and time.
16. volume – The amount of space that matter occupies.
17. density – The ratio of the mass of a substance to its volume (mass divided by volume)

Lesson 4

18. physical change – A change that alters the form or appearance of a material but does not make the material into another substance.
19. chemical change – A change in which one or more substances combine or break apart from new substances.
20. law of conservation of mass – The principle that the total amount of matter is neither created nor destroyed during any chemical or physical change.
21. temperature – How hot or cold something is; a measure of the average energy of motion of the particles of a substance
22. thermal energy – The total energy of all the particles of an object.
23. endothermic change – A change in which energy is absorbed.
24. exothermic change – A change in which energy is released.
25. chemical energy – A form of energy that is stored in chemical bonds between atoms.

Lesson 1: Describing Matter

• Matter is anything that has mass and takes up space.
• Matter can have many different properties that can be used to classify it.
• Chemistry is the study of matter and how matter changes.
• A substance is a single kind of matter that is pure.
  • Water is a substance.
• Every form of matter has two kinds of properties: physical and chemical.
  • You can observe physical properties without changing it into another substance.
    • shape,
  • A chemical property describes a substance’s ability to change into different substances.

Lesson 2: Classifying Matter

• We classify matter as elements, compounds, and mixtures.
• Elements cannot be broken down into any other substance by any physical or chemical means, they are the simplest substances. They’re all in the periodic table.
  • Atoms are the basic particles from which all elements are made. The electron cloud model is the most accepted one today. The elements have properties because their atoms are different. The proton is made of 3 subatomic particles:
    • protons (p+) – are positively charged, located in the nucleus
    • neutrons (neutral) – no change, found in the nucleus
    • electrons (e-) – negatively charged, are in constant motion around the nucleus
  • Molecules are groups of two or more atoms held together by a chemical bond, which is a force of attraction between two atoms.
    • A molecule of water is made of two hydrogen atoms and an oxygen atom, bonded together.
    • An oxygen molecule is made of two oxygen atoms.
• Compounds are substances made of two or more elements that are chemically combined in a set ratio.
  • Chemical formulas represent compounds (CO2 = carbon dioxide), they represent the number of carbon atoms to oxygen atoms (1 to 2). Different amounts of atoms represent diferent compounds, for example CO = carbon monoxide; the ratio of carbon to oxygen atoms is 1 to 1.
  • When elements combine tha compound derived has different characteristics.
• Mixtures are made of two or more substances are together (like compounds), but they are not chemically combined. Each substance in a mixture keeps its properties.
  • Heterogeneous mixtures are the ones where we can easily see the different parts and separate them, like sand and a salad. They are not necessarily uniform.
    • Emulsions are heterogeneous mixtures that can be broken apart into its constituents despite looking homogeneous, like hollandaise sauce.
    • A suspension is cloudy and heterogeneous, its particles are larger than 10,000 Angstroms. If a suspension is left to stand the particles will separate. Orange juice with pulp and sand with water are suspensions.
  • Homogeneous mixtures are very evenly mixed, it’s hard to see its parts and very hard to separate them, like milk and air we breathe (combination of gasses).
    • Solutions are homogeneous mixtures that consist of a solute (is dissolved in the solvent) and a solvent (dissolves the solute, water is the universal solvent). They can be a combination of solids, liquids and gasses.
    • A colloid is a solution that has particles ranging between 1 and 1000 nanometers  in diameter (10-1,000 Angstroms). These particles remain dispersed and do not settle to the bottom of the container. Gelatin is a colloid.
    • Alloys are metals made of two or more pure metals, they are solid + solid solutions, like bronze and steel.
  • Mixtures can be separated by distillation, evaporation, filtration, magnetic attraction and other methods.

Lesson 3: Measuring Matter

• Weight is the measure of the force of gravity on you, your weight could be different on other planets because the gravitational force is different.
  • The force of gravity would be more if the planet is more massive than Earth, and less if it is smaller.
• Mass is the amount of matter on an object, it does not change with your location or when the force of gravity changes. This is why scientists prefer to measure matter in terms of mass.
  • The International System of Units (SI) is used by scientists to measure the properties of matter; the SI unit of mass is the gram (g).
• Volume is the amount of space that matter occupies, it is found by multyplying length, height and width.
  • The SI unit for volume is the cubic meter (m2).
• Density is a measure of the mass of an object in a given volume, density can be expressed as the number of grams in a cubic centmeter (g/cm3). To determine density we divide mass/volume.
  • The density of water is 1g/cm3, objects with greater density will sink, those with lesser density (like oil, which separates from water and floats to the top because of this) will float.

Lesson 4: Changes in Matter

• A physical change alters the form or appearance of the matter but does not turn any substance in the matter into a different substance.
  • Changes of state occur when matter changes state (solid, gas, liquid…), they are physical changes.
    • When water (liquid) is heated and changes into water vapor (gas) a physical change in state occurs.
  • Dissolving, bending, crushing, breaking, and chopping are physical changes in shape or form.
    • The methods of separating mixtures, such as filtration and distillation, also involve physical changes.
• A chemical change, or chemical reaction, is a change in which a single substance breaks down into two or more other substances with new and different properties.
  • Hydrogen peroxide breaks down into water and oxygen when poured onto a cut in your skin.
  • Photosynthesis is a natural chemical change, several compounds combine with the Sun’s energy to form new substances.
  • Electrolysis, combustion, oxidation and tarnishing are other chemical changes.
• The law of conservation of mass or matter states that no matter is created in any physical or chemical change.
  • When water turns to vapor its mass is the same but its state isn’t.
• Every chemical and physical change in matter includes a change in energy (ability to do work or cause change).
  • Like matter, energy is never created or destroyed in chemical changes.
• Temperature is how hot/cold something is. Thermal energy is the total energy of the motion of all the particles in an object, it naturally flows from the warmer matter to the cooler matter.
  • An endothermic change is a change in which energy is absorbed (hotter), like the melting of ice.
  • An exothermic change releases energy (colder), like making ice cubes.
• Chemical energy is the energy stored in chemical bonds between atoms, it’s stored in food, fuel, and even your cells.
  • We gain chemical energy from food.
  • Burning fuel transforms chemical energy and releases some of it as thermal energy.
  • Chemical energy can change to other forms of energy, and other forms of energy can change to chemical energy.