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LaGreca Science
Unit 2
Chemistry Study Guide
UNIT 2 STUDY GUIDE
CHEMISTRY
Part 1: Matter is made up of atoms which then is composed of elements (6.P.2.1)
Question: What is matter and what is it made up of? How is it possible for matter to have different
properties?
All substances, including air, take up space and have mass.
Matter is everything around you. Matter is anything that has mass and takes up space.
The smallest unit of matter is an atom. The ancient Greeks found no smaller particles and therefore
called the particles they found “atoms” which means “uncuttable” in Greek.
Atoms are the building blocks of life. Atoms come together in different ways to form elements. Atoms
of different elements have different masses. Most atoms of the same elements have the same masses,
except for isotopes, but you don’t need to know about them this year!
Property-specific characteristics of matter. Some properties are physical, and some properties are
chemical in nature.
Atoms of the same element have the same properties (specific characteristics).
Atoms of different elements have different properties.
Elements come together to form molecules. Common elements can form to build very different
molecules. There are 120 different elements that come together to form millions of different
molecules. Two samples of the same substance contain the same type of atoms and elements!
Every atom of an element has both mass and volume! The measure of the gravitational force of an
object is called the weight. Different substances of the same size wll most like have a different mass.
For example, compare the mass of a tennis ball vs. a lacrosse ball of the same size and dimensions.
Molecules are groups of atoms bonded together in a way that letters are grouped together to form
words. They are connected together by chemical bonds. Every combination of atoms is a molecule
A compound is a molecule made of atoms from different elements. Can be broken down into a
simpler type of matter (elements) by chemical means (but not by physical means). Has properties
that are different from its component elements
Example: Water (H2O)
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Chemistry Study Guide
*** All compounds are molecules, but not all molecules are compounds. Hydrogen gas (H2) is a
molecule, but not a compound because it is made of only one element. Water (H2O) can be called a
molecule or a compound because it is made of hydrogen (H) and oxygen (O) atoms.
Mixture- A physical change, not a chemical change. Consists of two or more different elements
and/or compounds physically intermingled, can be separated into its components by physical
means, and often retains many of the properties of its components.
Example: Salt and water (NaCl and H2O)
Solution- A type of mixture where groups of molecules that are mixed and evenly distributed in a
system. Scientists say that solutions are homogenous systems. Everything in a solution is evenly spread
out and thoroughly mixed.
Solutions can be solids dissolved in liquids. Solutions can also be gases dissolved in liquids, such as
carbonated water. There can also be gases in other gases and liquids in liquids. If you mix things up and
they stay at an even distribution, it is a solution. You probably won't find people making solid-solid
solutions.
Periodic table of elements-a big grid that organizes the elements according to its atomic
structure. The rows are called “periods” and the columns are called “groups”
Elements are numbered according to their atomic number, which tells you how many protons an
atom has. (Note 6th graders do NOT need to know proton, neutron or electrons )
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Unit 2
Chemistry Study Guide
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Part 2: Identify and explain the changes in the states of matter and their properties of change (6.P.2.2)
Questions: What are the different phases of matter? How does matter behave during these different
phase changes?
Matter can have different chemical and physical properties
Molecules can move from one physical state to another (phase change) and not change their basic
structure. It has the same molecular structure whether it is a gas, liquid, or solid. Although its physical
state may change, its chemical state remains the same.
Physical change: when matter experiences a change in arrangement of molecules, such as in a phase
change, without changing the chemical structure (the elements remain the same)
Changes in the physical state are related to changes in the immediate environment such as
temperature, pressure, and other physical forces. Generally, the basic chemical structure does not
change when there is a physical change. Of course, in extreme environments such as the Sun, no
molecule is safe from destruction.
Chemical change: Chemical changes occur when the bonds between atoms in a molecule are created or
destroyed.
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LaGreca Science
Unit 2
Chemistry Study Guide
There are 4 states of matter:
Each of these states is also known as a phase. Elements and compounds can move from one phase to
another when specific physical conditions change. For example, when the temperature of a system goes
up, the matter in the system becomes more excited and active. If enough energy is placed in a system, a
phase change may occur as the matter moves to a more active state.
SOLID-
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LaGreca Science
Unit 2
Chemistry Study Guide
What is one physical characteristic of a solid? Solids can be hard like a rock, soft like fur, a big rock like
an asteroid, or small rocks like grains of sand. The key is that solids hold their shape and they don't flow
like a liquid. A rock will always look like a rock unless something happens to it. The same goes for a
diamond. Solids can hold their shape because their molecules are tightly packed together.
In the same way that a large solid holds its shape, the atoms inside of a solid are not allowed to move
around too much. Atoms and molecules in liquids and gases are bouncing and floating around, free to
move where they want. The molecules in a solid are stuck in a specific structure or arrangement of
atoms. The atoms still vibrate and the electrons fly around in their orbitals, but the entire atom will not
change its position.
See below how tightly packed atoms are in solids!!
LIQUID
Liquids are found between the solid and gas states. Examples of liquids at room temperature include
water (H2O), blood, and even honey. If you have different types of molecules dissolved in a liquid, it is
called a solution. Honey is a solution of sugar, water, and other molecules.
Liquids fill the shape of any container they are in. If you pour water in a cup, it will fill up the bottom of
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LaGreca Science
Unit 2
Chemistry Study Guide
the cup first and then fill the rest. If you freeze that cup of water, the ice will be in the shape of the cup.
The top of a liquid will usually have a flat surface. That flat surface is the result of gravity pulling on the
liquid molecules. Let’s go back to the cup for a moment. If you put an ice cube (solid) into the cup, it will
sit there and not change shape. As the cube warms and melts, the liquid water will fill the bottom of the
cup and have a flat surface on top.
Another trait of liquids is that they are difficult to compress. When you compress something, you take a
certain amount of material and force it into a smaller space or volume. You force the atoms closer
together. Most solids are very difficult to compress while gases are easier. You can find compressed
gases in SCUBA air tanks. Liquids are in the middle, but tend to be difficult to compress because the
molecules are already close together. You probably can’t compress a liquid with your hands. It takes a
lot of force.
GAS
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LaGreca Science
Unit 2
Chemistry Study Guide
Gases are everywhere. You may have heard about the atmosphere. The atmosphere is an envelope of
gases that surrounds the Earth. In solids, atoms and molecules are compact and close together. Liquids
have atoms that are spread out a little more. The molecules in gases are really spread out, full of energy,
and constantly moving around in random ways.
What is another physical characteristic of gases? Gases can fill a container of any size or shape. It
doesn't matter how big the container is. The molecules spread out to fill the whole space equally. Think
about a balloon. No matter what shape you make the balloon, it will be evenly filled with the gas
molecules. Even if you make a balloon animal, the molecules are spread equally throughout the entire
shape.
Liquids can only fill the bottom of a container, while gases can fill it entirely. The shape of liquids is very
dependent on gravity, while less dense gases are light enough to have a more freedom to move.
PLASMA
Plasmas are a lot like gases, but the atoms are different, because they are made up of free electrons and
ions of an element such as neon (Ne). You don't find naturally occurring plasmas too often when you
walk around. They aren't things that happen regularly on Earth.
http://kidsneedscience.tumblr.com/post/12196290467/plasma
https://www.youtube.com/watch?v=2osF6l6-zWg
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LaGreca Science
Unit 2
Chemistry Study Guide
To understand the difference between physical and chemical change:
When molecules move from one phase to another they are still the same substance. There is water
vapor above a pot of boiling water. That vapor (or gas) can condense and become a drop of water in the
cooler air. If you put that liquid drop in the freezer, it would become a solid piece of ice. No matter what
physical state it was in, it was always water. It always had the same chemical properties.
On the other hand, a chemical change would build or break the chemical bonds in the water molecules.
If you added a carbon (C) atom, you would have formaldehyde (H2CO). If you added an oxygen (O) atom,
you would create hydrogen peroxide (H2O2). Neither new compound is anything like the original water
molecule. Generally, changes in the physical state do not lead to any chemical change in molecules.
http://www.glencoe.com/sites/common_assets/science/virtual_labs/E03/E03.html
Heat is a source of energy that can change the state of matterwhich also causes particles in matter to
gain kinetic energy.
What is Kinetic energy? Watch this to review it:
https://www.youtube.com/watch?v=IqV5L66EP2E
Temperature- Temperature is the property of matter which reflects the quantity of energy of motion of
the component particles. There are several scales used to measure this value (e.g., Kelvin, Celsius,
Fahrenheit).
melting point-the constant temperature that an object melts. The temperature increases and the
atoms in an object vibrate faster. The molecules also move farther apart as the matter turns into liquid.
(THINK ICE TURNS TO WATER)
boiling point-the temperature in which a liquid will turn into a gas or vapor. The temperature increases
and the molecules move farther apart. (THINK LIQUID TO STEAM)
condensation point-the temperature in which a gas turns into a liquid. Heat is removed and the gas
changes into a liquid (THINK DEW)
freezing point-the temperature in which a liquid turns into a solid. The temperature decrease and the
atoms in an object vibrate slower. The molecules also move closer together as the liquid turns into a
solid. (THINK WATER TURNS TO ICE)
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LaGreca Science
Unit 2
Chemistry Study Guide
IMPORTNT TO KNOW! If two objects that have the same elements and the same melting point have
different masses (100g vs. 50g), the object with the smaller mass would melt faster, but the melting
point would remain the same.
Evaporation- is the process by which water changes from a liquid to a gas or vapor. Water boils
at 212 degrees F (100 degrees C), but it actually begins to evaporate at 32 degrees F (0 degrees
C); it just occurs extremely slowly. As the temperature increases, the rate of evaporation also
increases.
The amount of evaporation depends on the temperature, and it also depends on the amount of
water there is to evaporate. For example, there is not much evaporation occurring in the Sahara
Desert, but why? Although it can get extremely hot in the Sahara, it's just sand - there's just not
much water to be evaporated.
Condensation- is the opposite of evaporation. It takes place when water vapor in the air condenses
from a gas, back into a liquid form, and leaves the atmosphere, returning to the surface of the Earth.
http://study.com/academy/lesson/what-is-condensation-definition-examples-quiz.html
http://www.kidsgeo.com/geography-for-kids/0107-condensation.php
Sublimation- Sublimation is the conversion between the solid and the gaseous phases of matter, with
no intermediate liquid stage. An example of sublimation is most often used to describe the process of
snow and ice changing into water vapor in the air without first melting into water.
http://study.com/academy/lesson/what-is-sublimation-in-chemistry-definition-processexamples.html
Part 3: Compare the independent and dependent physical properties of pure substances
Questions: What are the properties of different types of matter? What is a chemical property and a
physical property? Why do some things float while others sink?
Matter can have different properties:
Chemical property-characteristics involved when a substance interacts with another substance to
change its chemical make-up
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LaGreca Science
Unit 2
Chemistry Study Guide
Physical property-are used to identify, classify or describe matter. These are characteristic that can be
observed using the 5 senses, WITHOUT changing the substance into something else.
http://examples.yourdictionary.com/examples-of-physical-properties.html
http://study.com/academy/lesson/matter-physical-and-chemical-properties.html
Solubility: a property of matter that can be observed without changing the identity of the matter
Solubility is the ability to dissolve into (become a part of) another substance. Something that dissolves,
like the sugar in our example, is called a solute. The substance that it dissolves into, like the tea, is called
the solvent. When a solute dissolves into the solvent, the end product is called a solution.
http://study.com/academy/lesson/solubility-lesson-for-kids-definition-rules.html
https://www.youtube.com/watch?v=zjIVJh4JLNo
https://www.youtube.com/watch?v=TglqdJ2CkHA
Solute-the substance that is dissolved in a solution. For example, salt when its dissolved in water.
Solvent-the substance the solute is dissolved in. For example, water when salt is dissolved.
Mass –a measure of how much matter is in an object. Mass is commonly measured by how much
something weighs. But weight can change for different locations (such as on the moon) while the mass
stays the same. Mass and weight are NOT always the same value!!!
TRY THIS-- MASS OR WEIGHT? https://www.mathsisfun.com/measure/weight-mass.html
Volume- the quantity of three-dimensional space occupied by a liquid, solid, or gas. Common units used
to express volume include liters, cubic meters, gallons, milliliters, teaspoons and ounces.
Density
 Density is a characteristic property of a substance.
 The density of a substance is the relationship between the mass of the substance and how
much space it takes up (volume).
 The mass of atoms, their size, and how they are arranged determine the density of a substance.
 Density equals the mass of the substance divided by its volume; D = m/v.
 Objects with the same volume but different mass have different densities.
Weight-a measure of the gravitational force of matter
http://www.scienceforkidsclub.com/mass-and-weight.html
https://middleschoolscience.com/chemistry/properties-of-matter/
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