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CST Prep
preperation for CST questions
60
Science
8th Grade
05/05/2009

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Cards

Term
What happens to reactants during chemical reaction?
Definition
The atoms and moecules of the reactant (original substances) rearrange during a chemical reactinon.
Term
What are examples of physical change?
Definition
Physical changes are NOT chemical reactions. Examples uncluded freezing, melting, boiling, evaporating, and condensing.
Term
What is the difference between products and original substances?
Definition
The products (new substances) have different properties than the orignial substances.
Term
How are physical changes different from chemical reactions?
Definition
Physical changes only change the form or appearance but NOT create new substances.
Term
What does the Law of Conservation of Matter say?
Definition
The Law of Conservation of Matter states that atoms are never created or destroyed. This means that atoms can only be rearranged not added or subtracted during a reaction.
Term
Are mixtures & solutions chemical reactions? Explain?
Definition
Mixtures and solutions are NOT chemical reactions because new substances are not formed
Term
What does a chemical equation show?
Definition
A chemical equation shows what happens during a reaction. There are always the same kinds of and numbers of atoms on both sides of the equation.
Term
What are the pH levels of acidic solutions? What do greater #'s mean?
Definition
A solution with a pH of 0-6 is acidic. Acids are sour and react with metals to make hydrogen gas. The greater the number, the less acidic a solution is. (A pH of 7 is neutral. Water is neutral.)
Term
What happens to energy during reactions?
Definition
Most reactions either absorb heat energy or release heat energy.
Term
What are pH levels of basic solutions? What do greater #'s mean?
Definition
A solution with a pH of 8-14 is basic. Bases are bitter, slippery, and can conduct electricity. The greater the number, the more basic a solution is.
Term
What is the structure of the atom?
Definition
The atom is made of a core of protons and neutrons surrounded by electrons.
Term
What are the parts of an atom?
Definition
The atoms has protons with a positive charge, neutrons with a neutral charge, and much smaller electrons with a negative charge
Term
What are elements?
Definition
There are about 100 different types of matter, each with their own properties and atomic structure, called elements.
Term
Describe the molecules in a solid
Definition
The molecules in a solid are locked in position and can only vibrate
Term
Describe the molecules in a liquid.
Definition
The molecules in a liquid are loosely connected and can move past one another and may collide with one another.
Term
Describe the molecules in a gas.
Definition
The molecules in a gas are free to move, they mover very quickly and collide frequently
Term
What are compounds?
Definition
Compounds are formed by chemically combining 2 or more different elements. Compounds have different properties from the elements that make them.
Term
What is the center of an atom?
Definition
The center of the atom is the nucleus made of protons and neutrons. Most of the mass of the atom is in the nucleus
Term
What forms the outside of the atom?
Definition
The outside of the atom is the electron cloud made of spinning very lightweight electrons
Term
How do atoms and molecules form special solids?
Definition
Atoms and molecules form some solids by building up repeating patterns like those found in crystalline solids and long-chain polymers.
Term
Describe characteristics of metals
Definition
Metals are good conductors of heat and electricity and have higher melting points
Term
Describe characteristics of non-metals
Definition
Non-metals are not good conductors of heat and electricity and have lower melting points.
Term
Describe characteristics of noble (inert) gasses.
Definition
Noble (or inert) gasses do not combine easily with other elements.
Term
Where are metals and non-metals found on the periodic table?
Definition
Metals are found on the left of the zig-zag line. Non-metals are found on the right of the zig-zag line.
Term
Where are noble (or inert) gasses found on the periodic table?
Definition
Noble gasses are found in the far right column of the periodic table.
Term
What is an isotope?
Definition
Isotopes are different versions of the same element. They have the same number of protons but different number of neutrons.
Term
Why is carbon important in the chemistry of living things?
Definition
Because carbon is able to combine with many different elements it plays an important role in the chemistry of living things. This means that carbon is often a part of living things.
Term
What types of molecules make up living things?
Definition
Living things are made of very small molecules like salt and water and they are made of very large molecules like proteins, DNA, carbohydrates, and fats.
Term
What can we read on a periodic table?
Definition
We can find the names, symbols, and atomic numbers of all the elements on the periodic table.
Term
What is an atomic number?
Definition
The atomic number is the number that identifies an element on the periodic table. It is the number of protons in that element.
Term
How do we describe forces?
Definition
Forces have both direction and magnitude (amount of force). The direction and magnitude can be shown by arrows.
Term
How do we find the cumulative (total) force?
Definition
Multiple forces can act on an object. Forves moving in the same direction are added. Forces moving in opposite directions are subtracted. Movement is cause by greater forces.
Term
What happens if the forces are balanced?
Definition
Balanced forces are equal and opposite forces. When forces are balanced, there is no movement
Term
What are different forces that can act on an object?
Definition
Forces actin on an object include gravity, friction, tension, compression, and normal force.
Term
What happens if forces are unbalanced?
Definition
When forces are unbalanced, the object will change its velocity (speed up, slow down, or change direction).
Term
What is density?
Definition
Density is mass per unit volume.
Term
What is buoyant force?
Definition
A buoyant force is the upward force of a liquid on an object. It is equal to the weight of the fluid the object has displaced (moved).
Term
How can we predict whether an object will float or sink?
Definition
An object will sink if it has a density more than the fluid in which it is placed. It will float if the density is less than the fluid.
Term
What is the density of water? What will float in water?
Definition
The density of water is 1.0 grams/mL. Anything with a density less than 1.0 gr/mL will float in water.
Term
How do we find the density of an object?
Definition
Density = mass (grams) / volume (mL or cm^3). (Volume can be found by placing an object in a grauated cylinder of water and seeing how much water is displaced.)
Term
What is a galaxy?
Definition
A galaxy is a cluster (group) of billions of stars.
Term
What are the different shapes of galaxies?
Definition
Some examples of the many different shapes are spiral, elliptical (oval), and irregular.
Term
Describe the Sun.
Definition
Our Sun is a medium yellow star found in one of the arms of a spiral shaped galaxy called the Milky Way
Term
Describe the different colors of stars.
Definition
Stars have different temperatures and colors. Colors include, red (cooler stars), yellow (medium temperature), blue, and white (hottest stars).
Term
Describe the different sizes of stars.
Definition
Stars can be very small dwarf stars, medium-sized stars like our Sun, or giant and super giant stars.
Term
What is an astronomical unit?
Definition
An astronomical unit is a unit of measurement (like a meter) that is used to measure distances in our solar system. (It is the distance from the Sun to the Earth.)
Term
What is a light year?
Definition
A light year is a unit of measurement (like a kilometer) that is used to measure distances in our universe. A light year is the distance light travels in a year or about 9.5*10^12 Km or 9,500,000,000,000 Km.
Term
Why do stars "shine"?
Definition
Stars are a source of light because they release energy.
Term
In space, why do moons and planets "shine"?
Definition
Moons and planets shine because they reflect the light from stars. Moons and planets do not shine by their own light.
Term
What types of objects are found in our solar system?
Definition

Our solar system consists of planets, planetary satellites like moons, comets (mostly made of ice), and asteroids (rocks) that orbit the sun.

Order of solar system:

Small, Solid, Rock-like planets: Mercury, Venus, Earth, Mars, Asteroid Belt (many asteroids),

Giant, Gas planets: Jupiter, Saturn, Neptune, (Pluto),

Kuiper Belt, (various objects, source of short lived comets)

Oort Cloud (may contain comets)

Term
How do you find the position of an object?
Definition
The position of an object is found by finding the distance and direction from a reference point.
Term
What is a reference point?
Definition
A reference point is an object that appears to be stationary and is compared to other objects to determine position or movement.
Term
 How do we determine if an object is moving?
Definition
Because objects are always "moving", scientists determine movement by comparing an object to a reference point. Movement is a change of distance from the reference point.
Term
How do we find average speed?
Definition
Average speed is determined by dividing the total distance by the total time. The speed along the object's path may vary (unlike with constant speed that stays the same.)
Term
Solve problems involving speed, distance, and time.
Definition
Use formulas V=D/T, D=V*T, T=D/V. Don't forget to find the total distance and the total time.
Term
What is velocity?
Definition
Velocity includes both the speed and the direction of an object.
Term
How can velocity change?
Definition
Velocity can change when an object accelerates by going faster, going slower, or changing direction.
Term
How can we show motion on a graph?
Definition
Motion can be shown on a graph by plotting the position and time or plotting the speed and time or plotting distance and time.
Term
What does the slope of a line in a distance-time graph show?
Definition
The slope of a line in a distance-time graph shows the speed of an object. The steeper the slope, the faster the speed. A horizontal line means no movement has occurred.
Term
What can be determined from a speed-time graph?
Definition
You can use a speed-time graph to determine the distance an object has traveled. (A horizontal line means a distance has been traveled.)
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