8th grade science final sigma667

Define what a reference point is relative to motion.

Define what a reference point is relative to motion.

A reference point is a place or object used for comparison to determine whether something is in motion.

Explain how motion is relative.

Motion is relative, because it is determined by a reference point.

What are valence electrons?

Electrons that are in the highest energy level of an atom. They are involved in chemical bonding.

Give an example of a halogen.

Chlorine is an example of a halogen

Give an example of a noble gas.

Helium is an example of a noble gas.

Why are halogens so reactive.

Halogens are so reactive, because they are close to having a full outer shell of electrons.

Why aren’t noble gases reactive?

Noble gases aren’t reactive, because they already have a full outer shell of electrons.

What is a conductor?

A conductor is a material that conducts or allows electricity an heat to flow through it

Explain what characteristic of metals tends to make them good conductors.

Metals are good conductors, because of the electrons tendency to drift between atoms.

Daltons theory

Atoms cannot be created or destroyed

Thomson theory

Positive and negative charges in an atom

Rutherfords Theory

Protons in the nucleus, electrons outside the nucleus

Bohr theory

Electrons orbit the nucleus

Which theory led to the idea of valence electrons

Daltons Theory

Define an insulator

An insulator is an object that traps heat

Give three examples of insulators

Wood, cardboard, and cloth

Define a mixture

A mixture is two or more substances that are together but are not chemically bonded.

Define a homogenous mixture

A mixture with hard to distinguish parts.

Give an example of a homogenous mixture

Sugar water

Define a heterogenous mixture

A mixture that features distinct components that can easily be seen and sorted.

Give an example of a heterogenous mixture

Pepperoni pizza

what is a colloid

A heterogenous mixture containing small, undissolved particles that do not separate or settle out if the mixture is left undisturbed

Give an example of a colloid

Milk

What is a suspension

A mixture in which particles can be easily separated by settling or filtration

Give an example of suspension

An oil and water mixture

Explain the difference between a colloid and a suspension

In suspensions particles can easily be separated by settling or filtration, while in colloids particles cannot easily be separated by settling or filtration.

Define a solution

A homogenous mixture of a solvent and one or more solutes

Define a solvent

A substance that is able to dissolve other substances

Define a solute

A substance that can be dissolved by other substances

Give an example of a solution

An example of a solution is grape juice, the water is the solvent, the sugar and other ingredients are the solutes.

Describe the difference between a solute and a solvent

A solvent can dissolve other substances, while a solute gets dissolved by other substances.

What changes might make a solute dissolve faster

Adding an catalyst could make a solute dissolve faster

Explain how you can use a flashlight to classify a mixture as a colloid or a solution

Shine the flashlight, it the mixture is clear then it is a solution, if there is a cloudy beam of light then the substance is a colloid

Define a physical change

A change that alters the form or appearance of an object without creating a new substance

Give four examples of physical change

Bending crushing melting and freezing

define a chemical change

A change in which one or more substances combine or break apart to form new substances

Give 4 examples of chemical change

Burning, synthesis, rusting, and digestion are all examples of chemical change

Define reactants

Reactants are substances that enter into a chemical change.

Define products

Substances formed as a result of a chemical reaction

Explain why chemical changes are represented by equations but physical changes are not

Because in chemical changes atoms are rearranged while in physical changes atoms are not rearranged

Explain what happens to the energy in a exothermic reaction

The energy goes up towards the middle of the reaction and down towards the end.

Explain what happens to the temperature after an exothermic reaction

The temperature decreases

Compare the energy levels between the reactants and products of an exothermic reaction

The energy levels are higher in the reactants

Explain what happens to the energy in an endothermic reaction

The energy starts low then goes high then goes to medium

What happens to the temp after an endothermic reaction

The temperature gets cold after an endothermic reaction.

compare the energy levels in an endothermic reaction would it be higher in the reactants or products

The energy levels are higher in the products.

How does surface area affect the rate of reactions

A greater surface area allows more of a substance to react, therefore increasing the rate of reaction

How does temperature affect the rate of a reaction

High temperatures increase the rate of reaction.

Explain what a coefficient is and what information it gives in a chemical equation.

The coefficient tells us how many molecules are present. A coefficient is the number before before each component.

Explain what a subscript is and what information it gives in a chemical equation.

The subscript next to the element tells us how many atoms are present in an atom.

Describe how you recognize something is a molecule in a chemical equation.

Describe how you recognize from the chemical formula when something is made of just one element or multiple.

When something is made of one element there will only be one capital letter. When something is made of multiple elements it will have multiple capital letters.

Explain what a balanced chemical reaction is.

This means there are the same of each element on both sides of the equation.

Why isn’t energy represented in chemical reactions.

Energy is not represented in chemical reactions, because energy is not a reactant.

Describe how you recognize a synthesis reaction.

In synthesis reactions there are more products than reactants.

Describe how you recognize decomposition reactions.

In decomposition reactions there are more products than reactants.

Describe how to recognize replacement reactions.

In replacement reactions there are the same number of products as reactants.

Describe what makes an open system.

an open system is a system where matter can enter and exit.

What is a closed system.

A closed system is a system where matter cannot enter or exit.

Which scientific law was observed when using a closed system.

The law of conservation of mass was used, because no matter entered or exited.

Explain what an ion is

Atom with + - charge

Explain the difference between an ion and a polyatomic ion

Polyatomic bonds are formed by covalent bonds, while ions are formed by ionic bonds

Explain how and why ionic bonds form

Ionic bonds form so atoms can get a full outer shell of electrons, ionic bonds form by atoms gaining and losing electrons.

Explain how and why covalent bonds form

Covalent bonds form when atoms share electrons. Covalent bonds are created in order to form full outer shells of electrons.

Describe the properties of an ionic compound.

Crystals, high melting/ boiling points, hard, brittle

Describe the properties of an covalent compound

Low boiling and melting points, and they are poor conductors

Explain what happens to ionic compounds in water

They dissolve in water

What might be formed by a covalent compound in water

A hydrogen bond

Explain which electrons are involved in bonding between atoms

Valence electrons

Explain what is different in the properties of ionic and covalent bonds

Covalent bonds have low boiling and melting points while ionic bonds have high boiling or melting points.

List 3 properties of an acid

Acids are corrosive, sour and have a ph less than 7

List 3 properties of a base

Bases are bitter, slippery and have a ph over 7

Describe what neutralization reaction is and what it does

A neutralization reaction is when an acid and a base combine to make a neutral salt

Describe why indicators are used and what they do

An indicator is something that changes color based on how acidic a substance is

Describe why acids like vinegar are stored in plastic or glass bottles

They are stored in plastic, because they would corrode metal containers

Describe a test that could determine if a substance is acidic or basic

Test it by dropping it on some litmus paper and seeing what color it is

How do you tell if an ion is an acid or base

An ion is more like an acid if it has a positive charge, if it is a base it will have a negative charge

What is a reference point

A place or object used to determine whether something is in motion

Explain how motion is relative

Motion is relative to the reference point being used

What’s a force

A push or pull is a force N is the unit

What’s is a contact force

A force that involve direct contact

What is a non contact force

A force that does not involve contact

Give types of non contact forces

Magnetism, electricity, and gravity

Give an example for each non contact force

Magnet pulling metal without touching, me falling towards the earth without touching it, a rubbed balloon attracting other objects.

Explain how an object moves if the forces acting on it are balanced

An object will not move if the forces acting on it are balanced

Explain how an object moves if the forces acting on it are unbalanced

An object will move to the side where the stronger force is pushing or pulling towards

How is speed calculated

Speed= Distance/Time

Explain how to determine speed from a distance vs. Time graph

Take the slope of the graph

How is velocity related to speed

Velocity is the speed which am object travels in a given direction

How is acceleration related to speed

Acceleration is the rate at which velocity changes

Define inertia

Resistance to change is inertia

Explain how mass and inertia are related

The larger the mass the greater the inertia

Explain how your bottle rocket was an example of newtons first law

Our rocket moved when there were forces and didnt move when there weren’t forces

Explain how Newton’s second law influenced the design of your bottle rocket

This influenced our decision on the amount of mass we wanted, we chose to use very lightweight materials

Explain how your rocket was an example of Newton’s third law about actions and reactions

The action was the rocket being pushed up, the reaction was the water being pushed down

Define friction

The force two surfaces exert on each other, when they rub against each other

What two factors affect friction between surfaces

The types of surfaces and how hard the surfaces are pushed together.

Define rolling friction

Rolling friction is when an object rolls across a surface

Define static friction

Static friction acts on objects when they are resting on a surface

Define sliding friction

Sliding friction is when two solid surfaces s