Grade 8 Science Midterm Exam Study Guide PDF

*Lessons included in the Midterm Exam:* 1. Scientific Method 2. **Matter** 3. **Changing states of matter** 4. **Physical & chemical properties of matter** 5. Atoms 6. Periodic Table: Metals & Non-Metals 7. Ions 8. Electric Charge & Static Electricity 9. Electric Current 10. Elect...

*Lessons included in the Midterm Exam:* 1. Scientific Method 2. **Matter** 3. **Changing states of matter** 4. **Physical & chemical properties of matter** 5. Atoms 6. Periodic Table: Metals & Non-Metals 7. Ions 8. Electric Charge & Static Electricity 9. Electric Current 10. Electric circuits **Lesson\# 1: Scientific Method** - Definition of the scientific method: it is a process that is used to find answers to questions about the world around us. - 6 steps of the scientific method: 1. Identify the problem. 2. Form a hypothesis. 3. Create an experiment. 4. Perform an experiment. 5. Analyze the data. 6. Communicate the results. Hypothesis: an educated guess, it's a possible, testable explanation for a scientific question - Difference between independent, dependent, and controlled variable. - Difference between control group and experimental group. Control group: Is the group that does not receive the treatment and is kept the same. Experimental group: Is the group that receives the treatment in an experiment. **Lesson\# 2: Matter** - What is matter? What is matter? *Matter is anything that has a mass and occupies a space. (**[Mass]** is a measurement of how much matter is in an object; **[Volume]** is the space occupied by an object)* - What are the three physical states of matter? *Scientists, through observations, classified matter into **three** main groups or physical states: Solid, Liquid & Gas* - Be able to demonstrate the particles in each physical state of matter by drawing circles. **Keep in mind, gas particles will occupy the whole container.** - What are the properties of each physical state? Properties of solids, liquids and gases? +-----------------------+-----------------------+-----------------------+ | **Solid** | **Liquid** | **Gas** | +=======================+=======================+=======================+ | - Particles come | - Particles far | - Particles very | | together; | apart | far apart | | particles are | | | | tightly packed | - Particles move | - Particles move | | | more quickly | very quickly | | - Particles move | | | | slowly | - Has no fixed | - Has no fixed | | | shape (indefinite | shape (indefinite | | - Has a fixed/ | shape) | shape) | | definite shape | | | | | - Has a fixed/ | - Has no fixed | | - Can't flow | definite volume | volume | | | | (indefinite | | - Has a fixed | - can't be | volume) | | (definite) volume | compressed | | | | | - can be compressed | | - can't be | - has a plane and | | | compressed | horizontal | - particles fill | | | surface | the entire | | - rigid (hard) | | container | +-----------------------+-----------------------+-----------------------+ **Lesson\# 3: Changing States of Matter** - Changing states of matter requires energy. Is heat energy added or released in melting, freezing, vaporization, condensation, sublimation, and deposition? - **What happens to matter when a change of state occurs?** Does a substance change its chemical property or only it's physical property like its appearance by Changing from solid to liquid or liquid to gas, etc.? **Lesson\# 4: Physical & chemical properties of matter** 1. *Physical state (solid, liquid, gas)* 2. *color* 3. *density: measure of the amount of matter in a given volume.* 4. *volume* 5. *mass* 6. *boiling point: the temperature at which a substance* *boils* 7. *melting point: the temperature at which a substance* *melts* 8. *electrical conductivity: measure of how well electric currents move through a substance.* 9. *solubility: ability of a substance to dissolve in another substance.* 10. *thermal conductivity: rate at which a substance transfers heat* 11. *malleability: ability to change shapes.* 12. *magnetic attraction: to be attracted/repelled to a magnet.* 13. *Shiny* 1. Flammability: ability to burn 2. Reactivity: to interact with another substance which leads to a new substance being created. **Lesson\# 5: Atoms** 1. Define an atom: *An atom is the smallest particle into which a substance can be divided and still be the same substance.* 2. List the three subatomic particles in an atom: protons, neutrons, and electrons. 3. Indicate the symbol, location, charge, and mass of each subatomic particle. *(Table)* *particle* *Symbol* *Relative change* *Mass in amu* *Location* ------------ ---------- ------------------- --------------- ------------------- *Proton* *p+* *Positive (+1)* *1* *Inside nucleus* *Neutron* *n* *Neutral (0)* *1* *Inside nucleus* *Electron* *e-* *Negative (-1)* *0* *Outside nucleus* 4. Label an atom: nucleus, electron cloud, protons, neutrons, and electrons. 5. Understand that "In a neutral atom, the number of protons is equal to the number of electrons". 6. Define atomic number and mass number of an atom. 7. Know how to calculate the atomic number and mass number of an atom. 8. What is the atomic representation? *Is the symbol of the atom with its atomic number written at the upper side and the mass number/ atomic mass written at the lower side.* 9. What is the atomic representation? Is the symbol of the atom with its atomic number written at the upper side and the mass number/ atomic mass written at the lower side. **Lesson\# 6: The periodic table: Metals & Non-Metals** 1. Explain what the periodic table is. It is a chart that organizes all the known chemical elements into groups based on their properties. 2. Explain how elements are organized in the periodic table and who organized it (Name of scientists). Dmitri Mendeleev first organized the elements by arranging them in order of increasing atomic mass. Henry Moseley reorganized Mendeleev's periodic table in order of increasing number of protons, or atomic number. 3. Define a period & group. How many periods and groups are there in the periodic table. Period: a period is a horizontal row of the periodic table, there are 7 periods in the periodic table. 4. Differentiate between metals, non-metals, and metalloids. 5. Know the location of Alkali metals, Alkaline earth metals, and transition metals in the periodic table. Alkali metals= group 1 Alkaline earth metals= group 2 Transition metals= groups 3-12 6. List the physical properties of metals and non-metals. 1. Metals occur in the solid state except for mercury it\'s in liquid. 2. Metals are malleable. 3. Metals are ductile (can be used in making wires such as copper, aluminum). 4. Metals conduct heat and electricity (they allow heat & electricity to pass through them. Metals are good conductors of heat and electricity). 5. Metals are shiny. 6. Metals are very strong and hard (except sodium and potassium). 7. Metals are known to be heavy. 8. metals are sonorous. They produce sound when they are rung or hit with any object. 9. Metals have high melting and boiling point. 10. Metals have high density. 1. Non-metals are brittle (hard but liable to break easily) and break into pieces when beaten. Example: Sulphur and phosphorus. 2. Non-metals are not ductile so; they cannot be made into thin wires. 3. Non-metals are insulators or poor conductors of electricity and heat because they do not lose electrons to transmit the energy. 4. At room temperature, they can be in the state of solids, liquids or gases. 5. They are non-sonorous. 6. They can be transparent. 7. Know the location of metals, metalloids and non-metals in the periodic table. Metals= left of the zigzag line Nonmetals= right of the zigzag line Metalloids= on the zigzag line **Lesson\# 7: Ions** 1. Define an ion. An ion is an atom that has gained or lost one or more electrons. This process changes the atom\'s electrical charge. Ions play a crucial role in many chemical reactions and biological processes. 2. What are the two types of ion: There are **[two main types]** of ions: 1**. Cations: positively** charged ions 2\. **Anions: negatively** charged ions 3. Define a Cation: Cations are formed when an atom loses one or more electrons 4. Define an Anion: Anions are formed when an atom gains one or more electrons 5. Calculate the total charge of a neutral atom. **[Check examples from worksheet and PPT/ Notebook]** 6. Calculate the total charge of ions: cation & anion **[Check examples from worksheet and PPT/ Notebook ]** **[Total Relative Charge in IONS]** - For ions, we use the same formula:\ Total charge = (number of protons) + (number of electrons)\ The result will be [positive for cations] and [negative for anions] **Lesson\# 8: Electric charge & Static electricity** - Electric charge: **It is a property that electrons and protons have that cause them to attract or repel each other.** - Electric force: **Any two charged objects exert a force on each other called an electric force. Electric force acts between objects even when they do not touch (Acts from a distance). Electric force can either pull objects together or push them apart.** - Friction: **Charging by friction occurs when two objects are rubbed together, causing a transfer of electrons between the objects.** - Conduction: **If a charged object and an uncharged object touch each other, the charged object can transfer some of its charge to the area it touches, and this is called conduction (Getting charged by contact).** - Induction: **a way of rearranging the charges within an object without touching it. For example, if an object with a negative charge is brought near another object with a negative charge, electrons in one object move away from the other object.** - Electric field: **a region around a charged object where the object's electric force is exerted on other charged objects.** - Static electricity: **The buildup of electric charge on an object.** - Static discharge:**It is when electric charges are released.** - Insulator: **Any material that does not allow electric current to pass through it.** - Conductor: **Any material that allows electric current to pass through it** - What are the types of electric charges? - **There are two types positive and negative charge.** - What is the interaction between electric charges? - **They repel and attract each other.** (coulomb's first law of electrostatics) - What are the two factors that affect the electric force between charges? - **Charge: If objects have like/ similar charges, they repel each other. The objects exert an electric force that pushes them apart. Two objects with unlike/ opposite charges attract each other. Each object exerts a force on the other, pulling the objects together. The greater an object's charge is, the greater the electric force is. This is true whether the objects repel or attract each other.** - **Distance: The distance between two objects also affects the strength of the electric force. The closer together the charged objects are, the greater the electric force is. As charged objects move farther apart, they attract or repel each other less strongly.** - Draw the electric field lines for single charges and for a pair of similar or different charges. - How can static electricity build up on different objects? - **When something is static, it is not moving. Static electricity is the extra positive or negative charge that builds up on an object until it eventually moves elsewhere. There are 3 methods: conduction induction and friction** - Draw the static charge and show their attraction/ repulsion between charged objects: Coulombs first law of electrostatics - What are the three methods of charging an object? - **There is friction, conduction and induction.** - Know examples on each method: **friction ( rubbing a balloon with your hair), conduction (van DeGraff generator), induction (electroscope).** - Why do we use electroscope and how do particles become rearranged when a negatively charged object comes near the electroscope? (What will happen to the two leaves/aluminium foils?) *Repulsion since the two leaves will be negatively charged; thus, they will repel)* Check Notebook notes/ PPT - **Electroscope is an early scientific instrument used to detect the presence of electric charge on a body. ** - What is static discharge and an example on it? - **If an object gains a static charge, the object doesn't hold the charge forever. When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. When static electric charges are released, this process is called static discharge. Lightning is an example of a huge spark of static electricity. Electric shock that an individual feel after going down the slides is also an example.** - Examples of conductors and insulators? - Conductors---\>**copper, steel, any metal, aluminium** - Inductors---\>**plastic, rubber, cloth, wood, glass** - Law of conservation of charge: Charge is conserved, neither created nor destroyed. **Lesson\# 9: Electric current** - What is an electric current? **The rate of flow of electric charges is called electric current. It describes the rate of flow of charges, such as the slow flow of many electrons through a wire. It is the amount of charge that passes a location in the wire every second. How much electrons are flowing.** (symbol I) - What is the unit of electric current? **The unit is called amperes often shortened to amps. The symbol for it is A.** (amps: amperes) (Unit Symbol A) - How do we measure electric current? **We measure it by using an ammeter.** - Do conductors and insulators allow electric current/electricity to pass through it? **-The materials which do not allow the current to pass through them, are known as poor conductors. They are also called insulators.** **- The materials which allow the current to pass through them are known as good conductors. Examples are copper, aluminium, etc.** - What is electricity? **Electricity is the flow of electrons.** - What are the types of electricity? **Static Electricity: Made up of electrons that do not move (transfer of charges between object not flow of charges), An example is the shock received between two people who touch after walking on Woolen carpet in cold weather.** **Current Electricity: Made up of moving electrons, this is the type used in our work, home, and daily lives.** - What are the two types of current electricity? **Direct current DC** **Alternating current AC** Direct current: **flows in one direction, usually generated from batteries.** Alternating current: **flows back and forth, used in homes and factories.** - Voltage: (Electromotive force; symbol U) **The pressure in a circuit that causes the electrons or current to flow. It is sometimes referred to as electromotive force (EMF).U is the symbol and Volt is the unit (V). Electrical pressure/voltage is measured with a voltmeter.** - Resistance: **Is the tendency of the wire to resist the flow of electrons or current through the wire. The unit of resistance is "Ohms". Within a circuit, electrical resistance is dependent upon size, length, temperature, thickness and the material of the conductor.** - What are the factors that affect the flow of electric current or increase electrical resistance: (size, length, temperature and material?) - What affects electric current? **Lesson\# 10: Electric circuits** - What is an electric circuit? **An electric circuit is a complete, closed path through which electric charges/ electrons can flow.** - **What are the parts of an electric circuit?** List the parts of an electric circuit. **All electric circuits contain Four basic parts: an energy source, an electrical wires (material type: conductors), a load, and a switch.** **\#1: Energy source: Common energy sources: batteries, and Electric generators.** **\#2 Electrical conductors/wires: Materials in which electric charges can move easily. Electric wires are often made of copper.** **\#3 load: It is a device that uses electrical energy to operate. Examples of loads include light bulbs, radios, computers, electric motors, any device that requires electricity to operate.** **\#4 Switch**: **A switch is a device that turns electrical devices on and off. It controls the flow of electric current.** - **When the switch is open, the circuit is open (it does not form a closed loop), so charges cannot flow.** - **When the switch is closed, the circuit is closed loop, charges can flow.** - How are electric circuits modelled? **One tool that can be used to model electric circuits is a circuit diagram.** **A diagram for an electric circuit shows all the parts in the complete circuit and the relationships among the different parts.** - What is the difference between conventional current flow and electron flow? **the main difference is that Conventional current flows from positive to negative and electron flows from negative to positive.** A diagram of a diagram Description automatically generated - What is a series circuit and how is it constructed? What is a parallel circuit and how is it constructed? You need to know how to draw an electric circuit (series and parallel)  What is the difference between series and parallel circuits? A screenshot of a computer Description automatically generated  - What is better to use for home appliances? Series or Parallel circuits? Why? **It is better to use Parallel circuits. If one load burns out the other load will continue working.** - How is the voltmeter and the ammeter connected? \- What are some safety practices that should be observed in doing electrical work?  - What are short circuits? A diagram of a circuit Description automatically generated **[Note:] make sure to review all worksheets given, quizzes and ppts.** - Review all ppt slides, worksheets and exercises that were solved in class. - Review assignments and quizzes completed on NEO.