Unit Preview Classwork
Name: _________________________
7th Grade PSI Complete as much of the Graphic Organizer below as you can based on what you already know. For each term you should give a definition of the term and up to three other things you remember about the term. One of your three may be an example of the term itself. Even if you don’t think you have learned about the term before, you should be able to find a definition for the term. In the last column, list any questions you still have about the term. Term and Definition
What I Remember
Atom
1.
My Questions
2. 3.
Element
1. 2. 3.
Molecule
1. 2. 3.
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7th Grade PSI
Chemical Reactions and Energy
Compound
1. 2. 3.
Pure Substance
1. 2. 3.
Mixture
1. 2. 3.
Heterogeneous Mixture
1. 2. 3.
Homogeneous Mixture
1. 2. 3.
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7th Grade PSI
Chemical Reactions and Energy
Physical Property
1. 2. 3.
Chemical Property
1. 2. 3.
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7th Grade PSI
Chemical Reactions and Energy
Signals of Changes Classwork
Name: _________________________
7th Grade PSI Complete the list of common signals that a change is occurring or has occurred. Remember, these signals are usually based on OBSERVABLE PROPERTIES. Some properties will require you to use a tool such as a thermometer or a ruler to determine how much change has occurred. The first one has been completed for you as a guide. Signal and Example
Observed Using
Measured Using
Phase change – melting candle wax melting
Eyes because it loses its shape and might change color
No special tools required
Phase change freezing Phase change – boiling Phase change condensing Color change
Odor change
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7th Grade PSI
Chemical Reactions and Energy
Flavor change
Taste buds UNSAFE, NEVER TASTE ANYTHING IN THE SCIENCE LAB
Temperature change Smoke produced
Light produced
Bubbles produced
Precipitate produced Mass change
Volume change
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7th Grade PSI
Chemical Reactions and Energy
Density change
Shape change
Texture change
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7th Grade PSI
Chemical Reactions and Energy
Classifying Physical Changes and Chemical Reactions Classwork
Name: _________________________
7th Grade PSI For each situation, describe whether it is a physical change or a chemical reaction and then explain your thinking. There may be more than one correct answer depending on how you think about the situation. Situation
Physical or Chemical
Thought Process
Butter melting
Physical change
It is still butter. It was a phase change from solid to liquid
Charcoal heating a grill Mixing sugar in water Heating sugar on the stove until it turns brown and starts smoking Digesting food
Breathing
Puddles evaporating
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7th Grade PSI
Chemical Reactions and Energy
Cutting your hair
Melting silver to make jewelry
Blowing bubbles
Melting cheese
Making cheese
Bleaching your hair Sharpening a knife Firework explodes Composting
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7th Grade PSI
Chemical Reactions and Energy
Conservation of Mass Classwork
Name: _________________________
7th Grade PSI
1. Are the laws of conservation of matter and conservation of mass interchangeable? Why or why not?
2. Hydrogen peroxide decomposes to give water and oxygen. a. What part of this chemical reaction represents reactants?
b. What part of this chemical reaction represents products?
c. Explain the difference between reactants and products.
3. Is it possible to start with 25g of reactants and end with 35g of products? Why or why not?
4. Consider the following equation: AgNO3 + FeCl2 AgCl +HNO3. Are the laws of conservation of mass and matter true in the reaction? Justify your answer.
5. In order to burn something in the laboratory, oxygen gas is needed. a. Where does the oxygen gas come from?
b. Is the oxygen gas a reactant or product? Explain.
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7th Grade PSI
Chemical Reactions and Energy
Conservation of Mass Homework
Name: _________________________
7th Grade PSI 6. Is it possible to start with 5g of one chemical and 10g of another chemical and make 15g of a third chemical? Explain why or why not. 7. Is conservation of mass and matter true in the reaction: AgNO3 + HCl AgCl +HNO3 ? Justify your answer. 8. Why is it hard to measure the amount of products produced when something burns?
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7th Grade PSI
Chemical Reactions and Energy
Balancing Equations Classwork
Name: _________________________
7th Grade PSI
9. Draw a balanced picture equation to show individual iron atoms combining with individual sulfur atoms to form iron (II) sulfide, which has the formula FeS. Identify the reactants and products.
10. Draw a balanced picture equation to show individual carbon atoms combining with individual fluorine atoms to form carbon tetrafluoride which has the formula CF4. Identify the reactants and products.
11. Use a chart to show that the following equation is balanced: N2 + 2O2 2NO2
a) Name the reactants: b) Name the products: c) Are the properties of the products and reactants the same? Justify your answer.
12. Balance the following equation: Fe2O3 + Al Al2O3 + Fe a) Name the reactants: b) Name the products:
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7th Grade PSI
Chemical Reactions and Energy
Balancing Equations Homework
Name: _________________________
7th Grade PSI
13. Draw a balanced picture equation to show individual calcium atoms combining with individual phosphorus atoms to form calcium phosphide, which has the formula Ca3P2. Identify the reactants and products. 14. Draw a balanced picture equation to show individual gold atoms combining with individual bromine atoms to form gold (I) bromide, which has the formula AuBr. Identify the reactants and products. 15. Use a chart to show that the following equation is balanced: CuOH + HF H2O + CuF a) Name the reactants: b) Name the products: 16. Balance the following equation: Li3P + Al AlP + Li a) Name the reactants: b) Name the products:
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7th Grade PSI
Chemical Reactions and Energy
Types of Energy Classwork
Name: _________________________
7th Grade PSI 17. Identify an example of each type of energy in the image below. Justify your choices. a) Kinetic Energy:
b) Chemical Potential Energy:
c) Electromagnetic Energy:
d) Thermal Energy:
18. Which has more energy a bus moving at 15m/s or a baseball moving at 15m/s? Why?
19. Which has more energy 5 kilograms of dynamite or 10 kilograms of dynamite? Why?
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7th Grade PSI
Chemical Reactions and Energy
Types of Energy Homework
Name: _________________________
7th Grade PSI 20. What is the major type of energy of sunlight? Why? 21. What is the major type of energy of a raindrop falling from the sky? Why? 22. What has more kinetic energy 10kg of bees flying at 10m/s or 10kg of birds flying at 10m/s? Why? 23. Which has more energy 100 calories of cookies or 100 calories of popcorn? Why?
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7th Grade PSI
Chemical Reactions and Energy
Energy Changes Classwork
Name: _________________________
7th Grade PSI Use the word/phrase bank below to fill in the Venn diagram. After using all the words in the word bank, come up with two new examples of each type of reaction and write these in the appropriate place on the Venn diagram. Endothermic
Exothermic
Word/phrase bank:
Baking bread
Reactants have lower energy than products
Absorb energy from surroundings
Burning a candle
Heats surroundings
Conserve mass
Chemical reaction
Conserve energy
Melting ice cubes
Reactants have higher energy than products
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7th Grade PSI
Chemical Reactions and Energy
Energy Changes Homework
Name: _________________________
7th Grade PSI 24. Define exothermic reactions. 25. Define endothermic reactions. 26. Is boiling water an endothermic or exothermic process? Justify your answer. 27. Is lighting a match an endothermic or exothermic process? Justify your answer. 28. Is baking a cake an endothermic or exothermic process? Justify your answer.
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7th Grade PSI
Chemical Reactions and Energy
Temperature and Thermal Energy Classwork
Name: _________________________
7th Grade PSI 29. If you know an object’s temperature, do you know how much thermal energy it has? Explain.
30. What properties of a substance influence the amount of thermal energy it possesses?
31. Which has more thermal energy, 500mL of boiling water or 250mL of boiling water? Explain your answer.
32. What must happen to the thermal energy of a substance during deposition? Explain why.
33. What must happen to the thermal energy of a substance during evaporation? Explain why.
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7th Grade PSI
Chemical Reactions and Energy
Temperature and Thermal Energy Homework
Name: _________________________
7th Grade PSI 34. Explain how two substances can be at the same temperature but have different amounts of thermal energy. Give an example. 35. Explain how two substances can be at different temperatures but still have the same amount of thermal energy. Give an example. 36. Which has more thermal energy, 500g of ice or 500g of steam? Explain your answer. 37. What must happen to the thermal energy of a substance during freezing? Explain why. 38. What must happen to the thermal energy of a substance during melting? Explain why.
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7th Grade PSI
Chemical Reactions and Energy
Energy Flow Classwork
Name: _________________________
7th Grade PSI 39. Explain when heat transfers between two objects.
40. For the following scenarios, explain which objects or substances gain energy and which lose energy: a. Bread baking in an oven
b. Ice forming in a freezer
c. Melting ice cream
d. Burning your hand on a hot stove
41. Two chocolate cakes are baking in an oven though one cake is much larger than the other. a. In which direction must heat flow in order to bake the cakes?
b. If both cakes reach a temperature of 400F, what can you say about the amount of energy transferred for the large cake versus the smaller cake?
42. Explain what happens when you put a cold pan in a hot oven with respect to energy.
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7th Grade PSI
Chemical Reactions and Energy
Energy Flow Homework
Name: _________________________
7th Grade PSI 43. When does heat transfer between two objects stop? 44. Explain how size affects heat transfer. 45. Why does water evaporate quickly in a patch of sunny sidewalk and more slowly on a patch of sidewalk in the shade? 46. Your friend touches an ice cube and it melts under his finger. He wonders why, his finger feels so cold when he touches the ice if he is hot enough to melt it? Explain to your friend what is happening when he touches the ice in terms of heat and energy transfer.
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7th Grade PSI
Chemical Reactions and Energy
Answer Key Signals of Changes Classwork Signal and Example
Observed Using
Measured Using
Phase change – melting candle wax melting
Eyes because it loses its shape and might change color
No special tools required
Phase change -
Eyes
no tools
Eyes
no tools
Eyes
no tools
Color change
Eyes
no tools
Odor change
Nose
no tools
Flavor change
Taste buds UNSAFE, NEVER TASTE ANYTHING
freezing Phase change – boiling Phase change condensing
IN THE SCIENCE LAB Temperature
Touch
change Smoke
thermometer for safety
Eyes and nose
no tools
produced
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7th Grade PSI
Chemical Reactions and Energy
Light produced
Eyes
no tools
Bubbles
Eyes
no tools
Eyes
no tools
Mass change
Eyes
scale/balance
Volume change
Eyes
ruler or graduated
produced Precipitate produced
cylinder Density change
Eyes
balance, ruler, graduated cylinder
Shape change
Eyes
no tools
Texture change
Touch
no tools
Classifying Physical Changes and Chemical Reactions Classwork Situation
Physical or Chemical
Thought Process
Butter melting
Physical change
It is still butter. It was a phase change from solid to liquid
Charcoal
Chemical
Charcoal burns to release the heat
heating a grill
reaction
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7th Grade PSI
Chemical Reactions and Energy
Mixing sugar in
Physical
water
change
Heating sugar on the stove until it turns brown and starts smoking
Chemical
Digesting food
Chemical
reaction
reaction Breathing
BEST : Chemical reaction 2nd: Physical change
Puddles
Physical
evaporating
change
Cutting your hair
Physical
Dissolving is a physical change
The smoke and color change are indications of burning.
The food is broken down and changed into forms your body can use. Chemical reaction because you breathe in oxygen gas and exhale carbon dioxide Physical change because you draw in air and just temporarily change its shape before breathing it back out. Air is a mixture of mostly nitrogen gas before and after the breath. The water evaporates which is a phase change
It is still hair, just in multiple pieces.
change Melting silver to make jewelry
Physical change
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7th Grade PSI
It is still silver. It was a phase change from solid to liquid and back.
Chemical Reactions and Energy
Blowing bubbles
BEST: Physical change 2nd: Chemical reaction
Melting cheese
Physical change
Making cheese
Chemical reaction
Bleaching your
Chemical
hair
reaction
Sharpening a
Physical
knife
change
Firework
Chemical
explodes
reaction
Composting
Chemical reaction
1)
Physical change because you are adding air inside to change the volume. Chemical reaction because you are breathing in oxygen gas and breathing out more carbon dioxide. It is still cheese. It was a phase change from solid to liquid. The milk needed to ferment to become cheese. The bleach reacts with the melanin in hair and makes it colorless. You are removing small bits of the knife to make it sharper. Heat and light are signs of a chemical change when they happen at the same time. The compost material breaks down into fresh soil.
Yes; Conservation of mass refers to the mass and means that the reactants and products must have the same total mass. Conservation of matter means atoms of reactants cannot change their types; they may only change how they are bonded
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7th Grade PSI
Chemical Reactions and Energy
together. If atoms change their types in a chemical reaction, then mass has also been changed. 2) a) Hydrogen Peroxide b) Water and oxygen c) Reactants are starting chemicals, products are what is made. 3) No, mass was gained. 4) No, several elements have changed meaning that the total mass of reactants and products will not be the same, which defies the law of conservation of mass. Since elements have change, matter has either been created or destroyed which defies the law of conservation of matter. 5) a) The air b) It is a reactant because it is a starting chemical, which allows burning to take place. 6) Yes. 5g+10g=15g This does not violate the law of conservation of mass because you end up with the same amount of mass that you started with. 7) Yes; the elements have not changed so matter/mass have not been created or destroyed. Furthermore, the elements are balanced. 8) Some of the products are gases. 9) Reactants: one Fe atom, one S atom, Products: one Fe atom with a double bond to a S atom. (A single bond may be acceptable at teacher’s preference) 10) Reactants: one C atom, four F atoms, Products: one C in the center with single lines to each F atom. F atoms at 12, 3, 6, and 9 o’clock positions. 11) 2 N each side, 4 O each side a) N2 , 2O2 b) 2NO2 c) The properties of the reactants and products will be different because they are fundamentally different substances, which is the very definition of a chemical change. 12) Fe2O3 + 2Al Al2O3 + 2Fe a) Fe2O3, 2AL b) Al2O3, 2Fe 13) Reactants: 3 Ca atoms, 2 P atoms, Products W shape with alternating Ca and P atoms at the points. Other shapes may be accepted as well. 14) Reactants: 1 Au atom, 1 Br atom, Products one Au atom with a single bond to the Br atom. 15) 1 Cu each side, 1 O each side, 2 H each side, 1 F each side a) CuOH, HF b) H2O, CUF 16) Li3P + Al AlP + 3Li a) Li3P, Al b) AlP, 3Li 17) Sample student response a) Kinetic energy- anything that is moving. EX: person’s arm reaching for food
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7th Grade PSI
Chemical Reactions and Energy
18) 19) 20) 21) 22) 23)
b) Chemical Potential Energy- the food because it contains calories that will be digested by the people later for energy. c) Electromagnetic Energy- radiation from the sun that can be absorbed by everything in the image. d) Thermal Energy- every object in the picture possesses thermal energy because thermal energy represents the kinetic and potential energy of atoms or molecules and all matter is made up of atoms that are moving. Furthermore, thermal energy is responsible for matter having a measurable temperature and all the objects in the image are at some temperature. Bus – same speed, more mass 10 kilograms, more of it Electromagnetic – light Gravitational potential – high up OR Kinetic – moving The same – same mass, same velocity The same – same amount of calories
Endothermic
Exothermic
Absorbs energy from surroundings
Reactants have lower energy than products
Conserves mass
Chemical Reaction
Melting ice cubes
Baking bread
24) 25) 26) 27)
Conserves energy
Student examples will vary
Heats surroundings
Reactants have higher energy than products.
Burning a candle
Student examples will vary
Reactions that gives energy to the surroundings Reaction that absorbs energy from the surroundings. Endothermic- energy is absorbed from surroundings to heat the water. Exothermic- energy is released to the surroundings in the form of the flame. www.njctl.org
7th Grade PSI
Chemical Reactions and Energy
28) Endothermic- energy is absorbed from the surroundings of the oven in order to heat and bake the cake. 29) No. Temperature is a property that can be directly measured unlike thermal energy. Thermal energy by definition is the average kinetic and potential energy possessed by atoms in a substance. Though they are not the same, temperature and thermal energy are proportional. 30) Mass, state/phase of substance 31) 500mL- both will be at the same temperature, but the mass is greater for the 500mL of boiling water. 32) Decrease-energy must be lost in order for the atoms/molecules to slow down enough to change phase from a gas to a solid. 33) Increase- energy must be gained in order to increase the speed of atoms/molecules to change phases from solid to gas. 34) Different masses or different substances. Examples will vary. 35) Different masses or different substances. Examples will vary. 36) Steam- particles are moving faster in a gaseous state increasing the kinetic energy of particles which in turn give the substance more thermal energy. This is because thermal energy is the average kinetic and potential energy of a substance’s atoms/molecules. 37) Decrease- energy must be lost in order for the atoms/molecules to slow down enough to change phase from a liquid to a solid. 38) Increase- energy must increase in order for the atoms/molecules to speed up enough to change the phase from solid to liquid. 39) When they touch and are different temperatures 40) a) Bread gains energy from heated baking pan b) Ice loses energy into surrounding freezer air c) Ice cream gains energy from surrounding air d) Hand gains energy from hot stove 41) a) Heat flows from the baking pan and from the surrounding air to the cake. b) The more massive an object is, the more energy it can gain or lose. Therefore the larger cake gained more energy in order to reach the same temperature as the smaller cake. 42) The hot oven transfers heat energy to the cold pan and heats it up. 43) Heat transfer stops when objects are the same temperature. 44) If objects are different temperatures, the bigger they are, the more surface area they have to use to exchange energy. 45) The sunny sidewalk has a higher temperature and more energy to transfer to the water. 46) Since your finger is at a higher temperature than the ice, heat flows from your finger to the ice. This means that your finger loses energy while the ice gains energy. The result in the loss of energy from your finger is that it “feels” cold.
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7th Grade PSI
Chemical Reactions and Energy
