Pure Substance

1.

2.

3.

Mixture 1.

2.

3.

Heterogeneous Mixture

1.

2.

3.

Homogeneous Mixture

1.

2.

3.

Physical Property

1.

2.

3.

Chemical Property

1.

2.

3.


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 – meltingcandle 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

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

Density change

Shape change


Texture change


Classifying Physical Changesand 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


Cutting your hair

Melting silver to make jewelry

Blowing bubbles

Melting cheese

Making cheese

Bleaching your

hair

Sharpening a

knife

Firework

explodes

Composting


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.


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?


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:


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


16.Balance the following equation: Li3P + Al AlP + Li



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?


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?


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.

Word/ phrase bank:

Baking breadReactants have

lower energy than products

Absorb energy from

surroundingsBurning a candle Heats

surroundings

Conserve mass Chemical reaction

Conserve energy

Melting ice cubes

Reactants have higher energy than products


Endothermic Exothermic

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.


Temperature and ThermalEnergy 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.


Temperature and ThermalEnergy 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.


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.


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.


Answer Key

Signals of Changes Classwork

Signal and Example

Observed Using Measured Using

Phase change – meltingcandle wax melting

Eyes because it loses its shape and might change color

No special tools required

Phase change -

freezing

Eyes no tools

Phase change –

boiling

Eyes no tools

Phase change -

condensing

Eyes no tools

Color change Eyes no tools

Odor change Nose no tools

Flavor change Taste buds UNSAFE, NEVER TASTE ANYTHING

IN THE SCIENCE LAB

Temperature

change

Touch thermometer for

safety

Smoke

produced

Eyes and nose no tools


Light produced Eyes no tools

Bubbles

produced

Eyes no tools

Precipitate

produced

Eyes no tools

Mass change Eyes scale/balance

Volume change Eyes ruler or graduated

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

heating a grill

Chemical

reaction

Charcoal burns to release the heat


Mixing sugar in

water

Physical

change

Dissolving is a physical change

Heating sugar on the stove until it turns brown and starts smoking

Chemical

reaction

The smoke and color change are indications of burning.

Digesting food Chemical

reaction

The food is broken down and changed into forms your body can use.

Breathing BEST :

Chemical

reaction

2nd: Physical

change

Chemical reaction because you breathe in oxygen gas and exhale carbon dioxidePhysical 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.

Puddles

evaporating

Physical

change

The water evaporates which is a phase change

Cutting your hair Physical

change

It is still hair, just in multiple pieces.

Melting silver to make jewelry

Physical

change

It is still silver. It was a phase change from solid to liquid and back.


Blowing bubbles BEST: Physical

change

2nd: Chemical

reaction

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.

Melting cheese Physical

change

It is still cheese. It was a phase change from solid to liquid.

Making cheese Chemical

reaction

The milk needed to ferment to become cheese.

Bleaching your

hair

Chemical

reaction

The bleach reacts with the melanin in hair and makes it colorless.

Sharpening a

knife

Physical

change

You are removing small bits of the knife to make it sharper.

Firework

explodes

Chemical

reaction

Heat and light are signs of a chemical change when they happen at the same time.

Composting Chemical

reaction

The compost material breaks down into fresh soil.

1) 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


together. If atoms change their types in a chemical reaction, then mass has also been changed.

2)a) Hydrogen Peroxideb) Water and oxygenc) 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 airb) 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, 2ALb) 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 sidea) CuOH, HFb) H2O, CUF

16)Li3P + Al AlP + 3Lia) Li3P, Alb) AlP, 3Li

17)Sample student responsea) Kinetic energy- anything that is moving. EX: person’s arm reaching for food


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.

18)Bus – same speed, more mass19)10 kilograms, more of it20)Electromagnetic – light21)Gravitational potential – high up OR Kinetic – moving22)The same – same mass, same velocity23)The same – same amount of calories


Endothermic Exothermic

Absorbs energy from surroundings

Reactants have lower energy than products

Melting ice cubes

Baking bread

Heats surroundings

Reactants have higher energy than products.

Burning a candle

Conserves energy

Conserves mass

Chemical Reaction

Student examples will vary Student examples will vary

24)Reactions that gives energy to the surroundings25)Reaction that absorbs energy from the surroundings.26)Endothermic- energy is absorbed from surroundings to heat the water.27)Exothermic- energy is released to the surroundings in the form of the flame.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 substance31)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 temperatures40)

a) Bread gains energy from heated baking panb) Ice loses energy into surrounding freezer airc) Ice cream gains energy from surrounding aird) 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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