ADDITIONAL TEXTS FOR READING AND UNDERSTANDING
TEXT 2
Boiling, evaporating and condensing
When a substance changes from one state to another, its particles don’t change. All that changes is the distance between the particles, their speed, and the attraction between them.
When a liquid becomes a gas, the particles move faster and spread out. The attractive forces between the particles become very weak. A substance in the liquid state becomes a gas by evaporation or by boiling. Evaporation happens when particles leave the surface of a liquid. The particles spread out to form a gas. Evaporation can happen at any temperature. Boiling occurs throughout the whole of a liquid. When you heat a beaker of liquid water, bubbles of water in the gas state form throughout the liquid. The bubbles rise to the surface and escape. The water is boiling. Boiling can only happen when a liquid is hot enough.1.2
When a substances changes state from gas to liquid, the particles move more slowly. They get closer until they touch each other. The forces between the particles are much stronger in the liquid. A liquid becomes a gas by condensation. A substance in the gas state condenses when it is cooled to its boiling point or below.
1. Name the change of state when a substance in the gas state becomes a liquid.
2. Describe how the movement of the particles changes when a substance boils.
TEXT 36TranslaTTexTet
Energy and changes of state
When a substance is in its solid or liquid state, strong forces hold the particles together. The forces between particles are much weaker when a substance is in its gas state.
In a liquid, the particles touch each other. Strong forces of attraction between the particles stop them escaping from the liquid. Particles in liquids move around. Some particles move faster than others. The faster moving particles have more energy.
Evaporation happens when some faster moving particles have enough energy to overcome the forces that hold the particles together. These particles escape from the surface of the liquid.
Boiling happens when, overall, the particles in a liquid move quickly enough to overcome the forces holding them together. A liquid needs energy from heating to make its particles move quickly enough. This is why a substance can only boil when it is at its boiling point. The boiling point of a substance depends on the strength of the forces between the particles in the liquid state. The stronger the forces, the more energy is needed to separate the particles, and the higher the boiling point.
When a substance is in its solid state, strong forces hold the particles in a pattern. Energy is needed to overcome these forces to make the solid melt. Your hand can supply enough energy to melt a small piece of gallium metal, or an ice cube. Much more energy is needed to melt copper. The melting point of a substance depends on the strength of the forces that hold the particles in a pattern. The stronger these forces, the more energy needed to make the solid melt, and the higher the melting point.
1. Describe how the strength of the forces between particles change when a liquid becomes a gas.
2. Describe and explain what happens to the particles when a liquid evaporates.
1. Complete the sentences using words from the list. You may use them once, more than once, or not at all:
Increases, decreases, stays the same
a. When liquid water boils, the distance between the particles …
b. When liquid water boils, the strength of the attractive forces between the particles … .
c. When steam condenses, the speed of movement of the particles … .
2. Match the term in the second column with the definition in the first column. Write the letter of the correct term on the lines provided.
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1. amount of material an object has in it |
a. density |
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2. amount of space an object takes up |
b. malleability |
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3. temperature at which a substance changes from a liquid to a gas |
c. matter |
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4. anything that has mass and takes up space
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d. dichotomous key |
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5. mass per unit volume |
e. melting point |
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6. characteristic that can be observed and measured |
f. physical property |
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7. uses physical properties to classify |
g. state of matter |
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8. solid, liquid, gas, or plasma |
h. volume |
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9. state of matter with particles vibrating in a fixed position |
i. physical change |
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10. characteristic that determines how a substance will react |
j. mass |
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11. mass can’t be created or destroyed |
k. conservation of mass |
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12. temperature at which a solid becomes a liquid |
l. chemical property |
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13. the distance between two points |
m. chemical change |
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14. process that does not change the identity of a substance |
n. solid |
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15. a substance with this physical property can be rolled into a sheet |
o. boiling point |
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16. change in the identity of a substance |
p. length |
3. Match the appropriate unit of measure from the second column with the objects in the first column by writing the letter of the correct unit of measure on the lines provided.
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1. length of a soccer field |
a. gram |
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2. volume of a bottle of soda |
b. centimeter |
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3. mass of a hamburger |
c. g/cm3 |
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4. length of your shoe |
d. meter |
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5. density of gold |
g. cm3 |
4. Mark each of the following changes with either a P for physical or a C for chemical.
1. a balloon expands as it becomes warmer
2. a soda bubbles and foams when you open it
3. milk sours
4. a substance changes color
5. developing a photograph
6. butter hardens after being in the refrigerator
5. Read the following description of silver. List each of the properties as either chemical or physical:
A white metal, malleable and ductile. Density is 10.5 g/cm3.Melting point is about 960°C; boiling point is about 2000°C. Does not react with water; does not react with oxygen in the air.
TEXT 3
Translate into Russian (in written form). Guess the meaning of any unfamiliar words:
A substance can be defined as a form of matter with a uniform and unchanging composition. Matter comes in three different states: solid, liquid, and gas. The physical properties can be observed without altering a substance’s composition. Chemical properties describe a substance’s ability to combine with or change into one or more new substances. Properties such as these can be influenced by external conditions like pressure and temperature.
Changes in matter can either be a physical or chemical change. A physical change alters the physical properties without changing its composition. Additionally, a chemical change or chemical reaction alters a substance’s composition. In a chemical reaction, reactants form products. During these chemical reactions, mass stays constant (i.e. mass is neither created nor destroyed). This pattern is called the law of conservation of mass.
Matter can be catergorized into two types: mixtures and pure substances. A mixture is a physical blend of two or more pure substances. Mixtures can be separated by physical means. A homogeneous mixture is called a solution. Matter also comes in the form of pure substances which can be either elements or compounds. Elements are substances that cannot be broken down into simpler substances by chemical or physical means. Elements are organized in the periodic table of elements. A compound is a chemical combination of two or more elements. A compound can be separated into its elements via a chemical change. Properties of compounds differ from the properties of their component elements. The law of definite proportions states that a compound maintains the same elemental composition in the same proportions, regardless of size, quantity, ect..
TEXT 4
Translate into Russian (in written form). Guess the meaning of any unfamiliar words:
A gas is a form of matter composed of particles in random motion. A gas will flow to conform to the shape of its container.
A liquid is also a form of matter. Like a gas, a liquid will also take the shape of its container. However, liquids have a constant volume. The forces of attraction between liquid particles limit the motion of the liquid molecules. In this way, the liquid will not expand to fill a container.
A solid is also a form of matter composed of particles in motion. However, unlike a gas and a liquid, a solid has a definite shape and a definite volume resulting from the strong forces of attraction between solid particles.
All mixtures can be separated into substances via physical changes. Substances have a definite, or fixed, composition that does not vary from one sample to another.