Chapter 3 Review

Write the procedure for finding the density of gasoline. A procedure is step by step instructions.

1. Determine the mass of a graduated cylinder without the gasoline. 2. Add the gasoline to the graduated cylinder and measure to determine the mass. 3. The amount of gasoline in the graduated cylinder is the volume of the gasoline. 4. Calculate the gasoline's density by dividing the mass by the volume.

A piece of magnesium metal has a mass of 56.5 g and a volume of 32.5cm³. What is the density of the magnesium?

1.74 g\cm³

What compounds are formed when methane gas is burned?

2 water atoms and 1 carbon dioxide atom are exchanged.

The elements phosphorus and oxygen form a compound with the formula P2O5. What is the ratio of phosphorus atoms to oxygen atoms in the compound?

2:5

What is the mass of 300 cm³ of liquid water? Explain your answer.

300 grams. Density is equal to mass divided by volume. The density of liquid water is 1.0 g\cm³, so 1.0 g\cm³=mass of water\300cm³. Mass is equal to 300cm³×1.0 g\cm³ or 300 grams.

What is a chemical change?

A chemical change is a change in which one or more substances combine or break apart to form new substances.

Compare and contrast a mixture and a compound.

A mixture is made up of two or more substances, whereas a compound is a pure substance made of two or more elements chemically combined in a set ratio. The individual substances in a mixture keep their separate properties. The properties of a compound are very different from those of the element that formed it.

What is a physical change?

A physical change is a change in a substance that does not change its identity.

Explain the difference between an endothermic change and an exothermic change. Explain how they can occur simultaneously.

An endothermic change is where energy is taken in. An exothermic change is a change in which energy is released\given off. They can occur simultaneously when a fire burns (exothermic) and you use the heat of the fire to warm your hands (endothermic).

Describe three ways in which compounds and mixtures differ.

Compounds are pure substances made up of two or more elements chemically combined, elements are combined in a specific ratio, properties differ from those of the combined elements. Mixtures are not pure substances and are made of two or more elements and\or compounds, properties are not combined in a specific ratio but in mixed ratios, mixed substances retain their individual properties.

Which of the following can be classified as a solution: pure water, fruit punch, cereal and milk in a bowl? Explain your answer.

Fruit punch solution because its parts retain their individual properties but are evenly mixed.

Explain the process of photosynthesis and how energy is transferred in the process. What forms of energy are used?

Hydrogen burns and gives off electromagnetic energy. The rays from the sun (electromagnetic energy) are absorbed by a plant. The plant uses that energy to create sugar molecules (chemical energy). The sugar molecules are turned into food for the plant. The plant then releases sugar molecules to other organisms (chemical energy).

Compare and contrast potential energy and kinetic energy. Provide examples of each type of energy.

Kinetic energy is the energy of matter in motion. A bouncing ball has kinetic energy. Potential energy is the energy of matter based on its position. A book resting on a table has potential energy. Although kinetic and potential energy are different, both may be related to changes in matter. Also, like all energy, both kinetic and potential energy can neither be created nor destroyed; they can only be changed into from one to another. Kinetic energy can turn into potential energy and potential energy can be turned into kinetic energy. For example, a ball resting at the top of the hill has potential energy, but as it rolls down the hill, its potential energy has transformed into kinetic energy.

What is kinetic energy? Give an example of a use of kinetic energy that you saw today.

Kinetic energy is the energy of matter in motion. Moving cars have kinetic energy.

What two quantities do you need to measure in order to determine the density of an object?

Mass and Volume.

Is pizza a homogeneous mixture or a heterogeneous mixture? What type of physical and chemical changes can pizza go through? EXPLAIN your answers.

Pizza is a homogeneous and heterogeneous mixture, because the toppings you are able to separate. You aren't able to separate the ingredients in the sauce or the dough. The toppings undergo a physical change when they are sliced and cut, and the dough when it is flattened out. The pizza undergoes a chemical change when it is baked in the oven.

How do you know that the burning of candle wax is an exothermic change.

The burning of candle wax releases energy in the for of light (electromagnetic energy) and heat (thermal energy). A change that gives off energy is an exothermic change.

If a samples of silver and lead each had a volume equal to 1 cm³, which would have the greater mass and how much would the difference in the masses be? Silver has a density of 10.5 and lead has a density of 11.3.

The mass of the lead would 0.8 grams greater than the mass of the silver.

What can you infer about the density of a material if a sample of it floats in water?

The material is less dense than water and has a density less than 1.0.

Ice has a lower density than liquid water. How does the volume of a kilogram of water change when it freezes to ice?

The volume of a kilogram of water increases when it freezes to ice.

Explain the differences in finding the density of a rectangular solid and finding the density of an irregular solid.

To find density of any solid object, you must measure its mass and volume. Then you divide the mass by volume to find the object's density. The mass of a rectangular solid and an irregular solid can be measured with a triple-beam balance. The volume of a rectangular solid may be calculated by measuring its length, width, and height and then multiplying the 3 values together. The volume of an irregular solid can be measured by submerging the object in water in a graduated cylinder. The water level will rise by an amount equal to the object in millimeters.

Suppose you dissolve some table salt in a glass of water. How could you prove that the dissolving was a physical change, not a chemical change?

You could prove that the solution was salt water by causing the water to evaporate and leave behind the salt or you could have them taste the solution.